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P14452: Subsystems Design Review

P14452: Subsystems Design Review . Review. Where we left off. Updated Engineering Specifications. Previous Functional Decomposition. Capture Data. Store Data. Power Device. Protect Device. Chosen Concept. Materials Analysis. Building a Better Box. Plan. Comparisons of Materials

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P14452: Subsystems Design Review

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  1. P14452: Subsystems Design Review

  2. Review Where we left off

  3. Updated Engineering Specifications

  4. Previous Functional Decomposition

  5. Capture Data

  6. Store Data

  7. Power Device

  8. Protect Device

  9. Chosen Concept

  10. Materials Analysis Building a Better Box

  11. Plan • Comparisons of Materials • Acetal Resin (Delrin®-150) • Polysulfone • Polyester (Ertalyte® PET-P) • Aluminum 6061 • Applied Loads • 100psig applied to external surfaces • 200F applied to bodies

  12. Acetal Resin (Delrin®-150) Properties ANSYS Simulation • Max Operating Temp • 180F • Yield Strength • 10400psi • Modulus • 450ksi • CTE • 278μin/in-°F • Cost: 1.5”x6”x6” sheet • $35.71 • Max Deformation • .060” • Max Stress • ?

  13. Polysulfone (PSU) Properties ANSYS Simulation • Max Operating Temp • 285F • Yield Strength • 10900psi • Modulus • 390ksi • CTE • 29.4μin/in-°F • Cost: 1.5”x6”x6” sheet • $147.83 • Max Deformation • .006” • Max Stress • 6862 psi

  14. Polyester (Ertalyte® PET-P) Properties ANSYS Simulation • Max Operating Temp • 210F • Yield Strength • 12400psi • Modulus • 490ksi • CTE • 33μin/in-°F • Cost: 1.5”x6”x6” sheet • $48.57 • Max Deformation • .007” • Max Stress • 9744 psi

  15. Aluminum 6061 Properties ANSYS Simulation • Max Operating Temp • 500F • Yield Strength • 40000psi • Modulus • 1000ksi • CTE • 13.1μin/in-°F • Cost: 1.5”x6”x6” sheet • $53.44 • Max Deformation • .003” • Max Stress • ?

  16. Weight Mass: Acetal: .0671 lb (30.4g) Polysulfone: .0586 lb (26.6g) Polyester: .0472 lb (21.4g) Aluminum: .1275 lb (57.8g) • Density: • Acetal: • .0513 lb/in3 • Polysulfone: • .0448 lb/in3 • Polyester: • .0361 lb/in3 • Aluminum: • .0975 lb/in3 Volume: 1.3075 in3

  17. Other Properties • Thermal Conductivity • Acetal: • 2.5 BTU-in/hr-ft²-°F • Polysulfone: • 3 BTU-in/hr-ft²-°F • Polyester: • 2 BTU-in/hr-ft²-°F • Aluminum: • 1160 BTU-in/hr-ft²-°F • Electrical Resistivity • Acetal: • 1015 ohm-cm • Polysulfone: • 1016 ohm-cm • Polyester: • 1012 ohm-cm • Aluminum: • 10-6 ohm-cm

  18. Pugh Analysis

  19. Case Geometry The Best Things Come in Small Sizes

  20. PCB Dimensions Show 3D Rendering

  21. Mounting • Two part solution • Flange Base • Through Hole in each corner • Can be used to mount directly • Adapter Plates • Attach to flange base • Allow for Mounting on existing holes • Allow for adhesive, zelcro, magnets, etc.

  22. Generalized Design • Rectangular Prism • 1-3 Ports for Analog I/O • 1 Micro-USB Port • Charging • Data Access • Flange Base • Fasten from Bottom • Locks access to inside of device when mounted • Provides Mounting Holes

  23. Microcontrollers Choosing a Better Brain

  24. Criteria 1: ADC Accuracy

  25. Criteria 2: ADC Type Successive Approximation Sigma-Delta 12-24 bit Accuracy Slow Sample Rate (<200kS/s) No External Low-pass Filter Filter is part of sampling process Must be careful of bit width effect on frequency range • 10-12 bit Accuracy • Fast Sample Rate (>200kS/s) • Requires External Low-pass Filter • Costs Board Space • 3 Op-amps (Bi-Quad) • Resistors and capacitors

  26. Criteria 3: Serial Throughput (SD) * at 10kHz sampling rate

  27. Criteria 4: I/O Capability • SD Card • 1 SPI interface • 1 Serial Clock • USB Data Access • 1 USB UART • ADC • 1-4 ADC Channels • GPIO • 1 Digital (SD) • >2 Digital for Hardware Sampling Rate (per channel)

  28. Criteria 5: Processor Speed • ADC requirement • 10000 Samples/s per Channel • May take more than 1 cycle per sample to read from ADC • Estimated Minimum Speed • 40000 Samples/s (4 Channels) • 2 Cycles per Sample Read • 112 Cycles per Sample Write • 5 Bytes Data • 1 Bytes Channel ID • 5 Bytes Timestamp • 2 Bytes “,” • 1 Byte CR • 4.56 MHz

  29. Microcontrollers STM32F373 MSP430F67XX 16-bit RISC ( 8-25 MHz) No Floating Point No DSP Instructions 3 Sigma-Delta ADC 24-bit 31 kHz per channel max DMA Interface ADC Synchronization 2 SPI (5 Mbit/s) 52 or 72 GPIO No USB • 32-bit ARM M4F (72 MHz) • Floating Point • DSP Instructions • 1-3 Sigma-Delta ADC • 16-bit • 16.66 kHz max per channel • DMA Interface • ADC Synchronization • 3 SPI (18 Mbit/s) • Up to 84 GPIO • 1 USB UART (12 Mbit/s)

  30. Input Conditioning The Large Signal Problem

  31. Attenuation Circuit Use resistor bridge to reduce the voltage for input to microcontroller Set a unity gain Also decreases the current going into the uC

  32. Simplified Circuit Simplified circuit

  33. Final Circuit

  34. Attenuator Non-ideality

  35. Power Source Phenomenal Cosmic Power. Itty Bitty Living Space.

  36. LiPo vs. Ultra Capacitor Ultra Capacitor (KEMET FT0H105ZF) LiPo Battery (All-battery.com 602025) Base: 25mm x 20mm Height: 6mm Area=3000mm^3 Voltage = 3.7V 240 mAh Max Current is 48mA for 5 Hours Weight = 4 grams Price for 5-10$3.25 each http://www.all-battery.com/polymerli-ionbattery37v240mah602025.aspx • Diameter = 21.5mm (0.846in) • Height = 13mm(0.512in) • Area= 1502mm^3 • Max Voltage 5.5V • 1F capacitance • Max current is 1.5mA for 30 mins • Weight = 10 grams • Price 1$4.23, 10$38.03 • KEMET FT Series pages 2-4

  37. LiPo Charging Spark Fun Power Cell – LiPo Charger/Booster Micro USB charging $19.99 breakout board for testing Eagle Files Available for PCB layout

  38. Schematic for LiPo Charging and Booster https://www.sparkfun.com/products/11231

  39. Components Required LiPo Charger and Booster • MCP73831/2: LiPo Charging IC • Can get free samples • TPS61200: 5 volt, 600mA boost converter • Can get free samples • Used for powering sensors and other components • JST connector $0.95 • Micro USB SMD Connector $1.95 • Resistors and Capacitors <$2.00

  40. Action Items The Road Ahead

  41. Mechanical Action Items Materials and Modelling Sensor Characterization Catalog Existing Sensors in Compressor Centralized Collection of Data Sheets Reference Card for Sensors Voltage Range Current Output Frequency Ranges Optimal Sampling Rate Voltage to Unit Conversion Factor • Choose Final Material • Solid Modelling • Small Device • Large Device • Ansys Simulations • Small Device • Large Device

  42. Electrical Action Items PCB Analog Analysis Attenuator Final Design Differential Amplifier Precision Voltage Reference Input Voltage Clamping Overvoltage Protection LiPo Charging Circuitry • Finalize Electrical Schematics • Small Device • Large Device • Finalize PCB Designs • Small Device • Large Device • Final Component Selection

  43. Computer Action Items Algorithms Processes Sampling Procedure Channel Switching Multiple Sampling Rate Switching DMA transfers Offload SPI Offload ADC Processor can focus on filtering and coordinating • Digital Filtering • Sample Ordering • Timestamp Calculation • Processor Initialization Routines

  44. Questions? El fin.

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