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Additional technical information for CanSat competition 2014

1. MINUS ENGINEERING Additional technical information for CanSat competition 2014 Information for users of the European CanSat kit prototype 2013 Reference CSUK TO1 Version 2 0 Date 25 09 2013 Issued By Hein Olthof Valid from 25 09 2013 Reviewed By Eric Smit Additional technical information for CanSat competition 2014 Reference CSUK T01 Version 2 0 Page 2 53 MINUS ENGINEERING Change record Version Date Chapter Remarks 17 January 2013 all Creation 25 September 2013 all General review T Minus Engineering This document is composed for STEM center York for the aid of the European CanSat competition 2014 MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 3 53 Table of contents OCU CU OM ca cesssteece estes ceseetneesasests E A E A A 5 ST ING AS SIONS EA EEN E EENE naa A E A T A TEE ESE E E 6 PUJOL CONS EIE a E T A T E TA T A E ANO 7 FSS Neh MO nE Laa MS OMS oases vac A AN T A I A A A S A I NNE A OA A A T NA 8 FNS SS TG IE OMe A E E A E E E E E 8 BSS 1 CS E E E E N E N AEA A E ANA E O AAN A E N AE NTE 8 Introd ction TO MEASUTEMENE TOOIS sc cc csicccssccsscsnnaseccctesscecsensscecteesssesscadtcoctsnctsesenestasessnssacssanstsod aueanonauaueudebsdetaeevenevesveneanee 9 Tq a E A terete srry entre vere treet ter mrerten vere A orert er frrrvers treet rer trerten firerer trie 9 POS REEE E E E A S A E E T ha ade t
2. Now the measurements are drawn into a graph with the sensor voltage on the X axis and the temperature on the Y axis The points should form a more or less linear line as indicated in Figure 38 Example calibration curve When this is done in a computer program usually the possibility exists to add a so called trend line This is a given function linear polynomial exponential etc of which the shape parameters are automatically adjusted such that the best fit of the curve with the measurements is obtained In this case a linear trend line is fitted as indicated in Figure 38 The options display equation on chart and display R value on chart are enabled With the first option the used formula is displayed while the second option shows the so called R value This value indicates how well the curve fits all the measurement points A value of 1 indicates a perfect fit the lower the number the worse the fit One can observe that the function of the linear fit has the same form as equation 1 8 This means that the values of a and b can be read directly from the displayed function In this case they are 10 743 K V and 8 6007 K respectively Now the calibration curve is determined and the actual data obtained from the CanSat can be converted into real measurements by applying equation 1 8 gt ae a MINUS ENGINEERING Additional technical information for CanSat competition 2014 Reference CSUK T01 Version
3. Today most scales are electronic The spring consists of a piece of material of which the elasticity or the factor n in formula 1 6 is well determined for example steel The amount of extension of the material s length is measured with an electronic device a sensor The internal electronic system monitors the sensor s output and display the right value on a display The tare function is completely integrated in the software of the electronic system Electronics voltage current resistance The core of the CanSat is an electronic system consisting of a microcontroller electrical power source sensors and actuators Electronic systems essentially consist of flowing electrons through conductors Each electron has a negative charge expressed in the unit coulomb Since electrons are flowing through the conductor charge is transported from one side of the conductor to the other This transport of charge is called current It is expressed in coulombs per second or amperes In order to make the electrons flow from one side to the other a difference in potential called a voltage expressed in the unit Volt is needed which essentially means that electrons want to leave or are repelled from one side and attracted to the other The higher the potential difference the faster the electrons will flow and thus the higher the current will be This is expressed in Ohm s law U 0 7 I R where e isthe current through the conductor
4. which is used to end most of the programing lines indicating to the computer that the statement before must be done before continuing The this tells the computer that everything behind the and on the same line is comment this is used to explain certain pieces of code Using the short example above lets describe what an operation is The program shown is a function called function If program calls function line 1 tells how this function is called In this case the function is defined as an integer int This means that the function will return a 16 bit value when finished One often used definition is void if no return value is needed The second part of line 1 defines the value that is given to this function when called Here the function needs a character or 8 bit value which is then placed in variable a The char a and char b C parts of line 1 and 3 are the definition of local variables These variables can be used inside this function and will be forgotten by the program when this function is left Line 4 defines two values as char without any starting value Line 4 defines the variable Data with a value of 10 to Start with Lines 2 and 11 define where the function function begins and ends with the brackets and By using a tab with the lines in between it is very clear where this function starts and where it ends This also makes it easier to see if the bra
5. controllers are based on a sequential processor surrounded by several hardware interfaces These interfaces include systems like memory analogue to digital converters and digital communication systems USA PBO PCINT0 CLKO ICP1 L1 PBI PCINTI OCIA J2 PB2 PCINT2 SS OCIB yy PB3 PCINT3 0C2A MOSI J2 PB4 PCINT4 MISO PDO RXD PCINT 16 12 PB5 SCK PCINTS PDI TXD PCINT17 gt 2 PB6 PCINT6 XTAL I TOSC1 PD2 INTO PCINT18 PB7 PCINT7 XTAL2 TOSC2 _ PD3 PCINT 19 OC2B INT1 PD4 PCINT20 XCK T0 M PDS PCINT21 OCOB T1 o PCO ADCO PCINTS PD6 PCINT22 OCOA AINO Sy PCL ADCI PCINTS PD7 PCINT23 AINI Sy BC2 ADC2 PCINT10 Sy PC3 ADC3 PCINT 11 Sy PC4 ADC4 SDA PCINT12 Se PCS ADCS SCL PCINT13 25 PC6 RESET PCINT 14 ATmega88PA _26 lt 26 28 pii d me ie 8 ae 3 16 17 AREF USB GND ig AVCC GND Thermal Pad D ATmega88PA Figure 18 Schematic view of the ATmega88PA micro controller The schematic is divided into an input output part U5A and a power supply part U5B As the micro controller is a part that has many connections sometimes up to 144 pins discussing all connections will not be part of this document For the Atmel micro controller of Figure 18 there are 3 different types of inputs that will be discussed The first type of connection is the general input output or GIO In the Atmel micro controller all
6. of the micro controller The V and GND pins are connected to 5V and OV the power supply used in this example As example for a temperature sensor a thermistor is used A thermistor is a temperature dependent resistor To measure the temperature with a thermistor there are 2 basic possibilities on can either put a voltage across the thermistor and measure the current or send a current trough the thermistor and measure the voltage Current R T cy R T v poures a c Figure 24 thermistor symbol and the measurement options Voltage R T thermistor 1 Source The methods shown in Figure 24 either need a current source or current measurement The simplest Current measurement is the use of a resistor with a fixed and predefined resistance to convert current in voltage The drawback of this approach is that the calculation of the temperature becomes more difficult 5V R T rl Analogue input of the micro controller R 10kQ OV Figure 25 readout of the thermistor Together with the resistor the thermistor can be connected like the pressure sensor in order to read the output voltage V E Vsource R PE ae measure Rir J R MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 32 53 Rem Vsource R R 91 10k 10k T V V measured measured The above formula describes the relation between measured voltage and the resistance of the the
7. Ampere A e U isthe voltage over the conductor Volt V e Ris the resistance of the conductor Ohm Q The resistance is essentially a figure that expresses how hard it is for electrons to flow through the conductor A high resistance means that a high potential is needed in order to achieve a certain current The resistance of a conductor depends amongst others on the material that the conductor is made of the size of the conductor length cross sectional area and the temperature MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 15 53 Multimeter An easy device to measure the electronic quantities is the multimeter It consists of an electronic measurement unit and two measurement probes A selection knob is used to choose which quantity is measured and in which range Measuring the properties at a certain electronic component is quite easy but it has to be done in the proper way The voltage over a component is measured by placing the multimeter in parallel with it indicated by 1 in Figure 5 When the selection knob is set to voltage the display will show the potential difference between the two measurement probes Current is measured by placing the multimeter in series with the conductor as indicated by 2 in Figure 5 In this setup the flow of electrons through both the conductor and the multimeter will be equal Therefore when the selection knob is
8. ENGINEERING 6 00 5 00 4 00 Thermometer temperature 3 00 7 00 Sensor output voltage Sensoroutput voltage V 1 00 Pd ggg 0 100 200 300 Time after start of calibration s temperature indicated by thermometer Figure 41 Example measurement graph with two Y axes MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 53 53 Other resources and further information http upload wikimedia org wikipedia commons 0 07 Lithium polymer battery 2811 1 volts 29 j http www produktinfo conrad com datenblaetter 650000 6 74999 650411 da 01 en AGFAPHOTO 9V_E_BLOCK pdf http www conrad nl ce nl product 650411 http upload wikimedia org wikipedia commons e e6 USMC Paratrooper http en wikipedia org wiki File Ram air square http www madehow com images hpm_ QO00 0005 0 _img0132 jpg http www nakka rocketry net xchute1 html
9. Knacke ISBN 13 978 0915516858 The normal shape that everybody recognises as a parachute is called the hemispherical design which has a high drag coefficient meaning it is very efficient a fair packing efficiency but is difficult to produce since it involves a lot of sewing Yii Hy Wd Hi yi y i i ee Figure 11 a traditional hemispherical parachute design source www madehow com The most used parachute for CanSats and sounding rockets is the cross shaped parachute sometimes referred to as cross formed X form or crucifix parachute due to its ease in manufacturing and good pendulum stability A good example can be seen in Figure 12 Additional technical information for CanSat competition 2014 Reference CSUK T01 Version 2 0 Page 22 53 fC MINUS ENGINEERING Figure 12 A cross shaped parachute source www nakka rocketry net MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 23 53 Lifting parachute A lifting parachute is a much more complex device than a normal drag parachute The device is basically the same as an airplane wing but instead of being a rigid structure it is inflated into its correct shape by the incoming air The wing will generate lift by the air which is flowing around it A small added problem with this lift is that it will come at a small price namely drag A lot of formulas that describe the b
10. and Y axis with the values of one quantity at the X axis and the values of the second quantity on the Y axis Usually the independent quantity is displayed on the X axis while the dependent quantity is set on the Y axis It is important that the range of both axes is chosen wisely all measurements should be displayed and the entire graphing field should be used If necessary a logarithmic scale can be chosen instead of a linear one so that a wider range of measurements can be displayed Discrete not continuous measurements should be displayed by a marker If desired the markers can be connected by lines Continuous functions may be indicated by a continuous line only The axes shall be labeled just as the columns of a table with measured quantity object and unit If more than one data series is displayed a legend should be provided so that the series are easily distinguished It is important to remember that some colors for example dark blue and red are not easy to tell apart when printed in black and white or grey shades If the range of the one data series differs significantly from the other a second X or Y axis may be added for clarity as visualized in Figure 41 Grid lines may be added to the graph for easier reading Finally a title or caption can be added to provide more information on the displayed values Additional technical information for CanSat competition 2014 Reference CSUK T01 Version 2 0 Page 52 53 a MINUS
11. connect to external circuitry or ground Figure 21 part of the datasheet from the MPX4115 pressure sensor Source Motorola The MPX4115A pressure sensor has 6 electrical contacts The datasheet of the sensor describes the function of each pin As seen in Figure 21 pin 1 is Vou pin 2 is GND pin 3 is V the other pins are N C or not connect pins For this component there is no predefined symbol which means we have to make one ourselves Since there are only 4 connections used the symbol will only contain 3 pins Vou or output voltage is an output so it is placed on the right side of the symbol GND is ground or negative power supply and is placed at the bottom of the symbol Vs or supply voltage is the positive power supply and will be placed at the top MIPX4115A Figure 22 self made symbol for the MPX4115 To connect the pressure sensor it is important to understand some of its characteristics The datasheet of a Component describes the operational characteristics These describe properties like sensitivity accuracy maximum and minimum operating voltages and current usage Table 2 characteristics sheet from the MPX4115 datasheet Operating Characteristics VS 5 1 Va TA 25 C unless otherwise noted P1 gt P2 Decoupling circuit shown in Figure 3 required to meet electrical specifications MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0
12. input output pins can be used in this manner Connections starting with PB PC or PD are GIO pins A GIO pin can be used as input where it will read a logical O or 1 depending on the voltage that is applied to it The GIO can also be set as output were the software determines if the pin is held high or low If the pin is held high then it will supply the same voltage as is being supplied at the VCC pin s When the GIO pin is held low it will drain current to make supply OV The second type of connection is the analogue to digital converter ADC Many micro controllers have ADC s on board These can be used to measure a voltage between OV and the supply voltage The precision of the measurement depends on the amount of bits the ADC provides Most ADC s are 10 bit A 10 bit ADC divides the voltage range in 2 1024 different steps where O is the minimum value and 1023 is the maximum value The ADC inputs of the micro controller can be recognised by the labels ADCO to ADC5 for the micro controller of Figure 18 MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 28 53 Input analog voltage Mm Oo OW Oo Wh 101 WW 111 Output in memory Figure 19 Basic principle of an ADC source wiki ulcape org The last connection that will be discussed in this document is the UART connection UART stands for Universal Asynchronous Receiver Transmitter A UART connection is a basic
13. receiver are required which is beyond the scope of this document There are two antennas used in receiving the information from the CanSat the first is the antenna on board the CanSat the second is the antenna used at the ground station The antennas need to be made with different requirements although the frequency of operation is similar for both antennas The antenna on board the CanSat needs to be isotropic or as much as possible which means that it transmits the same amount of power in all directions The antenna connected to the ground station can be pointed towards the CanSat and it can therefore be made as a high gain directional antenna which receives more electromagnetic waves from one direction then from another Additional technical information for CanSat competition 2014 Reference CSUK T01 Version 2 0 Page 44 53 ie MINUS ENGINEERING Figure 37 an Arrow which is a Yagi antenna for operation at 2 different frequencies Figure 37 shows a directional Yagi antenna that operates at two different frequencies The antenna has a 7 elements Yagi for 434 MHz and a 3 elements Yagi for 145 MHz For receiving the CanSat building a Yagi antenna might be a very good option since it can be constructed relative easily using wood and copper tubes There is plenty of information on the internet to build a Yagi antenna The CanSat antenna needs to be sufficiently robust to survive the launch on a rocket For the CanSat
14. resulting in a large lifting force and a small drag force A good example of a lift device would be an aircraft wing or ram air parachute The big advantage of this type of parachute is that it is potentially steerable when trimmed correctly The disadvantage is that they are highly complex to build difficult to trim and are less reliable in deploying correctly in the air Figure 9 a ram air parachute as modern parachutists use source USMC MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 19 53 The physics behind the drag parachute The physics behind the drag parachute and the lift parachute are similar in nature The formula s connected to the drag parachute are Farag ap Cas Where e Farag IS the drag force from the parachute N e pis the density of air kg m e Vis the airspeed of the parachute m s e Cais the drag coefficient e Sis the surface area of the parachute m7 The Ca or drag coefficient is a dimensionless number which depends on the shape of an object Basically it is a number that indicates how easy air or any other fluid is flowing around a shape If the object is very aerodynamic like for instance an airplane or a car this number is fairly low for example 0 2 If the Shape is not so aerodynamic such as a simple plate or a parachute shape the Cy will be very high for example 0 8 or higher Of course the
15. serial communication system used by many devices The com port of a computer uses the same protocol only with different voltages data_bits fe SS LOL start_bit stop_bit start bit input first data bit transition Le cycles later detected Figure 20 basics of UART communication For a UART connection the output of one device is connected to the input of a different device In Figure 20 the basic protocol is shown The connection is held high by the transmitter before the communication starts The transmitter starts the communication by making the line low for a predetermined time This is done to tell the receiver that data will be transmitted After this start bit one or several data bits are MINUS Additional technical information for CanSat competition 2014 ENGINEERING _ Reference CSUK T01 Version 2 0 Page 29 53 transmitted At the end of the transmission a stop bit is sent to make the line high again Normally 8 bits or 1 byte is transmitted between a start and stop signal Sensors The most basic sensors usually have an analogue output An analogue sensor provides an analogue voltage depending on the measured quantity For a pressure sensor the air pressure is converted to voltage As an example the MPX4115A pressure sensor will be used PIN NUMBERS m 1 Pin 1 is noted by the notch in the lead 2 Pins 4 5 and 6 are internal device connections Pin 1 is noted by the notch in the Lead Do not
16. set to current the display will show the amperes flowing through the conductor Finally the resistance of a conductor can be measured To do this it is required that the measured object is isolated from the rest of the electronic circuit in order to avoid interference of the other electronic components The multimeter is now placed in parallel with the object and the selection knob is set to resistance as indicated by 3 in Figure 5 It now puts a well defined voltage over the probes and the object and measures the current that flows With Ohm s law the resistance of the object can now be determined l 2 3 Figure 5 schematics of a multimeter MINUS Additional technical information for CanSat competition 2014 ENGINEERING _ Reference CSUK T01 Version 2 0 Page 16 53 Example of CanSat setup with the European CanSat kit There are of course numerous ways to construct your CanSat The construction is limited by certain constrains set by the organization Such as mass and size volume constrains But apart from those the engineering is only limited by your imagination and your building capabilities Try to make a baseline which is efficient but still all parts are easily accessible This way you have a fair amount of available space in your CanSat for your secondary mission but still you can easily switch part on site in case of emergency Some examples of how you could arrange your CanSat with the European CanSat kit
17. 01 Version 2 0 Page 11 53 Figure 2 Vernier caliper indicating a length of 11 4 mm courtesy of T Minus Angles A second quantity that is important in defining the geometry of objects is the angle The angle between two lines defines the orientation of one line with respect to the other Angles can be expressed in two types of units degrees deg or and radians rad The translation from degrees to radians and back is done via expression 1 4 0 4 Angle deg Buy Angle rad T Protractor The most widely used tool to measure angles is called the protractor A picture of such device is displayed in Figure 3 It consists of a scale in the shape of a half circle with tick marks at equal distances along the rim The angle of a certain corner is measured by aligning the straight edge of the half circle with its first side with the center mark of the circle usually the zero mark at the corner itself The angle is then measured by determining which tick mark is coinciding with the second side The accuracy of the protractor depends on the spacing of the tick marks just as for the ruler If the tick marks are spaced with 1 degree angles the measurement has an accuracy of 0 5 deg MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 12 53 Figure 4 schematic representation of a protractor source math amp 8geometry wikispaces com T square A t
18. 2 0 Page 49 53 mal a Ti D Ln D a Lu D Calibration measurements Measured temperature C Ba D iS co z 3 4 Recorded voltage V Figure 38 Example calibration curve aj D Ti D Ln D 5 Calibration measurements La D Linear trendline Pa D y 10 743x 8 6007 R 0 9997 Measured temperature C D Figure 39 Calibration curve with trend line Results presentation Now that the measurements are obtained they have to presented in a clear and unambiguous way so that other people can understand them and the conclusions that are drawn from it The most basic way to present results is the table An example is Table 5 The measured quantities are displayed in the columns while each measurement point is displayed in one of the rows It is important that the columns are labeled so that it is clear what the meaning of the presented values is The labels contain the quantity time temperature and voltage respectively the object that has been measured time thermometer sensor and the unit used to express the measured values s C V A title or caption can be added to clarify the conditions in which the measurements were taken and how they were obtained Finally the grid lines are displayed for readability MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 50 53 It is importan
19. 46 Introduction to data analysis sssscaessicoscsssovsssacsvsesodsenussasesotetseveusciusdsoussedtsasosossaotsdustsuueseesesuosadesandeiavessvadensoivaierg ssesdsauscveisessvendssases 47 From data to measurements CaUDrati ON sssini cet seca iienaa EEan Et i ae AENEA aAa AEEA EEEa ERE AAEE R 47 FS SUES FOS CMa ME NOM PAO P E E AE AA A A A A AA E O E E EE E O E T 49 other resources and further informatio Msasani iiiar AEAT E AENA 53 MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 5 53 Introduction This document was written as a technical add on for the CanSat kit user manual for the STEM center in York Since the STEM center works in 2013 2014 with the European CanSat kit prototype it lacked some technical information necessary for completing a CanSat competition This document is divided into a project management section a mechanical section and an electronics section The chapters are written for students and teachers in mind and try to teach technical background as well as hands on skills vital for completing a successful CanSat project MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 6 53 Defining missions The definition of a mission is very important because it will determine the complete CanSat project A mission statement is a statement that will give your project focus It shoul
20. 5 Reading of a CHOU Eienenn EAEE EESE 25 CD O I e EAEE A 26 VSS E EEE E E A EE A N 29 Ea aant E o g ENEE EE EEOAE EES EEEE ORE EEE ERI AANA AAE 55 MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 4 53 Batteries and power SYSTAIN ccccscssccsssrscssssssccsssssccsssrsesssssscesssrscssssrseessstsecsessscescsrseesssrseceessenscesserseesseesecsssrsecsserseessenseesees 34 BE E a E E EOE OTTEET OEE EEO EEOAE OONA 34 Advantages and GiSAAdVANTAGES ceessssssssssssesesescssssssssssesesescssssesesesesessssesesesesessesesesesesesesesesesesssceeseseseseeesecseaeseseeeseeaees 55 Calculations with a battery eeeesessesesesseseseseseseoseseseoseseseoseseseoseseseoseseeosessseoseseseosesrseosesseosesrseosesrseosesrseosesrosesesrosesssroses 55 Pary e AICS oopen aE ia AE E AE E EAE AA E 56 Introduction to soldering and circuit ASSEMDLY ee eessssssssesesescsssssscsesessscssesesesesessesesesesesessesesesesesesesesscsesesesesesecseseeeees 38 no 0 V6 ll 6 Frmenerererersvererecs raven pme E rary fire tr cnn tt ir rarer rer i nee err ent veer TeN Tree 39 RANO COE Oa sre Semen erent corr nnn tenet ere enrere raiment OTE OE EO 42 introduction to DFOGK aIMIMING iseseisana nin AEAEE R r R 45 Data inconsistencies es ssessessessssesesresseeserssesstoseeseessereeseeseeseestortestestessresteseeseesstesrestesereseoseeseessresteseeseesseesreseoseeseessreseesees
21. CanSat Some considerations for choosing a battery type may be e A rechargeable battery can obviously be recharged during the project which could result in a cost saving because you do not need to buy new single use batteries all the time e The energy density of a rechargeable battery is higher than a single use battery This means that for example 100 grams of rechargeable battery can contain more energy than 100 grams of single use battery This is a very important factor in aerospace engineering where every gram counts e The disadvantage of the rechargeable battery is that you will need special charging equipment to charge your battery This can be very expensive Charging a battery can be dangerous so always charge your battery on a non combustible surface and never let it be unsupervised e Note ALWAYS come to the launch site with fully charged batteries or a fresh single use battery Calculations with a battery The ESA CanSat kit needs voltages between 5 5V and 15V and has a power requirement of approximately 80 mA depending on the operation and the connected sensors When a device which needs 80 mA is connected to for example a battery of 550 mAh this means that it can run for 6 9 hours Of course this will just be a rough estimation since other factors like resistance current battery internal resistance battery temperature etc influence the actual battery lifetime In general the battery output voltage will dr
22. NUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 7 53 Budget constraints Every project has limited resources Examples of resources are production capacity financial volume and lots of others In this chapter the use of a budget to manage the limited resources is discussed The goal of a budget is to have an overview of the status of the resources so that the project does not overrun the requirements and other constraints Any budget starts with a topic the most obvious is financial Then the requirements determine the amount that can be used This can be a constraint like the cost of the CanSat but also an estimate of the resource that needs to be made available Now it needs to be shown that the project fulfills the requirements This is done by means of a budget table an example of which is given in Table 1 Table 1 an example of a simplified budget epee ness rat A007 ere po o C mam p o mae pooo 12 15 From this budget table it can be seen clearly that the sponsor income is less than expected and the expenses are more than expected resulting in a shortage This is a serious problem If you would have such a situation with mass or volume the CanSat would not be allowed to fly So it is very important to keep track of all resources In the project a number of requirements have will be given One of these requirements is with respect to the amount of reso
23. Page 30 53 Characteristic Symbol Min Typ Max Unit Pressure Range Pop f as tts kPa Supply Voltages _ vs f as _ sa _ 535 vae Supply ay Minimum Pressure Offset 3 0 to 85 C Yor 0485 f ozot 0275 vac VS 5 1 Volts a ll all al VS 5 1 Volts VS 5 1 Volts Accuracy 6 0 to 85 C VFss ee ee Response Time tR 1 m Output Source Current at Full Scale Output lor 01 madc Warm UpTime8 mS Offset Stability ts Vs 1 1 0kPa kiloPascal equals 0 145 psi 2 Device is ratiometric within this specified excitation range 3 Offset Voff is defined as the output voltage at the minimum rated pressure 4 Full Scale Output VFSO is defined as the output voltage at the maximum or full rated pressure 5 Full Scale Span VFSS is defined as the algebraic difference between the output voltage at full rated pressure and the output voltage at the minimum rated pressure 6 Accuracy error budget consists of the following Linearity Temperature Hysteresis Pressure Hysteresis TcSpan TcOffset Variation from Nominal 7 Response Time is defined as the time for the incremental change in the output to go from 10 to 90 of its final value when subjected to a specified step change in pressure 8 Warm up is defined as the time required for the product to meet the specified output voltage after the Pressure has been stabilized 9 Offset stability is the products o
24. RT line is made high and low by the transmitter depending on whether a digital O or 1 is transmitted To receive this signal the receiver needs to read the line at the right moment to determine whether a 0 or 1 is transmitted The moment at which the status of the data line is read is predetermined by the speed at with the transmission is made The transmitter sends a start bit to indicate the receiver to Start reading Then the data byte is transmitted followed by a stop bit One other common form of serial communication is via the I2C bus 12C bus stands for Inter Integrated Circuit bus The reason for calling this 12C instead of IIC is that mathematically times is squared writing 1 2 Officially the bus is called I squared C I C this became 12C to make it easier to write The 2C system uses two communication lines one data line and one clock line The advantage of this method is that the communication speed does not need to be set on beforehand Next to that it is possible to get feedback on communication quality MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 34 53 Batteries and power system In order to provide power to your CanSat you need to have an electrical power system There are numerous ways to power your CanSat but the most sensible way is to incorporate a battery Other options such as photovoltaic cells solar cells can be explore
25. a quarter wave wire antenna works very well The quarter wave describes the length of the antenna in reference to the operation frequency The transmitter of the CanSat kit works at around 434 MHz the precise frequency depends a bit on what team you are in This is done to protect each other from interference The required length of the antenna can be calculated by using the following equation oc B 108 E F 434 105 2479 Wherein e Lis the required antenna length 1 4 wavelength m e Cis the speed of light 300 000 km s m s e fis the operating frequency Hz The formula shows that the length of the antenna for 434 MHz should be around 17 3cm The wire can be soldered to the antenna contact of the transmitter board directly or when using a coaxial cable the antenna can be placed some distance away from the board When using a coaxial cable the last 17 5cm the outer conductor needs to be removed to form the actual 1 4 wavelength antenna Protect the insulation material as electric contact with metal surfaces might damage the transmitter MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 45 53 Introduction to programming There are many forms of programs such as computer programs websites mobile phone apps and many more These programs are used for many different applications from running your microwave oven to allowing you to check your bank account
26. aken and some numeric values of the voltages that your sensors recorded From this data set you want to deduce the actual quantities that your sensors measured such as pressure and temperature Then you want to present these quantities in a nice and clear way This chapter provides you with guidelines on how to perform these steps From data to measurements calibration The data that are received so far do not provide good insight into the quantities that are actually measured such as air temperature they are just voltages as obtained from the sensor outputs To obtain valuable measurements the voltages will have to be converted into the measured quantity This can be done by determining a calibration curve for the sensor A calibration curve essentially tells what output voltage can be expected when the sensor is subjected to a given temperature This means that the curve can be used in the reversed way as well it tells you what temperature the sensor senses when the output voltage is a given value Therefore measurements can be deduced from the data with this curve In most cases the relation between the sensed quantity and the output voltage is linear which means that it can be expressed as 0 8 Oe 4 Ven b Where e Qmeas IS the value of the measured quantity for example temperature K e V is the output voltage of the sensor V e ais the calibration gradient K V e bis the calibration offset K Calibration of the sensor
27. at the following is true mg I pV2cqS Where e mis the mass of the total system kg e gis the gravitational acceleration of 9 80665 m s m s e pis the air density kg m e Vis the airspeed of the parachute m s e cais the drag coefficient e Sis the surface area of the parachute m7 By combining these formulas we can calculate how big the parachute should be in order to have the desired descent time Furthermore by dimensioning the parachute you can also predict the impact velocity of your CanSat by taking the air density p as the value of ISA sea level of 1 225 kg m MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 21 53 Shapes of drag parachute The drag parachute can have all kinds of shapes and sizes The size of the parachute is a direct result of your drop mass the CanSat in this case and your desired descent velocity As with everything in engineering the shape of your parachute will be the result of all kinds of requirements for example e High drag coefficient e Packing efficiency e Manufacturability e Deployment velocity airspeed when opened e Deployment speed time from packed to fully opened e Deployment stability e Pendulum stability during flight There are many different kind of shapes to choose from many specially designed for different requirements A good source is the book Recovery System Design from Th
28. ckets are placed correctly Line 5 is an empty line used to make the program readable Line 6 is a comment line used for the same purpose Lines 7 and 8 are operations in this case small calculations to change variables Line 9 is a call to the function anotherfunction where the value of variable C is given to this function Line 10 determines what value the function function returns when finished Data inconsistencies The above program has 2 problems with variables The first one is on line 7 In this line an integer and a character are added together and the result is placed in a character The problem is that the integer is 16 bits and this is placed in an 8 bit variable So either b needs to be an integer or Data a character The second problem is that function returns an integer while the return line only provides a character The compiler will either provide a warning or error to indicate this mismatch MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 47 53 Introduction to data analysis At this point you are at the stage where your CanSat is fully operational You are able to perform measurements with the sensors and your CanSat can send the measurement data down to your ground Station where they are received If everything went well you received a stream of data lines Each line consists of a time mark indicating when the measurement was t
29. d be clear and concise When trying to write a good mission statement make sure to do a couple of iterations Any mission will start with a why question Why are you interested in A or B It could well be that what you want to do is not the best method to do it What we like to see is a mission and a number of options to fulfill the mission The reasons why your design was the best option should be made clear For the primary mission the reason why pressure and temperature are measured Is because we can determine the altitude from that So the primary mission would be to determine the altitude of the CanSat with the use of the temperature and pressure sensor If the last part was not demanded by the organization other methods of determining the altitude of the CanSat would be good as well But the team must explain why they made certain decisions An example of a mission statement that is not so strong Our team wants to make video recordings of the CanSat descent This is not a good mission statement because the why part is missing An improvement would be The CanSat will determine the number of animals in a 4 km 2 area centered on the launch site In a nutshell the mission statement is an answer to the question what does our CanSat team want to achieve and why Now perhaps it is easy to think of all kind of things that one can do with a CanSat but the and why part of the question is fundamental MI
30. d but are outside the scope of this chapter Battery types A battery is a device which consists of one or more electrochemical cells which produce electricity by converting the stored chemical energy into electrical energy Batteries are available in two types e Primary cells or single use batteries which are cheap and can be bought in the supermarket or hardware store The chemical energy in this type of battery is incorporated in the battery at the manufacturing process This type of battery CANNOT be recharged Figure 27 a single use 9V battery which can be bought at any local supermarket source AFGA e Secondary cells or rechargeable batteries which can be recharged by special charging equipment It is absolutely necessary to use the proper charging equipment The use of the improper charging equipment can result in fire and toxic fumes An example of this type of battery is a lithium polymer battery which can be seen in Figure 28 ff MINUS ENGINEERING Additional technical information for CanSat competition 2014 Reference CSUK T01 Version 2 0 Page 35 53 Figure 28 a lithium polymer battery which is rechargeable with special balanced charging equipment source Wikimedia org Advantages and disadvantages The rechargeable battery has several advantages and disadvantages with respect to a single use battery It depends on the requirements you have on a battery which battery you will need for your
31. design of custom made PCB s is not part of this document although some possible advantages will be addressed The last part of this chapter will provide a short introduction and checking method for soldering of the components A general form of nonspecific PCB s is the experimentation PCB with a solder grid The most general version has a grid of holes with a spacing of 2 54 mm or 100 mil Every hole is surrounded by a bit of copper to solder the components A circuit is built on such PCB by placing the components on the board and then using wires to connect them These wires need to be placed such that the connections of the schematic diagram and built circuit are the same Using short wires is better than long wires The longer a wire the more resistance it has If the wire resistance becomes high it will influence the circuit and result in unwanted behavior oo gt A v a nf 8B A lt gt A gt A A eee r E oe O ee k gt Q gt 4 T 4 i Figure 30 an empty CanSat kit sensor board courtesy of T Minus The PCB provided with the kit for the building of the primary mission is a semi specific PCB The PCB is designed in the shape of the main board with the solder able holes aligned such that they can connect to the connectors of the main PCB All the connections that go to the main board have an extra hole connected to them to make connecting wires easier Looking closely at th
32. ds Is done by 0 5 Mass kg 2 205 x Mass 1b Scale The mass of an object is normally measured with a scale A simple scale consists of a suspension hook connected to a calibrated spring and a pointer When an object is placed on the hook the spring will extend with a length proportional to the mass of the object 0 6 AL n M spring MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 14 53 Where e lt A indicates a difference or change of the quantity following it e L denotes the spring length m e Spring means that the length of the spring is meant e Mis the mass of the object placed on the lever kg e nexpresses how much the lever will extend at a given mass m kg The amount of displacement can be read from the position of the pointer In most scales there is an option included to tare the scale This means that the position of the pointer is manually adjusted such that it points to zero when no mass is put on the lever This is convenient when one wants to measure objects that have to be put in a container for example sand First the container is placed on the scale Since the container has a certain mass the pointer will indicate that a mass is placed on the scale The pointer position is then manually re adjusted to zero after which the sand is poured in the container Now the pointer indicates only the mass of the sand
33. e board the lines can be seen that make these connections Placing the components is a puzzle wherein the complexity depends on the amount of components and your personal demands on circuit size Placing the components close together makes it harder to wire the connections but it requires less board space Leaving room for the wires will ease the soldering later while it increases the board space required Building a PCB is planning ahead MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 39 53 Design of a dedicated PCB is a method to make soldering much simpler and creates less of a hassle with wires to connect everything Making a specific design provides more flexibility in the components that can be used On the general PCB the grid is 2 54 mm but most of the modern components are much smaller than that There are many programs available for making PCB s One that has a free license for non commercial use is the computer program Eagle After the PCB is designed in such a program it needs to be fabricated This fabrication can be done by dedicated factories Soldering Soldering is needed to make the components electrically connected To solder the components they need to be heated and then solder needs to be added The required soldering temperature depends on the type of solder used Solder made for electrical circuits melts at around 183 degrees Celsius fo
34. ehavior of a lifting parachute go way further then the scope of this CanSat project and go deep into aerospace engineering The most important factor is the ratio between lift and drag This ratio which is for simple lifting ram air parachutes around 3 to 5 is also Known as the glide ratio Basically this corresponds with the amount of horizontal distance can be obtained per vertical distance y high glide ratio a i Eat ee low glide ratio ea Y NS is ee Figure 13 the difference between a high glide ratio and a low glide ratio courtesy of T Minus In order to steer with a lifting parachute some steering lines can be attached to the leading edge of each side of the wing When one of these lines is pulled inwards the wing has more drag on that side than on the other side of the wing This difference in drag can be used to steer the wing into the proper direction If the parachute is not properly trimmed the wing can stall This means that the wing will stop flying because the air not smoothly flowing around the wing anymore Try to trim the wing forward again in order to reduce this stall tendency lt must be noted again that this type of parachute is definitely not recommended for beginners and is very difficult to produce deploy and fly MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 24 53 1 Parafoil k A WAN I Buin A IWY Suspen
35. ents These lines indicate an electrical connection with very low resistance In most systems copper wire is used for the connection but other options are possible as well Reading of a circuit In properly drawn schematics there are three methods to make the circuit readable The first is reading from left to right This means inputs are placed on the left side of the circuit and outputs on the right In the flash light circuit the battery is the input and the light bulb is the output The second method is working from top to bottom For electrical schematics this means high voltages are on the top of the diagram and low voltages are on the bottom The positive supply of the battery is drawn at the top and indicated by the longer line and the plus sign The last method is the method to draw the connections MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 26 53 Label Label Label O Label Not connected Connected Use of labels Use of labels junction junction Figure 16 schematic diagram of connected and not connected wires The labelled wires are connected In the simple schematic of the flash light there are only 3 connections in only one loop The simplicity of this circuit makes it very clear In more complicated circuits there are many more connections Figure 16 shows how to draw connected and unconnected crossings The two lines are connected when th
36. ey are drawn with an offset and not connected when they cross The power lines in an electrical circuit are normally connected to many components To prevent the situation where the drawing is unreadable because it would contain too many lines simple labels are used As shown in the Figure 17 all connections with 3V are connected together The same holds for the OV connections However for the flash light circuit using only labels does not make the schematic more readable Finding a balance between labels and lines is dependent on many aspects and to the choice of the designer 3V 3V Line2 Battery Switch Lamp OV Line2 OV Figure 17 different schematic representation of the flash light Using labels does not necessarily makes the diagram more readable Components There are many different electronic components available The core of every CanSat is built up with a few basic components These components are e A micro controller e A power supply e A transmitter e some sensors Inthis manual the T Minus CanSat kit is used as reference The same principles apply to other components MINUS ENGINEERING Additional technical information for CanSat competition 2014 Reference CSUK T01 Version 2 0 Page 27 53 The micro controller is the main controlling and calculating component of the CanSat There are many manufacturers of micro controllers which all make almost infinitely many different versions All of these
37. icate in a large project it is essential to have good presentation skills and a good concise and clear reporting style Both presentations and reporting are needed for your CanSat project A small report is needed to relay all project information to the judges of the CanSat competition Furthermore a small presentation is needed to accompany this report and to give more digestive information to people who did not read your report Presentation To give a presentation for a lot of people is something that everybody dislikes in the beginning Some people really find it scary in the beginning but it is a skill which everybody can learn very quickly Try to practice a couple of times for a full classroom Don t learn your presentation by heart because it could be the case that you are going to talk faster and faster when you do the final version in public Some Small tips for presenting e Try to be as relaxed and normal as possible This is not some Shakespeare play it is a technical presentation e Speak slowly don t try to rush everything to the end If you have a watch or a small clock take it with you on the stage You will directly see how much time you have left for your presentation You can either slow down or accelerate if the time demands it e Know your stuff If you did the research you will be the person who knows everything there is to know For questions about the subject you are the best person to answer it If you don t k
38. ions in each of which a certain measurable quantity such as length or mass is treated Length The first and probably most important quantity that is measured is the size of objects This can be the height of a CanSat or the diameter of a thread for example The quantity we are measuring in these cases is length defined as the distance between two known points Length can be defined in many units These units are roughly defined in two systems the imperial system and the metric system The imperial system is the most common system used in the US and the UK The metric system is mainly used in Europe The units in which a length is most conveniently expressed depends on the actual size that is measured The height of the CanSat is probably expressed in millimeters mm centimeters cm or inches in and the distance from your house to your school is most likely expressed in kilometers km or miles mi For the translation between one unit to the other linear translation rules are defined These express how many of one unit add up to another unit For example 100 centimeters make one meter and 1000 meters make one kilometer The other way around also works one centimeter is 1 100 of a meter which is 1 1000 of a kilometer In a formula this can be expressed as 0 1 Length m 1000x Length km Also the conversion from imperial to metric system is done via linear relations Length mm 25 4x Length in Length mi 1 609 x Length
39. kes Figure 33 photographs of bad soldering courtesy of T Minus Additional technical information for CanSat competition 2014 Reference CSUK T01 Version 2 0 Page 41 53 fC MINUS ENGINEERING Figure 34 photographs of good soldering courtesy of T Minus MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 42 53 Radio communication Radio communication is sending information from one place to another using electromagnetic waves also called radio waves Electromagnetic waves are generated at an antenna when an alternating electric current is connected to it The antenna transforms the electric current is electromagnetic waves At the receiving end of the communication the waves are transformed back into electric current by an antenna Using the radio waves to transfer information means that the information needs to be added to the radio frequency used Adding this information is called modulation and can be obtained in several ways The most basic form is to transmit a carrier frequency or not This is called continuous wave CW communication The most used form of CW is Morse code The biggest drawback of this is that the information transfer rate or baud rate is very low There are many other forms of modulation such as AM and FM These are used by radio stations With AM amplitude modulation the information is made to change the amplitude
40. km Most of the conversion factors from one unit to the other can be found on the internet or in your science book 0 2 Many tools exist to measure length The type of tool used depends mainly on the size of the measured object and its shape Ruler The ruler is the length measuring tool that everybody knows It consists of a straight piece of material with a series of tick marks at equal distance from each other which forms the scale of the ruler It is used for measuring linear lengths or lengths of objects with a straight edge Typical dimensions range from 10 cm to one meter Measuring with a ruler is easy the first tick mark typically the zero mark is kept next to the first measurement point and the value of the tick mark at the second measurement point is read from the scale The accuracy of the ruler is a figure that expresses the measurement error that is made with it This figure depends on the spacing of the tick marks If the spacing is for example 1 mm and one reads a value of 59 mm between the measurement points it means that the distance between the points may be anywhere between 58 5 and 59 5 mm This means that the accuracy of the measurement is plus or minus 0 5 mm This is usually expressed as MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 10 53 0 3 L 59 0 5 mm Caliper A special type of ruler is the caliper This device is equi
41. means therefore determining the values of a and b For some sensors this is very easy just check the data sheet of the sensor The gradient and offset should be given here However in most cases only a range of values is given the gradient and offset may be in between a certain minimum and maximum value Determining the exact values is therefore necessary The equipment needed to perform a calibration is a source of the quantity that is measured for the temperature sensor this is a device that can give the sensor a given well defined temperature for example a glass with water on a hot plate and a pre calibrated sensor such as a thermometer The thermometer and the sensor are both placed in the glass of water and the output from the sensor as well as the indicated temperature on the thermometer is monitored and noted down Now the temperature of the water is gradually increased by turning on the hot plate At given time intervals both the sensor output and the reading from the thermometer are noted The calibration can be stopped when 5 10 measurement within the desired range of temperatures are obtained An example of the noted values is given in Table 4 MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 48 53 Table 4 Example calibration curve measurements Time of measurement s Temperature of Temperature sensor thermometer C output voltage V gt o o
42. now the answer then you can always say that it is a good question and you will look for an answer and contact the person after the presentation e Have fun After a while you are not as scared anymore for speaking in public Try to enjoy it people in the audience will notice it and find it much easier to listen to it Reports For writing reports the ESA CanSat project has some nice self explaining report templates Try to follow these templates by filling in the required information In reporting it is always difficult to give enough information without overloading people with too much information Try to put details like electronic schematics in an appendix The document itself without the appendices should be a readable document for a technically educated person MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 9 53 Introduction to measurement tools During the production of your CanSat you will very likely need to measure certain quantities the diameter of your parachute the mass of your CanSat or maybe its battery voltage To do this you will need the proper tools Most of them such as the ruler or the scale you are probably familiar with Other tools such as the caliper may be new to you This chapter will describe some of the tools that you will most likely want to use Also the correct usage of them is explained The chapter is divided into four sect
43. of the carrier frequency In FM frequency modulation the frequency of the carrier is changed as depicted in Figure 45 The advantage of FM over AM is that the signal strength does not interfere with reception aucun Signal LAA ATA AAA AAA AA AA il i VATANINA TATATATA TATI NATANAT Carrier VU UU AAA CAAA A i T n fl P f i I I f it ie ry ati Aa Prec d ty yaya ph Y beac eee yy vy WLLL LE eA i E Li j ij f F i i il j k T C N a A oa Ce VY ki AAAAARABNAAA Af i f n AN AAAMAMALA LA IPEE aei FM rill iP Iiii an NY i Wve Ua Vu i Y y WEY Figure 35 the difference between AM and FM modulation The CanSat kit has a transmitter that modulates with Frequency Shift Keying FSK This means that it is transmitting a frequency when a logic 0 is transmitted and a different frequency if a logic 1 is transmitted as depicted in Figure 36 There are many other forms of modulation like QPSK where two bits are transmitted simultaneously MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 43 53 Data Carrier Modulated Signal Figure 36 frequency shift keying FSK The quality of the radio link depends mainly on three aspects the transmit power the receiver sensitivity and the used antennas The only aspect that can be influenced by the CanSat team is the antenna The other aspects can be influenced but then a different transmitter and
44. on the internet All programs have one thing in common they are written using a programming syntax This syntax is often called the programming language The syntax is a method to describe what the program needs to do Depending on the application a program either needs to be compiled before use or it is compiled while using the program Most webpages use languages that allow the web browser to compile or read the programming language directly Languages that can be used for this are HTML or JAVA Computer programs need to be compiled before use to change the program syntax in to instructions that the computer understands Every Computer processor has an instruction set of binary codes used by the processor to undertake certain actions This type of programming is used during the CanSat competition The micro controller provided in the CanSat kit is a small computer Micro controllers are used in many systems like robot welding machines The difference between a micro controller and the processor in your computer is that a controller is a processor with hardware control and memory in one component During the CanSat competition the C programming language will be used and Arduino will be used as compiler 1 int function char a 2 f char b C 4 int Data 10 5 6 comment 7 b a Data 8 C b 1 9 Anotherfunction C 10 return b 11 Above a short example of a program written in C is given To describe the entire lang
45. ool that is frequently used to draw corners with a defined angle is the T square This device is composed of two parts the block and the ruler The angle between the ruler and the block may be fixed at any angle between 0 and 90 deg For drawing the corner the ruler is fixed at the desired angle and the block is placed in alignment with the first side of the corner The base of the ruler is positioned at the place where the corner is to be drawn The corner can then be drawn by following the edge of the ruler with a drawing tool for example a pencil A zo MINUS ENGINEERING Additional technical information for CanSat competition 2014 Reference CSUK T01 Version 2 0 Page 13 53 p ii wT ea i py i prH prp pipe Tha 3 15 16 17 16 19 20 21 a2 24 l al DL 6 a ry Hebi belt tibtets cP tieedatatatelatebesel AAPA PRARARA ATA Figure 4 A T square source mathasteward com Mass The quantities that define the shape and size of an object are now discussed However there is one more property of the CanSat that is important to know its mass Determining the mass of the CanSat is necessary in order to size the parachute and to verify if the design meets the requirements Just like the quantity length the mass can be expressed in metric and imperial units Metric units are for example the kilogram kg or the gram g while the mass in imperial units is normally expressed in pounds lb The conversion from kilogram to poun
46. op during the lifetime of the battery This is highly dependent on the amount of current that is consumed Battery datasheets provide good reference for several types of current loading MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 36 53 The standard CanSat kit is powered by a simple single use 9V primary cell of which specifications can be found in Figure 29 Battery tips and tricks Having a good stable and reliable voltage supply is absolutely essential for having a good and reliable CanSat The CanSat electronics will only work when they are supplied with enough power If the voltage drops only a fraction of a second under the 5 5V strange things can happen such as resetting microcontrollers or loss of signal Make sure that the battery of the CanSat is fixed properly in the CanSat so that the battery leads are not momentarily disconnected when the rocket is accelerating or the parachute is deployed with a high shock Another thing that could happen is that some subsystems of your CanSat momentarily use a lot of power Due to this high power consumption the voltage that the battery supplies to the system drops which can result for instance in a reset of one or more microcontrollers Additional technical information for CanSat competition 2014 Reference CSUK T01 Version 2 0 Page 37 53 A MINUS ENGINEERING Specifications Chemical s
47. pped with a beak with two jaws One of the jaws is fixed to a ruler while the other can slide along the ruler It is therefore an ideal instrument to measure the size of rectangular and round objects The object is put in between the jaws the beak is closed around the object and then the measured value can be read Usually the jaws are made such that the caliper can measure inner size and outer size of objects as indicated by 1 and 2 in Figure 1 Also a depth gauge Is usually present so that the for example the depth of a groove or a hole can be measured The way this is done is displayed at 3 in Figure 1 iy 4 e a a T me em ee ee ee ee ee e a e e a a l m a F pases ee m aS ee a eee et ae Se hh A 2 pe Figure 1 different measurement methods with the caliper source craftsmanspace com The accuracy of measurements made with the caliper depends again on the spacing of the tick marks However usually the caliper is equipped with two scales a fine one and a coarse one Normally the coarse scale has a 1 mm Spacing between the marks and the fine one has a spacing of 0 9 mm Such caliper is called a Vernier caliper The scale is read at the point where the coarse and fine scale tick marks coincide as indicated in Figure 2 In this way measurements with 0 05 mm accuracy can be made Additional technical information for CanSat competition 2014 MINUS ENGINEERING Reference CSUK T
48. prototype 2013 are displayed below Of course you are totally free to choose any arrangement you would prefer Figure 6 Depending on your desired volume under the MCU board you can store your 9V battery there ae MINUS ENGINEERING Additional technical information for CanSat competition 2014 Reference CSUK T01 Version 2 0 Page 17 53 Figure 7 alternative ways to arrange your MCU and sensor board and transmitter Additional technical information for CanSat competition 2014 Reference CSUK T01 Version 2 0 Page 18 53 a MINUS ENGINEERING Parachute design and construction In order to slow down your CanSat you will need some sort of device that helps it to land This can be done in numerous ways but two types of recovery mechanisms are highlighted in this chapter e A drag device e Alift device The drag device is by far the simplest way of slowing the CanSat down it creates drag in order to reduce the speed of a falling object The most commonly known drag device is a parachute A parachute is a piece of fabric and cables which create enough aerodynamic drag to slow the object down to a lower descent velocity JAAN Figure 8 a simple parachute as used to slow humans down from a drop source USMC A lift device is much more complex than a drag device It is basically a system which creates lift by moving through the air The air moves over and under the cleverly shaped lifting surface
49. r leaded versions or around 230 degrees Celsius for lead free solders For making a good solder joint it is important that both surfaces are heated to more than the melting point of the solder If one of the surfaces is not hot enough the solder will not make a good connection which will result in a non functioning electric circuit Making the components too hot will damage them Anatomy of a good solder joint Pie lat Bright shiny finish shows Smooth concave meniscus mal good solidiication Shows good wetting from honzontal Sa l l Double sided pcb Singe sided peb with plated through holes Figure 31 the anatomy of a good solder joint The tip of the soldering iron is around 350 degrees This is hot enough to destroy almost all components Luckily it takes quite some time to break a component during soldering The time needed to make a good solder joint is much less then the time that the components can sustain the heat of the soldering iron Generally speaking it takes between 1 and 2 seconds to make a good solder joint In Figure 31 to Figure 32 are several pictures of good and bad solder joints Additional technical information for CanSat competition 2014 ff MINUS ENGINEERING Reference CSUK T01 Version 2 0 Page 40 53 GOOD JOINT BAD JOINT volcano shape dry joint dull copper tracks solder i stripboard J i ot a n R4 ia Drs am i 5 e wy uf A fai W hi
50. rmistor With this resistance the temperature can be calculated from the thermistor datasheet The NTCLE203E3103GB0 thermistor made by VISHAY BC Components is used to describe the basics of the temperature measurement This is a negative temperature coefficient thermistor which means that the resistance decreases with increasing temperature Table 4 part of the table describing the relation between temperature and resistance from the thermistors datasheet o 3256 19 87 12 49 8 059 400 The datasheet of the thermistor shows a table of the relation between temperature and resistance of which Table 3 is a part Using this relation the acquired resistance can be calculated back in to temperature ie ai Additional technical information for CanSat competition 2014 Reference CSUK T01 Version 2 0 Page 33 53 MINUS ENGINEERING Communication The last part of an electric circuit that will be discussed is digital communication There are two main options for communication serial or parallel In this document only serial communication will be addressed The serial communication method used by the CanSat kit as it is provided is UART With this communication method there is a dedicated line connecting the transmitter of one device with the receiver of the other If two way communication is required two lines are needed UART line Figure 26 schematic diagram of a UART connection The UA
51. se numbers are empirical and based on a certain area where this drag coefficient is calculated over For a normal circular parachute the drag coefficient will be in the range of 0 75 over the flat surface of a parachute The flat surface of a parachute is the surface area when you put a parachute flat on a table top The density of dry air can be calculated using the Ideal gas law Pp P55 7 R specific e Where e pisthe air density kg m e pis absolute pressure Pa Ropecific iS the specific gas constant for dry air The specific gas constant for normal dry air is 287 058 J kg K e 7 is absolute temperature at that altitude K Under normal circumstances the air density at sea level 15 C is approximately 1 225 kg m The temperature at altitude depends of course on the weather and the ground temperature As a general rule it can be stated that in the troposphere the lower layer of the atmosphere the air temperature decreases with approximately 6 5 K per kilometer MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 20 53 drag of the parachute weight of the total system Figure 10 constant descent velocity an equilibrium between forces courtesy of T Minus In case of constant descent velocity it can be stated that the weight of the drop mass or CanSat in this case parachute is equal to the drag force of the parachute This means th
52. sion line WV ji ah LIR J Li 1 L il ith T 4 i Var 1 l ti L i1 7 1 Li Suspension line ae Control line MN _ riser Payload A Figure 14 a cansat with a ram air lifting parachute source Miyazaki Laboratory Testing your parachute A parachute is very easy to test You can go to a high building where you have permission to drop something small from with such permission for instance your school building Measure the drop height in meters before you start It is good to have a person with a video camera standby to film all your tests for later analysis First throw your CanSat in a horizontal fashion to check if the deployment of the parachute is according to your desires Then throw your CanSat under an angle upwards so that the descent velocity is stable when it goes through the thrower s horizontal If you look later on the movie of your test you will be able to determine the time that the parachute spent descending from that point until it touches the ground Simple calculation can prove then what the average descent speed in meters second is Try to do these kinds of simple tests a couple of times and average your results for best accuracy MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 25 53 Introduction to electrical circuits To build the CanSat you as a team will need to make a small electrical circuit The
53. system used for the primary CanSat mission is provided but it needs to be put together There are many possible secondary missions of which most require additional electrical circuits This chapter will provide a short description of electrical circuits and the basics of designing and building them An electrical circuit is a network of electrical components designed to fulfill a specific task There are many different sorts of electrical circuits like your computer or a telephone More simple circuits are for example the light above the dinner table or a flash light The flash light circuit contains three components a battery a switch and a light bulb Switch Battery Lamp Figure 15 schematic diagram of a flash light Figure 15 shows a schematic representation of the flash light circuit In a schematic circuit diagram the components are represented by symbols Many different components have a dedicated symbol but there are also components that do not The meaning of the symbols depends on the system used There are two widely used systems the American and the European The reason symbols are used in circuit diagrams is to make it more readable Search on the internet for Electrical circuit symbols to find more The components are connected to each other by electrical wires In an electrical circuit the wires are normally not called components but connections In the above picture they are represented by the lines connecting the compon
54. t that the displayed values have the right significance This means that if the measurements of the thermometer are taken with 1 C accuracy they should be displayed with 1 C accuracy hence 15 C instead of 15 0 C This is especially important when a certain conversion via a formula is used to obtain the displayed value If for instance the output voltage of the sensor is read as being 3 63 V and the corresponding temperature is calculated with formula 1 9 the outcome would be 0 9 T 10 473 3 63 8 6007 47 59779 C However since the output voltage is measured with only three significant numbers the corresponding temperature should be rounded to three significant numbers as well hence a value of 47 6 C should be displayed Table 5 Measurements of temperature sensor calibration 1 Time of measurement s Temperature of Temperature sensor thermometer C output voltage V a E 60 34 2 55 90 41 3 05 120 48 5 63 150 53 4 10 Next to the table a second convenient way of displaying measurement results is by means of a graph An example is given in Figure 40 MINUS Additional technical information for CanSat competition 2014 NS ka ENGINEERING Reference CSUK T01 Version 2 0 Page 51 53 fs thermometer C wg D ha Z E E E 1 E 2 oo D 100 150 200 Time after start of calibration s Figure 40 example measurement graph A graph is composed by an X
55. taksaie senda E E E E T T 9 RE o TEENE E E TAA VA E O E E N O E N E E T 10 PUN K PA AE E AA AA A A A EE E E E E E EE E E E 11 PEOI e a EE E E E E TE 11 WSUS ce casas E E E E E E E E EE E T 12 PAE e E sou seeteeeetecne cece 13 ELE ae erates mage E E E EE E EE EE EEE EE E E 13 Electronics voltage current resistanCe ss sessesessessesessesessessesesseseoseseesesseseoseneosessesesseneosessesessesesseneosessesesseseoseneesene 14 MOLEO EO aseen a E E E EAE EE E TES 15 Example of CanSat setup with the European CanSat Kit ecssssesessssesessssesesessesesesessescsessesesessesesesseseseseceesesees 16 Parachute design and construction sessesseseesessesessesessessesesseneoseessessesesseneosessesesseseoseneoseeesessessesesseneosessesesseseoseseesessesenses 18 The physics behind the drag parachute cscsscscscscssssssssrscsssssscesscscsacscssssscsscatscesssscensceacsceesseceacausceseneneatsceessensas 19 Shapes of drag parachute ou cesesesescsccsesssesescssssssssssssssssssssesesesesesesesesesesesesesesesesesesessssnesseseseseseseseseseseseseseseseseseseeeeeses 21 Lifting parachUte jccenteesedessnesyessa ted esta ened osse sihnedi ned sev isletaeic gta eed ee ened ble isdedi osecas TENEO sr NKEA ESS VIAAS TAEVAS VAEVA NATASA s Nissi 23 TeS your pA e NU e OEA E 24 introduction to electrical CIPCUITS oe eececesecesecscscsesesesesesssesececscscscscsesesesesesesesesesecscscscscsesesesesesecscscscucscseseseseseseeeseseeeeseeeeees 2
56. uage in this document will not be possible and also not useful This is mainly because Arduino uses several libraries to make life simple Therefore this document will describe the bare minimum while more information can be found on the Arduino website or more general all over the World Wide Web Many examples can also be found in the Arduino program MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 46 53 The programming language can mainly be separated in 4 groups functions variables operations and formatting e Functions are bits of code that do several tasks Functions can be premade or user made A function is called during the program if the task it is made for is required e Variables as the name implies are used to store values that might change during the program A variable in C needs to be defined at the beginning of a function local variable or before the first function global variable There are several types of variables depending on the size they have e Operations determine what happens in the program such as adding two variables Operations can also compare variables to go through certain code only in certain situations e Formatting is required for the computer to understand what you want Some of the formatting is also used to make a program more readable for users Two of the many formatting aspects are 66 the semicolon
57. urces that can be spent on the CanSat A budget table is a great tool to be informed about the status of the expenditures and income Any budget table will have three parts an estimation realization and closing They will be discussed in short The first thing is to determine the budget what resources are available to spend In the CanSat case this can be limited both by what is available from the school or sponsors and what is allowed within the rules Then an estimation of the expected expenditures must be made Start with a group brainstorm about what is needed and then try to make a good estimation about the cost Also allow for some margin because there will be setbacks Now you have a great idea with an awesome CanSat but you need to have it finished in time Work on a time budget estimate what you need estimate the time you can spend and again some margin as you might have setbacks In general it is better to have a modest CanSat done with a high quality of work compared to a complex CanSat almost ready and with low quality work Also important is planning a team member can have time but he might not be able to work because a sensor is not yet delivered Hint generally we overestimate our own abilities With a budget you can recognize this and possibly fix it MINUS Additional technical information for CanSat competition 2014 ENGINEERING Reference CSUK T01 Version 2 0 Page 8 53 Presentation and reports In order to commun
58. utput deviation when subjected to 1000 hours of Pulsed Pressure Temperature Cycling with Bias Test Starting at the top of the Table 2 the pressure range is the range of pressures the device can measure The supply voltage indicates the voltage required on the V pin in reference to the GND pin to use the sensor The board provided with the CanSat kit has a 5V power supply which is within the range indicated in the table The supply current of this device is normally 7 mA with a maximum at 10 mA This Current can be used in calculations on required power supply or the expected battery life The next lines describe how the Vout pin reacts to the applied pressure This part will be required during calibration and analysis of the signal For this part it is important to note that the output is an analogue voltage Connecting the pressure sensor to a micro controller can be done in many different ways Two things are important in connecting this sensor the power supply and the fact that the output is analogue With the output of the sensor being analogue it needs to be connected to an ADC of the micro controller ar a MINUS ENGINEERING we Additional technical information for CanSat competition 2014 Reference CSUK T01 Version 2 0 Page 31 53 5V MPX4115A OV Figure 23 schematic diagram of a connected pressure sensor Figure 23 shows how this component is connected The output of the sensor is connected to an ADC input
59. ystem zinc manganese dioxide free of mercury and cadmium a ee Diameter 24 5 26 5 mm 15 5 17 5 mm pap Height 46 5 48 5 mm Weight approx 459 1 battery in blister pack with punch hole Nominal voltage 9 0 V 550 mAh 620 Q 24 hid 4 8 V Example discharge times Service life Load resistance 1800 2700 620 Discharge mode 24hd 1hd 2d End voltage 54v 54v 54v Initial 11 5hrs _ 16 8 hrs 38 5 hrs After 12 months of storage 6LR61 270 ame intemittent dechange cune Voltage v WILLD np BOLE z e Figure 29 typical datasheet of a zinc manganese dioxide battery which is supplied by the kit Source AFGA It is definitely not recommended to use the provided battery for flight It is a simple test battery to be used just for that testing the CanSat on the ground MINUS Additional technical information for CanSat competition 2014 NS ENGINEERING Reference CSUK T01 Version 2 0 Page 38 53 Introduction to soldering and circuit assembly With a schematic diagram of an electric circuit completed it is time to go from theory to practice To build an electric circuit you need the components and a printed circuit board PCB to place them on The PCB can either be one especially made for your circuit or a general PCB on which you make the connections of your circuit yourself This chapter will first show some component placement and connection methods for nonspecific PCB s The

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