Design and Implementation of On-board Electrical Power ... - OUFTI-1

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6.2.1 The second dissipation systemThe second dissipation system has been designed in section 5.4. A prototype was made onbreadboard, based on this design. A picture of the prototype is shown in the Appendix C.TerminalsThe terminals are:• Vbus: it represents the batteries bus.• GND: the ground.• Base: connected to the base of the transistor for measurements.• Collector: connected to the collector of the transistor.ComponentsThe transistor is the model that will be used on the flight model. It is in close contact witha large heat dissipater (the transistor may have to dissipate up to 2W of power).The TL1431 is a old plastic-case model (LP package).The shunt resistor is no included on the breadboard. It must be connected between the“collector” and the “GND” terminals. If the circuit is used without the shunt resistor, thetransistor cannot play its role and the shunt current will entirely pass through the TL1431.The maximum current in the TL1431 is 100mA.The resistors are axial leaded components.6.2.2 The protection circuitA prototype of the protection circuit (presented in section 5.5) was made on breadboard. Apicture of the prototype is shown in the Appendix.TerminalsThe terminals are:• In: there are two rows of pins, the upper pins for input (+) and the lower pins for input(-).• Out: there are two rows of pins, the upper pins for output (+) and the lower pins foroutput (-).• On: this pin is connected to the “ON/OF F ′′ input.• Fault: this pin is connected to the “F AULT ′′ output.92
• Rs: there are three pins for Rs (R set ).ComponentsThe MAX890L is the same model as planed for the flight model. Capacitors and resistors areleaded components.For Rs, two potentiometers were used in series, one of 0to100Ω and one of 0to10kΩ. Accesspins were soldered on the terminals of each potentiometer.There is a pull-up resistor on the “ON/OF F ′′ input.connected to ground to activate the circuit.There is a pull-up resistor on the “F AULT ′′ output.The corresponding pin must beTwo LED were included in the circuit: one between the In(+) and the “ON/OF F ′′ (it ison when the circuit is on), and one between the In(+) and the “F AULT ′′ (it is on when thecircuit is in fault mode).6.3 The engineering modelThe engineering model is a PCB in the PC104 standard, the real size of the PCB in theCubeSat. The design of the engineering model is supposed to be close to the design of theflight model. The engineering model integrates all the so far developed systems. It also canintegrate features devoted to tests, e.g. jumpers and test points.There are several reasons to make a real-scale prototype:• The electronical behavior of a circuit can be influenced by geometrical characteristics,such as the distance between components. Some measurements will only make sense ona real scale prototype.• Mechanical tests can be performed.• The on-scale model is the only way to know with precision the surface occupied by thecircuits.A picture of the engineering model can be found in the Appendix C.6.3.1 Included systems and interfacesThe engineering model of the EPS card was produced during this work. The following systemswere included in the design:• The dissipation system.• The 3.3V, 5V, and 7.2V converters with their input filters.93
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AcknowledgementsI want to thank the
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Contents1 Introduction 91.1 Cubesat
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4.4.2 Mean case . . . . . . . . . .
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B Power budget worksheet 106C Pictu
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design and the tests are delegated
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Chapter 2Requirements of the EPS2.1
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• The Single-Event Upset (SEU)Thi
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the P-POD. RBF pins must fit within
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Figure 2.6: Top view of the PC104 c
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Chapter 3Design of EPS architecture
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• Voltage (4) and current (5) at
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Figure 3.6: The equivalent circuit
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of our Lithium-Polymer batteries va
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Figure 3.12: I-V curve of a solar p
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3.3.3 CapacityA important value to
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Parameter SLPB723870H4 SLPB554374HN
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of the batteries is kept between -2
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Over Charge Prohibition 4.275 ± 0.
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supplied in 5V. The circuit will be
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Chapter 4The Power Budget4.1 Introd
Page 42 and 43: Figure 4.1: P-V curve of a solar pa
Page 44 and 45: 4.3.2 Efficiency of convertersTo at
Page 46 and 47: Figure 4.3: Consumptions in % in me
Page 48 and 49: Chapter 5Electrical Design of EPS5.
Page 50 and 51: V outV in= D. (5.1)Since D ≤ 1, t
Page 52 and 53: The power losses in the inductor ar
Page 54 and 55: ∆i L,1 + ∆i L,2 = 0, (5.16)V in
Page 56 and 57: Using the value of ∆i L given by
Page 58 and 59: There is no data about the case to
Page 60 and 61: Capacitor selectionFour 10µF ceram
Page 62 and 63: • Output voltage: 5V.• Maximum
Page 64 and 65: Figure 5.12: Burst mode operation (
Page 66 and 67: Figure 5.14: Simplified schematics
Page 68 and 69: Figure 5.15: Worksheet for 3.3V con
Page 70 and 71: sequently, the k was chosen above 0
Page 72 and 73: where G 1 is the initial control-to
Page 74 and 75: Figure 5.21: Measured Bode diagram
Page 76 and 77: Figure 5.26: Equivalence between th
Page 78 and 79: C f =12πf f R 0f,L f = R 2 0f C f
Page 80 and 81: Figure 5.37: Schematics of the firs
Page 82 and 83: R KR >1.45V100mA − 1.3A35= 23.07
Page 84 and 85: The schematics is shown on figure 5
Page 86 and 87: A commercial model meets all requir
Page 88 and 89: Figure 5.45: Schematics of the heat
Page 90 and 91: PrefixX7X5Y5Z5SuffixTemperature ran
Page 94 and 95: • The antenna deployment system.
Page 96 and 97: 6.3.3 TestsThe engineering model of
Page 98 and 99: 7.3 ActivitiesAs OUFTI-1 is designe
Page 100 and 101: 8.1.2 DesignA model of Li-Po batter
Page 102 and 103: [15] Fabien Jordan, Phase B Electri
Page 104 and 105: TaK = 273 + TaC;%Photo-current ther
Page 106 and 107: Appendix BPower budget worksheetIn
Page 108 and 109: 108
Page 110 and 111: Appendix CPictures of the prototype
Page 112 and 113: Appendix DSchematics of the enginee
Page 114 and 115: 876543213V3 CONVERTER AND INPUT FIL
Page 116: 87654321ANTENNA DEPLOYMENT CIRCUITB
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