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 Concept # 4 Power Source Start Capture Stop Capture Sensor Connection Set Sampling Rate Mount Device High Pressure High Temp Oily Env. Data Storage Processor Data Access Sample Bit Width Sample Rate UltraCap Reed Switch Timer 4-Wire Digital Knob Magnet Composite Insulated/Passive Gaskets/Plugs microsd μc USB 16-bit 10kHz

Materials Analysis Building a Better Box

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

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?

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

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

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

Weight Density: Acetal:.0513 lb/in 3 Polysulfone:.0448 lb/in 3 Polyester:.0361 lb/in 3 Aluminum:.0975 lb/in 3 Volume: 1.3075 in 3 Mass: Acetal:.0671 lb (30.4g) Polysulfone:.0586 lb (26.6g) Polyester:.0472 lb (21.4g) Aluminum:.1275 lb (57.8g)

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: 10 15 ohm-cm Polysulfone: 10 16 ohm-cm Polyester: 10 12 ohm-cm Aluminum: 10-6 ohm-cm

Pugh Analysis Delrin PSU PET Al Strength - + + Operating Temp - - + D A T U M Cost + + + Weight s + - Thermal Conductivity Electrical Resistivity s s - s s - Total 1/2 3/1 3/3

Case Geometry The Best Things Come in Small Sizes

PCB Dimensions Show 3D Rendering

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.

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

Microcontrollers Choosing a Better Brain

Criteria 1: ADC Accuracy Bit Width # of Values LSB (Accuracy) 10 1024 19.53 mv 12 4096 4.88 mv 14 16384 1.22 mv 16 65536 305 uv 18 262144 76.3 uv 20 1048576 19.1 uv 24 16777216 1.19 uv

Criteria 2: ADC Type Successive Approximation 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 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

Criteria 3: Serial Throughput (SD) Bit Width Bits/s (1 Ch)* Bytes/hr (1 Ch)* Bits/s (4 Ch)* Bytes/hr (4 Ch)* 10 100k 42.915 MB 400k ~172 MB 12 120k 51.498 MB 480k ~206 MB 14 140k 60.081 MB 560k ~240 MB 16 160k 68.885 MB 640k ~276 MB 18 180k 77.248 MB 720k ~309 MB 20 200k 85.831 MB 800k ~345 MB 24 240k 102.997 MB 960k ~412 MB * at 10kHz sampling rate

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) Criteria 4: I/O Capability

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

Microcontrollers STM32F373 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) 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

Input Conditioning The Large Signal Problem

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

Simplified circuit Simplified Circuit R B = R 2 + R 3 R L R 3 +R L V B = V L R 3 R 3 R L V B = V s R 1 R B R 1 R B +R L G = V L V S 1 1+R s R3 R2+R L R3+R L 1 2+ R 3 R L

Final Circuit

Percent of Error Attenuator Non-ideality Percent Error vs Sensor Output Impedance 8 7 y = -6E-09x 2 + 0.0008x + 0.0005 6 5 4 3 Series1 Poly. (Series1) 2 1 0 1 10 100 1000 10000 Sensor Ouput Impedance (Ohms)

Power Source Phenomenal Cosmic Power. Itty Bitty Living Space.

LiPo vs. Ultra Capacitor Ultra Capacitor (KEMET FT0H105ZF) 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 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/polymerliionbattery37v240mah602025.aspx

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

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

Components Required LiPo Charger and 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 Booster

Action Items The Road Ahead

Mechanical Action Items Materials and Modelling Choose Final Material Solid Modelling Small Device Large Device Ansys Simulations Small Device Large Device 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

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

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

Questions? El fin.