VAASAN AMMATTIKORKEAKOULU
Contents
1. 24652 The TL431 is a voltage regulator it controls the constant voltage to input into amplifier U4 s pin 3 The input voltage should be 4 096V This can be reached by adjust the trimmer VRI The amplifier gate A takes charge of controlling constant current through PT 100 R The current value is calculated by using the input voltage of U4A divided by R2 Ik Vy3 Ra 4 096 3 3k 1 2mA However in practice the amplifier circuit cannot reach the goal of generate the ideal constant current If current fluctuation can be controlled in a small range it can be seen as constant 110 Figure 6 current through the PT 100 In Figure 6 X axis shows the values of PT 100 in ohms Y axis shows the values of currents through PT 100 in mA 25 52 The maximum variation of the current is around 0 045mA It means the current change is so small that can be ignored So it is verified that the current through the RY PT 100 is constant From the right upper side of Ry the module function is amplifying the voltage over RL The amplifier gate B U4B amplifies the voltage over the PT 100 RL The ampli fied gain is calculated using R5 R3 R5 R6 R3 R4 is differential amplifier cir cuit required A R R3 100k 10k 10 In Figure 7 it shows the final output voltage variation refer to the RL PT 100 Figure 7 Output voltage of temperature sensor In Figure 7 X axis also shows the values of PT 100 in oh2. Figure 14 ODBC data source administrator 47 52 X N Connector ODBC Connection Parameters Data Source Name Description Named Pipe User e0600157 Password u u uuu Database e0600157_temperatu v Figure 15 ODBC connector It should be noticed that Excel 2007 just supports the 32bit mysql ODBC So only the 32bit ODBC data source administrator is compatible to configure the 32bit mysql ODBC In the operating system of windows 64bit the 32bit ODBC data source administrator application is under the folder of C Windows System32 Other ODBC data source administrator cannot find the mysql ODBC driver 48 52 6 TEST The system should be set up before the test as follows 1 Connect PCB to the 5V voltage source 2 Connect the 5V voltage source to STK501 AVREF 3 Connect PCB output pin to STK501 ADC input pin 4 Turn on the STK501 power source 5 Connect the STK501 to computer using RS232 The system can be controlled in the GUI application as Figure 10 after it is set up well The COM port will be detected automatically when the GUI application is started In Figure 10 the serial port settings are as shown Otherwise an exception error window is popped up Then the way of testing follows the steps shown below 1 In Modbus request block the function 0x03 and function 0x05 will be selected to test responses from the sensor slaves The received data can be r
3. Comparison of temperature sensors attributes 1 nccnenenne 13 Table 2 Descriptions of functions in GUI application oooocnoocccnnoccnonnnccnonccinnncnnnns 37 FlowChart 1 MCU operation process uunesscssssessnsenssnnennnnnensnnnennnnnnnnnnensnannnnnn 27 6 52 LIST OF APPENDICES APPENDIX1 Ready made PCB APPENDIX2 Components distribution APPENDIX3 Microcontroller Connection 7052 1 INTRODUCTION Control is not only the information processing it also implies the direct interac tion with the physical world Control systems include sensors and actuators which is needed to ensure that our automation system can help us manage our ac tivities and environments in desired ways Sensors provide inputs to control and automation systems by extracting information from the physical world Recently Data Acquisition system is widely used in the world With the devel opment of the modern industry process variables of temperature pressure flow rate and liquid level are main objects of observation Temperature is one of most important process variables among them For example in the fields of metallurgi cal industry chemical industry power industry machinery processing industry food industry and so on the temperature control system are required for all kinds of furnaces reactors or boilers Data Acquisition system is aimed to monitor the environment temperature and control the microcontroller The design of the sys
4. can be saved to the data base It should be noticed that all the frames in the communication belong to the protocol MODBUS and the Database mySQL is located in the school VAMK site 13 52 4 ANALYSIS 4 1 Temperature measurement device 4 1 1 Sensor camparison There are two kinds of sensors which are used widely They are thermocouple and resistance temperature detector RTD respectively A thermocouple is a device consisting of two different conductors usually metal alloys that produce a voltage proportional to a temperature difference between either ends of the two conductors RTD is sensor used to measure temperature by correlating the resistance of the RTD element with temperature Feature Thermocouple ao Response time Better Maximum temperature higher ruggedness Better costefficieney Better accuracy Better tongterm stabitty Better Standardization eeter Table 1 Comparison of temperature sensors attributes 1 Table 1 compares the attributes of two different sensors It shows the advantage for each sensor RTDs are generally considered to be among the most accurate temperature sensors available In addition to offering very good accuracy they provide excellent sta bility and repeatability RTDs also feature high immunity to electrical noise and are therefore well suited for applications in process and industrial automation 14 52 environments especial
5. commonly used components for microcontroller It can help us initialize the project when the specific components are not deter mined to use in the project The STK501 board is a top module designed to add Atmegal28L support to STK500 development board It consists of microprocessor Atmegal28L the 8 bit and 16 bit timer counter 10 bit analog to digital converter ADC The Universal Synchronous and Asynchronous serial Receiver and Transmitter USART and the memory J Tag is a programming used device which can be connected to the J Tag inter face on the board AVR studio is the programming IDE that uses gcc compiler 19052 4 3 1 Data flow in microcontroller Sensor signal ADC h MCU USART Atemegal28 microcontroller receives input signals from the signal conditioning circuit The signal will be processed by the analog to digital converter ADC firstly Then the output digital signal from the ADC will be sent to the temperate memory for MCU If the MCU need communicate with master station the data will be transmitted through the RS232 or RS385 interface using the USART 4 4 Protocol A communications protocol is a system of digital message formats and rules for exchanging those messages in or between computing systems and in telecommu nications Modbus is a serial communications protocol which is widely used in industrial electronic devices nowadays The reason
6. 0001 The total number of registers requested 0A84 The CRC cyclic redundancy check for error checking Response This response returns the ADC value in register 0 with device 01 01 The Slave Address 03 The Function Code read ADC Holding Registers 02 The number of data bytes to follow 1 registers x 2 bytes each 2 bytes 0015 The contents of register 0 0x0015 21 8B79 The CRC cyclic redundancy check Function 05 Request Slave Ad Function Start address Start address Status to write status to write CRC CRC dress code High Low High Low High Low This command is writing the contents of discrete coil 0 to ON and the slave address is 01 01 The Slave Address 05 The Function Code Force Single Coil 0000 The Data Address of the coil 36 52 FFOO The status to write FFOO ON 0000 OFF CACD The CRC cyclic redundancy check for error checking Response Slave Ad Function Start address Start address Status to write status to write CRC CRC dress code High Low High Low High Low The normal response is an echo of the query returned after the coil has been written 01 The Slave Address 05 The Function Code Force Single Coil 0000 The Data Address of the coil FFOO The status to write FFOO ON 0000 OFF CACD The CRC cyclic redundancy check for error checking 5 3 GUI application on master station This application is designed using the Qt language which is speci
7. 45 52 5 4 Excel displays data from the MySQL database A cut Calibri Ju AE gt Wrap Text General x Ha Copy Bste Format Painter Hien E OA A E SB EF H Merge amp Center Bra gt 58 EJ en Clipboard E Font E Alignment E Number E 620 G amp 2 B G D E F G H 4 5 IB Eu Bozen ar De 6 31 16 7 ZE ON 20 1537216 8 Sl ON 15 15 37 28 9 41 ON 10 15 37 28 10 a ON 28 15 37 32 dl 61 ON 30 15 37 35 12 21 ON 21 1537 37 13 81 OFF NULL 15 38 30 14 Sjal ON 15 15 38 20 15 101 ON 21 15 39 18 16 17 12 Figure 13 MySQL data in Excel Figure 13 shows the Database table named temperature in the Excel In the table slave address is displayed in the second column the state of ADC is displayed in the third column the temperature is displayed in the fourth column and the time is displayed in the fifth column Before Excel are connected to mysql database the ODBC need to be installed The mysql ODBC configuration is shown in Figure 14 and Figure 15 46652 dBASE Files Microsoft Access dBASE Driver dbf ndx md Excel Files Microsoft Excel Driver xls xlsx xlsm xlsb MS Access Database Microsoft Access Driver mdb accdb temperature MySQL ODBC 5 1 Driver temperature2 MySQL ODBC 5 1 Driver An ODBC User data source stores information about how to connectto the indicated data provider A User data source is only visible to you and can only be used on the current machine
8. ART register will be saved to receiving buffer in sequence The maximum size of buffer is 32byte The receive buffer will be reloaded if the USART is timeout in 10ms The MCU will configure the sending buffer after the USART receiving completes Then the data in the sending buffer will be transferred to the USART register in sequence This will make the USART send the data After all the data in the sending buffer are sent the receive status will be restored 5 2 3 Watchdog Watchdog is a separate counter counts if it starts It will force the system stop if the program is stuck wdt_reset this prevents a timout on enabling wdt_enable 7 WATCHDOG ENABLED don t forget to issue WDRs Watchdog prescaler chosen is 2048 KHz The timeout counts almost 2s If watch dog is not fed in 2s the program is forced to stop 5 2 4 ADC Analog to Digital Converter ADC transform the temperature analog signal to digital format in every 100ms if the ADC status is ON ADMUX is ADC Multiplexer Selection Register 32 52 ADMUX 0xDE ADMUX 0x00 Bit 7 6 REFS1 0 00 Voltage Reference Selection AREF Internal Vref turned off Bits 4 0 MUX4 0 00000 Analog Channel and Gain Selection Bits ADCO PFO ADCSR is ADC Control and Status Register ADCSRA 0x85 Bit 7 ADEN 1 ADC Enable Bit 5 ADFR 0 ADC Free Running Select no free run single mode Bits 2 0 ADPS2 0 101 ADC Presca
9. L2 and L3 measure the voltage drop across the RTD element Eo must have high impedance to prevent current flow in the potential leads 4 2 Analog to Digital Converter resolution Analog to Digital Converter ADC is an electronic device that converts voltage to digital number proportional to the magnitude of the voltage which we call it as reference voltage The resolution of the converter indicates the number of discrete values it can pro duce over the range of analog values 18 52 The configuration of ADC resolution in microcontroller has normally two types They are respectively 8 bit and 10 bit Here the n bit means there are 2 quantiza tion levels In practice Quantization error and non linearity are intrinsic to any analog to digital conversion However through the resolution selection the error can be reduced In the signal conditioning circuit PCB the output voltage range is between 0 7 1 5V which refers to the temperature approximately between 60 120 C If the system requires the accuracy to 1 C the quantization levels should be around 180 for ADC In the 8 bit ADC the quantization levels are 1 5 0 7 5 248 40 But in the 10 bit ADC the quantization levels are 1 5 0 7 5 2410 163 Apparently the 10 bit is approaching to the required value 180 So in order to reduce the quantization error the better choice is 10 bit resolution for the ADC 4 3 The STarter Kit STK The Starter Kit is a collection of
10. ad the temperature record through internet they can just connect their own appli cations to the Database 11 52 3 PROCESS DESCRIPTION Sensor Sensor gt Address 02 Address 01 Sensor Sensor Address 04 Address 03 Figure 1 System Structure In Figure 1 System is divided into two main parts They are the remote terminal unit RTU and the master station respectively The RTU is also composed of sig nal conditioning PCB part and microcontroller part 1 The part of signal conditioning PCB is shown where sensor address is marked The PCB connects to the temperature sensor PT 100 which will transform the physical temperature parameters to analog signals Then the signals will be amplified by the signal conditioning circuit on PCB In this case the processed analog signals can be output to the microcontroller 2 The part of microcontroller is shown where the MCU is marked The mi crocontroller will digitize the input analog signals with ADC and com municates with master station through RS232 or RS385 interface Moreo ver the MODBUS for RTU protocol is utilized in the communication be tween microcontroller and master station 3 The part of master station is shown where Master Computer and Data is marked The GUI application is designed on the master station which monitors the messages of communication and displays the temperature da 12 52 ta Furthermore any displayed temperature data
11. alized in GUI designing Graphic user interface is convenient to monitor the remote terminal interface RTU In Table 2 the following functions are realized in GUI applica tion Function Descriptions Serial Port Configure the serial port MODBUS Configure the Modbus frames MODBUS Monitor Display the send receive raw frame Register Display the received data in register 37 52 DataBase Configure the mySQL database Table 2 Descriptions of functions in GUI application 5 3 1 Serial port configuration Settings Serial port Baud Data bits Stop bits Parity Prolific USB to Serial Comm Port COM6 9600 por 1 none Y Figure 8 Serial port In Figure 8 it shows serial port configuration When the GUI application is started it will check the COM port of local computer The laptop in this system needs a peripheral of USB to Serial cable which will produce a COM port for application Baud rate is the value to measure how many symbol per second Each symbol can represent or convey one or several bits of data But in serial port there are only two logic levels 0 and 1 So it means the baud rate value equals to the bit rate value which indicates the transmission speed The system set the baud rate to 9600 baud which is required for the MODBUS protocol Data bits value in each character can be 5 for Baudot code 6 rarely used 7 for true ASCH 8 for any kind of data as this matches t
12. cnonnnccnnns 22 5 2 Digital signal processing in STK501 2200220ssssnseessnnennnnennnn 26 9 2 1 ES 28 322 A oO ae at Mate ects en Clear laa els hase aa 29 3 25 E 31 24 AD enorme 31 5 2 5 5 2 6 Modbus RTU protocol SettiMgS oooooccononcccnoncccnoncnononnconancconnnnnos 34 5 3 GUI application on master station ooooococconcccnoncnononcnonnncnonnncnnnnncnnnnnccnnns 36 5 3 1 Serial port CONEA A A a AER 37 33 2 MODAS TEQUES ESO is 38 5 3 3 MCU control box s function oonconncnnonnnnconccnoncnnnonncnnnconannncnnnonos 41 5 3 4 MySQL database control box s function eenee 43 5 4 Excel displays data from the MySQL database oooconnnccccnoccccnoncccnannnonns 45 6 TES ini biniel hinlitien 48 E DISCUSSION o 49 Oe CONCLUSION o ade ates states 50 AN o AA ee fee 50 8 2 2SINDAB es ee ee ner 51 O REFERENCES eu 52 APPENDICES LIST OF FIGURES AND TABLES 5 52 Figure 1 System Structure 11 Figure 2 2 wire circuit 1 16 Figure 3 3 wire circuit 1 16 Figure 4 4 wire circuit 1 16 Figure 5 Signal conditioning circuit 23 Figure 6 current through the PT 100 24 Figure 7 Output voltage of temperature sensor 25 Figure 8 Serial port 37 Figure 9 Modbus request setting 38 Figure 10 Get temperature value 41 Figure 11 MODBUS monitor 42 Figure 12 Database control 43 Figure 13 MySQL data in Excel 45 Figure 14 ODBC data source administrator 46 Figure 15 ODBC connector 47 Table 1
13. ction code is the request command It tells what the slave should do Several commonly used functions are introduced as below 1 Function 03 Read Holding Registers 39 52 Request Function code 1 Byte 0x03 Starting Address 2 Bytes 0x0000 to OxFFFF Quantity of Registers 2 Bytes 1 to 125 0x7D Response Function code 1 Byte 0x03 Byte count 1 Byte 2 x N Register value N x 2 Bytes N Quantity of Registers Example used in System Send data 01 03 0000 0002 c40b Received data 01 03 04 00 04 00 07 fa30 2 Function 05 Write Single Coil Request Function code 1 Byte 0x05 Output Address 2 Bytes 0x0000 to OxFFFF Output Value 2 Bytes 0x0000 or OxFFOO Response Function code 1 Byte 0x05 Output Address 2 Bytes 0x0000 to OxFFFF 40 52 Output Value 2 Bytes 0x0000 or OxFFOO Example used in System Send data 01 05 0000 ff00 8c3a Received data 01 05 0000 ff00 8c3a 3 Function 01 Read Coils Request Function code 1 Byte 0x01 Starting Address 2 Bytes 0x0000 to Ox FFFF Quantity of coils 2 Bytes 1 to 2000 0x7DO Response Function code 1 Byte 0x01 Byte count 1 Byte N Coil Status n Byte n N or N 1 N Quantity of Outputs 8 if the remainder is different of 0 gt N N 1 4 Function 06 Write Single Register Request Function code 1 Byte 0x06 Register Address 2 Bytes 0x0000 to OxFFFF Register Value 2 Bytes 0x0000 to OxFFFF Response Function code 1 Byte 0x06 Register Address 2 Bytes 0x0000
14. e Database for further processing 2 2 Problems to be solved If the objective above were fulfilled the following problems would be solved 1 To measure the temperature is actually to transform physical parameters to analog signals So different sensors should be compared and chosen ac cording to their own attributes In the control system the analog signal al ways needs to be manipulated for further processing In this case the sig nal conditioning circuit should be designed for the sensor 2 In computer architecture digital signal is commonly used in microcon troller or computers So the digital signal processing is necessary for trans forming the analog signals 3 To bridge the master station and RTU communication device is neces sary to be considered and communicational protocol also needs to be taken into account according to the devices we choose 4 On the master station user interface application is used to control the sensor system So the following functions should be integrated at least in the application according to the objective 10052 1 Display the temperature data sensor address and time at least 2 Turn on off the sensor system 3 Display the data frame 4 Analyze the protocol 5 For further processing the temperature data or massive data storage the Database is needed The system should have some functions to save the temperature data to the Database For example if people want to re
15. e humidity or pressure monitoring Other control functions can be added according to the specific work 51 52 For example in coolant temperature system if the temperature on a device is too high or too low aPWM wave can be generated to control the speed of fans so as to control the temperature on the device This system developed is only a prototype to learn more about the control system 82 Summary In this project the goal is to achieve concrete evidence that this sensor measure ment method and communication method of electronic devices can be used and implemented to the industrial applications as one developed here We just design develop and construct a prototype system based on the control system technology By accomplishing the project work I am gradually familiar with PCB design em bedded system programming Qt language and use of MySQL database There are a lot of difficulties during the development of my work Since I have no much prior experience with practical control system engineering the difficulties need to be solved by reading and referring to many related materials in this field during which skills and knowledge can be increased The system can be still improved in any aspects I would like to see the develop ment of the actual system go ahead in future 52 52 9 REFERENCES l Positive Analog Feedback Compensates PT100 Transducer Accessed 22 2 2012 http www maxim ic com app notes index mvp
16. ead in the Register block and raw data received and its frame structure data is shown in Modbus Monitor block Other functions are reserved for future use 2 The button Temperature controls to read the temperature data from sen sor And they are shown in row 1 and column 5 of Register block 3 The button ON OFF controls the status of ADC ON and OFF and the ADC index led in the MCU STKS501 4 If the button OPEN is pressed the application will connect to database and refresh the database at the same time The records in database will be cleared 5 If the button WRITE is pressed the formatted temperature data and re quest time shown in Register will be saved to the mySQL database at school 49052 6 Open the ready made Excel file which is created to show the table temper ature in mySQL The temperature data information can be checked here 7 DISCUSSION In this project some problems are discovered in the process But they are not solved for some reasons Some designs are easily misunderstood by users All of these wonders are discussed as below 50 52 1 The remote terminal unit is not integrated The sensor conditioning and digital processing devices are separated in two PCB They are connected through wires which will take up much more space and waste time in connection In the meantime the use of STK501 as MCU has a lot of un used components All of these will i
17. ee VAASAN AMMATTIKORKEAKOULU 00 0 VASA YRKESH GSKOLA UNIVERSITY OF APPLIED SCIENCES Mingliang Zhao DATA ACQUISITION SYSTEM USING ATMEGA 128L Information Technology 2012 1 52 FORWORD This thesis was made in Vaasa University of Applied Science during the academic year of 2011 2012 The special thank goes to my helpful supervisor Mr Menani Smail The supervi sion and support that he gave truly help the progression and smoothness of the project The co operation is much indeed appreciated My grateful thank also goes to the Mr Martila Jukka He offered me the thesis topic and gave me technique support during the project design Mingliang Zhao 01 Feb 2012 2 52 VAASAN AMMATTIKORKEAKOULU UNIVERSITY OF APPLIED SCIENCES Degree Program of Electronics and Information Technology Author Mingliang Zhao Title DATA ACQUISITION SYSTEM USING ATMEGA128L Year 2012 Language English Pages 52 2 Appendices Name of Supervisor Menani Smail Data Acquisition system is developed to monitor the environmental temperature and control the microcontroller System consists of remote terminal unit RTU and supervisory station PC Remote terminal unit connects to the physical equipment sensor PT 100 which comprises a signal conditioning circuit and a microcontroller The signal conditional circuit transforms the physical temperature parameters to analog signals and manipulates these analog signals Then micro controller will c
18. enable Led 7 on is receive enable Led 6 blinked is test for the timer Led 5 blink is ADC enable 34 52 5 2 6 Modbus RTU protocol settings When the USART check receiver buffer it will determine what the slave address function name register or coil start address read write data bytes and CRC code are The received data frame is transmitted from the laptop In general the function 01 03 05 06 15 16 are always used The meaning of the function can be revealed from its name The function name is shown as below Function 1 Read Coil Status Function 3 Read Holding Registers Function 5 Force Single Coil Function 6 Preset Single Register Function 15 Force Multiple Coils Function 16 Preset Multiple Registers The Function 3 and Function 5 are mainly used in our system The Function 3 takes charge of requesting for the temperature data The Function 5 changes the status ON OFF of ADC After all frames in the receiving buffer are checked the response frame will be set and transmitted Function 03 Request frame Slave Ad Function Start address Start address No of register No of register CRC CRC dress code High Low High Low Low This command is requesting the content of ADC holding registers 0 from the sensor slave device with address 01 35 52 01 The slave address 03 The Function Code read ADC Holding Registers 0000 The Data Address of the first register requested
19. he size of a byte or 9 rarely used 8 data bits are almost universally used in newer applications Stop bits sent at the end of every character allow the receiving signal hardware to detect the end of a character and to resynchronize with the character stream In the electronic device 1 stop bit is always set 38 52 Parity is a method of detecting errors in transmission The electronic device adds up the number of bits in a character and if the parity bit setting disagrees with the sum of the other bits the device reports an error Parity checking schemes work by storing a one bit digit 0 or 1 that indicates whether the sum of the bits in a data item is odd or even In this system none is set which means no parity bit This setting is approved in MODBUS protocol 5 3 2 Modbus request settings ModBus Request Slave ID Function code Start address Num of coils 1 Read Coils 0x01 Y 0 1 Display hex data 01 01 00 00 00 01 Send Figure 9 Modbus request setting The Figure 9 shows the MODBUS settings which will contribute to research about MODBUS protocol Slave is the request address It always take the first byte in the transmit receive frame Start address is the bytes to let the slave know from where of their register to send the data Number of coils is how long bytes of the data to be sent From the start address and the number of coils the required data can be found in the register Fun
20. id 3450 gt 2 Atmetga 128L datasheet Accessed 18 2 2012 http www atmel com Images doc2467 pdf gt 3 STK501 user manual Accessed 18 2 2012 http www atmel com Images doc2491 pdf gt 4 STK502 temperature monitoring system with LCD Accessed 23 2 2012 http www atmel com Images doc2529 pdf gt 5 MODBUS tutorial Accessed 23 2 2012 http www lammertbies nl comm info modbus html gt Qt serial port library configuration Accessed 23 2 2012 http code google com p gextserialport 6 Qt 4 5 and MySQL plugin with Mingw on Windows XP Accessed 21 2 2012 http christopher rasch olsen no 2009 04 14 qt 45 and mysql plugin with mingw on windows xp APPENDICES 1 2 APPENDICES APPENDIX1 Ready made PCB APPENDICES 2 2 APPENDIX2 Components distribution 4 APPENDIX3 Microcontroller Connection
21. ld amplify the analog signals for further use Hence in the first module the way of the RTD or PT 100 being connected to the signal conditioning circuit is very important Figure 2 2 wire circuit 1 Figure 3 3 wire circuit 1 Figure 4 4 wire circuit 1 Es is the supply voltage Eo is the output voltage 16 52 17 52 R1 R2 and R3 are fixed resistors L1 and L2 are lead resistance RT is the RTD PT 100 connection has 3 common ways to be implemented to the circuit Figure 2 shows that the temperature is determined by measuring resistance But when measuring the resistance of the sensing element RT the resistances of the leads L1 and L2 and cables R1 R2 and R3 are also measured So 2 wire con nection gives an error Figure 3 shows the way to compensate the error with 3 wire connection In this circuit there are three leads coming from the RTD instead of two L1 and L3 carry the measuring current while L2 acts only as a potential lead No current flows through it while the bridge is in balance Since L1 and L3 are in separate arms of the bridge resistance is canceled Figure 4 shows another way of choice to do the compensation with 4 wire connec tion 4 wire RTD circuits not only cancel lead wires but remove the effects of mismatched resistances such as contact points A common version is the constant current circuit shown here Is drives a precise measuring current through L1 and L4
22. ler Select Bits 32 ADCSRA 0x00 disable ADC In the ADC initialization the reference voltage is set to 5V The single mode is selected PFO receive the input temperature analog signal rpt100 5 float tempADC 1024 beta adcData adcCount uint16_t 1 0 385 rpt100 100 0 385 100 temperature from 100 to 200 rtp100 is the resistance value of the PT 100 tempADC is the value of ADC register adcData is the ADC buffer The beta value should be the amplifier gain times the constant current in the signal conditioning circuit The theoretical value is 0 01 10 0 001A However because 33 52 constant current and amplifier produce the error in practice the beta value should be adjusted in the calibration step The data in the ADC buffer is prepared to be transmitted through the USART So only the unsigned data type is accepted Since the temperature value ranges from 60 to 120 the data in ADC buffer or sent data is arranged to add 100 in case of producing negative data The temperature data saved in the ADC buffer is calculated according to the for mula below Ry 0 385 AT Rro This formula shows the relationship between temperature and resistance of PT 100 which has already introduced in the previous analysis 5 2 5 PORT PORTB OxFF set default 7 LEDs off DDRB OxFD Pin direction is output for 1 PORTB is reserved for the index led It is connected to the LEDS port Led 7 off is send
23. ly around motors generators and other high voltage equipment Since thermocouples measure wide temperature ranges and are relatively rugged they are very often used industrial and process applications where accuracy may be a less important factor However the data acquisition system is designed to measure the room tempera ture which is in a small range from 60 120 C The ideal temperature accuracy is 0 1 C So according to the previous statement the RTD is more suitable for our design Sensor type PT 100 belongs to the resistance temperature detector RTD The measurement range is 200 to 850 C It should be noticed that since the heat conduction in resistor takes time the re sponse time of thermocouple is better than RTD It means that the sensor PT 100 cannot reflect the environment temperature instantly There is a relationship between temperature and corresponding resistance For al most all pure metal resistors the relationship is in proportional According to the experimental statistic the relationship of PT 100 is in formula as below Ry 0 385 AT Rro Rr is the resistance at temperature T RT is the resistance at temperature To AT is the difference of T and To 4 1 2 Signal conditioning circuit In the signal conditioning circuit there are two important modules The first mod ule generates the analog signals according to the physical temperature parameters 15 52 The second module wou
24. ms Y axis shows the values of the output voltages 26 52 The voltage variation is 0 8V during the interval from 70 ohms to 1500hms The resistance interval corresponding to the temperature is between 60 and 120 C It is known that the temperature measured is proportional to the resistance of sensor PT 100 The PCB design is done by the PADS LOGIC and PADS The final CAM file is in appendices 5 2 Digital signal processing in STK501 In the STK501 digital signal processing is usually to convert the signal from an analog to a digital form by sampling and then digitizing it using an analog to digital converter ADC This digital signal then will be packaged in frame to send 1t to the laptop using USART The frame format is according to its function and the protocol MODUBS Start Initialize Devices gt Set PORTB output for LEDS Initial state is OFF Check the watchDog Set the watchdog Enable the watchdog Check the timer Every 100ms ADC runs one time Set the timer 10ms inerrupt Check the Com port MODBUS Set the ADC Single convert End Set USART RX TX complete interrupt FlowChart 1 MCU operation process 27 52 FlowChart 1 shows the microcontroller operation process The process mainly in cludes the analog to digital convention and da
25. n can only display the data temporarily So it is necessary to save the data which will be used in future MySQL is the most popular open source database server in existence currently It 1s commonly used for Web applications embedded applications and has become a popular alternative to proprietary database systems because of its speed and relia bility 21 52 It should be noticed that MySQL can run on UNIX Windows and Mac OS and the system connects the Database located in VAMK through the internet 22 52 5 DESIGN AND IMPLEMENTATION 5 1 Signal conditioning circuit design The objective of this circuit is generating appropriate electronic signals according to the temperature physical parameters The circuit is divided into two modules as its functions The first module generates constant current through PT 100 to pro duce the voltage signal for the PT 100 four wire connection requires the constant current input The second module amplifies the signal to make it available for ADC in microcontroller D1N4733 R5 100k R3 10k R4 AM 10k RL nal x C1 0 1u 3 2 LM324 R2 3 3K s VR1 1K SET 061 UJTL431 4 Figure 5 Signal conditioning circuit In Figure 5 it shows signal conditioning circuit design From the left lower side of RL the function of the module is to generate the constant current through the RL PT100 23 52
26. ncrease the price of system 2 The GUI application does not apply the function of automatically record ing the temperature from the sensor Some users think that the button Temperature and the button Write should be merged together and re peat this merged function in a timer interval 3 The data saved in the database can be shown in the GUI application It is inconvenient to check in Excel The first wonder is a problem caused by the PCB making capability Incorporat ing the signal conditioning circuit with MCU is available in the step of PCB de sign However it is not easy for making the PCB by individual The reason is the lack of professional tools and knowledge The second wonder is a misunderstanding The objective of this project is not only to build up a control system but also do a research about MODBUS protocol In this case every transmitted frame should be monitored in the application So the functions seem to be complicated The third wonder is also a misunderstanding caused by the objective of project The magnitude of the data record should be considered in the design If the data in database is large enough it is inconvenient to show them in the GUI application In addition the objective of project does not include displaying the data in data base The Excel work is just an adjunct to check the database value 8 CONCLUSION 8 1 Project development This project also can be expanded to the other fields lik
27. onvert analog to digital signals and send them through RS232 ca bling The term supervisory station also can be called as master station refers to the application GUI responsible for communicating with the RTUs which are distributed to measure the temperature of different places In this simple DATA ACQUISITION system the supervisory station is only composed of a single PC The thesis of DATA ACQUISITION system mainly concentrates on the electron ic and software design for this remote terminal unit as well as the software devel opment for the GUI on master station Keywords RTD Atmegal28 MySQL PADS MODBUS Qt 3 52 CONTENTS FORWORD ABSTRACT 1 INTRODUCTION espina daa seem aan 7 2 REQUIREMENTS ME Ne 9 E 9 2 2 Problems to DE SO di 9 PROCESS DESCRIPTION St 11 4 ANALYSIS siii id it 13 4 1 Temperature measurement device uursnsessnsessnseensnnenssnennnnennn nennen 13 4 1 1 Sensor camparison un ae 13 4 1 2 Signal conditioning circuit anne dias 14 4 2 Analog to Digital Converter resolution u enseessersnersnnesnnennnnennnnnsnnennne 17 43 Whe Sil atten Kit SIR A re 18 4 3 1 Data flow in microcontroller 22u0022022ersneenneennnesnersnnennne 19 A Protocols a eo Led e 19 dd User Interface castrado cool 20 4 6 Databases illa 20 5 DESIGN AND IMPLEMENTATION 22 2222220420022002sonnnennnennonsnensennnen 22 5 1 Signal conditioning circuit design oooonooccconocccooncncnonanononcnononcncnnn
28. s of ADC If counting from left to right for the raw data received the bit 8 to bit 11 are 0000 and FFOO respectively 0000 means the ADC 1s in the state of OFF while FFFF means the ADC is in the state of ON 5 3 4 MySQL database control box s function Registers DataBase Data type Register Data Slave Tempers Time DB Connection Holding Register 1 0 221 1 21 Vi am A Foren Holding Register 1 1 222 i 22 223 Fe o DB Written WRITE Figure 12 Database control In Figure 12 database group box has two buttons The button OPEN starts the mysql database It sets up the connection between the mysql database and the lap top and initializes the table which saves the temperature data information in Data base The button WRITE writes data to the database from the row 1 of table Reg ister The data includes information of slave address temperature and time Ex cept for these the states of the ADC are still to be written The below is mysql query language queryl exec drop table temp 44 52 throw away the table temp if it exists queryl exec create table temp ID int 100 primary key Slave varchar 15 SwitchStatus varchar 15 Temperature varchar 15 Time varchar 30 create table temp QString tableData QString insert into temp val ues 1 2 ON 3 4 arg dataCount arg slave_reg arg temprature_reg arg time_reg query2 exec tableData add the values in the table
29. s to use the Modbus in industrial environment are It has been developed with industrial applications in mind It is openly published and royalty free It is easy to deploy and maintain A RON ce It moves raw bits or words without placing many restrictions on vendors Modbus is often used to connect a supervisory computer with a remote terminal unit RTU in Data Acquisition systems 20 52 4 5 User Interface To fulfill the requirements of the system the following functions need to be real ized at least Supervise the communication frames in MODBUS Display received temperature data Display formatted temperature data Command to get the temperature data from the sensor SE O D S Command to save temperature data to Database In order to be more convenient for the users graphic user interface is proposed to be built For this reason Qt language which is designed for GUI application is chosen Qt language allows you to write advanced applications and Uls once and deploy them across desktop and embedded operating systems without rewriting the source code saving time and development cost Qt Creator is a cross platform integrated development environment IDE tailored to the needs of Qt developers It provides the code editor and integrated UI de signer The UI designer offer simple tools for the programming 4 6 Database Database can be used to save the data permanently while the previous GUI appli catio
30. ta transition 28 52 5 2 1 Timer Timer is typically digital counters that either increment or decrement at a fixed frequency which is often configurable and that interrupt the processor when reaching zero or a counter with a sufficiently large word size that it will not reach its counter limit before the end of life of the system TCCRO is Timer Counter Control Register TCCRO 0x00 bit6 3 0 timer select normal mode bit2 0 0 no clock source timer stop TCCRO 0x03 CLK 64 set prescaler Timer starts TIFR is Timer Counter Register TIFR 0x00 When TIMSK is set the bitO set to 1 automatically TIMSK Timer Counter Interrupt Mask Register TCNTO 0x83 255 123 1 64 8000000 1ms In the initialization the timer mode timer prescaler and timer value are set Timer interrupt can be started when the TIMSK and global interrupt is set Timer interrupt is divided into 3 intervals They are respectively Ims 100ms and 1s 29 52 1millisecond USART receiving timer out is checked If there is no data received currently the receive buffer will be reloaded 100millisecond ADC starts once and ADC register value is saved to the ADC buffer when the status of ADC is set ON Otherwise ADC will not start 1 second The led status is changed with the interval of 1s This is a test for timer The timer configuration is right 1f the led blinks in an interval of 1s which can be examined by a s
31. tem can also help us to learn the protocol MODBUS which is widely used in electronic devices The objective of doing this project is to acquire knowledge and understandings of the control system Apart from this the programming language and communica tion method will be learned and mastered In this thesis the chapter 2 raises up the problems needed to be considered accord ing to the objective of the project The chapter 3 introduces the system structure and how the system works The chapter 4 finds out the method to solve the problems in chapter 2 The chapter 5 introduces the design and implementation according to the structure of system The chapter 6 gives way of testing the system 8 52 The chapter 7 discusses the frequently asked questions and the problems that have not been solved The chapter 8 summarizes the process of doing this project 9 52 2 REQUIREMENTS 2 1 Objective In the Data Acquisition system Remote Terminal Unit RTU will measure the environmental temperature data between 60 120 C The GUI application on master station PC will send the requests of getting the temperature data or set ting the status of ADC on microcontroller In addition the GUI application will show the frames of different requests and feedbacks Every frame which is a pack of transmit receive data represents the different function in MODBUS protocol The temperature data got from the RTU will finally be saved to th
32. to OxFFFF Register Value 2 Bytes 0x0000 to OxFFFF 5 3 3 MCU control box s function 41 52 There are two buttons specialized to control the RTU One button reads the tem perature data from certain sensor salve The other writes to change the status of ADC ON or OFF If the ADC is in the state of ON there is temperature data to be read If the ADC is in the state of OFF the request will get null feedback File Help Settings Serial port Baud Data bits Stop bits Parity Prolific USB to Serial Comm Port come 9600 s 1 none ModBus Request Slave ID Function code Start address Num of coils 1 Read Coils 0x01 vo all a v Y Display hex data 01 01 00 00 00 01 Registers Data type Register Data Slave Tempers Time 1 21 19 59 i 2 Ea Figure 10 Get temperature value System Control DataBase DB Connection ModBus Monitor Raw data received 61 03 04 00 dd 66 de ea 51 ModBus requests responses nction cor artaddre umofcoi CRC u 3 0 2 0000 a 13 0 1 ea51 In Figure 10 1f the Temperature button in System control group box is pressed the received and send data will be displayed respectively in the table of Register text edit of Raw data received and table of ModBus request responses 42 52 In the table of Register the useful information of received data will be displayed in category The first column is t
33. top watch In the meantime the blinking led also shows that the Microcontroller starts working 5 2 2 USART USART universal synchronous asynchronous receiver transmitter is a piece of computer hardware that translates data between parallel and serial forms It is commonly used in conjunction with communication standards RS232 or RS485 UCSRO is USARTO Control and Status Register UCSROA 0x00 disable all kinds USART interrupt UCSROB 0x00 disable USART while setting baud rate UCSROB 0xD8 Bit 7 RXCIEn 1 RX Complete Interrupt Enable Bit 6 TXCIEn 1 TX Complete Interrupt Enable Bit 4 RXENn 1 Receiver Enable Bit 3 TXENn 1 Transmitter Enable 30 52 UCSROC 0x06 Bit 6 UMSELn 0 USART Mode Select Asynchronous Operation Bit 5 4 UPMn1 0 0 Parity Mode None Bit 3 USBSn 0 Stop Bit Select 1 bit Bit 2 1 UCSZn1 0 11 Character Size 8 bit UBRRO is USART Baud Rate Registers UBRROL 51 set baud rate low UBRROH 0x00 set baud rate high when fosc 8MHz UBRRO setting value is 51 In the initialization the transmitter and receiver transmitter and receiver complete interrupt are enabled The receiving index led is turned on System required serial port settings in USART as below Baud rate 9600 Char size 8 bit Stop bit 1 bit Parity None 31 52 When USART receiving completes the interrupt is triggered Then the data in US
34. ype of received data 16 bit means the maximum displayed value is 65535 2 16 1 The second column is register address which means where the received data are read Third column is received temperature da ta which is not formatted The fourth column is the slave address The fifth col umn is the formatted temperature value that can upload to Database The final column is the time to read the sensor The rows show all the useful information of received data of different register address ModBus Monitor Raw data received Clear 61 65 66 66 66 66 cd ca System Control 61 65 66 66 FF 88 8c 3a Temperature DataBase DB Connection ModBus requests responses Clear nection co art addre um of coi CRC 1 5 0 0 0000 Al 5 0 1 cdca DB Written 21 5 0 65280 0000 i i Nh a gt Figure 11 MODBUS monitor Figure 11 shows that the ModBus monitor group box can display the sent and re ceived data frame 43 52 In the text edit of Raw data received it displays one received data frame for each row In the table of ModBus request responses it shows the structure information of the received and transmitted data frame in category In Figure 11 the ON OFF button has been pressed twice in the example The ModBus request responses shows that the function code is 5 the register start ad dress is 0 the number of coils is 1 and the CRC can be checked The Raw data received shows the statu
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