Presentation on theme: "Design and Testing of a Self-Powered Wireless Hydrogen Sensing Platform Jerry Chun-Pai Jun, Jenshan Lin, Hung-Tan Wang Fan Ren, Stephen Pearton and Toshikazu."— Presentation transcript:
1 Design and Testing of a Self-Powered Wireless Hydrogen Sensing Platform Jerry Chun-Pai Jun, Jenshan Lin, Hung-Tan Wang Fan Ren, Stephen Pearton and Toshikazu NishidaUniversity of Florida
2 Motivation Behind a Self-Powered Wireless Hydrogen Sensing Platform Popular topic due to need of inexpensive sensor devices requiring minimal maintenance to monitor harsh and dangerous environs.Growing interest in hydrogen as a fuel cell, which is dangerous if not properly contained.Combustion gas detection in Spacecrafts and Proton-Exchange Membrane (PEM) Fuel CellsGreater than 4% of hydrogen concentrations are explosive.
3 Limitations Of Sensor Development Limitations of Energy Harvesting DevicesLimitations of Low-Power and Low- Voltage Commercial ComponentsLimitations of a Wireless SystemWireless Channel EstimationFCC Regulations
4 Energy Harvesting Techniques Solar Energy HarvestingSolar Cells are a mature commercial ProductDependent upon real-time lighting and temperature conditionsPulse Resonant Power ConverterSelf-powered and self controlledConvert input voltage of V to steady 2V outputVibration Energy HarvestingCollection of energy proportional to volume of deviceLimited to magnitude and frequency of vibrationsFor Proof of ConceptPSI D220-A4-203YB Double Quick Mounted Y-Pole PZT DeviceDirect Charging Circuit
5 Energy Harvesting Techniques cont. Solar Energy HarvestingVibration Energy HarvestingIXOLAR XOD17-04B Solar CellFour mounted PSI D220-A4-203YB Double Quick Mounted Y-Pole Bender (a) Direct Charging Circuit (b)Pulse Resonant Power Converter Functional Block Diagram (a) Bare die photo (b)
6 ZnO Nano-Rods as a Sensing Mechanism ZnO currently used for detection of humidity, UV light and gas detectionEasy to synthesize on a plethora of substratesBio-safe characteristicsLarge chemically sensitive surface to volume ratioIf coated with Pt or Pd, can increase device’s sensitivity to hydrogenHigh compatibility to microelectronic devicesSchematic of Multiple ZnO Nano-RodsClose-Up of Packaged ZnO Nano-Rod Sensor
7 Pt-ZnO Nano-Rod Sensors Sputtered with Pt coatings of approximately 10 Å in thicknessShow no response to the presence of O2 and N2 at room temperaturePt increases conductivity of Nano-RodsUp to 8% change in resistance after 10 min. exposure to 500 PPM of hydrogenGreater than 2% change in resistance after 10 min exposure to 10 PPM of hydrogen90% recovery within 20 seconds upon removal of hydrogen from the ambientPt-coated ZnO Nano-Rod - Relative Resistance Change for Various Hydrogen Concentrations
8 Comparison of ZnO Nano-Rods Coated with Different Metals Relative Resistance Change for Various Metal-coated ZnO Nano-Rods
9 Differential Measurement Wheatstone Resistive BridgeCan limit current consumption of resistive bridgeBest way to detect changes in resistanceDifference AmplifierUsing differential architecture of operational amplifier to subtract difference at input, and apply gainForm of differential measurement
10 Instrumentation Amplifier Provides High Impedance Input Buffers isolate V1 and V2 from resistive network of difference amplifierBuffers and provides gain before difference amplifierGain can be easily adjusted by varying a single resistor, Rg.
11 Differential Detection Circuit Since Pt-ZnO Nano-Rod devices react to both hydrogen and temperature, the use of a passivated ZnO as a reference resistor can mitigate the temperature dependency of the differential Detection Circuit.Rbias used to limit current flowing into both legs of resistive bridgeMaintains concept of a differential measurementInstrumentation Amplifier helps balance input offset voltages, while providing gain, and conditioning signal for ADC
12 Fabricated Pt-ZnO Nano-Rod for Use in Differential Detection Circuit
15 Microcontroller Selection REQUIREMENTSType of Program MemoryFlashProgram Memory8 kBRAM256 BytesI/O Pins22 pinsADC10-bit SAR ( successive approximation register )Interface1 Hardware SPI or UART, Timer UARTSupply Voltage Range1.8 V – 3.6 VActive Mode1 MHz, 2.2 VsupplyStandby Mode0.7 uA# of Power Saving Modes5Low-VoltageLow-Active CurrentLow-Sleep CurrentOnboard MemoryOnboard ADCSerial OutputReprogrammableFeatures of Texas Instruments’ MSP430F1232IPW
16 Microcontroller Operation Level Monitoring State MachineData Transmission State MachineRuns through state until a discernable presence of hydrogen is detected.Once hydrogen is detected, microcontroller forces RF front-end to transmit an emergency pulse to the central monitoring station before returning back to an idle mode.Hydrogen threshold level is at far less than dangerous levelsRuns through states until a discernable presence of hydrogen is detected.Once threshold is detected, the data from the ADC is queued onto the serial output port of the microcontroller to be transmitted.Once transmitted, state is reset to sleepFor constant tracking of hydrogen levels
17 Selection of a Modulation Technique MODULATION REQUIREMENTSRF Power Amplifiers and Oscillators have efficiencies of 50% at bestLow parts countLow Duty-Cycle, Low Data Rate.Expend energy only for transmission of DataLow complexityComparison of Complexity between π/4- DQPSK and OOK
18 Selection of RF Transmitter (1) 300 MHz Ming TX-99Onboard antennaOOK ModulationLow Part CountLow ComplexityTunable FrequencyColpitts OscillatorMing TX-99 Transmitter in OOK ModeMing TX-99 Transmitter
19 Selection of RF Receiver (1) 300 MHz Ming RE-99Onboard antennaExternal Antenna TapLow Part CountLow ComplexityTunable FrequencyEnvelope DetectionLittle DocumentationMing RE-99 Receiver SchematicMing RE-99 Receiver
20 Distance Measurements Received Power vs. Distance With Reference to Room ShapeShape of room resulted in a wave-guide effect at 10 metersLast successful data transfer occurred at 19.4 mReceived power at this distance was approximately -70 dBmCan assume Ming RE-99 Receiver sensitivity is approximately -70 dBm
21 Central Monitoring Station At the time, used Ming RE-99 ReceiverNI USB-6008 DAQ device for power to Receiver, and ADC to capture dataPowered from HP Laptop’s USB Port Running LabVIEW 7.1Moving Average Filter to differentiate data “pulse” from noiseMoving Average Filter ExampleLabview Block Diagram Code and Labview Front Panel Gui
22 Full System Integration and Testing orSchematic of Hydrogen ChamberSchematic of Hydrogen Chamber
23 Future Work: New Receiver Linx Technologies RXM-315-LR Replacement for Ming RE-99 since Rayming Corp. went out of businessOOK ModulationLow Part CountLow ComplexityRSSI/PDN-112 dBm SensitivitySystem Level Architecture for RXM-315-LRPin-Out of RXM-315-LR receiver, and receiver test board, shown with SPLATCH antenna
24 Future Work: Low-Profile Antenna Linx Technologies ANT-315-SP ‘SPLATCH’ Style AntennaGrounded Line, Microstrip Monopole AntennaAfter matching, -9dB gain, trade off for low-profile antenna5 MHz -10 dB BW, Center Frequency = 315 MHz‘SPLATCH’ dimensions, matched S-parametersAntenna Test Board w/ Matching Circuit
25 Future Work: Minimum Redundancy Minimum Energy Coding Mapping (n) source bits to message with a maximum of 2, or 3 “high” bitsExample: 6 source bits 6 source bits = 64 messages (symbols)Find Codeword of length (m) that allow for 64 symbols, with a maximum of high bits.64 = mC3 + mC2 + mC1 + mC0 ; m = 7Power ReductionAssumptions: for now, all source code symbols have equal probability of occurrences, and power is only consumed with the transmission of a high bit.So, Power Consumption Reduction is:By using a minimum energy coding technique, we can expect to reduce the power required to transmit an un-coded message by 20 to 40 percent.Proposed Source Coding Technique
26 Minimum Redundancy Minimum Energy Coding (cont.)
27 ConclusionsSuccessfully designed a low-power sensor interface for the Pt-ZnO Nano-Rod hydrogen sensing mechanismIn conjunction with the microcontroller, RF transmitter, and separate energy harvesting techniques, were successful in detecting and reporting the presence of 500 PPM of H2 in N2. (.05%) using Pt-ZnO Nano-rods as our sensing mechanismEnergy harvesting techniques include solar and vibration energy devices.
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