Home

Final Documentation - University of Central Florida

1. Online Available http www pulseox info pulseox limits8 htm Accessed Dec 10 2009 3 C Hill Limitations Poor Signal pulseox info para 2 May 22 2005 Online Available http www pulseox info pulseox limits2 htm Accessed Dec 10 2009 4 Discover and Learn 2009 Available http www wifi org Accessed 20 Sep 2009 5 Dr N Townsend Pulse Oximetry Medical Electronics Michaelmas Term 2001 online Available http courses cs tamu edu rgutier cpsc483_s04 pulse_oximetry_notes paf Accessed Sep 15 2009 6 Engineering Toolbox Sound Pressure 2005 Online Available http www engineeringtoolbox com sound pressure d_711 html Accessed Dec 9 20091 7 Federal Communications Commission Code of Federal Regulations Title 47 Federal Communications Commission October 2008 Online Available http www fcc gov Accesses Nov 20 2009 8 L Godfrey Choosing the Detector for your Unique Light Sensing Application 1997 EG amp G Optoelectronics Online Available http www engr udayton edu faculty jloomis ece445 topics egginc tp4 html Accessed Dec 7 2009 9 Texas Instruments Medical Applications Guide Pulse Oximetry Texas Instruments online Available www ti com Accessed Sep 15 2009 Section 11 Appendix C Permissions l Enpirion EP5368Q Permission RE Permission to reprint images for School Project Karen Boyle lt Kbo
2. Block Diagram for power of the TU 62 Figure 24 Battery Life Monttorimg ENEE 63 Figure 25 Configuration of EPS linia 64 Figure 26 Configuration of Digital Noise Filtering ccceeeeeeseeeeeeteeeeeeeees 64 Figure 27 Configuration of Transient Suppression ooocccccccccccnocanancncnnnnncnanannns 65 Figure 28 Overall block diagram for the HD 65 Figure 29 Block diagram for the display occccccincccccccnnnncccnncnnanancncnnnnccnnnnnnno 66 Figure 30 Block diagram for power of the RDU cceceeeeeeeeeeeetteeeeeeees 68 Figure 31 Battery Life Monttorimg AEN 68 Figure 32 ICL7673 Automatic Backup Battery Switch Configuration 69 Figure 33 Configuration of EPS Oli 70 Figure 34 Configuration of Digital Noise Filtering oooonooocccccnnnnnnncnnccccccccncnnnnn 70 Figure 35 Configuration of Transient Suppression ooooccccccccccncnonoaccnnnnnccnnnnnnns 71 Figure 36 MCU Controlled Gpeaker ne 72 Figure 37 MCU Controlled LED Status Indicators oooooooocccccnnnccinccccacanaccncnnnon 72 Figure 38 Primary Supply Powered LED ee 73 Figure 39 TSU Housing Diagram cocccccnnononococcnoncncnonannnannncnnnnnnnnnnnnnnnnnnccnnnnnn 75 Figure 40 LP 21P DIM ISO neta 77 Figure 41 DC 34P Diagram EE 77 Figure 42 Global functions and data types ccccccccccccnccconccccncnnccnnnnnnananoncnnnnnnns 79 Figure 43 The packet used for communicating with th
3. 6 Again this was just the bare battery and does not include the necessary safety features that the battery would need to keep it from dying There are also battery packs available that have the included safety needs A 3 2V 1500mAh LiFePO4 18650 battery pack with safety features costs 7 50 A COTS charger for a 3 2V LiFePO4 cell charges at 0 5A and costs about 15 As an alternative standard Li lon packs with safety features are also available A Li lon 18500 pack with the specifications 3 7V 3 5A charging current and 1400mAh is available for 15 This Li lon battery would meet the requirements and be smaller and lighter than the LiFePO4 but would cost substantially more A COTS charger for the 3 7V Li lon packs costs about 12 In both cases the COTS charger would need to be modified so that battery would not need to be removed from the RDU to recharge Although the cost difference of the batteries is large when the chargers are included in the price the differences are greatly reduced Ideally the battery would be recharged internally by the same AC DC Adapter that is the RDU s primary power source The LiFePO4 18650 battery pack retains 80 of the initial capacity after more than 2000 cycles 1500mA permits one eight hour cycle of the RDU plus some reserve This would give enough battery for more than 2000 uses of the RDU If the RDU were used once daily without its power source and then recharged the battery would still maintain 80 of
4. AVDD_DREG 29 cetto DIE ATTACH PAD a 232 R AS 1232 Es JE Antenna 50 Ohm C235 Es C235 1235 C236 Altemative filter that can be used to reduce the emission at 699 MHz below 54 dBm for conducted measurements Figure 6 6 CC 1 10 866 915 MHz application circuit Reprinted with permission from Texas Instruments Section 8 page IV Part Number Component Size in mm Number of IO Pins Extra Built in Features Cost in Dollars per Chip JN5148 8x8 21 2 4GHz Transceiver 12 bit ADC 12 bit DAC 4 wire Audio Interface 20 CC430 9x9 32 Sub 1GHz Transceiver 12 bit ADC 5 00 MSP430F233 12x12 48 12 bit ADC 2 50 MSP430F2616 12x12or 14x 14 48 or 64 12 bit ADC 12 bit DAC DMA Controller 5 85 MSP430FG437 14x 14 48 12 bit ADC 2x 12 bit DAC 3x Op Amps Analog Comparator DMA SVS LCD Driver 5 15 CC1110 6x6 21 Sub 1GHz Transceiver 12 bit ADC 4 85 Table 1 MCU Comparison designates that samples are available in low quantities for free or purchase 22 The Jennic JN5148 was a great MCU that could be used due to its small size adequate number of I O pins as well as its many useful built in features but its cost prevents it from being usable in this design The next best choice was Texas Instruments CC430 This chip was ideal
5. Block Diagram for the Antenna Power Summar TSU Mechanical Design The TSU is housed in a plastic case the LP 21P which is designed for holding PCBs The housing has external dimensions of 3 295 x 2 470 x 1 00 and internal dimensions of 2 655 x 1 775 measuring from the center of the screw posts The TSU housing holds the battery that powers the system and the TSU PCB The battery has a diameter of the battery is 0 55 and the length is 1 97 The TSU PCB has dimensions of 1 x 1 5 The absolute minimum distance needed for the battery and PCB to fit in the LP 21P is 2 05 x 2 97 Placing the battery and PCB as far from each other as possible yields a space of 0 42 The TSU is to be attached at the wrist Inside the bottom of the case two slots are cut with a width of 0 25 and a length of 1 00 each These two slots are 2 00 from each other A Velcro strap is fed through these slots and is used to secure the TSU to the wrist Two holes of diameter 0 25 are drilled into the sides of the casing The side of the case closest to the hand has one of these holes that serves as a connection point to the finger unit The other hole is used to connect the battery with the charger Sensor Mechanical Design The sensor consists of two major parts These parts are all found inside the sensor mechanical design and are instrumental in determining pulse and SpOz This includes the two LEDs and the photodiode
6. P2 6 PM_ACLK RF_ATEST 6 PM_RFGDO1 P1 0 PM_RFGDOO P3 P3 4 P3 3 P3 2 P3 1 P2 7 PM_MODCLK PM_DMAEO 3 0 PM_CBOUTO Figure 5 CC430F5137 pin designation Reprinted with permission from Texas Instruments Section 8 page lll The most important part of this chip was that it contains both an MCU and a transceiver This was ideal for the project because it will save space on the PCB thus allowing a smaller board to be created and a smaller overall product Since the CC430 can be programmed using familiar languages having both parts in one would not only save time programming but completely eliminated the need 19 to learn a new programming language The integrated real time clock was another plus This clock would allow the transmission to be programmed easily With these programmed on a real time clock coordinating the two units would be much easier This was another way to save power since the units would not have to run constantly Other aspects found on this chip included an on board comparator audio capabilities which may help run the speaker on the RDU sample and hold features and internal temperature and battery sensors These featured are all important to the design of this pulse oximeter Each of these features would save components and PCB space in the final design Pros Low power consumption Integrated MCU and transceiver Wake Up from standby in less than 5uA Small size of 9mm x 9mm 32 I O pins Real
7. Ter WEN ll Wm 0 095 9 SE Wm mm 740 70 7 C20 WEN mm EZ 11 1 DISP1 EE ii 5 09 72 2 F F2 O CTT 0 141 13 1131 A i 0 44 14 1 J2 S I EN 0 754 15 1 LED1 Po I a 3 40 16 1 LED2 A DESS 2 49 17 2 LED3 B ss I ff 1 33 LED4 18 1 LEDS Saas 2 33 19 1 LED6 SSE I RS 20 1 P1 gt I I 21 6 R1 R4 R5 MM i 0 071 R6 R7 R8 22 1 R2 E A i 0 073 23 1 R3 Wa LE E 0 071 24 1 R9 E sj Vi Sa 0 073 25 1 R10 Eee 0 071 26 3 R11 R12 MN a 0 073 27 1 GC fF Oe I E 3 13 28 1 Swi Eei 1 1 375 29 1 U1 z 2 44 30 1 U2 SES Ir 1 44 31 1 U3 as NE 1 57 32 1 U4 BE I SEE 5 15 33 1 U5 P I o 8 16 34 1 Y1 OoOo 1 30 Table 5 Receiving Display Unit 103 Section 4 Prototype Construction 4 1 Assembly The entirety of this project was assembled by the design team Though this limited the types of parts that could be used for the project it saved time and money over having the PCBs shipped out to be populated or waiting for mechanical designs to be completed from outside sources The design team used the facilities at the sponsoring company Fabrication equipment included soldering irons hot air guns solder a microscope to solder small components to the PCBs power drills oscilloscopes multimeters a micrometer for making accurate measurements hand tools such as screwdrivers and wrenches wires and anti static workspaces The first step was
8. The RSU should be tested to assure that it displays a different higher value after the group member has elevated their heart rate This assures that the unit can detect changes in pulse rate and not only a base reading Even though this value can be counted from simply checking the pulse by hand a comparison to a medical grade product should still be completed This can be tested at the same time that the SpO values are being compared By testing the pulse in more than one manner the unit is doubly protected and therefore safer To make the medical comparisons additional test conditions can be added For some nail polish that is dark can cause the readings to vary This should be tested to assess the unit s response in this case If polish results in a false or inaccurate reading this should be noted in the documentation to alert the user to this issue Some pulse oximeters can also give false readings if the user has 130 cold hands as this indicates low circulation If blood flow is limited the results may not be accurate Another possible issue is when administering oxygen The oxygen saturation of the blood may be of a high enough percentage even if the user is having breathing difficulties In these cases the user is absorbing enough oxygen but not expelling the proper amount of carbon dioxide Each of these issues can be tested in the hospital setting to compare the project s values with the of the hospital s pulse oximeter Any
9. minimum number of wanted prototype boards would cost 60 63 for the three TSUs and 58 28 for the two RDUs the price for three would be 2 more Sunstone offers their ValueProto PCB service that is an affordable solution for 49 small quantities of 2 layer boards The requirements for the ValueProto PCB are 2 Layers Up to 2 sides green solder mask with up to 1 side white legend tin lead finish only and holes that match their preset sizes A benefit to some is that even though this is a low cost service the board shape is not limited to rectangles Processing time for the boards would typically be two weeks and Sunstone offers free UPS ground shipping Three TSUs would cost 38 50 and two RSUs would cost 43 Compared to the costs of the PCBFabExpress services Sunstone s ValueProto PCB service costs less than the Bare Bones special and has the increased quality of the standard 2 layer board service The bonus of free shipping reduces the cost by another 20 to 30 Both fabrication options are viable for this project Self fabricating would save time but sending the boards out for fabrication might end up costing less Making the PCBs by hand would limit the number of layers able to be created even though having more layers may cost more to have fabricated Creating the PCBs by hand would require tools to be purchased that are not already found in the lab space available to the design team The differences in time costs and ease of c
10. oooooccccccccccnncconoocccnnnncncnannnnnnnncnnnnnnnns 15 Figure 3 CC1101 pin designation sciciiinsininicariiclijiicide 17 Figure 4 CC2520 pin designation EE 18 Figure 5 CC430F5137 pin designation cccccccececeeeeeeeeeeeeeeeeeeeeeeeeeeeneeeeeeees 19 Figure 6 CC 1110 866 915 MHz application crcunt renee 22 Figure 7 Saft LS14500 Dimensions ccccococcccccccccnnccccnnnnnannnnccnnnnncnnnnnnnn cnn ccnnnnnnns 27 Figure 8 Enpirion EP5368QI Typical Application Cireun 28 Figure 9 On Semiconductor NCP 1530 Typical Application Circuit 29 Figure 10 Battery Life Sense with Op Amp 30 Figure 11 TPS3808 Typical Application Circuit ssssseeeeneeeeseesenrrnrnrneserreee 31 Figure 12 Enpirion EP5368QI Typical Application Cireun 37 Figure 13 On Semiconductor NCP1530 Typical Application Circuit 38 Figure 14 Battery Life Sense with Op Amp EEN 39 Figure 15 TPS3808 Reset Delay CirCuit coccocccccnonncccccoccconccnnnnnnccnnnnnnnnnnns 39 Figure 16 A prototype of the PD 47 Figure 17 CC430 pin description seiccicitctrccecctticteiglbinteastentaiettinieieilicteettietaes 54 Figure 18 Overall block diagram for the TU 57 Figure 19 Block diagram for the Sensor cccccceeeeeeeeeeeeeeeeeeeeeeeeeeeeenneeeeeeeees 59 Figure 20 Transimpedance Amplfter AA 60 Figure 21 Digital to Analog Converter 61 PiQuIe 22 RE EE 62 Figure 23
11. 0 00 0 00 O 1 57 1 57 4 71 o o O OS 2 50 2 50 7 50 E a am Sa o o O 0 26 0 26 0 78 e SI al ez RS 856 al 000 E o 2 60 0 00 0 00 WEE 0 90 0 90 2 70 10 75 10 75 32 25 St 0 43 0 43 1 29 i 0 28 0 28 0 84 1 56 1 56 4 68 o n O O 2 70 2 70 8 10 PCB fabrication Sunstone 12 83 12 83 38 50 Rechargeable Battery Pack 11 95 11 95 23 90 TSU Total 67 12 37 87 137 52 RDU Price Actual Price x2 kee ail 6 14 0 00 0 00 BEE 5 09 5 09 10 18 11 43 0 00 0 00 EAS 126 pel Ss E o 1 57 1 57 3 14 O 3 13 3 13 6 26 o oo O O 2 49 2 49 4 98 E 1 33 1 33 2 66 E o 1 33 1 33 2 66 E Z tC 2 33 2 33 4 66 E 2 44 2 44 4 88 E 3 00 3 00 6 00 o o O OS 2 50 2 50 5 00 P 0 28 0 28 0 56 1 56 1 56 3 12 a 0 43 0 43 0 86 Project Box 2 56 2 56 5 12 PCB fabrication Sunstone 21 50 21 50 43 00 External power brick TOL 08269 6 00 6 00 12 00 RDU Total 76 37 58 80 117 60 Test Tools Wireless Packet Sniffer AEC15266U 49 00 49 00 49 00 Test Tools Total 49 00 49 00 49 00 Total 192 49 145 67 304 12 Table 7 Budget 3 In the four weeks before the documentation is due the writing should begin This assures that each part of the research and design is thoroughly documented Every aspect of the research and design should be written about including alternative parts and schematic designs that are available in case the primary circuit does not wor
12. 2 67 x 1 91 x 0 70 The tallest parts on the PCB are the LED array and seven segment display which are both 8 4mm approximately 0 331 tall For this unit the display and the LED should be flush with the face of the case Since they have such a variety two cases are considered If the dimensions change then there is an alternative The first is the LP 21P and the second is the DC 34P Both cases have mounting holes to allow screw to be passed through the PCB or the battery holder Each unit has a cover that can be removable or permanently attached by using a glue epoxy or Loctite This allows the units to be completed and tested with the components still accessible but keeps the user from upsetting the internal circuitry The LP 21P has dimensions of 3 29 x 2 49 This is slightly larger than what is necessary but accounts for variations in wall thickness that will make the internal dimensions smaller Figure 40 shows the dimensions of the box and how the external components will show on the face of the RDU as well as the internal structure of this case 76 r 3 29 inches OSpO O Pulse E 0 A o Signal RDU AC Battery Connected seydul BY A 8 Figure 40 LP 21P Diagram The DC 34P has dimensions 4 61 x 3 1 This part again assumes wall thicknesses and accounts for smaller internal dimensions This part has similar wall thickness and the final choice will d
13. 26 MHz because that is what the MAX6957 and the CC430 supports The chip select is active low when data is transmitting to the LED display driver The chip select must be active low for 9 5 ns before the clock goes high The clock width high and clock width low must be at least 19 ns apart and the minimum clock period is 38 4 ns The data in setup time is 9 5 ns and the data out of the MAX6957 has a maximum propagation delay of 21 ns This means that the data out provides a copy of the bits that were inputted 15 5 clock cycles earlier The data out is an optional pin that does not need to be connected if the MCU does not have the needed GPIOs 66 The display driver has 28 pins to control the segments of the LED screen and the LED array Since the display only requires 24 pins to run one of the status indicators a LED array uses those last four pins to control its display For more information about the status indicators see section 3 3 3 3 3 2 Power The RDU is configured to be as identical as possible to the TSU This is done to minimize the number of designs and reduce the required number of different parts to purchase The RDU s power system requirements are a primary constant power source an AC DC Converting Supply and a secondary backup battery power source The backup battery source does not need to be rechargeable so only COTS standard alkaline batteries is considered The backup battery is capable of powering the unit for more th
14. 33 L P3 s UCAORXD UCAOSOMI 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 LG UU HU HU HU UH MH S Y EFEEEEEEEELEEEGER FFESSSEESSS3BQ92 IRTL 2038022528 EEEIZESS SE ZESSOSS S259 a5 5533 Es i N ral SEEKEKEEKEEFER sg 82385 ES S88833 N E 33232 SEEEE ge Ae E Figure 1 MSP430F233 pin designation Reprinted with permission from Texas Instruments Section 8 page II Pros Samples Available 48 I O Pins 12 bit ADC Free IDE for MSP430 chips 51 Instructions Wake from standby in less than one microsecond Low power Five low power modes Two 16 bit timers 4 UCSI ports with support for 1 C synchronous SPI UART and IrDA Serial onboard programming Freely available sample code and user manuals Cons e The size is large for the TSU e No internal DAC 12 bits for control of the LEDs MSP430F2616 The Texas Instruments MSP430F2616 had many of the same features as the MSP430F233 and was included to show an example of the large variety of MSP430 s that were available This chip had 92kB of Flash 4kB of RAM and operated at 16MHz The MSP430F2616 could be upgraded if more RAM or 14 Flash was needed The MSP430F2616 had end equipment optimized for RF ZigBee applications This chip came in two sizes 12mm x 12mm and 14mm x 14mm with 48 and 64 I O pins respectively The pin designation diagram shown in Figure 2 was an example of the 14mm x 14mm chip with 64 I O pins The MSP430F233 also used 365uA
15. DigiKey shows five through hole buzzers carried in stock The first two are manufactured by TDK and come from the same family One has part number PS1240P02BT and the other is PS1240P02CT3 Both parts are circular with a 12mm diameter a voltage range of 3V to 30V peak to peak and a frequency of 4kHz The first has a height of 6 5mm with a 70dB sound pressure and the second has a 60dB sound pressure level and is 3 5mm tall The next three buzzers are from PUI Audio Each has a voltage rating of 3V and all are circular but each has a different size frequency and current rating The first has part number AT 2235 TT R This buzzer has a frequency of 3 5kHz a current rating of 3mA and a sound pressure of 75dB It has a 22mm diameter and is 8 2mm in height The second part is AT 2440 TWT R It has a frequency of 4kHz a current rating of 1mA and a sound pressure of 80dB This part has 24mm diameter and a height of 7 5mm Both of these parts have a voltage range of 1V to 30V peak to peak The final part is Al 3035 TWT 3V R The component has a frequency of 3 5kHz and a current rating of 9mA It has a sound pressure of 100dB a diameter of 30mm and is 20mm tall Its voltage range is from 2V to 5V All the listed panel mount buzzers on DigiKey require more than 3V of power Since the RDU cannot accommodate this the panel mount buzzers cannot be used Additionally space on the front of the RDU may be limited due to the display and LED indicators To keep t
16. Package Single Pole Dual Throw Serial Peripheral Interface Percent Blood Oxygen Saturation Texas Instruments Transimpedance Amplifier Transmitting and Receiving Software Transmitting Sensor Unit Universal Asynchronous Receiver Transmitter USART Universal Synchronous Asynchronous USCI Receiver Transmitter Universal Serial Communications Interface vi Section 1 Introduction 1 1 Executive Summary This project aimed to design a wireless remote monitored pulse oximeter There was one unit to measure and calculate heart rate and the oxygenation of the blood and a second to display these numbers The second unit contained visible and audible indicators to alert of dangerous conditions The design was unobtrusive comfortable for long term wear lightweight and portable The ultimate goals of this project were safety and security There were many people who benefit from the ability to have a constant wear pulse oximeter that does not interfere with their daily activities Similar products were expensive and offer less options This pulse oximeter was affordable include extra safety measures and offer many monitoring options These set the design apart from commercially available products The versatility of this design meant that it can be employed to help many different people in all types of situations The sensor unit consisted of a finger clip and a wrist unit The finger clip housed the LEDs and photodiode necessary for obtaini
17. The RDU will also be constantly checking the variables for drop in pulse blood oxygen saturation level low battery life of the TSU and time between receiving transmissions Upon detecting one of the conditions the RDU will sound an alarm that corresponds to the condition that was detected The TSU s main function will check the values of the input ports comparing the current value of blood oxygen saturation level battery life and pulse to the variable stored in memory When the current value and the variable are different an update will be made The main function will also send a packet periodically that contains pulse blood oxygen saturation level and battery life This packet will be sent to the transmitter transceiver through a serial data stream 52 Comparison The main difference between the first two possibilities is the first one uses interrupts extensively whereas the second does not There are many benefits to using interrupts One benefit is the MCU doesn t have to waste clock cycles and power checking the status register for new data The MCU can be put into sleep mode to wake on interrupt Of course this decision will be largely based on the type of MCU The difference between the last two possibilities is the third possibility uses interrupts and the second does not As previously stated there are many benefits to using interrupts The difference between the first two and the last two possibilities is all the send and receive
18. The full transmission test was performed at a distance of 35ft in a room with a wireless router multiple mobile phones Bluetooth enabled devices and worked as designed 5 3 4 Medical Comparison The medical comparison is a crucial part of this project The values obtained from the pulse oximetry equations must be compared to the values on a hospital grade product Each group member has a contact within a hospital that could potentially get the group access to such a device The equations are programmed into the MCU but the readings on the display must match those obtained from a higher grade and previously tested machine This can be tested in two different manners Before starting this test the TSU must be working properly up to the sensor Section 5 1 delineates tests to be performed on this unit Additionally the transmission tests from section 5 3 3 must be performed This assures the MCU in the TSU receives the proper information from the sensor send this information to the RDU which then shows the proper numbers on the display The sensor must be tested before the comparison to assure that the LEDs are luminous enough for the photodiode to obtain a reading This can be tested by shining the LEDs through a finger and measuring the current output of the photodiode If this value is high enough to indicate that it is receiving information the tests may proceed If not the LEDs need to be exchanged for others of higher brightness measure
19. These advantages do not hold up when the range of the devices was only about 1m Wi Fi Wi Fi operated in the 2 4GHz or 5GHz radio bands Wi Fi was a networking solution to connect multiple computers It operated according to specifications given by the Wi Fi alliance These specifications provided for well established connections that compensate for congestion in the network as well as error correction Wi Fi also had support for adhoc networks that were point to point between computers For simple point to point transmission of data for a wireless pulse oximeter these protocols were unnecessary All that was needed for the transmission of data between the TSU and RDU were simple unsecure broadcast signals Pros e Availability of parts e RF bands e Reliable error correction Cons Required external components to establish a connection Common RF bands interference More functionality than required Expensive overhead costs Radio Frequency Radio frequencies were a subset of the entire electromagnetic spectrum consisting of frequencies from 300Hz to 300GHz The common radio frequencies used in industrial scientific and medical ISM applications were 915MHz 2 45GHZ and 5GHz These bands could be used without special licensing or ownership granted by the Federal Communication Commission FCC For use in a wireless pulse oximeter the 900MHz band was sufficient Most modern wireless networking signals operate on the 2 45GHz and 5GH
20. Un 103 Table 6 Safe to turn on Drocecdure AAR 110 Table Cie Te EE 3 A D AC ADC AFC AGC BPM COTS CPU CRC DAC DC DFN DMA FPGA GND GPIO Hb HbO 1 0 12C IDE IR IrDA JTAG LC LED LQFN LQFP MCU List of Abbreviations and Acronyms Analog to Digital Alternating Current Analog to Digital Converter Automatic Frequency Compensation Automatic Gain Control Beats Per Minute Commercial Off The Shelf Central Processing Unit Cyclic Redundancy Check Digital to Analog Converter Direct Current Dual Flatpack No lead Direct Memory Access Field Programmable Gate Array Ground General Purpose Input Output Hemoglobin Oxygenated Hemoglobin Input or Output Inter Integrated Circuit Integrated Development Environment Infrared Infrared Data Association Joint Test Action Group Inductor Capacitor Light Emitting Diode Low profile Quad Flatpack No lead Low profile Quad Flat Package Micro Controller Unit MSOP Mini Small Outline Package NiCd NiMH O2 OLED PCB PSB PFM PWM QFN RAM RDU RF RISC SOC SON SOP SPDT SPI SpO TI TIA TRS TSU UART Nickel Cadmium Nickel Metal Hydride Oxygen Organic Light Emitting Diode Printed Circuit Board Power Supply and Batteries Pulse Frequency Modulation Pulse Width Modulator Quad Flatpack No lead Random Access Memory Receiving Display Unit Radio Frequency Reduced Instruction Set Computer System on Chip Small Outline No Lead Small Outline
21. assesses the ability to transmit data in a typical environment for this project The equipment is brought into a house with a wireless router several mobile phones wireless home phone microwave Bluetooth enabled computers and at least 3 rooms that can be traveled between Turn on the TSU then travel to a distance of 10 ft away from the unit with the packet sniffer Upon receiving a correct signal progress another 10 ft up to a maximum of 150 ft away traveling throughout the house and into different rooms When the signal grows weak and the packet degrades the maximum transmission distance in a typical environment has been found RDU Transmission Tests To adequately test the RDU an external programmable packet sender is needed The TSU cannot be used to prove that the error could not possibly be on the TSU transmission side of things For more information on the TSU and RDU software see section 3 6 For more information on the RDU see section 3 3 For more information on the RF used see section 3 4 Unit Test 1 The packet sender is programmed with the correct stub packet The packet sender transmits the packet to the RDU The RDU takes that packet and update its internal variables This should cause the RDU to show the stub information on the display Upon detecting there is a problem with the RDU packet receiving ability rerun the software unit tests for the RDU If the problem persists there may be something wrong with the radio core i
22. avoid using the alarm to test this functionality the software can be configured to flash a debugging LED upon entering the interrupt function this verifies that the interrupt is indeed being triggered Result The battery status indicators were tested to determine whether or not the software works correctly To do this a variable power supply was used To determine the accuracy of the TSU s monitoring circuit the output voltage of the power supply was slowly lowered and the output of the op amp was determined by the ADC and observed in the debug session In order to make the calculations easier the resistor divider was simplified Instead of using an 86 6kOhm resistor and a 100kOhm resistor two 100kKOhm resistors were used These values would divide the voltage source by two The input range of the ADC is 0 2 5V allowing us to accurately measure a voltage source up to 5V a value much higher than the battery s highest possible value The values read in during the debug corresponded with the calculated values The RDU backup battery monitoring circuit was tested using a similar method The user only knows whether or not the battery needs to be replaced soon through the alarm generated by the buzzer whereas the TSU s battery monitoring circuit displays battery life on a 4 LED array on the RDU Both circuits and software worked according to design 5 3 2 TSU Unit Test 1 The software is responsible for all calculations of the pulse and Sp
23. batteries would need to be configured in series to give a voltage of 3V The typical capacity of a single C cell battery was 8000mAh two in series would give 16000mAh A four pack of C cell batteries was available from Kmart com for 35 5 If the RDU were to be rechargeable it could feasibly be used to run the entire system for one complete eight hour use To fit these requirements a battery would need a working voltage at about 3 3V or higher 1200mAh or higher and would not be required to be small like the TSU battery Battery model numbers were usually the chemistry type followed by a 5 digit number The first two digits were the diameter and the second two were the length i e LiFePO4 18650 Lithium Iron Phosphate chemistry was 18mm in diameter and 65mm in length As a reference C cell batteries were about 26mm in diameter and 50mm in length If two C cell batteries were used that would require double those dimensions in volume which is a drastic increase LiFePO4 Lithium Iron Phosphate chemistry batteries offer large capacity high life cycle and smaller size Their weight compared to the energy density and life cycle was lower than other chemistry types The tradeoff for LiFePO4 batteries was that the cells have lower voltages A LiFePO4 18650 with the specifications of 3 2V 1200mAh and an 18A max discharge current was available from batteryspace com for 5 Another LiFePO4 18650 was available at 1500mAH with a 4 5A discharge rate for
24. being performed the current out of the battery should be monitored If the current is found to be abnormally large the board should be checked to make sure all of the connections are correct If the current drain of the circuit is simply more than what was estimated the battery tests should be repeated at the circuits accurate discharge rate Result The power system was tested differently than planned The battery was connected to a fully populated board The TSU worked according to design and the MCU was programmed A full 8 hour test has not been performed on a fully populated TSU though the TSU has been powered by the battery for at least 30 hours The TSU power system is fully operational 5 2 Receiving Display Unit 5 2 1 AC Supply This section goes over the required steps to fully test the AC DC adapter If at any point the AC DC adapter fails to perform as it should the circuit should be fully scrutinized and the testing should begin anew when the problem has been rectified The first test of the adapter is to test the outputs of the device to make sure they are within the specified range of the device The second test would be to temporarily connect the adapter to an unpopulated PCB and recheck that there are not any shorts throughout the board The third test is to connect the adapter to the DC DC Converter and connect the simulated load at the 3 3V output The fourth test is to connect the automatic backup circuit into the test
25. both on at the same time the photodiode will not work accurately Therefore testing this functionality is very crucial This functionality can be tested by looking at the LEDs and see if they are pulsing between the two LEDs To test if the interrupt is being generated the software flashes the debugging LED when the interrupt function is being accessed Unit Test 5 The TSU using an automatic gain control loop is responsible for powering the LEDs The LEDs are sensitive to large voltages so an automatic gain control loop can be used to make sure that enough power is given to drive the LEDs but not too much to blow them The automatic gain control loop must be tested to insure that the 12 bit DAC is working correctly and that not too much voltage is being generated The LED and photodiodes can be replaced with a large tunable resistor to generate a small current to be amplified and converted back to digital The value of the voltage can be measured with a multimeter and the voltage coming from the DAC should get larger or smaller depending on the current setting of the resistor Unit Test 6 The monitoring of the battery life also needs to be checked for validity The TSU is responsible for monitoring the information in the case that a low power state occurs the users are alerted to this fact This functionality is contained in the interrupt function that updates the battery life of the TSU This functionality can be tested by configuring the sof
26. both show through rectangular holes cut into the face Each LED has a separate circular cut out They also have panel mount LED holders to keep them in place Small circular holes are cut out of the housing over the speaker too This will allow more sound to escape the unit instead of being muffled or distorted Additional cutouts are made for the AC plug the switch and the batteries The AC plug has a small round hole large enough to fit the AC plug without having any open space to the inside of the unit The switch has a small rectangular slot that will allow at least the actuator of the switch to be outside the unit and be long enough to move it between positions The batteries have a larger cutout The battery holder is mounted inside the unit and a cover is created to allow the batteries to be changed without allowing access to the PCBs or other circuitry Polycase has a large selection of differently sized cases that could be utilized for this design Since the PCB and batteries determine the inside dimensions of the unit the selection is narrowed down substantially The PCB measures 2 0 x 1 50 and the battery holder for three AA batteries is approximately 2 50 x 2 50 This means the case is required to be at least 3 wide and 2 long or 4 wide by 2 long based on the orientation of the board and battery holder The battery holder being used is from Battery Space Its model number is BB3AA The dimensions of this part are
27. breadboard and connecting probes to the battery the positive input and the output of the Op Amp The voltages from these probes are recorded while the battery is discharged The circuit is drained at the battery not at the Op Amp A discharge should be attempted at this stage to establish the time to change the battery from the op amps reported voltage Test IV DC DC Converter To test the battery with the DC DC converter the battery is connected to the DC DC converter and the battery is drained at the DC DC output while the voltages at the battery and the DC DC output are monitored Discharging should be attempted at this stage to make sure the converter is working properly at different battery voltages The battery is not directly connected to the DC DC converter in the final system Test V RDU sub Battery System The fifth battery test to perform is to connect the battery to a partially populated board The board should have been tested for shorts before this point but should now be tested again This board should be populated with the switch DC DC converter and the test battery monitoring circuit The battery is connected temporarily to the first pin of the switch and the second pin of the switch is connected to the DC DC converter The battery is also connected through the test battery monitoring circuit The On Off slide switch is tested to make sure that the circuit turns off Discharging should be attempted at this stage and voltage s
28. checking the conditions correctly The second is that the correct sound is being made for each of the conditions Unit Test 3 The testing of the parsing of the packet received by the RDU is necessary for guaranteeing correct results The packet consists of the pulse of the user SpO2 of the user and the battery life of the TSU This function needs to be correct to receive correct values to update the variables The variables are then used for the display and the alarm If any of these values is inaccurate due to a bug in this function the results could yield a life or death situation This packet can be constructed manually to check for validity from a set of predetermined values Unit Test 4 The monitoring of the backup battery life also needs to be check for validity If the RDU is being run on the battery power for an extended period the backup battery will fail and the RDU will turn off When this happens the user will have to plug the RDU back into the wall or get new batteries The RDU has an alarm that should be triggered by low battery life of the RDU backup battery in addition to the low battery trigger to the low battery life of the TSU This functionality is contained in the interrupt function that updates the battery life of the RDU This functionality can be tested by removing the backup battery from the RDU since 124 the alarm for low power should be triggered For more information about testing the alarm see unit test 3 To
29. for the same reasons as the JN5148 What it lacks in built in feature it makes up for in number of I O pins In addition the sub 1GHz transceiver was the preferred frequency for this design The CC430 integrated a full sub 1GHz transceiver in one chip smaller than a standard MSP430 This chip was a very useful and new part to the market place which might make obtaining the chip difficult If it was unobtainable a MSP430 and CC1101 would be used to take its place Since the Texas Instruments parts were similar the design can be changed later if needed without significant change to the software The PCB layout would of course change drastically if the CC430 was unavailable and a separate MCU and Transceiver need to be used Texas Instruments offered a single chip MSP430 pulse oximetry design This design cannot be reproduced exactly for this project due to our need for wireless transmission and that an LCD would not be used However Texas Instruments design was a good reference for alternate methods and parts In their design the specific chip used was the MSP430FG437 Although the MSP430FG437 was a larger part it was very useful because of all the built in features ADC DACs operational amplifiers analog comparator etc Having these integrated reduced the number of external parts needed in the design This saves on board space of the PCB which more than compensated for the increased size of the chip The lower number of external parts also
30. goes back to sleep knowing that their parent is being monitored and will awaken them if a dangerous condition occurs Result The system level test has been modified according to each of the changes in the design and other tests The system was tested at a distance of 35ft in a building with multiple wireless routers operating on the same frequency and multiple cell phones The system correctly measured calculated and transmitted heart rate 134 Section 6 User Manual Figure 79 Wireless Heart Rate Monitor The TSU should be turned on before the RDU TSU Transmitting Sensor Unit 1 Place TSU on wrist with the velcro band around the wrist 2 Place finger clip on index or middle finger this provides the most accurate reading 3 Turn on TSU power switch 4 The TSU will connect to the RDU and will begin displaying heart rate in beats per minute and battery life 5 The TSU will operate continuously for a minimum of 8 hours Figure 80 TSU 135 RDU Receiving Display Unit Plug in RDU Turn on power switch Press Set button once HIT will be displayed The high value starts at 90 bpm and can be changed by the up and down arrows by 5 bpm increments When the desired high value is shown on the display press the select button to enter the value LO will be displayed The low value starts at 50 bpm and can be changed using the up and down arrows by 5 bpm increments 9 When th
31. initial capacity after 5 5 years A Li lon 18500 battery pack would retain 80 of initial capacity after 300 cycles At 1400mAh there would also only be one use of the RDU plus some reserve This would give enough battery life for more than 300 uses of the TSU If the TSU were used once daily then the battery would have lost 20 of its initial capacity after less than one year If this same use pattern was applied with the non rechargeable C cell batteries two batteries would have 16000mAh and would provide for 13 full uses of the RDU without an AC supply In one year of use the C cell batteries would need to be replaced 28 times at a cost of 70 However if the RDU is only run from AC power except for movement between rooms and occasional power outage then the batteries could conceivably only need to be replaced once a year at a cost of 2 50 Having a rechargeable battery would 36 mean less space required for the battery If the RDU were still primarily run only off the AC supply then the battery would almost never need to be replaced but at a much greater cost to produce Automatic Backup Switch The Intersil ICL7673 is an automatic battery back up switch It does this by automatically connecting the output to the greater of either of the inputs voltages If the primary voltage gets disconnected the ICL7673 switches to the secondary voltage until the primary voltage is reconnected Complete switching of the inputs and open drain out
32. into the SpO equation in place of H Solving for SpO yields the percent oxygen saturation of blood 3 2 1 Sensor The TSU uses two flashing LEDs that operate at 660nm and 940nm in conjunction with a photodiode to determine the SpO and pulse rate Figure 19 shows the block diagram of the sensor and how it interfaces with the MCU The following is a full explanation of what each part does and how they all work Current ADC In Photodiode gell OED SP 23 TR LT6004 IR LED APT1608F3C SML LXFTO603SRC TR Control Circuit DC DC Buck converter EP5368QI Max 1 5 Y Figure 19 Block diagram for the Sensor 59 Transimpedance Amplifier Low Pass Filter A passive low pass filter is used in the TSU to separate the DC component from the output of the transimpedance amplifier A 10kQ resistor and a 3 3uF capacitor to make a filter with a 3dB level at 0 5Hz The 3dB level of 0 5Hz was chosen since the AC component represents the beating of a human heart The heart normally beats at rates between 1Hz and 2 5Hz The AC component of any signal above 0 5Hz is very small DAC 4 FS 33V ElOA alk SR SRI 20k il GHD 3 2 2 Power The TSU s power system requirements are a rechargeable battery that is capable of powering the unit for more than one use between charges The battery is monitored by the system so that the user can be notified when the battery is in need
33. it the alginate will set in a manner that will allow the sensor components to be easily applied and for the sensor to perfectly fit the user 2 5 2 Transmitting Unit The TSU will be housed in a case that will be worn around the wrist of the user Two essential parts are necessary to do this a housing large enough for the main PCB of the TSU and a strap to hold this housing to the wrist of the person PCB Housing Many different materials can be used to house the PCB of the TSU Plastic metal and wood are among the easiest to find in different sizes and are easy to work with The housing must be large enough to hold the battery that powers the TSU It is possible to have a smaller housing that can only hold the PCB but that would mean the battery would be held somewhere other than in the case In order to connect to the LEDs and the photodiode a hole must be made in the 45 side of the case This hole will serve as the place holder for the connector used to connect the TSU main PCB with the power ground and data lines leading to the LEDs and the TIA Wood Enclosure Wood is an inexpensive material and is very easy to use to create a custom sized housing for the TSU A case of any size can be made to house both the main TSU PCB and the battery Wood is a very good insulator and would not create conditions for a short to occur in the PCB If a short were caused the wood could create extreme hazards as it is not fire safe and would ca
34. other intellectual property of the third party or a license from TI under the patents or other intellectual property of TI Reproduction of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties conditions limitations and notices Reproduction of this information with alteration is an unfair and deceptive business practice Tl is not responsible or liable for such altered documentation Information of third parties may be subject to additional restrictions Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice TI is not responsible or liable for any such statements TI products are not authorized for use in safety critical applications such as life support where a failure of the TI product would reasonably be expected to cause severe personal injury or death unless officers of the parties have executed an agreement specifically governing such use Buyers represent that they have all necessary expertise in the safety and regulatory ramifications of their applications and acknowledge and agree that they are solely responsible for all legal regulatory and safety related requirements concerning their products and any use of Tl products in such saf
35. power the LEDs as the output of the feedback loop Careful consideration must be given to the maximum output of the AGC to not damage the LEDs A maximum output must be determined so that the absolute maximum ratings of the LEDs are not exceeded The value of the feedback resistor in the transimpedance amplifier should be determined so as to correctly compensate for the attenuation of light as it passes through the body The AGC output is used only to provide a stable output and is not for amplification The following equations describe the change in the intensity of light as it passes through an artery of length 58 At wavelength A 7 7 1Q Crane At wavelength 1 L 1 10 eon eee Where e Co is the concentration of oxyhemoglobin HbO gt e Cr is the concentration of reduced hemoglobin Hb e on is the absorption coefficient of HDO at wavelength n e dm is the absorption coefficient of Hb at wavelength An log 9 11 1im1 log 0 12 1in2 If the two equations are combined so that R and the percentage of oxygenated hemoglobin HbOz is ar2R ari pope es S Co Cr 2 2 202 R la 1 01 If it is then assumed that the only changes in the attenuation of light while measuring pulse oximetry are due to the flow of arterial blood then the following equation can be obtained if the steady state component of the attenuation of light is maintained at the same level log 1 AC y 24 os 1AC R is then substituted
36. run on a single cell Li lon battery or multiple cell Alkaline NiCd or NiMH chemistry battery The step down converter operated at 600kHz fixed frequency PWM mode normally but if the synchronization pin was tied to ground the chip will automatically switch to a variable frequency PFM mode at small output loads for power saving The NCP1530 chip was a small 8 pin 3mm x 5mm Micro8 SOP One drawback of the NCP1530 chip was that it requires the use of an inductor and a diode in the standard layout The output voltage of this chip was set by the manufacturer requiring the purchase of the correct chip for the desired output voltage Figure 9 displays the typical application of the NCP1530 28 a L1 56yH Vin 2 8 V to 5 0 V 0 Vin LX Vout 3 0V D1 MBRM120ET3 syy NCP1530 Vout 2uF T ss Vr Css GND EN ku Cn L AAA CvREF Cour d F AIN Figure 9 On Semiconductor NCP1530 Typical Application Circuit Reprinted with Permission from ON Semiconductor SCILLC Section 8 page VI TSU Digital Noise Filtering The TSU DC voltage would need to be filtered to create a RF voltage and an Analog voltage The reason it needed to be filtered was to keep the digital noise off of those power lines This could be accomplished by using a simple LC low pass filter The circuits for the RF and Analog could be identical The voltage out of the regulator should pass into an inductor and then be tied to ground
37. the project deadline These two issues will be extremely stressful for the project as a whole Caution should be taken to assure that these issues are avoided These issues are able to be anticipated and hopefully prevented There will always be other issues that arise in the course of the project Avoiding as many as possible by being thorough with checking the project will be extremely helpful 4 3 Test Conditions Before populating the PCB it must be tested to determine that there are no shorts in the power supply wires First visually confirm the connections of the PCB to determine if any wires are touching or crossed Second measure the continuity 107 between the positive and negative power sources that connect to the battery Confirm that there are no connections Third measure the continuity between the voltage output pad of the DC DC converter and ground Last confirm that there is no continuity between the power pads and ground pads of all the integrated circuits Lastly each pad should be tested for continuity assuring that no nets are attached to others anywhere on the PCB 4 4 Alternatives 109 Section 5 Test Plans 5 1 Transmitting Sensor Unit Test Safe to turn on Before applying power to the TSU it must be verified that the circuit is assembled correctly First the resistance between all voltage sources must be measured with respect to ground If the resistance is zero or close to zero then most likely ther
38. the specifications of the design found in section 3 These functions are tested in section 5 3 In general the TSU functions are used to update the battery life regulate the voltage of the sensor calculate pulse and SpOz control the sensor and send 7 data to the RDU These functions meet with the specifications of the design found in section 3 These functions are tested in section 5 3 Figure 83 Global functions and data types Conclusions This project involved the choice of proper components to meet the design requirements A successful schematic design completely documents the two required systems The PCBs for the two systems were populated and tested by the design team The wrist mounted device performs the necessary calculations from the sensor and then transmits them wirelessly to the base station Due to difficulties that arose in the development of the pulse oximeter along with time constraints the function that calculates the oxygenation of blood is no longer performed Therefore a wireless heart rate monitor was built The only data that is gathered from the TSU is the pulse Since this change was made the RDU was modified to not have any LED status indicators Heart rate and TSU battery life are displayed and the audible alerts remain Section 8 Personnel Frank Bruno is currently a senior at the University of Central Florida He plans to graduate with his Bachelor s of Science in Computer Engineering in May
39. this warranty Except where mandated by government requirements testing of all parameters of each product is not necessarily performed Tl assumes no liability for applications assistance or customer product design Customers are responsible for their products and applications using TI components To minimize the risks associated with customer products and applications customers should provide adequate design and operating safeguards TI does not warrant or represent that any license either express or implied is granted under any TI patent right copyright mask work right or other TI intellectual property right relating to any combination machine or process in which TI products or services are used Information published by TI regarding third party products or services does not constitute a license from TI to use such products or services or a warranty or endorsement thereof Use of such information may require a license from a third party under the patents or other intellectual property of the third party or a license from TI under the patents or other intellectual property of TI Reproduction of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties conditions limitations and notices Reproduction of this information with alteration is an unfair and deceptive business practice Tl is not responsible or liable for such altered documentation Infor
40. when in active mode this was compared to 0 5uA when in standby mode and 0 1uA when in off mode This chip also featured a 12 bit ADC 12 bit DAC DMA controller and a supply voltage monitor The DMA controller allowed for certain hardware subsystems within the microcontroller to access system memory for reading and writing independently from the CPU The supply voltage monitor was used to monitor the supply voltage or an external voltage It could be configured to set a flag when the voltage being monitored drops below a user selected threshold The TI MSP430F2616 was a great microcontroller for this project The only thing that was not great about it is the size At 12mm x 12 mm being the smallest available there was limited room on the PCB for other components One of the pros of ordering parts from TI was that almost all of their products have samples available This helps bring down the cost of producing this project In addition TI had their own IDE for developing software for the MSP430 chips Another nice feature about this chip the DAC could be used with the TSU for controlling the LEDs This could lower the cost of the project as a whole because an additional part would not have to be purchased The DMA controller could be used to write data to memory coming in from SPI communication such as the packet coming in from the transceiver on the RDU The voltage monitor could be used to monitor the battery life of the TSU 5 DEE 35 8 S S
41. 2 Power Considerations The RDU was designed to match the TSU The reason for matching the circuitry to the TSU was to minimize the number of different components and for general design simplicity The RDU uses the same parts and methods for voltage regulation digital noise filtering transient suppression and battery life monitoring Some of the differences were that the RDU will not be powering the operational amplifiers for the sensor but was powering an LED Display driver a three digit 7 segment LED display an array of four LEDs and other LED status indictors The most significant power change was that the RDU will be a base station and as such plugged into an AC DC adapter only using its internal battery as a backup The backup battery could be two off the shelf C batteries wired in series for a voltage of 3V This enables the user to replace these only if they become drained In order to switch from the main power supply to the backup battery a device was needed that can automatically switch from the wall power source to battery RDU Primary Power Source The RDU is a base station and has a wall powered supply An AC DC adapter power supply was used as the primary supply There were many commercially available AC DC adapters with set voltages and currents One that was set at 5V would satisfy the need to be greater than the backup source for switching purposes Another quality that would be needed in the power supply was for the AC DC conve
42. 3 o e 25 o 2 gt 15 0 5 0 O oO N st wo O st Y WO LO O O OD o CH Q 17 FP oi OO OO OO cc N oo CH OH 0 oOo st N O oO Oo st gt Q Q FPF OO 7 D os 10 10 OO 7 O O O O O O O O O O D O rF Time Figure 78 Battery Drain Test 114 Test Il Charging through PCB Since the battery is recharged inside the enclosed system it is essential the battery be able to be charged through the intended connection To test this the battery is connected to an unpopulated board An unpopulated board must be used because the battery could not be safe to connect to other components or the other components might not be safe for the battery Next the charger is connected to its panel mount plug with wire leads connected to the board A full discharge and charge should be attempted while in this stage Result This test was performed for a complete charge cycle The TSU battery is safe to charge while the system is off Theoretically the battery could be charge while the system is in use but this is not within our specifications Charging the battery while the TSU is on could also add extra noise causing problems with the calculations Test Ill Battery Monitor Circuit The battery is tested through the monitoring circuit by setting up the circuit on a breadboard and connecting probes to the battery the positive input and the output of the Op Amp and recording the battery voltages as it is drained The circuit is drained at t
43. 99 lt 9 attach pad Q a g a C e 5 2 Y a Figure 3 CCI 101 pin designation Reprinted with permission from Texas Instruments Section 8 page III The CC1101 would be great for the use of communication It was highly flexible and has great options for low power applications This chips footprint was also very small 4mm x 4 mm Since the TSU had very limited real estate the parts that were used in the PCB need to be as small as possible The CC1101 also had no need for many external components that most radio frequency transceivers require such as a frequency synthesizer external filters or RF switches Since the project was on a limited budget it was good to have parts that do not require external components to function properly The CC1101 also supported asynchronous and synchronous serial receive and transmit modes In addition the CC1101 supported automatic frequency compensation that aligns the frequency synthesizer to the correct center frequency Pros Cons Samples Available Max 1 packet error Low current consumption 2 FSK GFSK MSK OOK and ASK supported Temperature sensor Flexible support for packet oriented systems Automatic CRC handling Wake on radio functionality for automatic low power Rx polling 64 byte Rx and Tx data 4mm x 4mm package with 20 pins Complete on chip frequency synthesizer no external filters or RF switch needed Automatic Frequency Compensation AFC was used to align the freque
44. D x z Q EE a 10 LEFEGCE L s se DOF o IN N vn gt gt Ow d d a a XOXF QQ PJ 1 TDI TCLK PJ 0 TDO GUARD CC430F513x AVCC_RF AVCC_RF RF_XOUT RF_XIN O Q VSS z Exposed die attached pad TAC E SW aaa aN ei mo e ei D D 0 P3 0 PM_CBOUTO Ph P2 7 PM_MODCLK PM The speaker on the RDU needs to create a sound for each of the different conditions that are explained in section 3 4 3 In order to create a sound using a MCU a PWM signal needs to be generated This can be generated using one of Timer_A s unused register and routing the output to pin 24 Refer to Figure 17 above for pin locations pin 24 is connected to a speaker drive circuit This is connected to the speaker For more information about the software see section 3 6 3 2 Transmitting Sensor Unit The TSU uses two flashing LEDs that operate at 660nm and 940nm in conjunction with a photodiode to determine the SpO and pulse rate The TSU then sends that data to the RDU for display The TSU is powered by a battery and uses a DC DC converter to regulate the operating voltages at 3 3V Following are block diagrams Figure 18 and explanations of the different elements of the diagrams and their corresponding parts Figure 18 Overall block diagram for the TSU A photo diode is used to measure the amount of light passing through the patient s finger Photodiodes operate by creating a small current proportional to t
45. ERS SESAKSFEx aEGR SHY MNAR OR ZAzZLLLPLERPPRELRLLLKE LILILILS SLL LLL LI LILI 80 7 70 67 64 DVeo J 1 so P7 6 P6 yA3 f 2 so P7 5 P6 4 44 3 se P74 P6 5 A5 4 57 J P7 3 pe s a6 5 se P7 2 P6 7 A7 SVSIN 6 55 Dez Veer TI 54 P7 0 xin fJ e 53 Dis xouT Da 52 D D Vener 10 80 pin 51 D Ps 7 TBOUTH SVSOUT PN PACKAGE Var Nere D 11 TOP VIEW 50 PS 6 ACLK P1 Q TACLK CAOUT 12 49 PS S SMCLK P1 1 TAO 13 48 PS 4 MCLK P12ITA1 14 47 P5 VUCB1CLK UCA1STE P1 3 TA2 15 46 _ P5 2UCB1SOMIUCB1SCL P1 4 SMCLK 16 45 D P5 1 UCB1SIMO UCB1SDA P1 5 TAO 17 44 D P5 Q UCBISTE UCAICLK P1 6TA1 18 43 P4 7 T8CcLK P1 7 TA2 19 42 P4 6 186 P2 0 ACLKICA2 20 41 p4 5 185 21 22 23 26 27 28 29 30 31 3233 Y 38 39 40 LH HHH EU UU GA WH H UU UU x 21 222 3330223238088 SSEESSSSRBEsRaBS ERE AEREA IEEE e E EEN ES 220099 El Va Ms Io EAS oa 23 2323 23 IZNNNORPO AAA EO ag 2298 lt 2852S9kEFE fa 2 68862225 ai x 559555455 a 32932222 S EJ IBAR Gef Figure 2 MSP430F2616 pin designation Reprinted with permission from Texas Instruments Section 8 page III 15 0 O n Samples Available 48 or 64 I O Pins 12 bit ADC 12 bit DAC Free IDE for MSP430 chips 51 Instructions Wake from standby in less than one microsecond Low power Five low power modes Two 16 bit timers 4 UCSI ports with support for 1 C sy
46. G E Ewen 738 Table 3 Sensor Quantity Designator Part Number Value Manufacturer Es 1 ITA u a I 1 02 2 1 Bt DEE a 1 56 3 1 DAC HE I E co 4 2 F1 F2 SS a 0 141 5 1 J 0 44 6 1 J2 0 731 7 1 J3 w 0 754 8 1 LED eeen I ee oo 9 1 LS1 PO Hi 0 90 10 1 P4 Des 0 11 1 Sw pes E oh 1 375 12 1 Ut i 1 44 13 1 U2 EES SE 1 57 14 1 U3 I E 55 15 1 Y1 SEH I 1 30 16 1 C19 0 095 18 1 C11 Po it a 0 275 19 1 C1 SCH E el 0 145 20 5 R3 R5 R7 R8 R10 El A ll 0 071 21 2 C12 C13 pm LH as 0 037 22 C2 C3 B ss W Le 0 275 23 7 C8 C9 C10 C14 C16 O Kee 0 369 C18 C20 24 1 R11 a ES 0 073 25 1 R9 A En PS 0 073 26 2 R2 R6 O e 2 0 071 27 1 R1 a ES BEER 0 073 28 6 ae C6 G7 C15 Po E 0 033 Table 4 Transmitting Sensor Unit 102 Quantity Designator Part Number Value Manufacturer Cost 10s 1 1 Al pea I PA 1 02 1 Bi Ee at 1 56 8 C1 C6 ee 9 WO 0 369 C10 C11 C12 C13 C14 C18 1 C2 E Oo 0 145 2 C3 C4 EE t i 0 275 4 C5 C7 C8 WE A 0 033 7 2 ots cio M Hl Des 0 037 8
47. Oz2 so the calculations have to be accurate Testing of the calculations is critical for medical applications since inaccurate values in a life or death situation can get someone killed The tests consist of a series of stub inputs and outputs that are compared to the correct value Unit Test 2 In order for the software to create accurate values it needs accurate data This test assesses the validity of the inputs received from the sensor The sensor is replaced with a component that mimics the sensor This component can be tuned to an appropriate value The value set is compared to the software s received value Unit Test 3 The TSU is responsible for constructing and sending a packet that contains the data that the TSU is collecting from the sensor The packet consists of the battery life of the unit the pulse of the user and the SpO of the user This packet needs to be constructed correctly for the RDU to parse and read the correct values Thus testing of this functionality is a critical aspect of the testing phase The easiest way to test this functionality is to construct the packet then print the contents to a console to be parsed manually to check for validity 125 Unit Test 4 The TSU is also responsible for controlling the LEDs and giving them power The LEDs that need to be controlled are the red and infrared LEDs The control LEDs function is responsible for changing between red and infrared If the red and infrared LEDs are
48. Pulse O Figure 16 A prototype of the RDU 47 Companies This research is about possible companies that plastic cases can be purchased from The boxes come in all shapes and sizes The goal of this research is to price out the different cases that are available for purchase and for what dimensions the RDU needs It is also a good idea to research many possible companies for price comparison and different types of cases Other companies could also be used as alternatives if the case purchased is of poor quality and another needs to be obtained Polycase Polycase has over 1400 styles sizes and colors of plastic electronic enclosures for projects They also offer customization of the cases that are purchased and free samples are available ToolLess ToolLess has been around for over 20 years and offers fully customized plastic enclosures and housings They offer a small set of generic plastic enclosures These generic plastic enclosures are then customized to suit the needs of their customer They will drill and cut the case up to the exact specification needed by the project PacTec PacTec has been around for over 30 years They specialize in plastic boxes that house PCBs They offer free samples for new parts and have a very good search that allows for external dimensions or PCB dimensions Their website is very helpful 2 6 Manufacturing and Fabrication There are two main options when it comes to fabrication of a printed circui
49. SPI 3 digit 7 LED Display 4 segmented Driver Display LDT A512RI MAX6957 Figure 57 Block diagram for the display Status Indicators Two forms of status indicators are used on the RDU The first is a small surface mount speaker that gives audible alerts and alarms There are four different alarms The critical health problem alarm is a constant loud tone that continues until the problem is remedied or the TSU is turned off and back on The loss of signal alert is a series of short beeps that repeat every few seconds while the condition is occurring The battery low warning is a single long beep occurring once a minute when the battery has less than one half hour of power left The second form of indication is panel mount LEDs One blue LED is used to indicate that the primary power supply is connected The LED remains on as long as the primary power supply is plugged in A pair of yellow LEDs is used with corresponding labels on the case One turns on when the information on the three digit seven segment display is the pulse and the other turns on when the oxygenation level is displayed An orange LED is used to indicate the status of the signal It is constant on while the system is receiving valid data and blinks when the system has not received valid or new data A bicolor red green LED is used to display the status of the RDU s backup battery Green indicates that the battery is in good health while the red indicates that
50. T 1 0 uF 22 uF T Optional Component Figure 13 On Semiconductor NCP1530 Typical Application Circuit Reprinted with permission from ON Semiconductor SCILLC Section 8 page VI RDU Digital Noise Filtering The TSU DC voltage needs to be filtered to create an RF voltage and an analog voltage The reason it needs to be filtered is to keep the digital noise off those power lines This can be accomplished by using a simple LC low pass filter The circuits for the RF and analog can be identical The voltage out of the regulator passes into an inductor and then is tied to ground with a capacitor If the inductor is chosen to be 1uH and the capacitor 10uF then the transfer function can be estimated to be one The alternate method is to use a ferrite bead to filter the power lines RDU Transient Suppression Transient currents can cause devices and circuits to fail where they should be able to work without issues and they are hard to detect when they occur This problem could be a large hassle to debug Fortunately it is easy to account for this problem in the beginning of a design To compensate for current transients in the power lines there is a capacitor at each major power connection This capacitor is connected on one side to its power connection and the other to the ground A smaller capacitor is connected parallel to the first These capacitors have a stored charge that is released if transient currents occur to keep t
51. The housing of these components has no bearing on their functions The mechanical design is important as it must not constrict the finger and also be able to fit different finger sizes The LEDs must be mounted so they are exactly opposite the photodiode This is the most critical aspect of the sensor mechanical design If this is not achieved the readings for pulse rate and SpO could be inaccurate as the LED light will be diffused through the finger and viewed at incorrect angles Thus a 90 premade Nellcor compatible sensor finger clip is used This ensures that the lights are properly covered and receive minimal ambient light interference Using a commercially available premade sensor allows the cost of the unit to stay low while not incurring much extra cost or hassle for the user The sensor used is Nellcor compatible and is available for purchase from medical suppliers Display The display unit consists of a three digit seven segmented LED display The three digit display shows the pulse or the SpO information The pulse and the SpO data alternate every second This may be slowed down to a couple seconds based on performance and user preference The display is interfaced with the MCU utilizing the Maxim part number MAX6957 The MAX6957 is a general purpose I O expander and LED driver An SPI communication is used to update the display unit Figure 57 shows the block diagram of the inputs and outputs of the components for display
52. U and that of the TSU is monitored using a voltage divider connected to a unity gain non inverting operational amplifier The output of the operational amplifier is connected to one of the MCU s analog to digital converter inputs The reported value is compared to a table of values obtained in the testing process to indicate the battery status The power sources for the RDU and TSU are connected to a DC DC buck converter to generate the steady voltage that the systems run on The converted output is filtered by a ferrite chip to create digital noise free RF and analog lines The analog lines are used to power the analog features and components The RF line is used solely by the MCU for its transceiver Capacitors that can handle any minor fluctuation in the power lines are used for transient suppression at the major connection points Displays The display unit consists of a 3 digit 7 segmented LED display The 3 digit display alternates between displaying the pulse and the SpOz information The pulse and the SpO data switch every second The display is interfaced with the MCU using the Maxim part number MAX6957 The MAX6957 is a general purpose I O expander and LED driver An SPI communication is used to update the display unit Status Indicators Two forms of status indications are used on the RDU A small surface mount speaker is used to give different audible alarms and alerts for the following conditions Critical medical status low batt
53. U sending a poacket 94 Figure 64 Flow diagram of the RDU receiving a packet oocccccccnnnccccccccccccos 95 Figure 65 Flow diagram of the RDU updating the display ooooooo o 95 Figure 66 Flow diagram for updating variables from the sensor data 95 Figure 67 Flow diagram for the control of which LED is om 96 Figure 68 Flow diagram for the automatic gain Control 96 Figure 69 Flow diagram of checking if an alarm needs to be sound 97 Figure 70 Flow diagram of updating the battery te 97 Figure 71 Block diagram for the RDU ccccccnnncconinccccnnccconnnnconaccccnnnncnnnnnnannos 98 Figure 72 Block diagram for the TU 98 Figure 73 Sensor Schematic Diagramm 99 Figure 74 RDU TOP Layer arica 100 Figure 75 RDU Bottom RE 100 Figure 76 TSU Top Layer e 101 Figure 77 TSU Bottom Layer E 101 Figure 78 Battery Drain Test een 114 Figure 79 Milestones EE 2 Figure 80 Global functions and data types cccccccccnncococcccncncnncnnnnnnannnonnnnncnnnannnns 8 Figure 81 RDU Schematic Diagram oooooccccccccccccccccnananononcnnnnncnonnnnnnnnncnnnnnnnnnnnnnns Figure 82 TSU Schematic Dia aMicianiniaita es Eege II Table of Tables Table 1 MCU Comparison REENEN 22 Table 2 This table is a comparison of the display possibilities 34 Table E EE 102 Table 4 Transmitting Sensor Un 102 Table 5 Receiving Display
54. UM gedet aches 65 A AAA EEE AT 66 Bo EE 67 E o ee 70 A O 73 30 Mechanical Desi aid 74 A EE 74 E cats n E a nia oot ses 75 3 5 3 Receiving Display sionista ao 76 30 SO MW aaa 77 3 7 Explicit Design SUMMALY EE 87 3 7 1 Block Diagrams ee ee hee eer 97 e Ee 99 SEET uterina 99 3 7 4 DIM Ol ENEE 102 Section 4 Prototype Construction oooocccccccccccnonanaooccnnnncnonnnnnnnnnncnnnnnnnnnnnnnnnnnnnos 104 AN ASC ita 104 E 105 ES LOSRCONMCINONS NN 107 AA e EE 108 SEH Test Tt 110 5 1 Transmitting Sensor Unit Tos Linton 110 ST Battery ie EE 113 5 2 Receiving El A EE 116 el AG OUD DIY EE 116 De 2 Bale E E 118 SR TEE 120 Ne ee 121 SZO PAPAIN tai acai a et te ele aac ci ce a a ta asics 122 Ee 123 53 RR etches ite citar cates cine R ee esa ete oe eG REEE 124 NN WT EEN 125 53 3 TMansmission TOSIS eege 127 5 3 4 Medical GOMPATSON serca nnn 129 5 4 Sub System EE ee 131 ER LEVEI eege 133 Section 6 User Manual EE 135 Section 7 Administrative Content 1 E e Le EE 1 Lok Oe 1 7 3 Project Summary and Conclusions ccoo canediveeeesdancsemngeeesavedenice 5 S ction 8 Personne EE 9 Section 9 Appendix A Schematics oooccccccccccccncoooooncncnnnccnnnnnnnnnnnncnnnnnnnnnnnnananonons l Section 10 Appendix B References en III Section 11 Appendix C Permissions un IV Table of Figures Figure 1 MSP430F233 pin designation ccccccccnnncnococcccniccnonananancnncnnnncnnnnnnnns 14 Figure 2 MSP430F2616 pin designation
55. Wireless Pulse Oximeter Design Team 7 Frank Bruno Matthew Ecklund Heather Grenitz Eric Roberts May 3 2010 Sponsored by Better World Engineering LLC Orlando Florida http www betterworldengineering com Edited Revision Table of Contents Section 1 Introduction EE 1 1 1 Executive Summary ei cada 1 ere 2 1 3 Comparison to Existing Products aiii id 3 1 4 Project Specifications cccccecceceeeeeeeeeceeneeeeeeeeeeeeeeeeaaaeeeeeeeeeseeeseenneeeeeeeees 4 Section 2 EE 6 2 1 Wireless Applications ee 6 Pe Processing A Nae nace sca 12 A eege 13 222 Manso Nena 16 2 2 3 Microcontrollers with built in Transceiver 19 2 2 4 Transceiver with Built in Microcontroller 21 2 2 5 Processing Unit Comparison ssssssesseseeeseererrreeeserrrrrrnnnresserrrrrrnn n 21 2 3 Transmitting Sensor ASS O n 23 2 3 1 LEDs and Leite 24 2 3 2 Power Considerations oooooococcccnccccconononononcnnnnoncnnnnnnnnnnnncnnnnnnnnnnnnnnnnnnnos 26 2 3 3 Operational GEES c2rcctcceatettictetaiiscteaitintalaideniatattictelatdiatelstiuecat ce 30 2 4 Receiving Display Unit ee 32 A E E E E 32 2 4 2 Power E Eed TEE 35 2 4 3 Stats e e TEE 40 2 5 Mechanical Desi Mazos alli 44 2 5 1 Sensor EE 44 2 5 2 Transmitting WE E 45 2 5 3 RECEIVING Display TE 46 2 6 Manufacturing and EI oasis 48 2 7 Software Oli e bes 51 MOECHON O DESIGN ii 54 3 1 MierocontrollerTransceiver EE 54 Sie Transmitting Sensor TEE 57 EE 59 9 22 SE 61 3 3 Receiving Display
56. XOSC32M_Q2 XOSC32M_Q1 Figure 4 CC2520 pin designation Reprinted with permission from Texas Instruments Section 8 page Ill u lt O mn Very small Low power consumption Low operating voltage Good radio Automatic CRC Collision avoidance Fast data rate Small number of GPIOs and 1 SPI port 18 Cons e Needs external MCU e Uses 2 4GHz ZigBee 2 2 3 Microcontrollers with built in Transceiver CC430F5137 The Texas Instruments CC430 was a sub 1GHz wireless transceiver microcontroller module It was a true system on chip design It was a combination of two different TI parts the MSP430 and the CC1101 and contained features of both The CC430 was designed for use in ultra low power designs and contained five low power modes to extend battery life Typically this MCU was used for portable sensor units which was precisely the application of this project The chip contained up to 32kB of flash memory 4kB of RAM two timers an ADC a clock modules and 32 I O pins among other features Figure 5 displays the pin designation for the CC430F5137 RGZ PACKAGE E TOP VIEW SS 2 S Oe 9s ZS SG o Rae SZ o SZ o 238 Sos g 882 ES P SES La BE lt lt 22 zaxa KK O SS o OO 2 S 0XXwyoOZREE EFFES TEF SESILEZAE ee BE A T Lf 39 7 P22 PM_TA1CCR1A CB2 A2 P2 1 PM_TA1CCROA CB1 A1 P2 0 PM_CBOUT1 PM_TA1CLK CBO AO gt CC430F513x Exposed die attached pad PM_TAOCLK
57. able to house the LEDs and photodiode These options are shown in section 2 5 1 In the end a premade sensor is chosen for multiple reasons First the premade sensor is known to work and is properly situated to measure with little to no ambient light interference This means that the measurements are more accurate than if a sensor is made for the project Since the design 74 must be safe this accuracy is a great advantage and is necessary to live up to the specifications of the project Additionally using a premade sensor allows compatibility The sensor used in this design is Nellcor brand Ensuring compatibility makes the unit more desirable Not having to create a sensor for every unit keeps the cost down Using a premade sensor therefore keeps the unit practical 3 5 2 Transmitting unit The TSU s main PCB has dimensions of 1 x 1 5 and the battery which are housed within the TSU has a size of 17mm diameter x 67mm length The outer dimensions of the casing of the LP 21P are 3 295 x 2 470 x 1 00 and the inner dimensions are 2 655 x 1 775 measuring from the center of the screw posts The length of the battery is 1 97 The width of the battery is 0 55 and the width of the PCB is 1 5 This makes a minimum width of 2 1 to house both components and the parts are placed opposite each other in the TSU housing Both the battery and the PCB are secured inside the housing The housing is held in place on th
58. akes the unit bulky and they could be heavy Pulse oximeter products like this were used periodically such as after being on oxygen or checking to see if external oxygen was necessary Southeastern Medical Supply model number CMS 50E was one such product This product had the ability to be linked to a computer for data interpretation It contained an OLED display lithium ion rechargeable battery and alarm functions The Nonin Onyx 9560 was similar type of unit It used built in 7 segment displays to indicate pulse rate and percent oxygen saturation It also had integrated Bluetooth to transmit data wirelessly to a medical specialist This unit costs over 450 which was much too expensive This project aimed to design and create a more practical less expensive product The closest product to the aim of this project was the Nonin Avant 4000 It utilized a finger clip sensor a wrist watch display and a remote monitoring display The unit used Bluetooth technology to transmit data from the sensor to the base This product only had a receiving distance of ten meters but included alarms and boasts an eighteen hour battery life in the sensor and wrist watch unit However this unit cost was nearly 2 000 This product had many of the same design aspects that are aimed for in this project This project aimed to exceed the receiving radius of the base and cut down the cost by a substantial amount The unit did not have all the features the Avant 4000 contai
59. an be powered by the Li lon battery pack The output voltage is set with the 3 pin VID selector so the output voltage is 3 3V by connecting all three of the voltage select lines to ground The EP5368QI requires only two external capacitors for operation but four is used The 4 7uF 0603 capacitor is required at the VIN by the system Two 10uF 0805 capacitors are used at the VOUT pins to improve ripple performance A single 0 01uF 0603 capacitor is connected in parallel to the 10uF capacitors at the output to improve transient suppression The cost for this component is less than 2 Figure 25 shows how the EP5368QI is configured in the TSU BATT is the power from the battery and 3 3V is the output power for the system to use Figure 25 Configuration of EP5368QI Power Line Filtering The Analog and RF power lines for the CC430 is filtered to keep the digital noise off them This is accomplished with 1kQ 250mA 0402 ferrite chip as shown in Figure 26 The ferrite chip prevents any high frequency electrical noise from entering those sensitive lines 33V 3 3V_ RE 3 3V 3 3V ANA Figure 26 Configuration of Digital Noise Filtering 64 Transient Suppression A pair of capacitors is placed at each major power connection to account for transients in the lines To do this a 10uF capacitor is connected between the power connection and ground A 0 01uF 10000pF capacitor is also be connected in parallel to the first These give a path to
60. an one use before being depleted This gives the user at least that one use if the primary power goes out and the user is already asleep The battery is monitored by the system so that the user can be notified when the battery has been depleted and needs to be replaced The major difference for the RDU is that it uses a battery only as a backup source if its AC DC adapter is disconnected In order to have the circuit switch to the backup source the Intersil ICL7673 automatic battery back up switch is used There is an on off switch so the unit can be turned off when it is not in use The voltage that is passed from the automatic power switching circuit is regulated by a DC DC converter to convert the larger voltage AC DC converting supply or smaller voltage battery to the exact 3 3V that is required by the system Lastly the 3 3V that is supplied for the system is split and put through a filter to keep the digital noise off of the RF and Analog power lines The block diagram for the RDU Power subsystem is shown below in figure 30 The method used for transient suppression is not shown in the block diagram RDU Power Source The device is powered by an AC DC adapter as the primary source and three 1 5V COTS alkaline batteries configured in series as the secondary source The AC DC adapter that is used is the TOL 08269 5V adapter that is FCC CE certified and rated at 1A This adapter is the wall wart style requiring no extra power cables The DC o
61. an operational amplifier while the switched integrator TIA 30 had internal feedback capacitors and switches The OPA2380 was the high speed TIA and the IVC 102 was the switched integrator TIA 1 2V 3 3V o o Figure 11 TPS3808 Typical Application Circuit Reprinted with permission by Texas Instruments Section 8 page III OPA2380 The OPA2380 was a high speed TIA It required external components to perform its functions It had a high gain bandwidth of 9OMHz and a slew rate of 80V us The open loop gain was 130dB The power supply voltage range was from 2 7V to 5 5V and pulled a quiescent current of about 7 5mA The OPA2380 came ina small 3mm x 5mm MSOP 8 size It had very low 1 f noise and had a very low drift voltage averaging at about 0 03uV C The OPA2380 was designed to be used in high speed photodiode applications such as measuring pulse oximetry where many samples must be taken every second IVC102 The IVC102 was a switched integrator transimpedance amplifier It had 3 internal capacitors that can be connected to provide a capacitance that ranges from 10pF to 100pF It also had 2 internal switches that were used to reset and integrate the output voltage The internal capacitance created an integrating operational amplifier that follows the equation Vo adt The amount of time that Switch 1 the integrating switch was closed determines how long the circuit integrated and as a result determines the voltage output of t
62. ance of their core materials The LiFePO4 18500 with the specifications of 3 2V 800mAh and an 8A max discharge current was available from batteryspace com for 3 However this was just the bare battery and did not include the safety features that the battery needed to keep it from dying There were battery packs available that had the included safety needs A 3 2V 1500mAh LiFePO4 18650 battery pack with 26 safety features including 3 8V peak 3 2V working and 2 5V cut off would cost 7 50 A COTS charger for a 3 2V LiFePO4 cell can charge at 0 5A and would cost about 15 As an alternative standard Li lon packs with safety features were also available A Li lon 14500 AA size battery pack with 4 2V peak 3 7V working 2 5V cut off 3A limited and 750mAh was would cost 10 This battery would be ideal for the design due to size but the 750mAh was just slightly too low for the requirement to get multiple uses between charges A Li lon 14650 with the same specifications but with 940mAh costs 11 A Li lon 18500 with the same specifications but with 1400mAh costs 15 A COTS charger for the 3 7V Li lon packs would cost about 12 In both cases the off the shelf charger would need to be modified so that battery would not need to be removed from the TSU to recharge Although the cost difference of the batteries was large when the chargers were included in the price the differences in cost was greatly reduced 4 2 min 5 5 max flat area
63. and BC interface so it is easy to communicate with either of these components The benefits of the SPI interface over the 12C interface are as follows The SPI interface has full duplex communication SPI has higher throughput than BC SPI has complete protocol flexibility which means that the message is not limited to 8 bit words The SPI interface uses lower power than lC There is no need for precision oscillators and the LED display driver does not need a unique address Transceivers are also not needed The SPI interface allows for all of the numbers to be displayed with the use of only four of the GPIO s of the MCU Figure 29 shows how the MCU and the display interact SPI 3 digit 7 LED Display segmented Driver Display LDT A512RI MAX6957 Figure 29 Block diagram for the display The SPI 4 wire interface consists of three outputs from the CC430 inputs to the LED display driver data in clock and chip select and one input to the CC430 from the LED display driver data out The data in and data out consists of an arbitrary size message according to the SPI interface For this communication a byte of information that tells the LED driver which segments to turn on is used The first 4 bits of the serial transmission is the data bits and contains what digit to be displayed The second 4 bits of the serial transmission is the command bits and contains which 7 segment digit displays the data bits The clock is chosen to be
64. ant and pour the etchant into the tray Etching should take 5 to 20 minutes depending on the size of the board Using plastic tongs remove the board from the tray Now all the exposed copper should be gone and only the places with the toner should remain After properly disposing of the etchant wash everything that came into contact with the etchant After the board has been washed and dried it is time for drilling Drill holes of appropriate size according to what type of parts will be placed on the board Once drilling is complete remove the toner to expose the copper underneath with steel wool Mount all of the parts to their appropriate locations and solder the pins of the components to the copper The total cost of doing the self fabrication process depends on the equipment that may need to be obtained The cost of a copper double sided board is about ten dollars The cost of the etchant is about seven dollars for a sixteen oz bottle The cost of the transfer film is about ten dollars for a pack of five Not counting the drill drill bits and possible mistakes the total cost is about 27 dollars per board assuming that each board consumes all or most of the etchant Commercial Fabrication The other option is to have the PCB fabricated by a commercial fabrication company This method would not require the design team to have any knowledge of fabrication techniques Commercial fabrication is beneficial if the boards that are being created are s
65. ant as the calculations because there could be nothing wrong with the calculations but the display is not displaying the correct numbers Each digit that is used shall be tested to show that communications between the MCU and the 7 segmented display is correct Unit Test 2 The alarms of the RDU also need to be tested This feature is one that if it doesn t work correctly it could be a life or death situation The first alarm that tested is the danger alarm This is a critical alarm If the SpO 2 drops below a certain percentage this alarm needs to go off signaling that this is a potentially dangerous condition The next alarm is the low power alarm that signals that the TSU has a battery life less than 30 minutes This is also an important alarm because if the battery dies in the middle of night without an alarm to signal that it is not monitoring pulse and SpOz this could be a life or death condition The last alarm tells the user that the RDU has lost the signal to the TSU This could have happened for a few reasons the RDU or TSU have been taken out of each other s range the TSU s battery has died or there is interference between the TSU and RDU and they are unable to effectively communicate These alarms are a critical feature for this project and need to be tested for full functionality The functionality of the alarm is broken up into two parts The first part is to test if the interrupt function is being accessed correctly and the function is
66. are only two items whose placement is pertinent The first was the battery It was installed in the unit so that its terminals are close to their connections on the PCB Once this was determined the battery was secured in place permanently The second was the wires out of the unit to the finger sensor clip These were placed so that they follow the shortest path from the PCB to the sensor as well as have strain relief on its attachment to the PCB The orientation of the PCB was determined based on these two critical components Once this was decided the board only needed to be pressed against one side of the unit and a hole drilled in the appropriate place After the units were assembled they could be tested according to the sub system level test plans see section 5 4 Modifications were made as necessary for the units to operate effectively These modifications included changes to the PCB Since the boards did not change size or shape no mounting changes were necessary within either unit Additionally the major components on the board such as the display and the MCU were only changed or moved if absolutely necessary Most changes were made to the passive components like the resistors capacitors and inductors This was because a voltage drop was too low for a part to work properly or the current to a certain component was too small These passive parts were easily interchanged as they were of standard footprint sizes They could easily be adde
67. arm does not beep or emits improper notification sounds the software of both MCUs should be checked to assure that the low battery signal is being properly sent received and interpreted Result The buzzer was first tested by applying a voltage to determine functionality During testing it was determined that the PWM was not necessary The danger condition was tested by setting the danger condition within the MCU This produced the desired continuous sound The loss of signal and low battery sounds were then tested These two sounds were changed The loss of signal alarm is a fast pulsing sound and the low battery sound is a slow pulsing sound The loss of signal sound does not currently function according to design Whenever a finger is removed the loss of signal alarm is made since the TSU will not perform calculations and will not transmit 5 3 Software The need for software testing on this project is plentiful Since most of the external hardware is channeled through the MCU and therefore the software that controls the MCU software plays a critical role in this project Each of the unit tests in this section shall cover all of the functions that the MCUs provide 123 5 3 1 RDU Unit Test 1 The display unit of the RDU needs to be tested thoroughly to insure that it has been interfaced correctly In addition each segment needs to be tested to insure that it is in working order The display of the SpO and pulse is almost as import
68. at run on extremely low power 2 2 1 Microcontrollers MSP430F233 The Texas Instruments MSP430F 233 featured ultra low power consumption with five low power modes and the ability to wake from standby mode in less than one microsecond This chip had a 16 bit RISC CPU with 16 bit registers two built in 16 bit timers a 12 bit A D converter a comparator two universal serial communication interface modules up to 48 I O pins 8KB Flash 1KB RAM operated at 16 MHz roughly 12mm x 12mm in size and was available as either a LQFP or QFN The MSP430F233 had many alternative components to fit any need whether it be more or less RAM Flash or processing power This chip was end equipment optimized for Wireless Communication applications The MSP430F233 had 48 I O Pins as shown Figure 1 below 12 bit ADC Free IDE for MSP430 chips and 51 Instructions This chip had a larger size with fewer integrated features than other microcontrollers do 13 y x Ge x o 232 LEz3E32 EREECHEN G4 ZazeeeRPFPekkeee GITT LTE 64 63 62 53 DVoc 1 48 P5 4 MCLK P6 3 A3 2 47 J P5 3 P6 4 A4 3 46 P5 2 P6 5 A5 4 45 P5 1 Peeae 5 44 P5 0 P6 7 A7 SVSIN 6 43 P4 7 TBCLK Maer D 42 D P46 XIN 8 41 P45 XOUT f 9 40 P44 Vener 10 39 P43 Maer Neser D 11 38 D P4 2 TB2 P1 0 TACLK CAOUT f 12 37 P4 1 TB1 P1 1 TAO 13 36 P4 0 T80 P12TA1 14 35 P3 7 P1 3 TA2 15 34 D P3 6 P1 4 SMCLK 16
69. ate ZigBee also had error correcting protocols and generic RF did not by default The software and hardware would have to implement the ability to do this though Both the ZigBee and generic RF had many parts that were available to be interfaced with a microcontroller ZigBee had low data rates and generic RF the data rate could be determined by the bandwidth of the signal being sent ZigBee used a network structure The network structure was not necessarily needed Conclusions Generic RF had much less functionality when compared to ZigBee Bluetooth or even Wi Fi Although this functionality was not required it could have been very useful The overhead for using ZigBee would strain the project s budget The generic RF 900MHz band may be a little cluttered but it used less power Power consumption was the major concern of this project Therefore the generic RF 900MHz communication used for the communication method for this project FCC regulations In order to transmit data from the TSU to the RDU a radio frequency transceiver was used To do so Federal Communications Commission regulations were considered The transceiver on the microcontroller of the TSU transmitted at a frequency of 915MHz making it part of the Industrial Scientific and Medical ISM band The ISM bands allowed for any amount of RF power generated within the specified tolerance of each ISM band The 915MHz ISM band had a tolerance of 13 0MHz 11 Under section 15 23 pa
70. ately 100m Class 2 used up to 2 5mW of power and could transmit approximately 10m and Class 3 used up to 1mW of power and could transmit approximately 1m For this project Bluetooth transmission could have been used An external Class 2 Bluetooth device could have been interfaced with the processing device Other house appliances such as the wireless home telephone ZigBee and Wi Fi clutter the 2 4 GHz ISM band Therefore this could have been a problem 6 when dealing with noise corrupting a packet that was being sent The Bluetooth protocol has ways to deal with this type of interference On the other hand Bluetooth has a few problems with wall penetration which could have posed some problems Despite these facts the Bluetooth serial interface could have been used to transfer a packet containing the information that was needed to send Unfortunately the user would have to initiate a pairing between the TSU and the RDU Pros e Does not require devices to be in straight Line of Sight position e Low battery consumption e Many robust profiles Cons e User must initiate pairing e On the cluttered 2 4 GHz ISM band e Low penetration qualities Bluetooth had many appealing features a robust stack of protocols and good ways of dealing with interference Many small electronic devices utilized the Bluetooth stack to communicate as an alternative to wires All of these options made Bluetooth a good choice for the wireless communication betw
71. ation under the IrDA protocol The next layer up was the Infrared Link Access Layer Protocol IrLAP It represented the Data Link layer of the OSI model Communication devices were divided into a primary device and one or more secondary devices Since the primary device controlled the secondary device the primary device could have been the TSU and the RDU could have been a secondary device The IrDA also required the IrLAP In addition a required layer the Infrared Link Management Protocol IrLMP provided for multiple logical channels and provided a list of services The last specification was an optional one but for this project it was required The Infrared Communications Protocol IrCOMM let the infrared device act as a serial or parallel port Pros e Immune to radio interference e Low power consumption e Receiver didn t need to search for frequency e Blocked by walls e Daylight causes interference e Required direct line of sight Although Bluetooth ZigBee and other forms of personal area networks had surpassed infrared communications there still was a place for very short range communication that had direct line of sight Despite that for this project very short range communication was probably not going to be sufficient Even though this form of communication could have been used the power consumption would have been too much Infrared had advantages that make it better than its competitors such as immunity to radio interference
72. ave a problem shining brightly enough through the finger cot and the photodiode may have trouble receiving accurate information too Finally the sensor clip can be molded out of silicon or alginate The latter is used by dentists orthodontists oral surgeons and periodontists to make molds of teeth which are then converted to plaster casts These materials are soft when set and can be tailored to fit many different finger sizes To make this kind of sensor housing a small container or cup can be filled with the material The LEDs and photodiode can be lightly glued to the finger and then the finger can be set into the material When the material sets the LEDs and photodiode will have a place to be set where they will be in perfect alignment The material can be removed from the bucket or cup and shaped into a comfortable design to allow for movement of the finger being measured as well as those next to it This design allows for many trials of design and molds since a pound of alginate powder can cost under 20 and only a small amount need be used per mold This will also allow for the sensor to be tailored to fit each individual patient As a marketable idea this could be included into a kit for making a personal sensor A mold can be made in the shape of the outside of the sensor Each kit would contain some alginate powder and a finger cot with the sensors attached to the outside By slipping on the finger cot and then molding to the outside of
73. ay if the switch is in the one two position the system is on and when the switch is in the two three position the system is off DC DC Conversion The Enpirion EP5368QI is used for voltage regulation of the TSU The EP5368QI is a complete system on chip synchronous buck converter with integrated inductor PWM controller MOSFETs and compensation in a small 3mm x 3mm QFN package This chip is ideal for noise sensitive RF as well as area constrained applications like that of the TSU The EP5368QI is powered by the Li lon battery pack The output voltage is set with the 3 pin VID selector and the output voltage is 3 3V when connecting all three of the voltage select lines to ground The 4 7uF 0603 capacitor is required at the VIN by the system Two 10uF 0805 capacitors are used at the VOUT pins to improve ripple performance A single 0 01uF 0603 capacitor is connected in parallel to the 10uF capacitors at the output to improve transient suppression The cost for this component is less than 2 Figure 33 below is a diagram showing how the EP5368QI will be configured in the TSU Vsw is the voltage that comes from the On Off switch which is 3 3V that is output from the buck converter for the system to use Power Line Filtering The Analog and RF power lines for the CC430 are filtered to keep the digital noise off them This is accomplished with 1kQ 250mA 0402 ferrite chips as 69 shown below in Figure 34 The ferrite chip prevents any high frequen
74. c 9 2009 at 11 22 AM To Steve West onsemi com My senior design group is designing a wireless pulse oximeter and we are considering the use of the ON Semiconductor NCP 1530 step down converter for our device As part of the design processes we are required to submit a document with all of our designs and figures Can we use the figure in the NCP1530 data sheet that shows the typical application of the NCP 1530 Thank you Eric Roberts Steve West lt steve west onsemi com gt Wed Dec 9 2009 at 1 26 PM To Eric Roberts lt eroberts ce knights ucf edu gt Ce Steve West lt steve west onsemi com gt Dear Mr Roberts Please consider this email a blanket Copyright Permission to utilize the current ON Semiconductor figure in the NCP1530 data sheet that shows the typical application of the NCP1530 Please be sure to include the copyright attribution of Used with Permission from ON Semiconductor SCILLC If you need any additional assistance you may contact me directly Best Regards Steve cc File Steve West Global Technical Publications Manager ON Semiconductor 5005 E McDowel Rd Phoenix Arona 85008 602 244 3882 steve west onsemi com Quoted text hidden VIII
75. cation methods available for this project They were Bluetooth ZigBee Wi Fi and RF communication While Bluetooth ZigBee and Wi Fi were forms of RF communication this RF communication was a unique protocol designed specifically for this project This research also looked into Infrared as a possible communication method Infrared had no stipulations as far as what range of frequencies communication applications need to be but devices usually conform to standards set by the Infrared Data Association IrDA Bluetooth Bluetooth was an open wireless protocol for exchanging data over short distances from fixed and mobile devices creating personal area networks PANs It was originally conceived as a wireless alternative to RS232 data cables It could connect several devices overcoming problems of synchronization Bluetooth used a radio technology called frequency hopping spread spectrum which chops up the data being sent and transmits chunks of it on up to 79 frequencies In its basic mode the modulation was Gaussian frequency shift keying GFSK It could achieve a gross data rate of 1Mbps for Bluetooth 1 0 1 3Mbps for Bluetooth 2 1 and 54Mbps for Bluetooth 3 0 Bluetooth provides a way to connect and exchange information through a secure globally unlicensed Industrial Scientific and Medical ISM 2 4GHz short range radio frequency bandwidth There were three classes of Bluetooth Class 1 used up to 100mW of power and could transmit approxim
76. ccurred after the voltage returns above the threshold level The TPS3808s are available in either a 2mm x 2mm SON package or a 3mm x 3mm SOP The cost is 3 per chip The chip is ideal for use in the RDU where only a good bad battery status is needed unless a rechargeable battery option is used An application circuit with a single 3 3V power source and a 20ms delay is shown in Figure 15 3 3V Figure 15 TPS3808 Reset Delay Circuit Reprinted with permission by Texas Instruments Section 8 page III 39 2 4 3 Status Indicators LEDs The RDU requires the use of many different indicators There will be LEDs as well as an alarm Each will have a specific function that will alert the user to conditions happening either with the patient or within the RDU An LED will be used to indicate that the RDU has power from the wall outlet and a bicolor LED will be used to indicate the life status of the internal backup battery Additional LEDs will indicate whether the display is showing the pulse rate or the SpO2 and whether the RDU is receiving signal from the TSU An LED array will show the status of the TSU battery For convenience these LEDs will be different colors The signal LED will be orange the bicolor LED will be green and red the blue LED will indicate if there is AC power the TSU battery array will be green and yellow LEDs will be used to show which measurement is being displayed The first option for the LEDs is surface mount par
77. circuit in the previous step The fifth test to be performed is to connect both the battery and the adapter to the automatic backup switch The last power test is to connect the AC DC adapter and the battery to all of the power circuitry and test all of the connections Test Specification The point of the specification test is to run the AC DC adapter through a simulated load record the voltage and current leaving the adapter The simulated load can be calculated with the simple V I R equation The intended test current should be run through a power resistor equal to max voltage of the AC DC adapter 5V divided by the test current The RDU is estimated to draw less than 150mA so the first test is to discharge the battery at a 150mA rate If needed the AC DC adapter can be tested at higher currents but the adapter s limit is 1A Test Il Power Connections through PCB This test checks if the AC DC adapter is connected on the PCB to all the correct solder pads To test this the adapter is connected to an unpopulated board An 116 unpopulated board must be used because the AC DC adapter could not be safe to connect to other components or the other components might not be safe for the battery All of the pads should be probed to make sure no voltages are leaking into pads that are not supposed have them Test Ill DC DC Converter To test the AC DC adapter with the DC DC converter the adapter is connected to the DC DC converter and a
78. com Broadband www ti com broadband DSP dsp ti com Digital Control www ti com digitalcontrol Clocks and Timers www ti com clocks Medical www ti com medical Interface interface ti com Military www ti com military Logic logic ti com Optical Networking www ti com opticalnetwork Power Mgmt power ti com Security www ti com security Microcontrollers microcontroller ti com Telephony www ti com telephony RFID www ti rfid com Video amp Imaging www ti com video RF IF and ZigBee Solutions www ti com lprf Wireless www ti com wireless Mailing Address Texas Instruments Post Office Box 655303 Dallas Texas 75265 Copyright 2009 Texas Instruments Incorporated Ill Texas Instruments 2008 Permission IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries Tl reserve the right to make corrections modifications enhancements improvements and other changes to its products and services at any time and to discontinue any product or service without notice Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete All products are sold subject to Tl s terms and conditions of sale supplied at the time of order acknowledgment TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with Tl s standard warranty Testing and other quality control techniques are used to the extent Tl deems necessary to support
79. ction point to connect the TSU with its finger unit The other hole on the side of the TSU is to connect the battery with its charger RDU Mechanical Design The RDU is housed in a unit that fits the PCB and batteries It must be sturdy enough to protect these two parts but thin enough that it can be drilled through The RDU is the base station and must stand on its own as well as be visible from many different angles The parts mounted to the case include the 7 segment display five indicator LEDs an LED array the switch and the AC DC adapter plug The housing is made out of ABS plastic It is hollow with mounting screw holes predrilled on the inside There is also a battery cover created so that the backup batteries may be replaced without giving the user access to the internal circuitry Thus the RDU is sturdy visible from afar self contained and allow easy access to changeable parts Software The software required by the project is broken up into two parts the RDU and the TSU The RDU is the receiver of the information from the TSU and it main job is to display the information and alert the user to status of the TSU The TSU is the originator that collects the data to be transmitted to the RDU The diagram below shows the functions and data types needed for this architecture In general the RDU functions are used to update the display sound the alarms received data from the TSU and update the battery life These functions meet with
80. cy electrical noise from entering those sensitive lines Figure 33 Configuration of EP5368QI 3 3V 3 3Y RE E 1 3 3V 3 3Y ANA F Figure 34 Configuration of Digital Noise Filtering Transient Suppression A pair of capacitors is placed at each major power connection to account for transients in the lines A a 10uF capacitor is connected between the power connection and ground A 0 01uF 10000pF capacitor is also connected in parallel to the first These will give a path to ground for any transient currents to keep them from interfering with the performance of the device The transient suppression is shown in Figure 35 where the power signals connect to the CC430 3 3 3 Status Indicators The RDU has several types of information besides the patient s vital readings to communicate to the user as such there are multiple forms of status indicators Two forms of indicators will be used a speaker for audible warnings and numerous LEDs for visual statuses The speaker gives alerts for dangerous medical conditions as well as loss of signal and critically low power Many different panel mount LEDs are used to display status and indicate the information being displayed Two LEDs alternate in correspondence with whether the current display is the pulse or the blood oxygen saturation Other LEDs display the battery status of the RDU and the battery life of TSU Another 70 is used to indicate if there is a good signal and a fina
81. d in parallel with resistors already installed on the PCB For more information on possible issues see section 5 and section 4 2 The build process was one of the most critical parts of the project It was completed as soon as possible to allow more time for testing and making changes Once the first assembly was completed the project took off and moved smoothly Waiting for the PCBs and components was the rate limiting factor of the assembly After the first PCBs were assembled and the mounting placements determined the build was simple Since the PCBs did not change even if the components did the original mounting placement was the final one This simplified the build and allowed changes to the PCB to be made easily without having to choose properly working circuits versus changing the housing of the unit 4 2 Issues There are many issues that can be anticipated before the project is completed By addressing these issues before beginning the build and test process some may be avoided Issues can become costly and time consuming so every effort 105 is made to prevent them Some cannot be stopped but by expecting them extra time and budget can be allotted in order to deal with them more effectively A first issue that should be accounted for is PCB shorts During manufacturing some nets may be connected where they should not This causes many other errors to occur If a net is shorted from a lower voltage or current to a higher one c
82. d were not compared since it was 10 determined based on initial research that these methods would not be used in this design Bluetooth vs ZigBee For the wireless needs of this project Bluetooth did not make any sense to use Bluetooth was designed for connectivity between laptops phones PDAs and personal computers as a general cable replacement Bluetooth also used more power for the distance that it was traveling than ZigBee While Bluetooth had many rich profiles none of them apply to this project without being overkill ZigBee on the other hand had a much further range for the power consumption In addition many manufacturers were integrating low power MCUs with ZigBee transceivers ZigBee became a much more desirable option ZigBee did not exceed the aim of the project since there was no need to send that much data 720kbps was more than enough to get all of the data sent from the TSU to the RDU in under a second RF vs ZigBee ZigBee was a specific protocol that utilized the 2 4GHz ISM band The generic RF could utilize the 900MHz or 2 4GHz ISM band For this project the 900 MHz band was more appropriate than the 2 4GHz The generic RF would have less power consumption than the ZigBee Both the generic RF and ZigBee had microcontrollers with built in RF radios and ZigBee protocols ZigBee was secure whereas generic RF was not ZigBee had a standard transfer protocol but the generic RF could transmit any size packet at any r
83. discrepancies should be thoroughly documented and included with the final product as warnings If the group is unable to test the project against a hospital unit significant issues will arise Notably since the unit must be compared to a medical grade product one needs to be purchased if it cannot be borrowed This would be impossible on this budget due to the cost of those units For more information on these products see section 1 3 The unit that is used for this medical comparison must be FDA approved as well Without this the unit is unsafe and not fit for use This issue is not expected but it is taken into consideration The budget allotted to the group from the sponsors does not allow for the group to purchase a pulse oximeter see section 6 1 Any extra costs have to be paid by the design team The goal of this project is to create a safe product This means that the medical comparisons are of the utmost importance Improper readings can cause a user injury or could even be fatal If possible these medical comparisons should be completed more than once before the project is completed This assures that the units are as safe as possible and no harm will come to a patient using them Result A small easy to use off the shelf pulse oximeter was used to perform the medical comparison While wearing the finger clip of the wireless heart rate monitor the user also wore the off the shelf pulse oximeter The TSU measures within the specif
84. ds can be made if there are internal layers These layers cannot be created using self fabrication The price difference between self fabrication and having the boards made is surprising The cost of fabricating eight boards by hand is over 200 This does not include the prices of the tools that would have to be purchased which can be very expensive It also does not take into account practicing the process or expected mistakes However all the manufacturing services have prices between 100 and 150 including estimates for shipping Thus having the boards manufactured would be more cost effective and much less of a hassle The option for which company to use remains open and depends on the final 50 sizes of the PCBs and whether or not they require internal layers Before sending out the boards the layout and routing would have to be thoroughly reviewed by the design team 2 7 Software Options The MCU software for this project is slightly different from the RDU to the TSU The RDU receives the packets sent from the TSU The RDU also has the outputs to the display status indicators and speaker The TSU has the input from the sensor to get the information needed to compute the pulse and blood oxygen saturation level Possibility 1 The RDU will fire an interrupt when it receives the packet that will update the variables for the values of battery life blood oxygen saturation level and pulse The RDU will also have an update display func
85. e HD 79 Figure 44 Flow diagram of the TSU starting up 80 Figure 45 Flow diagram of the RDU Starting up 81 Figure 46 Flow diagram of the TSU sending a packet 82 Figure 47 Flow diagram of the RDU receiving a packet eeeeeeeeeeeeees 82 Figure 48 Flow diagram of the RDU updating the display oooooooocccccccccncnnno 83 Figure 49 Flow diagram for updating variables from the sensor data 84 Figure 50 Flow diagram for controlling which LED red or infrared is on 84 Figure 51 Flow diagram for updating the DC component from the DC DC COIN SIS EE 85 Figure 52 Flow diagram for the automatic gain Control 85 Figure 53 Flow diagram of checking if an alarm needs to be sound 86 Figure 54 Flow diagram of updating the battery life on the RDU 86 Figure 55 Flow diagram of updating the battery life on the TSU 87 Figure 56 Block Diagram for the Antenna 87 Figure 57 Block diagram for the display AEN 91 Figure 58 Block diagram of the Status Indicators ooonnnocccnnnncoccccnnnacacncnnnnns 92 Figure 59 Global functions and data types cccccccccccononononoconcncccnnnananannncnnnnnonns 93 Figure 60 The packet used for communicating with the HD 93 Figure 61 Flow diagram of the TSU starting up 93 Figure 62 Flow diagram of the RDU Starting up 94 Figure 63 Flow diagram of the TS
86. e TSU and RDU Infrared The frequencies of the Infrared light were from 300 GHz to 400 THz The frequencies are higher than microwaves but less than visible light Infrared transmission used an infrared LED to create a signal by turning on and off the LED It then beams this light signal through a focusing lens A receiver used a photodiode to read the beam and filters out ambient light This method was commonly used in remote controlled devices such as television and speakers Near infrared or commonly referred to as IR A was the frequency range from 120 to 400THz The IrDA defined its specifications in this range The IrDA specifications were ideal for use in medical instruments test and measurement equipment laptop computers and cellular phones Examples of the IrDA specifications were Infrared Physical Layer Specification Infrared Link Access Layer Protocol Infrared Link Management Protocol and Infrared Communications Protocol Each specification provided a service with each specification lying on top of the others to create a model similar to the Open System Interconnection model For this project infrared was a viable solution for the communication method that could be used This project could have utilized each of the following specifications defined by the IrDA if chosen The Infrared Physical Layer Specification IrPHY was the lowest level of the IrDA specifications This layer 8 was required for any form of infrared communic
87. e ability to see and hear its warnings from afar is important Each LED indicator and display must be at least flush with the face of the unit if not raised off of the front case The RDU must remain compact and lightweight Though issues that would conflict with these objectives are not anticipated any changes to the mechanical design must keep these two properties in mind Software Figure 59 Global functions and data types Figure 60 The packet used for communicating with the RDU Figure 61 Flow diagram of the TSU starting up Figure 62 Flow diagram of the RDU starting up Figure 63 Flow diagram of the TSU sending a packet Figure 64 Flow diagram of the RDU receiving a packet Figure 65 Flow diagram of the RDU updating the display Figure 66 Flow diagram for updating variables from the sensor data 95 Figure 67 Flow diagram for the control of which LED is on Figure 68 Flow diagram for the automatic gain control Figure 69 Flow diagram of checking if an alarm needs to be sound Figure 70 Flow diagram of updating the battery life 3 7 1 Block Diagrams 97 Status LEDs 5 24 3 digit 7 LED Display segmented Driver LDT A512RI 4 CC430 LED Array SSF LXH400GD SSA LXB435SUGD LT6004 DC DC OpAmp Speaker PWM Buck converter Battery Drive Circuit EP5368Q Monitoring Circuit Geiss Automatic External power s
88. e are two forms of power There is an AC connection to the wall This allows the unit to work without battery consumption There also is a backup battery pack This allows the unit to be moved from room to room without losing power The unit automatically switches between outlet power and battery power if the AC is unplugged This means there never is a break in monitoring making the unit much safer for use in high risk cases The RDU has a battery indicator to show when the backup batteries need to be replaced Additionally it is able to indicate when the TSU battery is low and needs to be charged As mentioned in the specifications see section 1 4 the wireless transmits a minimum distance of 100 feet This allows both units to be used in separate rooms without causing an interrupt in monitoring The RDU is equipped with an alarm that sounds when the RDU and TSU are no longer wirelessly connected This signals that the RDU is no longer monitoring the pulse rate and SpO value When the measurements of pulse rate and SpO reach a certain threshold the RDU will sound an alarm The alarm may have different sounds for each alert This makes certain that no dangers are overlooked or go unnoticed It also assures that if the sensor falls off or is not reading properly the person watching the display will know and can rectify the situation All of these alarms and indicators are safety features ensuring that the unit always is working and monitoring
89. e desired low value is shown on the display press the select button to enter the value akWND O CON UP a DOWN 8 E SET 8 Ze Ag Figure 81 RDU When both units are turned on and the finger clip is on a finger the user s heart rate will be displayed If the user s heart rate goes above or below the high or low value respectively the danger alarm will sound This danger alarm is a loud continuous tone If the TSU goes out of range or is turned off a fast one second tone will be made every two seconds If the TSU s battery is low then a longer two second tone will be made every four seconds The battery should be then replaced 136 Section 7 Administrative Content 7 1 Budget The budget consists of all the parts required for this project to make the TSU and the RDU This generic budget for one of each of the main components is fully expandable up to as many as needed The sponsor requires the project to create two RDUs and three TSUs The main constraint on the budget is that the sponsor is only willing to invest for 300 to 500 dollars for this project Many samples have been received instead of having to pay for the parts This helps alleviate the strain on the limited budget Table 7 shows the budget of this project The left half of the table shows the cost of each of the parts if they were all paid for and only one of each component was created The right half of the table shows the cost of the project w
90. e is a short and it is not safe to apply power In such a case continue with the safe to turn on test and determine the cause and location of the short after all steps have been taken Second visually verify that all integrated circuits have been placed with the correct orientation as specified in the design section Third verify that all diodes are oriented in the correct direction Fourth verify that all scaling resistors have the correct value Table 6 outlines the steps in the safe to turn on test Step Action 1 Resistance check 2 IC Orientation 3 Diode Orientation 4 Scaling resistors Table 6 Safe to turn on procedure Voltage Test After applying power to the TSU voltage levels must be verified This is needed to confirm that all components will operate within their given ranges as well as confirm that voltage references for the ADCs and the DAC match those in the software in the MCU This is important since the MCU performs the pulse oximetry calculations using the output of the ADCs First measure the output voltage of the DC DC converter Second measure the voltage on the voltage reference pins of the ADCs and the DAC Confirm that these values match the expected values in software LED Test First apply a voltage to the red and infrared LEDs one at a time and measure the current used by each Visual verification of an infrared LED is possible by using a camera with filtering techniques Verify t
91. e rate and the percent blood oxygen saturation Also it must be able to properly display the values computed in the microcontroller First is whether the display is working or not This can be tested without the completed project The display needs only to be connected to a power source to verify that it works Each segment has its own pin and can be tested individually to simply check that each LED does work and corresponds to the correct pin This should be done before connecting the display to the PCB which makes it easier to test as well as making sure that it won t have to be removed and replaced Result The display was tested on a bread board Power was applied to each of the pins and all segments as well as the decimal points worked correctly After installing the display on the RDU board the RDU was programmed so that the 3 digit display counted up from 0 to 999 changing values every second This test was performed and the display performed flawlessly This test showed that the display could change quickly between different values as well as do so as controlled by the MCU Next the display must be able to show the two sets of numbers pulse rate and SpO2 Once the microcontroller is programmed the display should switch between two different numbers on the set time interval Even if the numbers are not correct based on the medical values this switching is important to the workings of the RDU Before testing the correctness of t
92. e search for an appropriate alarm or buzzer At first glance the selection of alarms in the set frequency range is very slim but there are over 300 buzzers with frequencies between 3 and 5kHz The buzzer must also run on a low voltage as power is a major concern for this design Size constraints are critical in this project so the first choice will be a surface mount buzzer but through hole and panel mount cannot be counted out Small through hole parts can be as convenient as surface mount and panel mount parts would save space on a PCB One surface mount part to be considered is PUI Audio part number SMT 0540 T 6 R This buzzer is a 5mm x 5mm surface mount part which runs on a peak to peak voltage of 3V but an overall allowed voltage from 2V to 4V peak to peak and a current of 100mA Its center frequency is as 4kHz with a 500Hz tolerance and a sound pressure of 78dB Another part is Sonalert part number AST1628MATRQ This speaker has a large voltage tolerance of 1V to 25V peak to peak but it is only rated for a current of 5mA The frequency is rated at 4kHz and has a sound pressure of 75dB It also has a footprint of 16mmx16mm which is fairly large for this application A third option is the Murata Electronics part number PKLCS1212E40A1 R1 This part has a 12mm x 12mm footprint which is slightly too large but not unreasonable It has a voltage rating of 3V peak to peak a maximum voltage of 25V and a sound pressure of 75dB minimum
93. e wrist by a Velcro strap that is fed through two slots in the bottom of the TSU Each slot has dimensions of 1 x 0 25 and will be 2 00 from each other Two sides of the TSU have holes of diameter 0 25 The hole on the 2 470 side is used as a port for charging the battery inside the housing The power cord of the battery charger is plugged into a panel mount plug on the unit and removed upon completion of the charging cycle The hole on the 3 295 side of the TSU serves as the connection point between the finger unit and the TSU PCB The cable coming from the finger unit with the LEDs and photodiode connects to the TSU main PCB The housing is arranged on the wrist so that the connector to the finger unit is pointed in the direction of the hand This is done so that the finger unit can be connected to the TSU housing easily Figure 39 is an illustration of the housing for the TSU main PCB and battery Figure 39 TSU Housing Diagram 75 3 5 3 Receiving Display Unit The RDU is the base station of the wireless pulse oximeter It contains the display LED indicators alarms and its own power source The unit stands freely has an AC power adapter and is able to be unplugged and moved from room to room It is housed in a standard case purchased online and which has been modified to fit the design s needs The unit has several different holes drilled into the face and the back The display and battery life LED array
94. ed on the width of the LCD The graphical LCD counter part of the 0 56 LED starts at about 25 The LCD s power consumption was better than the LED s but with the RDU running on AC power it would not be an issue 7 segmented 14 segmented LCD OLED Power Low Low Very Low Extremely Consumption Low Cost Low Low High High Flexibility Low Low High High Implementation Easy Easy Hard Hard Character Size up to 7 up to 7 varies varies inches inches Table 2 This table is a comparison of the display possibilities Conclusion The 7 segment display and the 14 segment display were very similar in the sense that they were LEDs and relatively easy to use Since the RDU s display must be large enough to read across a room the LCD component was much more expensive and out of the price range required by the budget In addition the status indicators could always be incorporated as individual LEDs see section 2 4 3 for more information So now the question is whether to use 14 segments or 7 segments A 14 segment display would be preferred to a 7 segmented display if a need existed for more than numerical information The saturation of oxygen in blood is a percentage displayed as a decimal The pulse of a human being is at a maximum a 3 digit number Given these facts there was no need for more than three digits or a 14 segment display Therefore the choice is the 7 segment display 34 2 4
95. ed which proved to be too large to fit in the RDU case 5 2 5 Alarm The alarms on the RDU are a critical part of this project They alert the user to dangerous conditions Without these alarms the design becomes much less safe for the user and is ineffective There are three different alarm sounds a long continuous sound for measurements falling below the safety threshold short beeps for loss of signal and one short beep per minute when the TSU has a low battery It is important that the alarms are working properly so that the unit is as safe as possible The first way to test the buzzer is to ensure that when a voltage is applied a sound is emitted The buzzer emits different sounds for different applied waves Different waveforms should be tested to assure that the buzzer is working properly It is necessary to produce multiple sounds so many waveforms may need to be tested to obtain the proper sound The MCU can output a waveform of varying frequencies from this pin thus controlling the noise the 122 buzzer makes The frequency into the buzzer should be tested using a waveform generator to find the frequencies that obtain the correct sounds When the buzzer is installed the MCU can be programmed to emit a pulse to the buzzer This requires no data from the TSU Without either unit fully assembled the software can create the pulse in the MCU By forcing an output from the MCU the circuitry that connects the buzzer to the MCU ca
96. eds to be changed This is a bi colored panel mount LED with only two leads It can be assumed that they are connected in parallel but in opposite directions The red anode is connected to pin 17 and the green anode is connected to pin 16 The cost of this bi colored LED is 2 33 Figure 37 is an image showing where the MCU controlled status indicators are connected The resistors are in place to limit current into the LEDs and for debugging purposes Figure 36 MCU Controlled Speaker Figure 37 MCU Controlled LED Status Indicators A late addition to the design is a separate LED that is included only to give a visual indication that the AC DC power adapter is connected to the system The 72 Dialight 558 0803 007F 3 5V blue panel mount LED is used to indicate that the wall plug is connected A blue LED is used here because there was a need to use a different color LED than the others that were used and the blue LEDs are primarily found with a voltage requirement of 3 5V The only place in the RDU that there is that much voltage available is at the input of the AC DC power adapter The cost of this blue LED is 3 40 Figure 38 below shows the location of the primary power connected LED Figure 38 Primary Supply Powered LED 3 4 Wireless Antenna Radio core 3 5 Mechanical Design 3 5 1 Sensor The mechanical design of the sensor clip is the most flexible part of the design There are many options that are vi
97. een the TSU and the RDU The power utilization was low and since battery life of the TSU was a major concern Most likely the protocol that had the least power consumption will be chosen ZigBee ZigBee was a specification for a suite of high level communication protocols using small low power digital radios based on the IEEE 802 15 4 2003 standard for wireless personal area networks WPANs The technology defined by the ZigBee specification was intended to be simpler and less expensive than other WPANs such as Bluetooth ZigBee was targeted at radio frequency applications that require a low data rate long battery life and secure networking The low cost allowed the technology to be widely deployed in wireless control and monitoring applications the low power usage allowed longer life with smaller batteries and the mesh networking provides high reliability and larger range This communication method was another great option for this project An external ZigBee device could have been interfaced with the processing device In addition many microcontroller units came with ZigBee transceivers built in The space that could have been saved would allow for a smaller PCB and in turn made the TSU less bulky Other house appliances such as the wireless home telephone and the microwave Wi Fi and Bluetooth share the 2 4 GHz ISM band The noise that can be generated by these devices would have to be dealt with ZigBee had low data rates but for this p
98. elected the part LDT A512RI from the manufacturer Lumex could be used 14 segmented LED The next basic display was the 14 segmented LED display They were most commonly used in microwave ovens car stereos and VCRs They were capable of displaying all letters of the alphabet and the numbers 0 9 This could also be implemented the same as the 7 segmented display but would need to use 5 bits of our MCU s GPIOs per digit Two of the Maxim part MAX6954 could be used to drive the 14 segmented display utilizing fewer outputs from the MCU Like the 7 segmented LED this technology had been widely used and was a time tested solution to this problem Even though this was not a determining factor it has low power consumption If selected the part LDS E5002RI from the manufacturer Lumex could be used LCD The liquid crystal display LCD was the next display considered for the display of the RDU Digital watches and calculators commonly use LCD displays There were a few different types of LCD displays The two that displays considered here were the graphical and alphanumerical LCD displays Graphical LCD displays contain a pixel area Creation of graphics requires manipulation of the pixel area A benefit of a graphical LCD display was that all of the LED status indicators can be displayed A graphical LCD would have a graphic for signal strength battery life of the TSU and battery life of the backup battery in the RDU These were also more expens
99. epend on the final dimensions of the board and the desired orientation of the internal circuitry Figure 41 shows the dimensions of this case and its internal structure id 4 6 inches Q O O Spo O Pulse w 0 A o a Signal RDU AC a Battery Connected K O Figure 41 DC 34P Diagram 3 6 Software Assembly vs C C Conclusion Figure 42 Global functions and data types E E E 9 Figure 43 The packet used for communicating with the RDU Software Flow Diagrams 79 Figure 44 Flow diagram of the TSU starting up Figure 45 Flow diagram of the RDU starting up Figure 46 Flow diagram of the TSU sending a packet Figure 47 Flow diagram of the RDU receiving a packet 82 Figure 48 Flow diagram of the RDU updating the display Figure 49 Flow diagram for updating variables from the sensor data Figure 50 Flow diagram for controlling which LED red or infrared is on Figure 51 Flow diagram for updating the DC component from the DC DC converter Figure 52 Flow diagram for the automatic gain control Figure 53 Flow diagram of checking if an alarm needs to be sound Figure 54 Flow diagram of updating the battery life on the RDU 86 Figure 55 Flow diagram of updating the battery life on the TSU 3 7 Explicit Design Summary MCU Antenna Figure 56
100. er and backup batteries this test is completed in three stages First the AC power should be connected The voltage coming in should be of the proper value Additionally at this point the batteries should not be in use To check this the batteries should be taken out while the unit is on to assure that it remains powered up Next it should be verified that the unit can switch between the two power supplies When the AC is unplugged the unit should automatically switch to battery power without shutting off Then the voltage across the battery should be tested The battery should have the proper voltage and be able to keep the unit turned on Finally the voltage should be tested on the other side of the voltage converters in the same manner as it was tested on the TSU An oscilloscope should be utilized to assure a Clean DC signal is flowing into the circuit The MCU in the RDU should now be programmed with certain test cases to execute These should test the display the indicators and the alarms in various orders Each has previously been tested but now must be incorporated with the entire unit This means that the MCU should be able to turn on the display and switch between two different numbers while illuminating the correct indicator LED This is critical to the project as the user must know which measurement is being displayed at any moment in time Next each number should drop below the threshold to assure that the alarm sounds with the pro
101. er would be able to recognize the change and transmit the new battery level The TPS3808s were available in either a 2mm x 2mm SON package or a 3mm x 3mm SOP The cost was about 3 per chip The drawback to using this circuitry was that it was mainly intended to monitor one or more different voltages and trigger if any of the voltages drop below the threshold value so that the microcontroller can turn off before it runs out of power Since this was the case and microcontrollers run at standard voltage ranges the number of available TPS3808s was limited The available thresholds are 4 65V 3 07V 2 79V 2 33V and further below this amount The main problem was that only two of those voltages were within the specified range of the batteries that could be used but since batteries do not drain linearly it would be difficult to extrapolate the battery life at any instant Adjustable threshold voltage TPS3808s were available that could be tuned by external resistors were also available Then the problem became excessive board space usage for battery monitoring An example circuit of how the TSP3808 was used to monitor multiple voltages is shown in Figure 11 2 3 3 Operational Amplifiers Amplifier Circuit A transimpedance amplifier is necessary to convert the current output of the photodiode to a voltage Two types of TIA configurations work well to meet this requirement a high speed TIA and a switched integrator TIA The high speed TIA consisted of only
102. ery voltage and loss of signal Various panel mount LEDs are used to indicate the status of the following aspects of the system Orange for the Signal and loss of signal Green array for the remaining TSU battery life Green Red for the RDU battery status Blue for primary power source connected and yellow for which information is being shown on the display Sensor Mechanical Design The sensor mechanical design is one of the least critical aspects of the project There are many viable options for the casing of the sensor and the final product may incorporate any one of them The final design is based on the budget and the amount of time left to work on this mechanical design Leaving this to the end does not cause any disruption to the flow of the project as it is not a critical component of the testing The final design should incorporate the goals of the sensor that it is small and comfortable and based on the budget and time remaining TSU Mechanical Design The TSU is housed along with its battery in a case that is attached to the wrist The TSU housing is made out of a plastic material to provide strength as well as a good insulating material The case has a Velcro strap that is used to hold itself to the wrist The wrist strap is connected to the case through two slots on the bottom There are two holes on the side of the TSU housing one on the side and the other on the side with the hand The hole closest the hand is used as a conne
103. esignated by TI as military grade meet military specifications Buyers acknowledge and agree that any such use of TI products which TI has not designated as military grade is solely at the Buyer s risk and that they are solely responsible for compliance with all legal and regulatory requirements in connection with such use TI products are neither designed nor intended for use in automotive applications or environments unless the specific TI products are designated by Tl as compliant with ISO TS 16949 requirements Buyers acknowledge and agree that if they use any non designated products in automotive applications TI will not be responsible for any failure to meet such requirements Following are URLs where you can obtain information on other Texas Instruments products and application solutions Products Applications Amplifiers amplifier ti com Audio www ti com audio Data Converters dataconverter ti com Automotive www ti com automotive DSP dsp ti com Broadband www ti com broadband Clocks and Timers www ti com clocks Digital Control www ti com digitalcontrol Interface interface ti com Medical www ti com medical Logic logic ti com Military www ti com military Power Mgmt power ti com Optical Networking www ti com opticalnetwork Microcontrollers microcontroller ti com Security www ti com security RFID www ti rfid com Telephony www ti com telephony RF IF and ZigBee Solutions www ti com lprf Video amp Imaging www ti com video Wireless www ti com wi
104. ety critical applications notwithstanding any applications related information or support that may be provided by TI Further Buyers must fully indemnify TI and its representatives against any damages arising out of the use of TI products in such safety critical applications TI products are neither designed nor intended for use in military aerospace applications or environments unless the TI products are specifically designated by TI as military grade or enhanced plastic Only products designated by TI as military grade meet military specifications Buyers acknowledge and agree that any such use of TI products which TI has not designated as military grade is solely at the Buyer s risk and that they are solely responsible for compliance with all legal and regulatory requirements in connection with such use TI products are neither designed nor intended for use in automotive applications or environments unless the specific TI products are designated by TI as compliant with ISO TS 16949 requirements Buyers acknowledge and agree that if they use any non designated products in automotive applications TI will not be responsible for any failure to meet such requirements Following are URLs where you can obtain information on other Texas Instruments products and application solutions Products Applications Amplifiers amplifier ti com Audio www ti com audio Data Converters dataconverter ti com Automotive www ti com automotive DLP Products www dlp
105. functionality will need to be read written from to an I O port This decision will also be based on the selection of an MCU with integrated transceiver or an MCU paired with transceiver transmitter or receiver Of the possibilities the first possibility is the most appealing Testing Considerations The software shall be made unit testable and system testable The unit tests will be based on each of the main functions for the RDU and TSU The RDU unit tests will consist of receiving update display update variables and sounding each of the individual alarms The TSU unit tests will consist of transmitting and updating the variables from the inputs The system test will consist of a typical use of this product such as attaching the pulse oximeter to a person and turning it on while a person on the other side of the room monitors the person s pulse and blood oxygen saturation level 53 Section 3 Design 3 1 Microcontroller Transceiver P2 2 PM_TA1CCR1A CB2 A2 P2 1 PM_TA1CCROA CB1 A1 P2 0 PM_CBOUT1 PM_TA1CLK CBO P1 7 PM_UCAOCLK PM_UCBOSTE ROSC P1 6 PM_UCAOTXD PM_UCAOSIMO P1 5 PM_UCAORXD PM_UCAOSOMI VCORE DVCC P1 4 PM_UCBOCLK PM_UCAOSTE P1 3 PM_UCBOSIMO PM_UCBOSDA P1 2 PM_UCBOSOMI PM_UCBOSCL A0 P1 1 PM_RFGDO2 TA1CCR2A CB3 A3 PM_RTCCLK CB4 A4 VREF VeREF a N A P1 0 PM_RFGDOO RGZ PACKAGE d TOP VIEW Ww ia Ei LL Ww x 5 wo o O E Q o O Es we s O gt mE Co E as
106. ge Low Power consumption 4 Wire Audio Interface 21 GPIOS Cons e No samples available e High Cost Part e On cluttered 2 4GHz Band e Samples not Available 2 2 4 Transceiver with Built in Microcontroller CC1110 The Texas Instruments CC1110 was a low power sub 1 GHz system on chip solution designed for low power wireless applications This chip used an enhanced 8051 MCU 8x the performance of a standard 8051 and had 32 kB of Flash and 4 kB of RAM Like the CC430 the CC1110 had an integrated CC1101 The CC1110 featured a 12 bit ADC I C interface two USARTs one 16 bit and three 8 bit timers and 21 GPIO pins A major benefit was that this chip was a very small 6mm x 6mm 36 lead QFN package The downside to this size was the reduced number of built in features A typical application circuit for the CC1110 was shown below in Figure 6 2 2 5 Processing Unit Comparison Ideally the MCU that would be used needs to be relatively small 12mm x 12mm or less In addition it would need to have a large number of I O pins 20 or more to control the various circuits in both the TSU and RDU As a bonus the MCU should have built in technology that could be used to reduce the size of the TSU such as ADCs DACs or Transceivers Due to the projected budget for this design it was also important that the MCU be low cost Table 1 shows a summary of the possible MCUs 21 2 0 V 3 6 V power supply 30 DCOUPL Cam D 2 10 DVDD
107. ght from the PCB to the front of the unit The most effective of these would be a flexible pipe This would allow the PCB to be mounted in any position and the light to be directed to any area of the unit Lumex offers nearly a hundred LEDs in these colors with package sizes ranging from 0805 up to 3632 The company also offers light pipes that would bring the light from the surface of the PCB to the front of the unit Lumex offers five different flexible light pipes many different right angle and vertical light pipes as well as light pipe arrays that would cover multiple LEDs in a single part The benefit of using Lumex parts is similar to what was pointed out in section 2 3 1 The company offers samples and this would cut the cost of the project a great 40 deal Because of the limitations of using surface mount parts and the potential extra cost of using light pipes panel mount LEDs are also considered Panel mount LEDs come in all different varieties Plain LEDs generally have two through hole leads that must be soldered directly into the PCB These would also require a plastic mounting piece that would hold the LED on the face of the RDU and not allow it to fall through or out of the unit These will be the least expensive option but the stiff leads may pose problems when mounting them on the PCB If the display and LED array are taller than the panel mount LED the light would have to be lifted off the board With this type of LEDs doing th
108. gn Several different parts were considered for application to this project One company Lumex offered a large variety of LEDs in all colors varying millicandela luminosity ratings and required voltage Unlike other companies they offer samples of most of their products for limited or no charge They had surface mount LEDs in different footprint sizes from 0402 up to 2 5mm x 2mm gull wings This variety makes it easy to find an LED for whichever mechanical design was chosen Lumex only offered three surface mount IR LEDs and has no gull wings Their part numbers were OED CL 23F TR OED EL 23A TR and OED EL1206C160 TR Each had a different forward voltage power dissipation and footprint The LED for this requirement could be chosen when the design was finalized The best options from this manufacturer for the red LED were part numbers SML LXFTO603SRC TR and SML LXFMO603SRC TR which were both 0603 sized Another company was Advanced Photonix This company offered multi LED surface mount components that were designed for use in pulse oximeters Part number PDI E833 contained one forward facing red LED and one reverse facing IR LED This would be extremely helpful for the project since the LEDs were very small and already connected The part was extremely expensive at 27 77 Since a variety of other LEDs were abundant this costly part was not the best choice for this design 24 A third was a company called Kingbright This business offer
109. ground for any transient currents to keep them from interfering with the performance of the device The transient suppression is shown in Figure 27 where the power signals connect to the CC430 Figure 27 Configuration of Transient Suppression 3 3 Receiving Display Unit The main components of the RDU are the antenna circuit the MCU the display the speaker and the power Figure 28 is the Block diagram for the RDU For more information about the MCU the speaker the display power status indicators and antenna see sections 3 1 3 3 1 3 3 2 3 3 3 and 3 4 Transceiver Status Dispi 3 ispla Indicators RS Antenna Speaker Figure 28 Overall block diagram for the RDU 65 3 3 1 Display The display unit consists of a 7 segmented 3 digit LED display The 3 digit display displays the pulse or the SpOz information The pulse and the SpO data is alternating every second This may be slowed down to a couple seconds based on performance and user preference The display is interfaced with the MCU utilizing the Maxim part number MAX6957 The MAX6957 is a general purpose I O expander and LED driver It has 28 individually configurable ports They can be configured as a logic input a common anode LED constant current segment driver The MAX6957 has an SPI compatible 4 wire interface that connects the MCU to the MAX6957 Maxim also makes a part that is capable of interfacing with a 2 wire BC interface The MCU has a built in SPI
110. hat the LEDs are operating according to datasheet specifications Transimpedance Amplifier Test In a light controlled environment measure the output of the transimpedance amplifier Using the red LED connected to a power supply and the photodiode connected to the transimpedance amplifier shine the red LED through a finger with the photodiode on the opposite side of the finger Record the output voltage and determine if the value is safe to use with the AGC circuit Repeat this step holding the LED within 2 of the photodiode simulating the approximate distance 110 it would travel through a finger and determine if the output voltage is safe to use with the AGC circuit Low Pass Filter Test The simple low pass filter that feeds into the inverting input of the differential amplifier is absolutely essential to the operation of this pulse oximeter The purpose of having the differential amplifier is to subtract the DC component of the voltage that comes from the output of the transimpedance amplifier Pulse oximetry is measured by using only the AC component from the output of the photodiode The low pass filter passes all frequency below 0 5Hz where 0 5Hz is the 3 dB level of the filter Test the low pass filter using the LED and photodiode to source the transimpedance amplifier First begin by using the red LED with a constant voltage applied to it Second measure the voltage of the output of the transimpedance amplifier and the output of
111. he amount of light incident upon it The output of a photodiode is current and is often in the range of microamps In order to accurately calculate pulse oximetry data this small current must be converted to values recognized by a microcontroller namely binary values 57 There are multiple steps required to convert the small current to binary values that can be used to correctly determine the percent oxygen saturation level of the hemoglobin and the pulse rate First the current must be converted to a voltage This is needed so that an analog to digital converter can be used The analog to digital converter solves the problem of changing data to a binary format so the microcontroller can perform its calculations Current is converted to a useful voltage by using a transimpedance amplifier A transimpedance amplifier utilizes an operational amplifier to do the current to voltage conversion while amplifying it to a voltage that can be worked with easily Second according to the requirements established by the equations used to determine the attenuation of light caused by oxyhemoglobin the DC component of the signal must be removed Removing the DC component of the signal is done through the use of a simple low pass filter and a differential amplifier The low pass filter is used to strip away the AC value of the signal leaving only the DC component The DC component is then subtracted from the original signal DC amp AC using the differential am
112. he amplifier Switch 2 was the reset switch and should only be closed after the output voltage was read These two switches must be controlled by a timing circuit or a microcontroller so as to maintain a consistent time for integration The IVC102 had a gain bandwidth of 2MHz and a slew rate of 3V us The power supply voltage was from 4 75V to 18V The IVC102 cames in a 6mm x 8 7mm SO 14 package and pulled a quiescent current of 4 5mA The drift voltage with reference to temperature for the IVC 102 was 30uV C 31 2 4 Receiving Display Unit The RDU has a display and LEDs to show the pulse rate and percent oxygen saturation It contains a battery life indicator as well as alarms to alert the user to certain threshold conditions This was the base station and remote monitoring system Most important to this system was its portability and ease of use Thus all components that need to be changed must be easy to reach and the unit must be lightweight and not have many wires The display shows the pulse rate and SpO in an alternating manner This may was done either on a timed loop or on the press of a button It was able to show at least three digits The measurement being displayed was indicated by a reading on the display or a light nearby There also were indicators for the battery on the TSU the backup battery on the RDU two for indicating which measurement was being displayed and for the wireless connection between the two units Ther
113. he battery not at the Op Amp A full discharge and charge should be attempted at this stage Result The battery monitor circuit was tested differently than planned A variable voltage supply was used to apply different voltages to determine if the MCU correctly measured the voltage used to simulate a low battery As the value of the voltage supply s output was reduced the MCU responded by correctly sending battery level to the RDU Test IV DC DC Converter To test the battery with the DC DC converter the battery is connected to the DC DC converter and the battery is drained at the DC DC output while the voltages at the battery and the DC DC output are monitored A full discharge and charge should be attempted at this stage Result The DC DC converter was tested using a variable voltage supply The converter worked according to specification Test V TSU Power System The final subsystem test for power to perform before connecting the battery to a populated board is to connect the battery to a partially populated board The board should have been tested for shorts before this point but should now be tested again The On Off slide switch should also be tested at this point to make sure that the circuit turns off for charging A full discharge and charge should be attempted at this stage 115 At this point the battery is ready to be included in the system Its final test is to run the TSU for a full 8 hour period While this test is
114. he equations the display must be able to show the values for both measurements This can be tested by simply programming the microcontroller with two distinct numbers to be displayed If the display can switch between the two numbers and display them properly then the display is properly connected to the microcontroller and the display driver If the display does not display the numbers properly or does not switch between the two then the part footprints and the connections must be checked This part of the testing also assures that the LED driver is working properly If it is the numbers are shown properly on the seven segment display If it is not no numbers will show or they may be displayed improperly However this could also be caused by an error in coding The LED driver cannot be directly tested as it is only inputs and outputs 120 Finally the display must be able to show the values being computed Whether or not these values are medically significant the display must properly show the numbers from the microcontroller To test this the numbers being computed must be known so the displayed values can be compared This can be tested with or without the TSU Without the TSU the microcontroller must be programmed with certain input values The end numbers can be computed by hand using the same equations programmed into the microcontroller If the value displayed matches that computed then the display is working properly With the TSU t
115. he first test of the TSU battery is to perform the necessary discharges on a simulated load to find the battery life After the discharge tests are recorded the battery life can be estimated The second test is to temporarily connect the battery to an unpopulated PCB and check that the battery can be charged from the charger through the PCB Once this is confirmed the third test can be performed with the battery monitoring circuit The point of the third test is to make sure that minimal current is drawn by the circuit and the output of the Op Amp displays the correctly reduced voltage Another discharge test can be performed at this point to compare the discharge of the battery to the output of the Op Amp s reported voltages The fourth test is to connect the battery to the DC DC Converter and discharge the battery at the 3 3V output The fifth test is to connect both the DC DC converter and the battery monitor circuit Once these tests are completed the battery is ready to 113 be included in the system The final test to be performed with the battery is to run the completed TSU on the battery a full 8 hour use Test l Discharge The point of the discharge test is to discharge the battery on a simulated load through its working voltage range and record the voltage of the battery versus time The simulated load can be calculated with the simple V I R equation The intended current should be run through a power resistor equal to max voltage
116. he unit portable it must not be too large Thus surface mount and through hole alarms are much preferable Since the alarms should be loud enough to sound through the unit so long as a few small holes drilled into the face will allow it Drilling small holes would not take up as much space as an entire panel mount part this is reasonable for the design 43 2 5 Mechanical Design The mechanical design for this project consists of three parts the TSU case the RDU case and the sensor clip The RDU will be a small box that has a three digit display and some LED status indicators as well as an alarm The goal of the RDU is to have a case that is light weight and portable The TSU should be similar to a watch in design The box should be able to be mountable to a strap that can go around the wrist It should also be lightweight not bulky and have an adjustable strap so that anyone can use it The commercial versions of the pulse oximeter come in many different shapes and sizes The sensor unit can be in the form of a clip rubber slide in or just a piece of tape Each of these options will be analyzed The following research provides information about each of the different options for the RDU TSU and sensor clip 2 5 1 Sensor Clip The mechanical design for the sensor may prove difficult The standard design is a finger clip Usually it has a rubbery material on the inside that helps it not slip off the finger as well as protecting the compone
117. he value computed in the microcontroller must be known If the transceiver is working the clip can be attached to a finger and the display should show the medically significant value of the pulse rate and SpO value This ties into the medical comparison section 6 3 3 This is part of the sub system level tests and needs many other sections of the project to be working properly Result The display was tested on a bread board Power was applied to each of the pins and all segments as well as the decimal points worked correctly After installing the display on the RDU board the RDU was programmed so that the 3 digit display counted up from 0 to 999 changing values every second This test was performed and the display performed flawlessly This test showed that the display could change quickly between different values as well as do so as controlled by the MCU 5 2 4 Indicators There are two status indicators on the RDU They indicate whether the display is showing the pulse rate or the SpO 2 These indicators must be tested along with the rest of the unit to ensure that they are working and turning on at the right moment The first step is to test that the LEDs are working This can be done without the project being completed The LEDs must light up when attached to a voltage source that is within its working range If the LEDs do not light up they are not usable for the project If they do then they can be installed into the unit and tested
118. he variables for drop in pulse blood oxygen saturation level low battery life of the TSU and time between receiving transmissions Upon detecting one of the conditions the RDU will sound an alarm that corresponds to the condition that was detected The TSU s main function will check the values of the input ports comparing the current value of blood oxygen saturation level battery life and pulse to the variable stored in memory When the current value and the variable are different an update will be made The main function will also send a packet periodically that contains pulse blood oxygen saturation level and battery life to the RDU 51 The previous two possibilities are based on a MCU with an integrated transceiver The project currently is leaning toward using that approach For sake of completeness this possibility and the next will explain how the software in the MCU will communicate with an outside transceiver transmitter or receiver Possibility 3 The receiver transceiver will fire an external interrupt on the MCU when it receives the packet The MCU will read the input ports and get the packet The data from the input ports are read and the variables for the values of battery life blood oxygen saturation level and pulse are updated The RDU will also have an update display function that will be called every couple clock cycles The update display function will update the display and status indicators with the correct value
119. hem from interfering with the performance of the device 38 RDU Battery Life Monitoring The expected remaining battery life is estimated by using an operational amplifier connected to an analog to digital converter and having the expected battery life recorded for comparison in the microcontroller This is accomplished by connecting the battery to a voltage divider connected to the positive terminal of a non inverting unity gain operational amplifier An example of this circuit is shown in Figure 14 The resistor values are large in the ten to hundred thousands such that the voltage are divided by an amount that makes the output of the operation amplifier capable of being connected directly to the microcontroller on an ADC input The battery is drained at the rate the system would dissipate the charge to determine the status of the battery As the battery is being drained the voltages are recorded as time progresses to give the battery life for this specific design Figure 14 Battery Life Sense with Op Amp An alternative method is to use choose a chip that triggers when the battery reaches a key voltage An example of this type of chip is the Texas Instruments TPS3808 The TSP3808s are a family of microprocessor supervisor chips that monitor system voltages and can generate a reset signal when the voltage drops below a preset voltage or if the manual reset pin is driven low The reset remains low until the adjustable delay time has o
120. his should not be counted on however and though it may limit the design it is important that proper parts be chosen Other issues that may arise include the possibility of overheating In order to test the system the batteries in both units will have to be drained This is the only way to get an accurate battery life measurement This means running the units 106 for several hours and watching as the battery voltage drops Running the units for such a long time may cause them to overheat Overheating presents many problems Components can be damaged and need to be replaced the PCB can melt or burn the batteries could go bad and the units could potentially catch fire This can also happen if there are shorts between components or nets or if a very high voltage or current is applied to the circuitry The units should be monitored carefully for changes in temperature voltage and current measurements within the PCB as well as ensuring the power supplies are in proper working order before turning them on The wires on the unit may also cause issues If a wire has a break it will not properly carry voltage or current This can cause the unit to not work or might cause inaccurate pulse and SpO 2 measures Great care must be taken with the wires since they are easy to break but are critical to the unit In the event that a wire is broken it may take a lot of testing to find out precisely which wire it is that is having an issue Broken wires tha
121. hold condition is reached A series of shorter beeps will emit when the RDU loses signal from the TSU When the TSU battery has only thirty minutes of power left the RDU will emit a short beep once every minute The speaker must be loud enough to be heard by the user but since the unit is portable it does not need to be loud enough to be heard outside of the room it is in The human ear is generally said to be able to hear any frequency between 20Hz and 20kHz though there is a considerable variation between individuals Higher frequencies tend to be shriller and generally thought to get attention quicker Thus the frequency of the alarm should be between 3kHz and 5kHz This will make the alarm within a range that most can hear and be of a high enough frequency to draw attention quickly Sound pressure is also an important consideration Since the alarms must be heard the sound pressure must be of a certain decibel dB level in order to be noticeable The sound pressure is determined by not only how loud something is but how far a person is away from it when the sound is heard The lowest decibel level the human ear can hear under normal conditions is approximately 10dB Loud voices come in at 70dB For reference when a person is 10m from a motorcycle they will hear it at 88dB Inside a subway the train is heard at 94dB The threshold for hearing noises comfortably is at 100dB and a person will go deaf around 120dB 2m from an amplifier play
122. hould all be set firmly into the face of the RDU This assures that they are always be visible and will not fall into or out of the unit Any of the parts mounted to the inside of the units such as the batteries battery holders and the PCBs should be firmly attached These components and parts should not wiggle or be loose All wires should be checked for frays and none should be strained or stretched When this is complete the entire system can be tested Result The sub system level test was performed in parallel with the other tests due to time constraints Both the TSU and RDU work correctly on their own 5 5 System Level The system level test consists of the typical operations of this project by the user Tests include going out of range low power of the RDU backup battery low power of the TSU battery dangerous conditions occurring and displaying the data to the user The following scenario shows the general operation of the product Similar scenarios can be enacted to ensure that the units perform according to their specifications The user places the TSU onto their elderly parent The user then goes into another room to watch TV The user places the RDU on the table next to them plugs it into the wall and turns it on The unit should show that it is receiving signal through the LED indicator Upon receiving data the RDU should update the LED array to show the current battery life of the TSU The RDU should also be alternating be
123. hould be recorded at the battery battery monitor DC DC converter and the switch Test VI RDU Battery System The last test to perform on the battery power system before the battery is ready for the RDU system is to connect the automatic backup switch into the previous circuit between the battery and the switch Discharging is attempted at this stage to make certain the correct voltages and currents are available at the DC DC converter when the system is powered by the battery The next test is covered in the Primary Power test section After that test the battery is ready to be included in the system Its final test is to run the RDU on the battery for a full 8 hour period While this test is being performed the current out of the battery should be monitored If the current is found to be abnormally large or small the board should be checked to make sure all of the connections are correct If the current drain of the circuit is simply more than what was estimate the battery tests should be repeated at the circuits accurate discharge rate 119 Result The battery backup system has been removed from the RDU Though all tests showed the battery monitoring circuit and the automatic switch as working no further tests were performed 5 2 3 Display The display is tested in three ways It must have all its segments working and be able to display numbers The display must be able to switch between two numbers so it can display both the puls
124. icates registrations and technical data must be kept readily available for inspection by the FCC Since under section 15 23 no registration or authorization is required due to low quantity the TSU and RDU was exempt from this requirement 2 2 Processing Unit Microcontroller vs FPGA FPGAs and microcontrollers MCUs were two possible options for the processing unit of this project Both were capable of being programmed to perform the actions necessary for calculating SpO2 and pulse rate running the LEDs and transmitting and receiving data The included abilities programming language and size were what separate the two for this design An FPGA contains many features They were able to create any logic function and could be interfaced with other FPGAs to solve complex combinatorial mathematic problems FPGAs were programmed using hardware description languages HDLs which program logic functions into an executable file that the FPGA could read The HDL file was generally based off a higher level program s mathematical model such as those created in MATLAB FPGAs were designed to be programmed by the user in the field making them extremely easy to debug They could also be programmed to prevent any more modifications making them desirable in marketable products FPGAs were generally their own PCBs and may be large 12 MCUs contained some similar features to FPGAs but also offered other options Rather than an HDL MCUs could be prog
125. ication of 2 beats per minute after 30 seconds of use Since the MCU should ideally have a faster processing speed this time would be shorter but within the current operating conditions a minimum of 30 seconds is needed to determine a correct heart rate 5 4 Sub System Level Before the entire project can be tested each unit must be checked The TSU and RDU must be able to run separately before they can work together Throughout the testing different aspects of each unit were tested separately Each unit as a whole must now be tested The TSU is tested first This test should start at the battery The battery should be outputting the proper voltage when measured with a multimeter If the battery is low it should be recharged For more information on the battery see section 5 1 1 Next the voltage should be measured on the other side of the voltage converter This may be best done with an oscilloscope to assure that it is a DC signal with no voltage noise The oscilloscope should show a flat line at the 131 battery s voltage value If the battery and voltage control circuitry is in working order the next step is to test the MCU and the sensor To test the MCU on this unit the number that is going to be transmitted must be known The value can be printed to a computer screen for testing purposes No changes to the preexisting code should be made at all That is the code should still transmit the number but more code can be added to in
126. ing rock music if the sound pressure is maintained for too long At 150dB even a short exposure will cause hearing loss There is no real limitation on voltage range of the alarms except the limitations of the battery Resistors can be placed between the MCU output which controls the sound and the alarm itself to limit the voltage going into the buzzer Additionally the alarms do not need to be preprogrammed to be capable of more than one sound Buzzers and alarms can be found in continuous intermittent or pulsing tones or any combination The MCU can control this through software By turning the output on and off the MCU can make even an alarm with only continuous tones into an intermittent buzzer This widens the search to include all buzzers and alarms not just those capable of the sounds necessary Having many options is key for projects because the design will limit the voltage output and it is better to have fewer constraints at the start If the MCU has an internal clock any pulsing or intermittent tone can be created by programming an on off time interval for the pin that controls the alarm If there is no internal clock external components can create this effect or the software can be programmed with a number of holds instead of a set time interval For more information on the MCU see sections 2 2 and 3 1 Additional information on software can be found in sections 2 7 and 3 6 42 Once again DigiKey is the best place to start th
127. is may cause the stiff leads to snap off the board Other panel mount LEDs have shorter leads and come with pre attached wires to attach to the PCB Some of these types also have their plastic mounting piece already assembled as well The parts can become costly but will save a lot of time during assembly Lumex offers panel mount LEDs in a variety of sizes The size best suited for this unit are small but easily visible 3mm or 5mm The company offers front and rear inserted panel mount LEDs completed with plastic or metal mounting parts All are offered with optional insulated wire lead lengths As previously mentioned the company is preferred because of the ability to obtain samples DigiKey is a very good source for less specialized LEDs like those needed for this unit Their LED category contains nearly 800 LEDs in orange yellow blue and green red parts They come from many companies such as Chicago Miniature Lighting Kingbright Vishay Fairchild among many others The LEDs come in a variety of sizes mounts and with or without wire leads DigiKey s search tools allow the multitude of LEDs available to be narrowed by color s and or wavelength s size mounting type millicandela luminosity rating lens style or color package size forward voltage and other measurements This allows the LEDs to be specifically chosen based on the parameters of the design Because there are so many options Digikey helps narrow down an overwhelming s
128. ith the sampled parts removed to create one of each and the amount required by the sponsor 7 2 Milestones The milestones for this project are set according to the importance of the task More important tasks warrant more time spent completing that section of the project The milestones for this project are designed to maximize time researching to ensure that the finished design has the best possible circuitry as well as time prototyping and testing to allow the product to be perfected before it is finalized This section outlines the milestones of the project as well as delineates tasks to be completed in the weeks spanning the project development The first four weeks are spent analyzing and researching The analysis should incorporate viewing existing products and creating a set of objectives These objectives set the direction of the entire design The analysis should continue until the group approves of the objectives and they are consistent with the motivation of the project The research can begin after the objectives are set It should continue until the group feels that they have a working knowledge of the intricacies of the project goals and how to accomplish them Research should be conducted on every aspect of the project should be thorough and should provide multiple alternatives Following this the design begins and continues for seven weeks until the documentation is due The research need not be completed when the design start
129. itry of the design Finally the circuit boards were fabricated the board populated with components and testing commenced The goals of this project were simple but important and achieving these objectives resulted in an exceptional overall product The finalized design for this project achieved accurate measurements effective transmission and extensive 1 safety protocols This assured that the design achieved its objective to be safe and secure giving its users peace of mind and comfort 1 2 Motivation The motivation for this project was the desire to monitor the health of infants It was widely believed that when an infant dies of Sudden Infant Death Syndrome SIDS the death could be prevented if the pulse rate or oxygen saturation was closely observed The exact cause of SIDS is unknown but any measure that can be taken to prevent it will be useful and comforting Since infants cannot help themselves or explain how they are feeling external sensors will be useful to diagnose a variety of medical conditions and prevent others Pulse oximetry can be used to keep track of other conditions as well People with seizure disorders Sleep Apnea breathing difficulties or irregular heartbeats can use constant wear pulse oximeters to help monitor their condition Also many athletes use them to record their pulse rates while exercising Most hospital and commercial pulse oximeters are bulky and unwieldy The monitoring equipment and their at
130. ive than the alternatives of the same height and width parameters An alphanumerical LCD displays show most printed ASCII characters Alphanumerical LCD displays were less expensive than the graphical LCD display but do not show graphics LCDs have the ability to display more information than the 7 segmented and the 14 segmented display However it cannot be interfaced with a multiplexer like the 7 segmented or 14 segmented display LCD displays require a LCD driver IC when interfacing with a MCU and had very low power consumption If selected the part LCM 12232GSF from the manufacturer Lumex could be used 33 OLED The organic light emitting diode OLED displays were fairly new technology This technology had many benefits over the other types of displays compared here It had extremely low power consumption They were brighter thinner lighter more flexible and have large fields of view This technology was not as developed as the other display types and thus isn t cost effective for this project at this time Comparison Table 2 below summarizes the above descriptions The LEDs were inexpensive and easy to interface whereas the LCDs were more expensive came in much smaller character sizes and required an LCD driver to interface The typical LEDs 0 56 7 segment displays cost about 2 and similarly a 0 56 14 segment display cost about 5 The numerical LCD counter part of the 0 56 LED start at about 20 and going upward bas
131. k Keeping proper documentation means that a viable second option is not difficult to design This keeps the design process running smoothly and allow the testing and prototyping phases to flow as well When the design process is completed the schematic diagrams PCB layouts and test plans should be completed The next stage in the project is to order the parts have the PCBs fabricated and begin to populate the PCBs Depending on component lead times and PCB turn around time it could potentially take a while for everything to be delivered To account for this two weeks is allotted for waiting for these parts In the case that the parts are all delivered sooner than this the extra time can be shifted to testing During this time while the parts are arriving the software is written This ensures that at least one goal is being worked on at all times It also makes certain that while the PCBs are being populated the software is ready for testing This also means that when the PCBs are finished the software coding is completed Having these two events coincide eliminates delays and allow for the PCBs and code to be tested together The TSU and RDU build continues through testing as does the software coding Any significant changes made to the PCBs require a rebuild and may require the software to be recoded too The TSU is built first followed by the RDU Some of the tests can be completed without both units populated If issues were to arise i
132. k converter with integrated inductor PWM controller and MOSFETs in a small 3mm x 3mm QFN package This chip operated at a switching frequency of 4MHz which made it ideal for noise sensitive RF applications as well as area constrained applications like the TSU The EP5368QI could be powered by a 2 4V to 5 5V input and the output had a low ripple voltage of 4mV peak to peak The output voltage could be set via a 3 pin VID selector and there were seven programmed output voltages The output voltage could also be set by connecting the selection pins to Vin and using an external voltage divider at Vout and the provided equation Ra 200kQ Rp 1 206x10 Vour 0 603 This device regularly outputs at 600mA but could be set to output at 700mA if needed The EP5368QI required only two external capacitors for operation The cost for this component was less than 2 Figure 8 was the diagram of the typical application circuit ENABLE Vsense Vin P Your o Vin Vout Fee 4 7uF 22uF ped EP5368QI d VM E E e Voltage Vex Select Ju SR Figure 8 Enpirion EP5368QI Typical Application Circuit Reprinted with permission from Enpirion Inc Section 8 page II Another option was to use the ON Semiconductor NCP1530 PWM PFM step down converter Like the EP5368QI this chip generated a supply current of 600mA and could be powered in a low voltage range 2 8V to 5V for the NCP1530 The NCP1530 was specifically designed be used in systems that
133. l is turned off and on in a quick succession LEDs LEDs are used to give visual indications for the various statuses that are reported to the user The LEDs are configured with their anode tied to the microcontroller at one of its GPIOs and the cathode is tied to ground The signal indicator is a single Lumex SSI RM3091SOD 150 2V orange panel mount LED that is controlled for the following parameters the LED is lit on for good signal and the 71 LED blinks when there is a loss of signal This orange LED is tied to pin 21 port 3 0 The cost of this orange LED is 2 49 Two of Chicago Miniature Lighting s 5100H7 2 1V yellow panel mount LEDs are used to display whether the information on the 7 segment display is Blood oxygen level or the pulse These yellow LEDs are tied to pin 20 port 3 1 and pin 19 port 3 2 The cost of these yellow LEDs is 1 33 apiece The Lumex SSA LXB425SUGD is an array of four green LEDs that is used to display the battery status of the TSU in a percentage form in groups of twenty five percent i e 25 50 75 and 100 This array of green LEDs is controlled by the same LED Driver chip that is used for the 7 segment display and as such will not need to be connected to the microcontroller directly The Dialight 558 3001 007F LED is a bi colored 2 1V green and 2V red panel mount LED that displays the status of the RDU backup battery Green indicates that the battery status is good and red indicates that the battery ne
134. l LED shows that the primary power source is connected Figure 35 Configuration of Transient Suppression Speaker There is also a speaker that gives audible alerts for dangerous conditions as well as warnings for loss of signal and very low power The dangerous conditions audible alarm is a constant long beep that will continue until the condition changes or the TSU is powered off and back on again The loss of signal alarm is triggered whenever the RDU has failed to receive new information for the patient after a required time limit and is a series of beeps The low power alarm given when the TSU has less than 30 minutes of operation is a single warning beep occurring once a minute The PUI Audio SMT 0540 T 6 R is a small 5mm x 5mm x 2mm surface mount speaker that is used for the audible alarms This speaker is rated for 100mA 3V peak to peak and is powered in the range of 2 to 4V peak to peak The SMT 0540 T 6 R is set at 4000 500 Hz and the sound pressure level at 10 cm distance is 78dBA The cost of this speaker is about 3 The speaker is controlled by generating a PWM signal at pin 24 port 2 6 on the MSP430 This signal is fed into a small low pass filtering circuit and then connected to the surface mount speaker This circuit is shown below in figure 36 The low pass filter designed with a corner frequency near 3 7kHz The tone of the speaker is related to the duty cycle of the PWM signal To generate beeps the PWM signa
135. lans begin on time as being unable to finish the tests could render the project unusable The start of each task should always start on 4 or before its scheduled date but may not end when the next step begins Ina sense the milestone is a flow chart They are a guide to indicate how the project s construction progresses 7 3 Project Summary and Conclusions Pulse oximetry The TSU measures the percent oxygenation of blood and heart rate and then transmits the data to the RDU to be displayed This is accomplished by measuring the attenuation of light as it passes through the body Oxygenated hemoglobin and reduced hemoglobin the red substance in blood are measured to determine the oxygenation of blood These two forms of hemoglobin attenuate different wavelengths of light than other tissues in the body Therefore red and infrared LEDs are shone through a finger or other peripheral body part The attenuation of these two wavelengths of light is measured through the use of a photodiode MCU Antenna A combination microcontroller transceiver chip is used to control all of the circuitry in the two systems pulse oximetry sensing battery monitoring data transmission information display and status indication The transceiver part of the MCU is connected to a chip antenna to transmit the pulse oximeter data alarm status and battery status between the systems Transmitting Sensor Unit The photodiode used to measure the red and infrared
136. leaning but is only useful if the parts are inexpensive enough to make many sensors This could also necessitate using more than one sensor per day as sweat hand washing and daily activity could weaken the adhesive on the tape and cause it to slide off the finger This is the least expensive mechanical design but the money saved may be spent on gathering the parts necessary to make many of these sensor types This design also presents the possibility of constricting the blood flow if improperly applied 44 A fourth option is to use two finger cots to make a water proof but disposable sensor This can be created by sliding a finger cot over a finger or model of a finger gluing the LEDs and photodiode to the outside and then sliding another finger cot on top The wire leads would trail out the end but the sensor would remain water proof This is another inexpensive alternative to fabricating a hard plastic clip This design as well as the previous two could cause the finger to be constricted To combat this the finger cots can be pre stretched using a larger model finger However this may present another issue If the finger cot is stretched too far the readings will be inaccurate while the finger cot slips and rotates around the finger Also it may no longer be waterproof if the finger cots slip along each other Many components would be necessary for this concept and may drive up the cost of an otherwise inexpensive design The LEDs may h
137. lights has a current output in the order of microamps In order to calculate the pulse oximetry data and transmit these values wirelessly to the RDU this current must be converted to a binary number values understood by a microcontroller This is done through the use of an operational amplifier configured to be used as a transimpedance amplifier or a current to voltage converter a low pas filter a differential amplifier and an ADC The transimpedance amplifier is connected to the output of the photodiode and changes the current output to a voltage while amplifying it to a value on the order of volts Due to the fact that there is always blood in the arteries and that it ebbs and flows according to the beating of the heart pulse oximetry data is measured using the AC component of the measured light The DC component represents the amount of arterial and venous blood that is always present while the AC component represents the change in volume of blood Therefore the DC component must be subtracted from the signal The differential amplifier subtracts the DC component of the signal which was obtained through the use of a low pass filter and outputs only the AC component of the signal This AC component of the signal is then passed to one of the ADC inputs on the microcontroller In order to correctly calculate pulse oximetry after subtracting the DC component of the output signal the DC component must be kept at the same value This is achieved by co
138. ll and compact but not designed for long periods of use and can only be monitored closely by the person wearing the unit Generally the unit contains a wrist unit to display the information and a finger sensor These types of units are also helpful in aviation High altitudes mean thinner air and less oxygen Some aviators such as those piloting fighter jets emergency transports or participating in an air show may also need to monitor their pulse rate Exciting or nerve wracking jobs such as these could cause elevated heart rates and diminished oxygen saturation If a pilot loses control because of a pulse oximetry issue the results can be disastrous Monitoring this data can keep a pilot from crashing or causing other dangers One such product was the Southeastern Medical Supply CMS 50F This unit contained a fingertip sensor with a short wire to a wrist unit that displays the measurement data It had built in alarms an OLED display and 3 a built in rechargeable lithium ion battery This unit cost was almost 500 and does not offer a remote monitoring solution There were also pulse oximeters that consisted of only a finger clip sensor with a screen built in These products were useful if pulse oximetry data only needs to be checked at certain times Since the screen was attached these units were truly wireless as they have no connections to any other unit and were completely self contained They could be unwieldy since an integrated screen m
139. losure Metal is not a very useful product when it comes to cases for this project The reason is that metal conducts electricity which causes noise for other parts Metal also requires the box to be cut using special tools not like wood or plastic In addition audible alerts from an internal speaker would be very difficult to hear if a metal case was used Conclusions The metal case will not be used because of reasons stated above Wood is also inexpensive but it would cause the RDU to look unprofessional The primary drawback to wood is the inability to sanitize the surface Wood and plastic will both require tools to adapt the case properly to the projects desired appearance Wood requires knowledge of properly assembling and creating a box of the correct dimensions whereas with plastic a box of proper dimensions can be purchased and only mounting of parts is required Plastic is inexpensive and can be purchased online Therefore a plastic case will be utilized for the RDU Figure 16 shows a prototype of the RDU utilizing a plastic case The five LEDs on the top of the face are status indicators for the battery life of the TSU that is broadcasting nearby The antenna is on top at a 90 degree angle with the box The display is in the center of the RDU with the status indicators to the left showing what information is currently being displayed The speaker will be mounted such that the sound can be heard as far away as possible SPO O
140. m to see the maximum throughput that can be used and to see the response time These tests are broken into two parts tests for the TSU and tests for the RDU TSU Transmission Tests To adequately test the TSU an external packet sniffer is needed The RDU cannot be used to prove that the error could not possibly be on the RDU reception side of things For more information on the TSU and RDU software see section 3 6 For more information on the TSU see section 3 2 For more information on the RF used see section 3 4 Unit Test 1 The software is configured to construct a packet with stub data and send it as if it was sending it to the RDU An external packet sniffer reads this packet The packet is decoded and compared with the stub data that was sent Upon detecting there is a problem with the TSU packet sending ability rerun the software unit tests for the TSU If the problem persists there may be something wrong with the radio core in the chip itself and the chip may need to be replaced 127 Unit Test 2 This test is a throughput test The software is configured to construct a packet with stub data and send it as if it was sending it to the RDU An external packet sniffer reads this packet The packet is decoded and compared with the stub data that was sent The software slowly speeds up the rate of transmission to see how fast the stub data can be sent and successfully decoded before the data becomes corrupt Unit Test 3 This test
141. mall or have very complex traces multiple layers and blind or buried vias By using Altium Designer to do the PCB layout and routing the various forms of the needed Gerber files can be generated Unfortunately having the PCB fabricated would require a longer amount of time for the boards to be made and the process would cost substantially more There is always the possibility that the boards could come back from the fabricator and have hard shorts or other flaws but there is just as much if not more risk in self fabrication For estimating the TSU will be considered to be roughly 1 x1 5 and the RDU to be 1 5 x 2 PCBFabExpress offers a two layer Bare Bones PCB special There would be no solder mask and no legend for these PCBs and there is a minimum order quantity of four boards The boards themselves will be about 60mils thick have a minimum trace width of 6mils and a minimum hole size of 15mils Another requirement is the PCBs should only have plated holes and no more than 25 holes per square inch The cost for this option is a 40 lot charge plus 0 60 per square inch At these prices there would be four TSUs at 43 60 and four RDUs at 47 20 This would give one extra TSU and two extra RDUs but would be almost twenty percent of the project budget The offset to the price is that there is 5 day turn around so the boards would be made fairly quickly PCBFabExpress standard 2 layer 10 day turn around service with only the
142. mation of third parties may be subject to additional restrictions Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice TI is not responsible or liable for any such statements TI products are not authorized for use in safety critical applications such as life support where a failure of the TI product would reasonably be expected to cause severe personal injury or death unless officers of the parties have executed an agreement specifically governing such use Buyers represent that they have all necessary expertise in the safety and regulatory ramifications of their applications and acknowledge and agree that they are solely responsible for all legal regulatory and safety related requirements concerning their products and any use of Tl products in such safety critical applications notwithstanding any applications related information or support that may be provided by TI Further Buyers must fully indemnify TI and its representatives against any damages arising out of the use of TI products in such safety critical applications TI products are neither designed nor intended for use in military aerospace applications or environments unless the TI products are specifically designated by TI as military grade or enhanced plastic Only products d
143. ments After the transmission tests See section 5 3 3 are finished the sensor clip is connected to a finger The MCU on the TSU performs the computations of SpO This means that the data being sent to the RDU is simple numbers From this two tests can be performed First the transmission of a calculated value can be tested The TSU sends a computed number to the RDU The input values can be hard coded into the MCU on the TSU instead of being read from 129 the photodiode The MCU on the RDU receives the information and display it on the unit s display If the display matches the number computed in the TSU then the transmission of the calculated value is working properly This can happen even if the number is not medically relevant or accurate When the TSU and RDU are showing the same number the equation must then be checked The test for medical relevancy can be accomplished by placing a sensor from a hospital pulse oximeter on one hand and this project s sensor on the other the values can be compared The sensor must have 2 accuracy in either direction However the hospital s sensor has a similar tolerance The project must match the hospital sensor to near perfect since any errors are compounded If the numbers do not match the software programming must be checked to assure that the equation is properly coded If the equation is correct the hospital pulse oximeter and the project display will show the same number If the eq
144. mitted from the TSU the RDU also switches This may require knowing the output from the MCU inside the TSU and that the display is working properly This assures that the signal the TSU is sending is being properly interpreted by the RDU as in transmitting the pulse rate value from the TSU results in the RDU receiving a pulse rate value and not a SpO value When this is verified the indicator lights are known to be working properly Result All of the LEDs were checked with the correct resistor value determined by the current requirement of the LED and were confirmed to be working In the system the LEDs were very dim if on at all It was determined that using the corresponding MCU pin as the source for the LED would not be the best way to apply power to the LEDs A new circuit was developed that connected the base of a BJT to the MCU pin so as to act as a control line The output of the voltage regulator was used as the power source This implementation provided a good solution to the problem of dimly lit LEDs This solution proved to work well but due to current limitations and space constraints the LED status indicators are not installed on the RDU The RDU draws 350mA to power the DC DC converter the MCU the LED battery power indicator and the display so it was determined that the status indicator LEDs would be removed These status indicator LEDs drew approximately 75mA To build this new LED control circuit another small board was us
145. n be tested This also assures that the chosen pulses still emit the proper sound from the buzzer If the sound is not right the MCU can be reprogrammed with new pulses This guarantees that the RDU emits the proper sound and no alarms are too obscure to understand their warning After the TSU and RDU are properly transmitting and receiving the alarms must be tested again The software in the TSU can send the signal of a danger condition and a low battery condition by being programmed with the information directly This assures that the alarms sound at the proper time and with the proper sound If the sounds are mixed or not present the RDU software must be checked By shutting off the TSU the alarm for loss of signal can also be tested This test does not require any sensor input The final test is to use the sensor clip to create danger conditions When the sensor clip is being worn by a group member the alarm should not sound By removing the sensor clip a danger condition can be simulated This assures that the measurements being sent to the RDU are accurate and that the threshold levels are set properly If the buzzer sounds with the proper noise the final test is to check the battery alarm If it does not sound software on both units must be checked The TSU battery should also be drained to test the battery low alarm If the proper buzzer sound is emitted then the tests are complete and the alarms are working properly and safely If the al
146. n testing parts of the TSU that are also present in the RDU the changes can be made to the RDU before even one board has been fully populated This practice keeps from driving up the cost of the project by preventing component losses and assuring that the PCBs are not wasted The final few weeks of the project are spent working on the final documentation and completing higher level tests These include the transmission sub system and system level tests These final checks require that both units be working simultaneously and that most of the coding is proper This is the final part of the project Once the system level tests are completed and everything is deemed to be in working order the final documentation is completed The milestones of this project are general guidelines They do not require the amount of time that should be spent on each task If something is finished early the rest of the time is allotted to other important aspects If one phase is completed it can still be revisited The milestones are general guidelines to show how the project should progress Many of the deadlines are concrete such as documentation due dates presentations and project completion The milestones present a flow of the project and indicate approximately when each stage should start The only tasks that are expected to require as much time as they have been given are tests on both units and the software Great care should be taken to assure that the testing p
147. n the chip itself and the chip may need to be replaced Unit Test 2 This test is a throughput test The packet sender is programmed with the correct stub packet The packet sender transmits the packet to the RDU The packet sender slowly speeds up the rate of transmission to see how fast the stub data can be sent and successfully decoded before the data becomes corrupt This may causes unexpected results in the RDU Upon detecting erroneous results in the RDU display software the way the RDU is updating the display may have to be updated for the faster transmission rate Unit Test 3 This test assesses the ability to receive data in a typical environment for this project The equipment is brought into a house with a wireless router several 128 mobile phones wireless home phone microwave Bluetooth enabled computers and at least 3 rooms that can be traveled between Turn on the RDU then travel to a distance of 10 ft away from the unit with the packet sender Upon receiving a correct signal progress another 10 ft up to a maximum of 150 ft away traveling throughout the house and into different rooms When the signal grows weak and the packet degrades the RDUs alarm should go off Upon the alarm going off the maximum reception distance in a typical environment has been found If the alarm does not go off rerun the software unit tests for the RDU Result Transmission worked from the TSU to the RDU and correctly displayed heart rate
148. nal from the sensor unit e Update all status indicators and oximetry data at a minimum of once every second e Be able use a battery if no alternating current is supplied e Be able to operate on battery power for a minimum of eight hours one use e Have an alarm system that utilizes sound and lights to alert the operator that the pulse oximetry levels have reached dangerous levels Section 2 Research 2 1 Wireless Applications The United States government and other countries regulated what can be transmitted through the air Whether it was radio waves or more generally microwaves the US government separated the responsibility of allocation of the electromagnetic spectrum into two divisions first the Federal Communications Commission FCC and second the National Telecommunications and Information Administration NTIA The FCC regulated the allocation of the radio spectrum for non federal use such as state local government commercial private and personal use The NTIA regulated the allocation for federal use such as the Army the Federal Aviation Agency and the Federal Bureau of Investigation Since this wireless application was for non federal purposes the FCC was the governing body allowing the project to transmit data with a radio wave The FCC bands designated for personal private and commercial applications are the Industrial Scientific and Medical ISM bands The research that follows looked into all of the different communi
149. nchronous SPI UART and IrDA Serial onboard programming Freely available sample code and user manuals DMA controller Supply voltage monitor O O 5 n The sizes were large for the TSU e More Power consumption than other MSP430s 2 2 2 Transceiver CC1101 The CC1101 was a low cost sub 1 GHz transceiver designed for very low power wireless applications The chip was mainly intended for the ISM and SRD frequency bands at 315 433 868 and 915MHz but could easily be programmed for operation at other frequencies in the 300 348MHz 387 464MHz and 779 928MHz bands The RF transceiver was integrated with a highly configurable baseband modem The modem supports various modulation formats and had a configurable data rate up to 500kBaud The CC1101 provided extensive hardware support for packet handling with a max packet error of 1 data buffering burst transmissions clear channel assessment link quality indication and wake on radio functionality for automatic low power Rx polling and automatic CRC handling Also 2 FSK GFSK MSK OOK and ASK were supported The main operating parameters and the 64 byte transmit receive FIFOs of CC1101 could be controlled via an SPI interface The CC1101 was available in a 4mm x 4mm QFN package with 20 pins as shown below in Figure 3 16 GND DGUARD 2RBIAS GND Ra 20 SCLK 1 15 AVDD SO GDO1 2 14 AVDD GDO2 3 13 RF_N DVDD 4 12 RF_P DCOUPL 5 11 AVDD GND 6 78 9 10 r i oo X Exposed die O
150. ncy synthesizer to the received center frequency Support for asynchronous and synchronous serial receive transmit mode for backwards compatibility with existing radio communication protocols Needed external components in order to function 17 CC2520 The CC2520 was a 2 4 GHz transceiver that operates using the ZigBee standard IEEE 802 15 4 It used very low power for transmission While receiving the CC2520 used 18 5mA It had a programmable output up to 5dBm While transmitting at 5dBm the CC2520 used 33 6mA and used only 25 8mA transmitting at OdBm This chip had an output data rate of 250kbps The chip used CSMA CA to assess the clarity of a channel in order to avoid transmitting data in a noisy environment The MCU automatically added a CRC This chip had only 768 bytes of RAM onboard The CC2520 had a 4 wire SPI port to enable serial communication with other devices Six GPIOs were included for any other functions that may need to be preformed Also included in this chip were a random number generator and an interrupt generator This chip did not have an internal ADC or DAC The CC2520 came in a very small package The chip was 5mm x 5mm and came in a standard 28 pin QFN package as shown below in Figure 4 It had an extended operating temperature range of 40 to 125 C It could operate on a very low voltage power supply ranging from 1 8V to 3 8V O 1 2 3 4 5 6 7 oo d 8588058 AGND S acd exposed 58552 Z attached pad
151. ndicate the statuses of the TSU battery the RDU battery and whether or not there is a signal from the TSU The RDU shall update all status indicators and pulse oximetry data at a minimum of once very second The RDU shall be able to operate on battery power for a minimum of eight hours The eight hour period is considered one use cycle The RDU shall have an alarm system comprised of lights and sounds that alert the operator that pulse oximetry levels have reached dangerous levels The receiving unit may use sound to alert the operator if battery statuses are low The Wireless Pulse Oximeter shall e Measure percent oxygenation of the blood and pulse rate e Have sensor and receiving units TSU and RDU operate together wirelessly at a distance of 100 ft Transmitting Sensor Unit TSU shall e Send pulse oximetry data and battery life to the receiving unit wirelessly Send data to the RDU at a minimum of once every second Be able to operate for a minimum of eight hours one use Sample oximetry measurements at a minimum of once every 400 ms Poll battery status at a minimum of every 10 minutes Have an accuracy of 2 70 100 Adult Pediatric 3 70 100 Neonatal for SoO2 2 BPM for pulse Receiving Display Unit RDU shall e Display the pulse oximetry data of the patient e Be able to display a 3 digit number e Be able to indicate the statuses of the sensor unit s battery the receiving unit s battery and if there is a sig
152. ned but was an overall better option for those on a limited income as might happen when a patient is on disability for the illness that necessitates pulse oximetry monitoring The prototype designed for this project cost was under 500 to make which lead to a production cost of around 200 and allowed remote monitoring from up to one hundred feet away This set it apart from other products available on the general market Hopefully this design sets a new standard and helps many people find affordable and comfortable long term use pulse oximeter units 1 4 Project Specifications The wireless pulse oximeter shall measure the heart rate and percent oxygen saturation of the blood and then transmit data to its display unit The two units of the pulse oximeter the Transmitting Sensor Unit TSU and Receiving Data Unit RDU shall be able to operate together wirelessly at a minimum distance of 100 ft The transmitting unit the TSU shall have an accuracy of 2 SpO 70 100 oxygenation for adults and children and 3 70 100 oxygenation for neonatal patients The TSU shall have an accuracy of 2 BPM for pulse The TSU shall sample data at least once every 400ms and shall poll battery status at 4 least once every 10 minutes Data shall be sent to the RDU at a minimum of once every second The RDU shall display the pulse oximetry data of the patient A 3 digit number shall be able to be displayed on the RDU The RDU shall be able to i
153. ng point connected to the positive terminal of a non inverting unity gain operational amplifier The configuration for the operational amplifier is shown in Figure 24 using a Linear Tech LT6004 The max voltage of the battery is 4 2V which is just over the max voltage that can be applied to the pins of the CC430 The values of the resistors are chosen such that the voltage is reduced by half so that the output of the operation amplifier is capable of being connected directly to the microcontroller on an ADC input This value can then be compared to values at the 25 increments of the battery life reduced by the same amount in the software Figure 24 Battery Life Monitoring Power Switch The TSU uses an OS102011MA1QS1 On On slide switch to turn the system on and off This switch is configured with the first pin connected to the battery 63 voltage and the second pin connected to the voltage in the DC DC converter The third pin is left floating This way if the switch is in the one two position the system is on and when the switch is in the two three position the system is off DC DC Conversion The Enpirion EP5368QI is used for voltage regulation of the TSU The EP5368QI is a complete system on chip synchronous buck converter with integrated inductor PWM controller MOSFETS and Compensation in a small 3x3mm QFN package This chip is ideal for noise sensitive RF as well as area constrained applications like that of the TSU The EP5368QI c
154. ng pulse oximetry data The wrist piece held the processing unit and power source It obtained data from the finger clip calculated the medical values and wirelessly transmitted to the base The base unit displayed the value and contained alarms and indicators This was a single unit that was entirely self contained Research for this project began with the processing unit Different options were identified compared and a microcontroller with a built in transceiver was chosen This chip was present in both the base station and the wrist unit It controlled all the functions of the entire pulse oximeter Next the power options were considered The units were able to continue working for at least one entire night The circuitry was designed around these parameters Each unit had a unique set of circuits that allowed its individual tasks to function This research was critical to the overall design as it provided the essential circuitry as well as alternate options Design began with the circuit board and schematic layouts Parts were chosen from the research and the passive components were added The major components were placed in block diagrams that show the flow of the design and how each unit worked together Next the schematics created were assessed for accuracy Once completed the schematics were used to lay out the circuit boards Each component had a specific footprint and these were connected with copper traces to create the physical circu
155. ntrolling the amount of voltage that powers the red and infrared LEDs The DC component is measured by the ADC of the microcontroller and then compared with the desired value to be maintained The output of the microcontroller to the LEDs changes based on the 5 difference between this measured DC value and the desired DC value This output is converted to an analog voltage through the use of a DAC The microcontroller samples this pulse oximetry data and transmits it wirelessly to the RDU Power System The power systems for the RDU and TSU are very similar since the two are sister units one has the sensor the other displays the information The TSU runs on a rechargeable battery pack with built in safety features that is capable of being recharged within the system while the power is off The RDU runs on an AC DC adapter and uses COTS batteries for backup The TSU battery charger and the RDU AC DC Adapter both connect to the same style panel mount barrel connector on their respective systems Since the RDU has the backup battery it has circuitry to automatically switch to the backup when the AC DC adapter is disconnected or unplugged The RDU switches back to the AC DC adapter when it is reconnected because it is a higher voltage source than the COTS batteries The system is capable of running on the COTS batteries solely for multiple uses before the batteries are drained to the point that they need to be replaced Both the batteries of the RD
156. nts and wires A mechanical design such as this will take too long and be too costly for this project because of the amount of design work and the materials that go into it The design team does not have the ability to fabricate this type of design so it would need to be specially fabricated and produced by a third party which would be too time consuming and costly If a pre made clip could be obtained and taken apart without damage the parts inside could be removed and it could be modified for use in this project There are some other possibilities for the mechanical aspect of the finger sensor The LEDs and photodiode can simply be attached to regular fabric and wrapped around the finger and attached using Velcro or elastic This would make the sensor more comfortable and less obtrusive However it would be difficult to make spaces in the fabric so the LEDs and photodiode could stick out and not come in direct contact with the finger and the parts and wires would need to be waterproofed inside the fabric Additionally if this is improperly attached it could reduce blood flow and cause erroneous pulse and SpO readings Another option is to make a sensor bandage It would consist of simply the parts on either side of the finger and some kind of tape to go around the finger Disposable sensors similar to this are in production already in lieu of sanitizing sensors constantly These are helpful for constant use because of the negated need for c
157. nts should be tested for correct voltages and currents The final test is to run the RDU on the power system for a full 8 hour period While this test is being performed the voltages and currents out of the battery and the AC DC adapter should be monitored If the current is found to be abnormally large or small the board should be checked to make sure all of the connections are correct If the current drain of the circuit is simply more than what was estimate the AC DC adapter tests should be repeated at the circuits accurate discharge rate Result The AC DC adapter was tested and worked as specified All connections on the PCB are correct The DC DC converter was tested and had some major problems on the RDU Extensive testing did not yield conclusive results A new DC DC converter was obtained The LMZ10504DEMO board was connected and correctly powered the RDU system The automatic battery backup switch 117 worked correctly but was removed from the system due to overheating The automatic switch is specified to work under 200mA The RDU draws more than 350mA of current which caused significant overheating Another automatic switch could not be found with the same footprint in the required time frame The RDU power system test was modified due to the lack of an automatic battery backup switch The RDU is only powered by one source currently by the AC DC adapter All subsystems of the RDU work correctly when connected to this power sou
158. oO 50 0 3 7 5 0 1 Dimensions in mm Figure 7 Saft LS14500 Dimensions Reprinted with permission from Saft America Inc Section 8 page V The number of life cycles for the LiFePO4 18650 battery pack would be at 80 of initial capacity after greater than 2000 cycles At 1500mAh there would be three TSU uses plus some extra This would give the battery life cycle more than 6000 uses of the TSU If the TSU were used once daily then the battery would still maintain 80 of its initial capacity after 16 years The number of life cycle for a Li lon 18500 battery pack would be at 80 of initial capacity after 300 cycles At 1400mAh there would be three TSU uses plus some extra This would give the battery life cycle more than 900 uses of the TSU If the TSU were used once daily then the battery would have lost 20 of its initial capacity after only 2 5 years When comparing a LiFePO4 14500 with only 450mAh and a Li lon 14500 with 750mAh The LiFePO4 14500 would have lost 20 of its capacity after 5 5 years but would not be able to get a full use of the TSU by that point The Li lon 14500 would have lost 20 of its capacity in less than a year but would still be able to have one full use of the TSU at that point 27 TSU Voltage Regulator DC DC Converter The TSU would need a low power switching converter to maintain the 3 3V that was desired The Enpirion EP5368QI was a complete system on chip synchronous buc
159. of 2010 He is currently an intern with Lockheed Martin Simulation Training and Support He has already started graduate coursework and plans to pursue a Master s of Science in Computer Engineering focusing on the Intelligent Systems track in the fall of 2010 Matthew Ecklund will graduate with a Bachelor s of Science in Electrical Engineering in May 2010 He is a participant in the UCF Lockheed Martin College Work Experience working on the DAGR missile and launcher platform Heather Grenitz will graduate from the University of Central Florida in May 2010 with a Bachelor s of Science in Electrical Engineering She plans to start her career after graduation by working at a company dealing with military projects or analog systems Eric Roberts will graduate and receive his Bachelor s of Science in Electrical Engineering in May of 2010 He currently works as a Junior Engineer at Better World Engineering but plans to continue his career with a major company dealing with power generation and alternative energy sources Section 9 Appendix A Schematics Figure 84 RDU Schematic Diagram Figure 85 TSU Schematic Diagram Section 10 Appendix B References 1 C Hill Limitations Carbon Dioxide pulseox info para 2 and 3 Sep 4 2005 Online Available http www pulseox info pulseox limits3 htm Accessed Dec 10 2009 2 C Hill Limitations Other Issues pulseox info para 1 Jan 1 2009
160. of charging There is an on off switch so the unit can be turned off when it is not in use The voltage from the battery is regulated by a DC DC converter to convert the steadily draining battery to the exact 3 3V that is needed by the system Lastly the 3 3V that is supplied for the system is split and put through a filter which keeps the digital noise off of the RF and Analog power lines The block diagram for the TSU Power subsystem is shown in Figure 23 below Not shown in the block diagram is the method used for transient suppression 61 3 3V_ ANA Reduced Battery Voltage DC DC Buck converter Battery EPS368QI Monitoring Battery Voltage Circuit Switch OS102011MA1QS1 Battery Voltage LT6004 OpAmp Battery Voltage Battery Pack LC SY14650 3A Figure 23 Block Diagram for power of the TSU TSU Battery The main power for the Transmitting Sensor Unit is the single Li lon 14650 battery pack Part Number LC SY14650 3A The choice of the Li lon 14650 is due to voltage and current capabilities at its recorded 940mAh charge capacity This Li lon battery pack is assembled using a Sanyo 3 48Wh cell The reason to use the preassembled battery back as opposed to the single cell is because the assembled battery back has included safety features for the battery protection 62 from over voltage and under voltage with threshold cutoffs at 4 2V and 2 5V a current limit of 3A and protection from sho
161. of the battery 4 2V divided by the test current During the discharge tests the battery charger is also tested Checking the output of the charger before connecting the battery to make sure it is outputting the correct voltage for the intended battery is required The TSU is estimated to draw less than 50mA so the first test is to discharge the battery at a 50mA rate If it is obvious that this discharge rate is not causing any problems the discharge rate is increased so that the battery life curve can be fully recorded It is very important during the discharge test to make sure the battery is not discharged completely this would cause the death of the battery The built in safety features of the battery should prevent this from happening but as a precaution the battery is closely monitored when it gets close to 2 5V The battery safety PCB is supposed to limit discharging to a 3A rate prevent charging above 4 2V and discharging below 2 5V Result To perform the discharge test we measured the current the TSU required The TSU draws 55mA of current Then we designed a simulated load at a resistance of 5 Ohms to speed up the battery drain test We used a multimeter with an rs 232 port DMM_View was the computer program used to record the voltage values on the load These values were then plotted to produce the graph below From this we obtained the threshold values for the battery monitoring circuit 4 5 4 3 5
162. omponents may be blown This not only causes damage to the component itself but may also ruin nearby components and cause more damage to the board Caution must be taken to inspect the boards and compare it to the original PCB layout This enables the group to catch errors before they become larger problems It also makes the build less intensive and leave more time for testing and perfecting the finished build Another issue that could arise is having improper footprints in the PCB This is most important on the integrated circuits op amps and the MCU Since the MCU has so many pins it is critical that they be properly placed Some pins are very specific and if the proper net is not hooked up to the proper pin major malfunctions will arise Double or triple checking the footprints is a critical step in the design and build process If parts are swapped then the footprints may not be the same Thus the boards should not be fabricated until the design is finalized for all components that have multiple and specific pins Passive components do not have these types of problems but care must be taken to place the correct size footprint on the PCB Since the group is assembling the board it is critical that the parts are able to be soldered by at least one member This means that complex parts requiring difficult or extremely precise soldering cannot be used If a problem is encountered the sponsoring company may be able to populate a few components T
163. ordering all the parts Before anything could be assembled the parts were chosen and purchased either from an online retailer or a store in the area The list of suppliers can be found in the design portion of this document see section 3 The manufacturers are listed and most parts were ordered from DigiKey unless they were specialized non stock or could be sampled freely from the manufacturer All parts and manufacturers used in the final design can be found in the schematic diagrams figures 73 74 and 75 and their supporting documentation see sections 3 2 3 3 and 3 7 Once the components began to arrive the PCBs were populated The components were soldered to the boards in the lab provided by the project sponsor The boards were assembled with only the major components at first Only two PCBs were fully assembled at first After testing any necessary modifications were made to the other PCBs without wasting time and money by removing other components Since the PCBs were small and could not be worked on by more than one person at a time the rest of the team began tooling the housings for the two units The RDU is contained within a simple box but needed holes cut out for the display status indicators and speaker These were machined according to the PCB layout and where it would mounted inside the box The TSU is also housed in a small box Cutouts to attach the wrist strap were machined on either side The box also needed small holes
164. per tone at the correct 132 time The MCU should simulate all the test conditions again to assure that they are working properly For more information on these tests see section 5 2 Each PCB has a series of test points that indicate where critical measurements should be taken Where the voltage and current is especially important it should be noted A multimeter should be utilized to test all of these very carefully If the multimeter probes accidentally hit other components near the test points it could cause a short and damage components Thus small measuring probes should be used and as much of the probe as possible should be insulated If necessary small pieces of solid wire can be placed in the test points and the multimeter can measure the value between the wires farther away from the PCB itself This is to assure that the maximum length is covered and protect against shorts Each test point has a predetermined value that should be measured and checked Before the unit is completed these measurements should match the current or voltage level that needs to show at each point If the values do not match passive component values can be changed to obtain the proper levels Additional sub system level tests should include assuring that the mechanical design is completed properly This means that the AC adapters in each unit should be easily accessible from outside the case but should not protrude from the unit Also the status indicators s
165. plifier so as to leave only the AC signal The differential amplifier can be used to amplify the signal even more This AC signal represents the ebbing and flowing of blood through the body the pulse and is therefore the most important component It is an AC voltage directly proportional to the changing current from the output of the photodiode Last the AC signal must be converted from an analog voltage to a binary number An analog to digital converter is used to perform that task Before doing so however the AC signal must be sampled and held at a constant voltage to correctly convert to a binary form This sample and hold function is performed by the input terminals of the ADC In order to correctly utilize the pulse oximetry equation that does not factor in the DC component the DC value of both wavelengths of light must be controlled at a constant level An automatic gain control circuit must be used The principle of automatic gain control is that a circuit alters output based on input so that the output is a constant value To do so an AGC circuit must take the form of a negative feedback loop In this circuit the output of the AGC is used to power the LEDs while the feedback comes from the DC component of the output of the transimpedance amplifier The microcontroller simulates the AGC circuitry by comparing the feedback voltage with the desired voltage The input to the ADC is the feedback value and the output of the DAC which is used to
166. properly 2 4 1 Displays There are many types of displays available The goal of this research was to outline several types list the pros and cons compare between the others and draw a conclusion of which type was appropriate for this project This project required the display of the pulse and blood oxygen saturation level to the user The digits should be able to be read from across a medium sized room This 32 limits the options to character size of about 0 4 x 0 4 per digit Optionally the display shows non numerical information such as the signal strength battery life of the TSU and battery life of the backup battery in the RDU All of this information could be shown on the display but this is not a necessity Section 2 4 3 of this document will cover research of other options to display this information 7 Segmented LED The basic 7 segmented Light Emitting Diode LED display most commonly used in digital clocks electronic meters and any other electronic devices that only need to display numbers This display requires very minimal effort to set up and can be interfaced with a MCU using 8 simple 16 1 multiplexers for each digit and use 4 bits of our MCU s GPIOs per digit The Maxim part MAX6954 can drive the 7 segmented display utilizing fewer outputs from the MCU The 7 segmented display was probably the most widely used and was time tested Even though this was not a determining factor it had low power consumption If s
167. puts takes about 50us The ICL7673 is available as an eight lead SOIC The ICL7673 can be powered by 2 5V to 15V and the peak currents at the primary and secondary voltages are 38mA and 30mA respectively The ICL7673 requires that the voltage difference between the primary supply and the backup be at least 50mV A high current battery backup application circuit is given in the data sheet that describes how to use external transistors if greater currents are needed by the device RDU Voltage Regulator DC DC Converter The RDU needs a low power switching converter similar to the TSU to maintain the 3 3V that is desired The Enpirion EP5368QI is a complete system on chip synchronous buck converter with integrated inductor PWM controller and MOSFETS in a small 3x3mm QFN package This chip operates at a switching frequency of 4MHz which makes it ideal for noise sensitive RF applications as well as area constrained applications like the TSU The EP5368QI can be powered by 2 4V to 5 5V input and the output has a low ripple voltage of Amy p p typically The output voltage is set via a 3 pin VID selector and there are seven programmed output voltages The output voltage can also be set by connecting the selection pins to Vin and using an external voltage divider at Voyr using the provided equation Ra 200kQ Rp 1 206x10 Vour 0 603 This device regularly outputs at 600mA but can be set to output at 700mA if needed The EP5368QI requires only two ex
168. ragraphs a and b equipment authorization was not required for devices that were not marketed and not constructed from a kit and were built in quantities of five or less Since the FCC recognized that an individual builder may not have the means to perform measurements required to determine compliance with regulations the builder was expected to design using good engineering practices to conform to regulation to the greatest extent practicable Provisions in section 15 5 of the FCC code still apply Under section 15 103 paragraph c an exemption from specific technical standards in part 15 was given to a digital device used exclusively as industrial commercial or medical test equipment As the wireless pulse oximeter was to be used solely for the purpose of medical monitoring it qualifies as exempt from regulation except as required under Sections 15 5 and 15 29 Section 15 5 stated operation of an intentional unintentional or incidental radiator is subject to the conditions that no harmful interference is caused and that interference must be accepted that may be caused by the operation of an authorized radio station or by any other radiator or ISM equipment The TSU and RDU complied with all such requirements All transceiving parts within either system would be obtained through an electronic component distributor and would therefore comply with these requirements Section 15 29 set forth the requirement that all certif
169. rammed in assembly or a high level programming language such as C These chips contained their own integrated timers crystal oscillators and many I Os Generally MCUs were implemented in automatically controlled applications that did not require and may not even allow for external user input Other features found in MCUs may include internal ADCs and DACs to allow for signal processing and control timers receivers or transmitter as well as many input and output ports Since the goals of this project necessitate small size FPGAs were not ideal for this design Additionally the design team was more familiar with programming languages allowed by an MCU The math necessary to calculate SpOz and pulse rate did not require the complex math functions achieved using an FPGA the MCU was the best option for this project Considering the amount of possible features found already integrated into MCUs there were a variety of options available These options could be narrowed down by the necessities of this project Since there were many LEDs that need to be controlled the MCU for this project must have many I O ports available for programming The ideal MCU for this project would also have transmission and receiving capabilities built in The rest of the necessities were governed by the objectives of the project low power consumption small size and ease of use The MCU that required the least amount of external ICs would be preferable as well as those th
170. rce 5 2 2 Battery Backup This section goes over the required steps to fully test the battery If at any point the battery fails to perform as it should the circuit should be fully scrutinized and the testing should begin anew when the problem has been rectified The first test of the RDU battery is to perform a necessary discharge on a simulated load to find the battery life of the device The second test would be to temporarily connect the battery to an unpopulated PCB and recheck that the battery does not have any shorts through the PCB Once this is confirmed the third test can be performed with the battery monitoring circuit The point of the third test is to make sure that minimal current is drawn by the circuit and the output of the Op Amp displays the correctly reduced voltage Another discharge test can be performed at this point to compare the discharge of the battery to the output of the Op Amp s reported voltages The fourth test is to connect the battery to the DC DC Converter and discharge the battery at the 3 3V output The fifth test is to connect both the DC DC converter and the battery monitor circuit The sixth test is to include the automatic backup switch into the circuit in the fifth test Once these tests are completed the battery is ready to be included in the system The next test to be performed on the battery includes the AC DC adapter and the automatic backup switch which is covered in the Primary Supply section Te
171. re highly responsive Photodiodes were also generally very inexpensive and came in many sizes They had no built in gain and so required an external amplifier but these were generally simple and easily created circuits Phototransistors could be more convenient than photodiodes because they had built in gain These were normal BJTs where the lens allows in light which then creates current in the base region of the transistor Phototransistors have limited standard packaging options large variations in sensitivity and restricted wavelength sensitivity For this project sensitivity was key and thus a photodiode was the best choice for the design Next there was the decision between a PN junction and PIN structure A PIN diode was a lower quality rectifier because of its large intrinsic region but was much more sensitive than PN junction diodes In this design a PIN diode was preferred Lumex offered photodiodes that were designed to work with their LEDs This was helpful because they would be sensitive to the infrared LED as well as the red Lumex did not specify whether their diodes have PIN structure or a PN junction The company offered only three photodiodes with part numbers OEDOHPI1210B 60A OED HPI1210C160 RT and OED SP 23 TR All three had wavelength ranges that encompass both the red wavelength of 660nm and the IR wavelength of 940nm However the first two have peak wavelengths of 980nm which was outside the range needed to be measured Thi
172. reation will be the determining factors in how the PCBs are made Self fabrication has the benefit of not requiring a wait time to have the boards made Sending out the boards requires a lead time that depends on how busy the manufacturer is at the time This will allow more time to be slated for building testing and possible revisions Having that extra time will allow for a more complete final product that works to the best of its abilities Additionally if the board needs to be changed it could be recreated in the same day This means that revisions would be more thorough as the new parts would not have to fit in the places of the old parts which also creates a more professional looking final product Since the boards will not be viewable to the user this is not an immediate concern However if parts are not placed on the correct footprint shorts could be caused on the board which may increase the cost by necessitating new components to be ordered Sending out the PCB for fabrication would eliminate the issue of errors If the company makes a mistake the boards will be fabricated again and the team can spend that time working on other aspects of the project instead of trying to fix the board Since self fabricating a PCB would take one person a whole day mistakes would end up being costly in time and budget A plus for getting the boards fabricated by a manufacturing company would be the ability to have more than two layers Smaller boar
173. reduced the budget Compared to the other chips that were available although the CC1110 could be used it did not match up in features or abilities for the same price The CC1110 would also require controlling a large number of external devices which would be a struggle due to its limited number of GPIOs 2 3 Transmitting Sensor Unit The non invasive measurement of arterial oxygen saturation in the blood is pulse oximetry Two advantages to measuring this pulse oximetry data are the safety to the patient and relative immunity to electromagnetic interference This non invasive technique was done by pulsing light through a small thin peripheral point on the body such as a finger or earlobe and measuring the intensity of the light as it passes through and leaves the body Hemoglobin the colored substance in blood is the carrier of oxygen It absorbs light relative to the amount of oxygenation The two forms of hemoglobin oxidized hemoglobin HbO2 and reduced hemoglobin Hb absorb light differently at varying wavelengths The two wavelengths of light most commonly used to measure the oxygenation of blood were 660nm and 940nm These two wavelengths of light must be shone through the finger and detected by a photosensor The TSU must then transmit the pulse oximetry data to the RDU 23 2 3 1 LEDs and Photosensors The main concerns for this project were power consumption and size Thus the LEDs and photodiodes must have small footprin
174. reless Mailing Address Texas Instruments Post Office Box 655303 Dallas Texas 75265 Copyright 2008 Texas Instruments Incorporated VI IV Saft LS14500 Battery Permission RE SaftBatteries com Permission to ri Dec 4 2009 use Images at 8 11 AM White Jennifer lt Jennifer White saftbatteries com gt To EROBERTS EE knights ucf edu Eric Yes this is fine Best Regards J ennifer J ennifer White Business Development Specialist Saft America Inc 828 879 5096 Phone 828 443 0236 Cell 828 879 3981 Fax From eroberts ee knights ucf edu SMTP EROBERTS EE KNIGHTS UCF EDU Sent Saturday November 28 2009 8 00 48 PM To lithium sales Subject SaftBatteries com Permission to use Images Home gt Contacts gt North America gt USA gt Mr Eric Roberts Company Student of University of Central Florida Mail mailto eroberts ee knights ucf edueroberts ee knights ucf edu Telephone Hello My senior design group is designing a wireless pulse oximeter and we are considering the use of the Saft LS14500 batteries to power our devices As part of the design processes we are required to submit a document with all of our design sand figures Can we use the figure in the LS14500 data sheet that displays the dimensions of the LS14500 Thank you Eric Roberts Vil V ON Semiconductor NCP1530 Permission Permission to Reprint Images 2 messages Eric Roberts lt eroberts ee knights ucf edu gt Wed De
175. roject the main concern was power Since there was not much data that needs to be transmitted it should not matter that much ZigBee provided a very low power physical layer with the ability to transmit up to 75 meters The fact that for an individual device to pass the 7 ZigBee certification it must have a battery life of at least two years showed how low power the ZigBee communication method was Pros e Transmission range between 10 and 75 meters 33 and 246 feet and up to 1500 meters for ZigBee pro Maximum output power of the radios is generally OdBm 1mW Easily implemented Flexible network structure Small physical footprint Individual devices must have a battery life of at least two years to pass ZigBee certification e Many manufacturers are integrating MCUs with ZigBee transceivers Cons e Oncluttered 2 4 GHz ISM band e Low data rates up to 720kbit s ZigBee had many appealing features extremely low power and a good transmission range These features made a ZigBee device very useful for a low power low data rate transmission devices like the TSU The fact that many microcontrollers now integrate with ZigBee was another bonus The ZigBee specification came with some overhead costs It had to be determined whether the cost was worth having the good battery life and low power that came with After looking at all alternatives conclusions will be drawn and that will be the wireless technology used to transmit the data needed from th
176. rsion to happen outside of the RDU enclosure to reduce the inference that could be caused if the power adapter were close to the antenna The GS18A AC DC single output desktop power adapter was powered by 100Vac It had a 3 pole AC inlet and had a 73 efficiency rating The 5V GS18A had a current range of 0 to 3A It had a four foot cable between the adapter and the 2 1mm barrel plug DC output The GS18A was available for 25 and required the separate purchase of a standard power cable The TOL 08269 was a 5V AC DC adapter rated at 1A was FCC CE certified and was of the wall wart style requiring no extra power cables The DC output was a center positive 5 5mm x 2 1mm barrel connector The TOL 08269 was available from sparkfun com for 6 RDU Battery The RDU required a larger amount of current then the TSU at a low voltage for a very long period and will need a small enough power source The voltage range of the microcontroller was from 1 8V to 3 6V so the system should be designed to run at roughly 3V or 3 3V The RDU draws more than 150mA for a length of approximately 8 hours the time required by the TSU This would require 1200mAh per use This battery could have been rechargeable but this was not necessary since the battery would only be used if the primary power source fails or if the RDU was being moved between rooms Since the battery does not need to be rechargeable it could easily be two standard alkaline C cell batteries The C cell
177. rt circuit The dimensions of the Li lon 14650 battery pack are 17mm 0 67 in diameter by 67mm 2 64 in length Its weight is only 27g 0 95 oz which is roughly the weight of 11 pennies The battery pack comes with 4 wire leads that is directly wired to the board or connected through an inline connector to save board space This battery is available from batteryspace com for 11 The charger that is used for this battery pack is the Smart Charger 0 5A for 3 7V Li ion Polymer Rechargeable Battery Packs Part Number CH UNLI3705 which is recommended for this pack This battery charger has an AC voltage input range of 100 to 240 VAC anda max input power of 6W The output of the smart charger is 4 2VDC at 0 5A The power output connection is a nearly 5 foot cable with a standard 5 5mm x 2 1mm barrel connector at the end This connects to a mating socket directly on the TSU so that the battery is not removed in order to be charged There is a bicolor red green led indicator on the charger red indicates charging green indicates fully charged The charge time is calculated using the formula Charge time Ah rate of pack x 1 5 0 5A charge current For the 940mAh Li lon 14650 battery pack the charge time should be just under three hours This charger is available from batteryspace com for 12 Battery Monitoring The expected remaining battery life is monitored by connecting the battery to a resistor divider connected to ground with the dividi
178. s While completing the design research should be continued This milestone indicates when the design process should start The design process should take aspects from the research and expand them into working schematics of each unit The most critical components are chosen first and research needs to be done to assure that the proper passive and other components are included This ensures that the critical components are able to properly function together in the units Below is a graph of the milestones January 11 January 21 February 11 February 21 March 1 March 11 ansmitting Receiving Software Transmitter Software ee Codo zz Coding Completed Initial Code Review Finialize Testing ET i Deploy Receiver Software T Cod CD Fa Coding Completed Initial Code Review i Testing Completed 315 Transmitting Sensor Unit Order all parts Heather i Wait for ess Ready to build pia Bug a Ready totest Test TSU Completed 4 34 Receiving Display Unit Order all parts Eric te a Ready tobula 49 Build Ready to test a 2118 oy RDU Completed TE System Level Testing Medical Comparasion Finalize Testing Project Complete 47 Figure 82 Milestones Chart TSU Price Actual Price x3 EEN 6 14
179. s LEDs in a variety of footprints and heights Kingbright had a larger selection of IR LEDs than other manufacturers In such small sizes these LEDs would be ideal for this project The IR LEDs came in a variety of footprints but since this design required such a small size the part numbers AP1608F3C and APT1608F3C were mainly considered Part APT1608F3C had a smaller thickness than the other and was relatively inexpensive at 0 12 per LED This was an ideal size and cost for this project Kingbright did not offer samples but since their products were so inexpensive this was not a hindrance They did not offer any red LEDs in the correct wavelength of 660nm Perkin Elmer had many surface mount LEDs with 660nm wavelengths They had two varieties wide viewing angle and high power output but both had the same forward voltage and similar footprints The first had the part number CR50UR with a footprint of 3 2mm x 1 27mm and the second was SR10URB with a footprint of 3 2mm x 1 6mm Perkin Elmer did not offer any IR LEDs in the correct wavelength of 940nm There were many different types of photodetectors available as well Photodiodes both PN junction and PIN structure and phototransistors could be found for applications on this project Photodiodes were generally larger and allow in more light when compared to phototransistors and other sensors They could measure small values of optical power were sensitive to many different wavelengths and we
180. s a major drive behind this design However medical applications tend to be the most costly of endeavors Similar products for sale were priced upwards of 500 For more information on existing products see sections 1 3 This design aimed to be much less expensive and more user friendly It was designed to have many safety features that will prevent losses in monitoring and alert the user to dangerous conditions as well as provide an alternative to the expensive products on the market This project was for use on adults but was a starting point for making smaller units that can be used for monitoring babies and infants The design had maximum protection and safety with minimum cost 1 3 Comparison to Existing Products There are many different types of equipment used to measure pulse oximetry The commonly known device is the one used in hospitals to monitor patients receiving care especially those at risk for cardiac or pulmonary distress There are also products to be used at home and while exercising to monitor critical life signs These products vary in size shape and ease of use The goal of this project was to create a product unlike others found on the general market It was unique because of its wireless application which allows remote monitoring Pulse oximeters used in hospitals are very large and generally display other vital signs They are usually on a stand that can be seen over the patient lying on the bed When the patient need
181. s means that the sensitivity at 660nm was low The third had a peak wavelength of 900nm which was much more suited for this project Vishay Dale offered a large variety of photodiodes but many were very similar to each other There was only one that had a peak wavelength near the two 25 wavelengths needed The part number was TEMD5010X0 It had a spectral bandwidth of 430nm to 1100nm and a peak wavelength of 940nm This chip s active area was large at 7 5mm approximately 2 74mm x 2 74mm which was desirable for this design since the light may be deflected by the finger and with the LEDs placed next to each other the larger sensitive area may be necessary Perkin Elmer also offered a couple different photodiodes but there was only one that was well suited this project Part number PFD10 was a PIN diode and the best suited photodiode for this design It had a large active area of 2 59mm x 2 59mm as well as a low height of 1 3mm lts peak wavelength was at 880nm but its spectral bandwidth was 530nm to 1000nm The PFD10 boasted a fast response time high sensitivity and low noise but was difficult to find for sale to obtain pricing information 2 3 2 Power Considerations TSU Battery The TSU required a small amount of current at a low voltage for a long period and would need a small enough power source that the whole unit could be worn around the wrist with comfort The voltage range of the microcontroller was from 1 8V to 3 6V so the s
182. s or set of lights The RDU main startup function will be checking the variables for drop in pulse and blood oxygen saturation level low battery life of the TSU and time between receiving transmissions Upon detecting one of the conditions the RDU will sound an alarm that corresponds to the condition that was detected The TSU will fire an interrupt when it receives updated information from the sensors about the pulse and blood oxygen saturation level This interrupt will update the variables storing the information for the pulse and blood oxygen saturation levels The TDU will also have a send function that will be called every couple clock cycles This send function shall construct the packet with the pulse blood oxygen saturation level and battery life It will then send this information to the transmitter transceiver to be sent to the RDU This transmission of data from the MCU to the transmitter transceiver will be a serial data stream Possibility 4 The RDU s main function will check the value of the first bit of the input port when it sees a 1 it has received a packet It will then give a clear to send to the receiver transceiver The receiver transceiver will send the data serially to the MCU The MCU will read the data and update the variables for the values of battery life blood oxygen saturation level and pulse The RDU will periodically update the display and status indicators based on the difference in time since the last update
183. s to move there are wires all over that need to be repositioned as well Going to the restroom becomes a complicated process When combined with an IV there is an overabundance of wires and parts that must be moved so the patient can adjust These parts tend to be most accurate because their size allows more processing power than a compact portable unit For hospital stays these devices are plainly preferable as they are used in high risk situations where accuracy is more important than comfort However a smaller unit may be preferable for patients who need to stay in the hospital but are not in critical condition Patients may need to be monitored if they are in the hospital for a treatment or procedure but a smaller unit may be used if they are not at risk of cardio pulmonary distress Hospital vital sign monitors cost upwards of 3 000 and was extremely impractical and unnecessary for constant home monitoring For athletes training the body is an important part of their sport Runners swimmers and other athletes may want to monitor their pulse rate while exercising to ensure they are not putting themselves at risk Their percent oxygen saturation would be helpful if they must keep track of their breathing while working out Patients who are in rehabilitation might also use this wrist watch type pulse oximeter to monitor themselves It will help them train their bodies without putting them at risk of additional complications These units are sma
184. s would need to be large in the tens and hundred thousands and be chosen such that the voltage would be divided by an amount that makes the output of the operation amplifier capable of being connected directly to the microcontroller on an analog input This value could then be compared to values at 25 increments of the battery life In order to obtain the 29 25 increments of battery life the battery needed to be drained at the rate the system would dissipate the charge As the battery was being drained the voltages would need to be recorded as time progresses to give the battery life for this specific design a Figure 10 Battery Life Sense with Op Amp An alternative method would be to choose a chip that triggered when the battery reaches key voltages An example of this type of chip would be the Texas Instruments TPS3808 The TSP3808s were a family of microprocessor supervisor chips that monitor system voltages and could generate a reset signal when the voltage drops below a preset voltage or if the manual reset pin was driven low The reset would remain low until the adjustable delay time had occurred after the voltage returned above the threshold level In order to use this type of circuitry a few different threshold TPS3808s would need to be used and arranged in parallel Each of the reset pins would need to be connected to individual pins on the microcontroller Whenever the voltage crossed the specific threshold the microcontroll
185. simulated load is connected at the DC DC output while the voltages at the adapter and the DC DC output are monitored The AC DC adapter is not directly connected to the DC DC converter in the final system The On Off slide switch is tested at this point to make sure that the circuit can turn off Test IV Automatic Backup Switch Part The fourth test is to connect the automatic backup circuit into the test circuit in the previous test with the AC DC adapter switch and DC DC converter The specifications test is attempted at this stage to make certain the correct voltages and currents are available at the DC DC converter when the system is powered by the primary source Test V Automatic Backup Switch Part II The fifth test to be performed is to connect both the battery and the adapter only to the automatic backup switch The point of this is to specifically test the operations of the automatic backup switch Items of interest are the voltage and current out of the backup switch as well as the switching time required If there is a significant drop in voltage during the switching process it needs to be compensated for in the system to maintain operation Test VI RDU Power System The last power test is to connect the AC DC adapter and the battery to all of the power circuitry This includes all of tests on the battery battery monitor AC DC adapter automatic backup switch On Off switch and DC DC converter All of the interconnecting poi
186. st l Discharge The point of the discharge test is to discharge the battery on a simulated load through its working voltage range and record the voltage of the battery versus time The simulated load can be calculated with the simple V I R equation The intended current should be run through a power resistor equal to max voltage of the battery 4 5V divided by the test current The RDU is estimated to draw less than 150mA so the first test is to discharge the battery at a 150mA rate If it is obvious that this discharge rate is not causing any problems the discharge rate is increased so that the battery life curve can be fully recorded From the battery life cycle the value is needed where the RDU has depleted the majority of it backup and has less than one full use of the RDU remaining This value is used later by the MCU to update the related indicator value Test Il Battery Connections through PCB This test checks if the battery is connected on the PCB to all the correct solder pads To test this the battery is connected to an unpopulated board An 118 unpopulated board must be used because the battery could not be safe to connect to other components or the other components might not be safe for the battery All of the pads should be probed to make sure no voltages are leaking into pads that are not supposed have them Test Ill Battery Monitor Circuit The battery is tested through the monitoring circuit by setting up the circuit on a
187. struct the MCU to also print the number to a screen The finger sensor should be attached to one of the design team members A multimeter should be used to assure that current is coming out of the photodiode If it is not refer to section 5 1 2 Then the voltage should be measured on the other side of the amplifier If a strong voltage value is present the amplifier circuit is working properly This voltage is passed into the MCU to compute the pulse rate and SpO This value is output to a screen and transmitted to the RDU It is critical that this number is medically relevant For more information on the medical comparison see section 5 3 3 Since the MCU does not hold record of the voltage passed in it may be pertinent to measure this voltage with an oscilloscope This assures that the voltage is changing according to the beats of the heart This change allows the MCU to compute the pulse rate For more information on how this works see section 2 3 Once it is guaranteed that this unit is working properly the RDU can be tested The added code should be removed from the MCU before the next step This assures that the code flows properly and is not constantly performing unnecessary steps The MCU should not be cluttered with test coding and this should all be erased before the system level tests if possible The RDU is tested in a similar manner to the TSU in that the first tests should be on the power supplies Since this unit has both AC pow
188. t board The board can be self fabricated or the board can be sent off to a company to be fabricated The self fabrication option is good for those who know how to do it or those that are on a tight budget In addition self fabrication is preferred when on a tight schedule since sending out printed circuit boards to be fabricated takes a lot of time or when a low quantity of boards is necessary Self Fabrication The process of fabricating a board is a long and tedious process lt is also rife with problems Mistakes are likely to happen Unfortunately some of those mistakes will strain the budget to replace what has broken Some basic requirements for self fabrication are a software layout tool such as ExpressPCB some press n peel printed circuit board transfer film an iron to transfer the layout to the board etchant a drill a tray and of course the board itself The first step is to layout the board using a software layout tool Once the board is laid out the board layout must be printed onto the printed circuit board transfer film The printed circuit board transfer film is then ironed onto the board itself 48 Once the circuit is ironed onto the board the board is ready for etching Etchant is a chemical that reacts with exposed copper and removes it from the board This way only the copper hidden under the printed part will remain Place the board in the tray slightly elevated off the bottom of the tray Slightly warm the etch
189. t happen inside the insulation will not be visible and may sometimes connect and other times are open This makes it extremely difficult to determine where the error is created This applies to internal wiring as well When the batteries and panel mount parts are wired to the PCB the wires must be in good condition There should be no strain on any internal wire along its length or at its connections to the component or the board It is important to use a strain relief technique on both ends of every wire Some components come with wire holders to eliminate strain but those that don t will require some silicon or epoxy to keep the wires from wiggling too much at their weakest points Each wire should have enough extra length that it is not pulled taut but should be short enough to not get snagged or interfere with other parts Using silicon also prevents shorts between exposed ends of wires which could ruin parts and cause the unit to overheat A final issue that may be run into is the budget and time Since there are distinct possibilities for physical errors and issues there may be a necessity to reorder components or have PCBs fabricated again Some parts are very pricey and ordering more strains the budget Extreme caution should be taken with the expensive components such as the MCU Waiting for the new components to arrive also waste time that could be spent doing tests This may cause the unit to not be completely functional at the end of
190. t have slots along the interior sidewalls are designed to hold PCBs firmly in place while maintaining a sufficient distance between the PCB wires and the case 2 5 3 Receiving Display Unit There are many options for creating the box that would house the printed circuit board and its components such as the speaker on off switch display and antenna The options that will be discussed during the course of this research are wood plastic and metal Wood Enclosure Wood the basic element that has been used to construct furniture can be utilized to create a case to house the RDU electronics A simple case made of a good wood could be expensive but a single sheet of plywood could make the box needed for the RDU Using a saw and a drill cut outs can be made for the 46 display and each individual LED indicator There would also be a need for some small holes around the area of the speaker to guarantee the sound being produced by the speaker can be heard Plastic Enclosure Plastic is a very useful product that has many uses in today s society Many companies sell plastic cases of various sizes that will fit different printed circuit board layouts Many companies sell project boxes that can be easily adapted to fit the project s needs In addition since a baby monitor is very similar to the case that is needed a baby monitor could be purchased the internal components removed and the case adapted to suit the project s needs Metal Enc
191. tached wires make it difficult for the patient to move and sleep They are not designed for constant wear outside the hospital and are very expensive to purchase for home use Therefore the purpose of this pulse oximeter was to eliminate cables and allow for comfort and ease of use in the home The sensor is wireless and has a remote monitoring station This provided parents with the ability to monitor an infant s breathing and heart rate from separate locations in the home It also allows nursing homes and home care facilities to monitor the pulse rate and percent oxygen saturation of any person under the care of the facility without limiting the resident s movement or being in the way of their everyday activities Pulse oximeters can be used for a variety of alternate applications as well Heart rate can show stress fear and excitement Anyone can use a pulse oximeter to keep track of when exercise is done in a safe cardiovascular range Many athletes utilize pulse oximetry to help them train their breathing while exercising Pilots also use pulse oximetry to assure their pulse rate and percent oxygen saturation are within the healthy range while they are in a thinner atmosphere This could prevent dangerous conditions in flight and possibly save lives Because of the wide variety of uses for pulse oximeters this project had a large potential market Designing marketable products is part of the engineering profession Improving quality of life wa
192. td 0S102011MA1QS1 Bette EPS3680Q1 E vr u oltage Monitoring PPI 9 Automatic power switch ICL7673 Circuit Battery Voltage patisry Voltage Backup Battery COTS Battery 3Vor AC Supply Equivalent TOL 08269 Figure 30 Block diagram for power of the RDU Figure 31 Battery Life Monitoring Automatic Backup Switch The ICL7673 works by automatically connecting its output to the greater of either of its supply voltages In this case the primary supply is the constant 5V AC DC adapter and the secondary is the three COTS 1 5V AA alkaline batteries As previously stated the AC DC adapter was chosen at 5V so it would always be 68 considered as the primary source by the ICL7673 If the AC DC adapter is disconnected the ICL7673 switches to battery power until the AC DC adapter is reconnected in If the battery is fully depleted the system will shutoff The configuration of the ICL7673 is shown below The LED shown in Figure 3233 will let the user know that the unit is running on the primary source when it is lit Figure 32 ICL7673 Automatic Backup Battery Switch Configuration Power Switch The power switch for the RDU is shown in Figure 2 above It is an 0S102011MA1QS1 ON ON slide switch used to turn the system on and off This switch is configured with the first pin connected to the battery voltage and the second pin connected to the voltage in the DC DC converter The third pin is left floating This w
193. ternal capacitors for operation The cost for this component is less than 2 Figure 12 displays the typical application circuit ENABLE Vin Vin ats EP5368QI Voltagef Select T Figure 12 Enpirion EP5368QI Typical Application Circuit Reprinted with permission from Enpirion Inc Section 8 page II Another option is to use the ON Semiconductor NCP1530 PWM PFM step down converter Like the EP5368QI this chip generates a supply current of 6 00mA 37 and can be powered in a low voltage range 2 8V to 5V for the NCP1530 The NCP1530 is specifically designed be used in systems that run on a single cell Li lon battery or multiple cell Alkaline NiCd or NiMH chemistry batteries The step down converter operates at 600 kHz fixed frequency PWM mode normally but if the synchronization pin is tied to ground the chip automatically switches to a variable frequency PFM mode at small output loads for power saving The NCP1530 chip is a small 8 pin 3x5mm Micro8 SOP The major drawback of the NCP1530 chip is that it requires the use of an inductor and a diode for a standard layout The output voltage of this chip is set by the manufacturer requiring the purchase of the correct chip for the desired output voltage Figure 13 displays the typical application of the NCP1530 L1 56H Vin LX Vout 3 0V Vin 2 8 V to 5 0 V D1 MBRM120ET3 SYN NCP 1530 Weak ss Vaer Css m GND EN Cin CVREF Cour L 24F
194. the battery needs to be changed The bicolor LED switches to red when the battery has less than one eight hour use of the RDU remaining The status of the TSU s battery is displayed using an array of green LEDs This takes the form of a bar graph style displaying the percentage of battery life in 25 increments Figure 58 shows the block diagram of the status indicators 91 3 digit 7 segmented Display LDT A512RI LED Display Driver MAX6957 Speaker Drive Circuit Speaker SMT 0540 T 6 R Status LEDs Figure 58 Block diagram of the Status Indicators LED Array SSF LXH400GD SSA LXB435SUGD RDU Mechanical Design The mechanical design of the RDU is critical as this unit acts as the base station for this design The unit stands on its own the batteries switch and AC plug must be accessible the indicators and display must be visible from many angles the alarms must be loud and attention grabbing and the unit must be portable The RDU must be large enough on the inside to fit the batteries as well as the PCB The face of the unit must have enough area to fit the five LED status indicators and the seven segment display There must also be enough area to allow the switch and AC plug to be mounted Additional area is needed to create a battery cover The backup batteries must be accessible so that they may be changed before they die Since the RDU houses most of the safety features of this design th
195. the low pass filter with an oscilloscope The oscilloscope should show only a DC value as the output of the low pass filter Repeat this step using the finger of someone with a higher pulse i e someone that has recently done exercise Confirm that AC values corresponding to a normal heart rate are being filtered Differential Amplifier Test Test the output of the differential amplifier by applying a voltage to the non inverting input and a lower voltage to the inverting input Using an oscilloscope determine that the output follows the following formula where Ap is the differential gain as determined by the resistors and the Vin values are the non inverting and inverting inputs Vou Ap V in Vin Repeat this test using a variety of voltages to verify that the results follow this equation closely One such test should be performed using a voltage that is significantly smaller 0 01V than the non inverting input LED Select Test DAC Test Result 5 1 1 Battery Power This section goes over the required steps to fully test the battery If at any point the battery fails to perform as it should then the circuit should be fully scrutinized and the testing should begin anew when the problem has been rectified When charging the battery the LED changes color on the charger to indicate the charging status The red light indicates that the battery is charging and the green light indicates that the battery is fully charged T
196. time clock 5 Low Power modes Familiar programming language Cons e Fewer ADCs than other options e Not yet available for sample or purchase which could slow the project JN5148 The Jennic JN5148 was 2 4 GHz wireless transceiver microcontroller with a 32 bit RISC CPU 32MIPs and up to 21 Digital I Os It was an excellent single chip solution for wireless sensors The integrated 2 4GHz transceiver had built in cyclic redundancy check The JN5148 had 128kB of ROM and 128kB of RAM which provided plenty of memory to run both ZigBee protocols and an embedded application An Internal 12 bit ADC and two 12 bit DACs provided excellent integration into many microcontroller circuit designs reducing the number of external components needed The JN5148 s low power consuming design enables the chip to be powered by a single coin cell battery which was ideal for this project This chip also has a four wire digital audio interface for interfacing directly to most audio codecs a feature that would be useful for the RDU s alarm indicators The JN5148 was available as a small 56 pin QFN of 8mm x 8mm Its downfalls were that it transmitted on the crowded 2 4GHz frequency band and was a very high cost component at about 20 per chip with no free samples available 20 0 O n Low power consumption Integrated MCU and transceiver 2 4GHz wireless transceiver 32 bit RISC CPU 21 GPIOs Internal 12 bit ADC 2 internal 12 bit DACs 8 x 8mm QFN packa
197. tion that will be called every couple clock cycles The amount of time will be chosen based what uses the least amount of power and be still acceptable by the user The update display function will update the display and status indicators with the correct values or set of lights The RDU main startup function will be checking the variables for drop in pulse and blood oxygen saturation level low battery life of the TSU and time between receiving transmissions Upon detecting one of the conditions the RDU will sound an alarm that corresponds to the condition that was detected The TSU will fire an interrupt when it receives updated information from the sensors about the pulse and blood oxygen saturation level This interrupt will update the variables storing the information for the pulse and blood oxygen saturation levels The TDU will also have a send function that will be called every couple clock cycles This send function shall construct the packet with the pulse blood oxygen saturation level and battery life It will then send this information to the RDU Possibility 2 The RDU s main function will check the value of the packet status register when it sees it has received a packet it will update the variables for the values of battery life blood oxygen saturation level and pulse The RDU will periodically update the display and status indicators based on the difference in time since the last update The RDU will also be constantly checking t
198. to allow the wires out to the sensor clip After the most comfortable wearing position was determined these holes were drilled to allow for the shortest wires to be used The wires have enough length to allow the hand to move and rotate easily but are short enough that a minimal amount of signal is lost Also these wires have a small enough gauge to allow them to bend easily but thick enough that they will not break effortlessly These wires are 28 gauge wires and have protective casing with shielding inside a rubber sleeve This protects the wires from the outside elements as well as protecting the patient in case of breaks in the wire Finally when the cases were properly drilled and the PCBs were populated the boards were installed in their respective boxes The RDU installation was especially important The display sits just so in the face of the unit If the display is situated too far into the case the numbers are not visible If it is too far out of the case it is unsightly and looks unprofessional The mounting of the RDU 104 board is critical to the overall look of the unit and the project as a whole This section of the build requires many measurements to be taken accurately and checked multiple times It was time consuming but once mounts were in place the PCB could be changed without needing the measurements to be made again The TSU mounting was much less critical since no components show through the face of the unit There
199. ts These can be soldered to the bottom of the board Holes can be drilled into the case so the lights will show through The PCB can then be mounted to the box with the LEDs in their respective places This could pose two problems Displays those used for showing the two measurements and LED arrays are generally very tall when compared to most surface mount components The difference in height would look unprofessional on the front of the RDU The second issue is creating the PCB In order to mount the LEDs in the front of the unit the PCB layout would be restricted to the locations of the lights The LEDs would have to remain in a certain place limiting the locations of the other components However surface mount LEDs are much less expensive than panel mount LEDs and may prove advantageous if the project is constrained by its budget In the case of using a surface mount LED some considerations must be taken into account These indicators must be easily viewed so small package sizes are not ideal LEDs smaller than 0805 size will not be easy to see from a distance Therefore 0805 is the smallest size that will be considered for this design Additionally the LEDs must have a wide viewing angle so they can be seen from up close far away and a variety of angles There are many companies that sell surface mount LEDs in the colors necessary for this unit The only way surface mount LEDs would be useful is by utilizing light pipes to bring the li
200. ts with low profiles and low power consumption However the LEDs had to have a high enough intensity to shine through a finger and the diode had to be sensitive enough to sense the changes in intensity with the pumping of blood through veins in a finger Thus those chosen had to have a balance between power consumption and luminosity In order to keep the light as intense as possible a clear lens with no diffusion coating of any sort was also necessary For applications in pulse oximeters two LEDs are necessary The first was a red LED with a wavelength of 660 nm and the second was an infrared IR LED with a wavelength of 940 nm Because these values are so specific the number of LEDs that could be used was diminished especially when considering that the colors of light were each a range of wavelengths The wavelengths necessary for this application were common so even though they were specific they were readily available The different options for the mechanical design of the sensor clip affect the choice of LED for this project see section 3 5 1 Surface mount LEDs have the smallest package size but without a PCB to mount to it would be difficult to attach to wires Using gull wing leads would provide a similar mounting size as well as allow for wires to be easily attached and a flat surface to mount to any type of finger band In this way a small PCB could be utilized for a clip type of sensor or no PCB would be necessary for a fabric desi
201. tware to flash a debugging LED upon entering the interrupt function to verify that the interrupt is indeed being triggered Unit Test 7 The converted result from the analog to digital converter from the DC DC buck converter needs to be tested for validity The input is used in the calculations of the pulse and SpOz so this needs to be valid for accurate calculations To check if the interrupt is being generated correctly the software can be configured to flash a debugging LED upon entering the interrupt function Result The primary functions of the TSU were tested extensively The sensor clip and the LED select circuit were tested first This circuit worked correctly The circuit was measured by using an oscilloscope to test the output of the differential amplifier The LED select circuit was programmed to switch at a rate of 1024Hz and the output of the op amp showed distinct voltage values with a waveform at 1024Hz The AGC was tested by changing the amount of light incident on the photodiode The intensity of light from the red and infrared LEDs depends on the DAC output 126 to the LED select circuit The red light was observed visually to change significantly under different conditions An oscilloscope was utilized measuring the op amp output to confirm that both lights would increase or decrease in intensity 5 3 3 Transmission Tests The focuses of these tests are to see the effects of the environment on our transmission strea
202. tween the value of the SpO and the pulse of the elderly parent The LED indicator labeled SpOz indicates that the item currently being displayed 133 is the SpOzs and the LED indicator labeled pulse indicates that the item currently being displayed is the pulse The backup battery status is displayed on the LED labeled backup The user then decides that they would like to unplug the RDU and travel into another room in the house to go to sleep Upon unplugging the RDU from the wall the RDU should automatically switch from the wall supply to the backup battery As the user travels throughout the house the RDU loses signal and the status is displayed on the LED of the RDU labeled signal The RDU then sounds a loss of signal alarm to indicate to the user that they are going out of range of the TSU The user then returns to watch some more TV and plugs the RDU back to the wall the RDU should automatically switch from the backup battery to the wall power The user and the parent fall asleep The TSU clip falls off of the parent s finger while they sleep and the TSU records no pulse and no SpO Upon the RDU receiving this new data the RDU should update the display to display the new data and since this is a dangerous condition the alarm should sound This wakes the user up and the user sees that the display is reading no pulse or SpO The user runs into the parents room to find them ok but the clip has just fallen off The user replaces the clip and
203. uation has been double checked and is known to be properly coded but the RDU is still displaying the incorrect value then the equation is incorrect The equation needs to be reprogrammed or a new equation needs to be found that is more accurate If this does not fix the problem the design may have to switch to a lookup table Hospital use pulse oximeters employ lookup tables to save computing power The coding would change significantly but since accuracy is critical to this project it would be worthwhile to change it Without a proper medical comparison the project cannot be considered safe This section is of the utmost importance to the design A lookup table can be obtained from hospital grade pulse oximeter manufacturers If a lookup table can be found it would save time and effort attempting to find a new equation The pulse rate is also tested Since a person s pulse can be obtained without any medical equipment this part is much easier to compare By placing two fingers on any major artery usually the carotid in the neck the pulse rate can be counted This makes it easy to check that the value obtained from the sensor transmitted and displayed on the RDU is the proper value of the pulse rate This should be tested multiple times Each group member should have their pulse taken by the unit to assure that it is correct The pulse display should also be tested by raising the heart rate If a group member runs their pulse will increase
204. upply into the LEDs needed for this project The final indicator is an array of green LEDs This will show the remaining battery life of the TSU This indicator is the most important If the TSU battery dies the monitoring of the patient is interrupted LED arrays can sometimes come with up to or over 100 LEDs For this design only four or five LEDs will be needed in the array For this DigiKey is again an excellent source The site has seventy eight different four and five green LED arrays They are in packages of chassis mount through hole and through hole right angle as well as different lens types voltages and shapes The parts can easily be narrowed down when the design is completed Manufacturers in the DigiKey list for green LED arrays include Kingbright Lumex and Chicago Miniature Lighting among others Each LED array has a specific set of values that will be matched to the parameters of the circuitry These indicators are essential to the safety measures of the system as well as the ease of use Thus choosing appropriate components is essential to the final design as well as the look and feel of the two units 41 Alarms An alarm or buzzer is needed for this design as well as the LED indicators The alarm will be used to alert the user to dangerous conditions such as pulse rate or SpO gt z that is too low loss of signal and low power on the TSU Three different sounds are necessary A long continuous beep will sound when a thres
205. use burns with the smallest flame The strength of the case would depend on the type of wood used Different types of wood that could be used are plywood balsa wood and basswood All three of these woods can be obtained easily through hobby shops Balsa wood in the size needed for the TSU housing may be too weak and break easily Plywood is strong but is likely to splinter Basswood is very similar to balsa wood but is slightly heavier and stronger A wood enclosure of this size should be constructed using high quality glue designed for use on wood Plastic Enclosure Plastic enclosures come in a variety of sizes and materials One plastic case that can be used to house the TSU PCB and the battery is the LP 21P by Polycase It is made of ABS plastic and as such is lightweight and very strong ABS plastic is flame retardant and safe to use and store in high temperature environments It is a very good insulator making it very useful for PCBs and will not cause a short in the circuitry The dimensions LP 21P are 2 47 W x 3 295 L x 1 0 H Metal Enclosure Metal provides a very strong very durable material that would perform well Metal however introduces the problem of shorting the wires on the PCB Ifa PCB were to be mounted in such a way as to isolate the metal connections from the metal casing the problem of shorting wires would not arise Many companies manufacture metal cases that are designed to address this issue Metal cases tha
206. ustomers should obtain the latest relevant information before placing orders and should verify that such information is current and complete All products are sold subject to Tl s terms and conditions of sale supplied at the time of order acknowledgment TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with Tl s standard warranty Testing and other quality control techniques are used to the extent Tl deems necessary to support this warranty Except where mandated by government requirements testing of all parameters of each product is not necessarily performed Tl assumes no liability for applications assistance or customer product design Customers are responsible for their products and applications using TI components To minimize the risks associated with customer products and applications customers should provide adequate design and operating safeguards TI does not warrant or represent that any license either express or implied is granted under any TI patent right copyright mask work right or other TI intellectual property right relating to any combination machine or process in which TI products or services are used Information published by TI regarding third party products or services does not constitute a license from TI to use such products or services or a warranty or endorsement thereof Use of such information may require a license from a third party under the patents or
207. utput is a center positive 5 5mm x 2 1mm barrel connector The TOL 08269 is available from sparkfun com for 6 The choice of a 5V supply when the microcontroller only requires 3 3V is to specifically satisfy the nature of the automatic switch so that the ICL7673 always chooses the AC DC as the primary source Currently the batteries being considered are AA cells Three AA cells give the secondary power source 4 5V and 8100mAh If it is determined that larger capacity batteries need to be used then the system will be converted to use those which would require a change of the RDU case Battery Monitoring The expected remaining battery life is monitored by connecting the battery to a resistor divider connected to ground with the dividing point connected to the positive terminal of a non inverting unity gain operational amplifier The 67 configuration for the operational amplifier is shown below in figure 31 using a Linear Tech LT6004 The max voltage of the battery is 4 5V which is well over the max voltage of 4 1V that can be applied to the pins of the CC430 The values of the resistors are chosen such that the voltage is reduced by half so that the output of the operation amplifier is capable of being connected directly to the microcontroller on an ADC input This value can then be compared to known values of the battery and determine the good bad status Reduced Battery Voltage DC DC LT6004 ne e Switch OpAmp
208. witch Switch ICL7673 0S102011MA1QS1 External Backup Power Battery TOL 08269 O T S C Sized Figure 71 Block diagram for the RDU Current ADC in e Amp Photodiode T6004 OED SP 23 TR IR LED APT1608F3C Red LED SML LXFTO603SRC TR Control Circuit Max 1 5 V Buck converter EP536801 Figure 72 Block diagram for the TSU 98 3 7 2 Schematics The schematics are shown below in figures 73 74 and 75 They show all of the pins used by the MCU on both the TSU and RDU The schematics also show a close up on the sensor Figure 73 Sensor Schematic Diagram 3 7 3 PCB Layouts The PCB layouts are show in figures 76 77 78 and 79 99 Figure 74 RDU Top Layer Figure 75 RDU Bottom Layer Figure 76 TSU Top Layer Figure 77 TSU Bottom Layer 101 3 7 4 Bill of Materials Quantity Designator Part Number Value Manufacturer Cost 10s 1 2 C1 C2 PSSS MI 0 51 2 1131 SES I 0 064 3 1 LEDA es 0 42 4 1 LED2 Ea I ZA 0 26 5 1 PINT Ee l 6 1 R1 E Wi WS 0 081 7 1 R2 E A 0 081 3 OR
209. with a capacitor If the inductor was chosen to be 1uH and the capacitor 10uF then the transfer function could be estimated to be one The alternate method was to use a ferrite bead to filter the power lines TSU Transient Suppression Transient currents could cause devices and circuits to fail where they should be able to work without issues and were hard to detect when they occur This problem could be a large hassle to debug but fortunately it was easy to include the solution to this problem in the beginning of a design To compensate for current transients there should be a capacitor at each major power connection to account for transients in the power lines This was accomplished by using a capacitor and connecting one side to the power connection and the other side to ground A smaller capacitor could also be connected in parallel to the first These capacitors had a stored charge that would be released if transient currents occur to keep them from interfering with the performance of the device TSU Battery Life Monitoring The expected remaining battery life could be estimated by using an operational amplifier connected to an ADC and having the expected battery life recorded for comparison in the microcontroller This could be accomplished by connecting the battery to a voltage divider connected to the positive terminal of a non inverting unity gain operational amplifier An example of this circuit was shown in Figure 10 The resistor value
210. with the system To test that the LEDs work within the system a voltage must be applied through the PCB that they are attached to This assures their pins are connected to the proper voltage nets the soldering has been properly completed and the nets are giving the correct voltage If the LEDs do not illuminate the voltage can be tested using a multimeter By attaching the multimeter to the solder traces that the LEDs are connected to the correct voltage can be verified If the voltage is incorrect then at least it is known that the LEDs are in working condition If the voltage reading is correct the LED may have been installed backwards If this is not the case then the LED may have gone bad and should be replaced When the RDU is working the LEDs can be tested for switching measurements One should illuminate when the output is pulse rate but the second should remain unlit The second should illuminate when the output is SpOz and the first 121 should turn off If this is not the case the LEDs may have been wired incorrectly The inputs should be checked to assure that each is connected to its proper positions Another possibility is that the MCU was improperly programmed and has its outputs switched between the two LEDs This requires the software to be checked and possibly rewritten in certain parts When the TSU is working properly and is functioning with the RDU the LEDs can be tested to assure that when the new numbers are trans
211. yle enpirion com gt Mon Dec 7 2009 at 2 00 PM To eroberts ee gmail com lt eroberts ee gmail com gt Hello Mr Roberts You may use the figure on the data sheet Good luck Karen Karen Boyle Enpirion Inc Perryville III 53 Frontage Road Suite 210 Hampton NJ 08827 Phone 908 894 6017 Original Message From Margaret Nolin Sent Friday December 04 2009 8 07 PM To Karen Boyle Subject FW Permission to reprint images for School Project think this customer is in Florida Margaret Original Message From eroberts ee gmail com mailto eroberts ee gmail com On Behalf Of Eric Roberts Sent Friday December 04 2009 3 08 PM To Margaret Nolin Subject Permission to reprint images for School Project Hello My senior design group is designing a wireless pulse oximeter and we are considering the use of the Enpirion EP5368QI buck converter for our device As part of the design processes we are required to submit a document with all of our designs and figures Can we use the figure in the EP5368Ql1 data sheet that shows the typical application of the EP5368Q1 Thank you Eric Roberts Il Texas Instruments 2009 Permission IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries Tl reserve the right to make corrections modifications enhancements improvements and other changes to its products and services at any time and to discontinue any product or service without notice C
212. ystem was going to be designed to run at roughly 3V or 3 3V The TSU should draw less than 50mA for a length of approximately 8 hours the average recommended time for an adult to sleep This would require 400mAh per use This battery would need to be rechargeable in order to maintain a daily usage and should be capable of multiple uses before needing to be recharged To fit these requirements a battery was needed with a working voltage at about 3 3V or higher 800mAh or higher and should be relatively small about AA size or less Battery model numbers were usually the chemistry type followed by a 5 digit number The first two digits were the diameter and the second two were the length i e LiFePO4 18650 had Lithium Iron Phosphate chemistry was 18mm in diameter and 65mm in length As a reference AA batteries were about 14mm in diameter and 50mm in length In Figure 7 showed the dimensioned drawing of a Saft LS14500 battery This battery was not included in the research because it was not classified as rechargeable A relatively new type of battery chemistry available was the LiFePO4 Lithium Iron Phosphate These batteries offered a large capacity high life cycle and lower size Their weight compared to the energy density and life cycle was lower than other chemistry types The tradeoff for LiFePO4 batteries was that the cells have lower nominal voltages LiFePO4 batteries could be less costly than standard lithium ion batteries due to the abund
213. z bands This would cause a lot of interference Although the 900MHz band also had a lot of interference due to its open availability it could be easily utilized and found in many transmitting integrated circuits For this project a general RF communication operating on the 900MHz band was most effective The main difference between RF communication on the 900MHz band and Bluetooth ZigBee and Wi Fi operating on their own specific bands was that there was no protocol associated with general RF This allowed the project to create its own protocol Having a generic protocol that works for most situations like Bluetooth ZigBee and Wi Fi was great but there were times when it is overkill In situations like these a new protocol could be developed and used to transmit and receive data This protocol would only work for this project specifically and would only work for the project for which it is intended Pros Availability of the 900 MHz band Flexibility to create a protocol Manufacturers were integrating MCUs with RF transceivers Many common transceiver parts available Low power No overhead Cons Unsecure Common RF bands interference Loss of generalization Loss of helpful protocols Loss of error correcting protocols Comparisons The major contenders are compared in this section The result of this section yields what method of communication would be used for transmission of the data from the TSU to the RDU Wi Fi and Infrare

Final Documentation - University of Central Florida

Contents

Download Pdf Manuals

Related Search

Related Contents