Group 9 Energy Harvesting

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Group 9 Energy Harvesting
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Week 6 Agenda

• Gantt Chart
• Tasks Accomplished
• Technical Report
• Transducer Testing Results Analysis
• Geophone Testing Vibration Profiles
• Ordered more PZT transducers
• Summary

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Gantt Chart
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Tasks Accomplished

• Added mass to individual transducers
• Continued testing energy harvesting circuit on
  shaker table
• Identified resolved several experimental issues
  
• Voltage rectification
• Transducer current measurement
• Continued documentation

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Energy Harvesting Block Diagram
Designed Testing Piezoelectric Board
AC Rectifier Currently being Researched
Charge Controller Voltage Regulator
Capacitor vs. Li-Ion
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PZT Circuit Modifications
Added Mass to Individual Transducers

• Increase sensitivity of transducers
• Lower resonant frequency
• Originally fR 180Hz.
• Improve output characteristics

• Added 0.80 gram washers to each transducer
• Mounted on vertical edge
• Bonded with Super-Glue

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Frequency Response(200mV Peak-Peak Input Voltage
gt 0.015 Gs)
Resonant Frequency 33 Hz
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Frequency Response(500mV Peak-Peak Input Voltage
gt 0.04 Gs)
Resonant Frequency 33 Hz
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Frequency Response from MSI Spec(Single
Transducer with varying masses)
Resonant Frequency approximately 40Hz
Graph taken from MSI Transducer Spec Sheet
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Testing Analysis
Conclusion 20 transducers connected in parallel
behave as hypothesized. - Voltage Constant
- Currents Add
Chart taken from MSI Transducer Spec Sheet
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Current Output Results

• Measured DC voltage current across 4.2O resistor
• Current on target with original estimations
• Power is too low!

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Rectifier Support Circuitry

• Full-wave rectifier attached to the PZTs using
  Si-diodes
• 1 uF capacitor added to flatten waveform
• Flat up to 10 kOhm (100Hz) to 32.1k Ohm (32Hz)
  output impedance (to be minimized)
• Additional Support Circuitry
• Design initially put on hold due to energy
  harvester problems
• Debate on Li-Ion vs Capacitor dependant on
  finding low-power charge controller (lt 50 uW)
• Put aside temporarily to focus on perfecting
  energy harvester
• Will use prior quarters hardware to test
  performance if output is adequate

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Transducer Application

• Estimated Power Output as an Energy Source
• 5 sec/ 5 min power cycling (for 50 mA motes)
• Energy harvester ideal output gt 200 uA
• Experimental Output Result
• Maximum current recorded of 38 uA for 20 PZT
• 100 used in original estimations for 200 uA
• Extremely small output resistance (4.2 Ohms)
• Full power analysis to be done in coming week

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Sample Vibration Profiles
Source Energy Scavenging for Wireless Sensor
Nodes with a Focus on Vibration to Electricity
Conversion p30 by Shadrach Joseph Roundy
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Next Week

• Reassemble circuit and begin extensive testing
• Power output characteristics
• Mass Variance
• Determine internal impedance of circuit
• Research adequate environmental applications
• Continued geophone testing of candidates
• Continue documentation