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Wirelessly-Charged UHF Tags for Sensor Data Collection. Dan Yeager Pauline Powledge Richa Prasad David Wetherall Joshua Smith Intel Research Seattle University of Washington Electrical Engineering University of Washington Computer Science and Engineering. Outline.
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Wirelessly-Charged UHF Tags for Sensor Data Collection Dan Yeager Pauline Powledge Richa Prasad David Wetherall Joshua Smith Intel Research Seattle University of Washington Electrical Engineering University of Washington Computer Science and Engineering
Outline • Motivation for Wireless Sensing • Prior Work • The Wirelessly-Charged Power Model • The Passive Data Logger (PDL) • Experimental Results • Future Work
Motivation: Wireless Sensing • RFID Sensor Applications • Blood plasma • Frozen & Refrigerated Food • Chemicals • Sensor-enhanced RFID tags exist, what is the problem?
Motivation: Wireless Sensing • Problem: No visibility during transport TaggedGoods TaggedGoods No RFID Coverage RFIDReader RFIDReader Supplier Shipping Customer
Prior Work DEVICE COMPARISON
Our Prior Work: WISP Programmable Onboard sensors UHF RFID Tag Passive Benefits Problem Reader proximity
A New Power Model: Wirelessly Charged Sensors CONCEPT Wirelessly charge via RF power Passive Tags Active Tags Battery-free sensor data logging MOTIVATION RFID Wireless Charge RFID Wireless Data Download TaggedGoods TaggedGoods Data Logging No RFID Coverage Supplier Shipping Customer
A New Power Model: Wirelessly Charged Sensors CHARGE TIME CAPACITANCE REQUIREMENT Our Prototype 1 day runtime, 2 hour charge time at 1 meter
WISP-PDL Implementation - Hardware RFIDReader Passive Data Logger (PDL) Tag Sensor Storage Capacitor Analog Front End Power Management Microcontroller Flash Memory Antenna Storage Capacitor + IC + Antenna
WISP-PDL Implementation - Firmware STATE DIAGRAM Sensor Measurement RFID Communication Sleep Mode Data Logging
Sending Data in RFID Gen 1 Reader Tag Tag Memory EPC ID Sensor Data Charge remaining Historical Sensor Measurements Time elapsed since last reset Lack of address space!
Sending Data in RFID Gen 2 Tag Reader Tag Memory User Memory ID Memory • Sensor Data • Charge remaining • Time elapsed since last reset • Historical Sensor Measurements EPC ID • Fully compatible with Gen 2 specification
Milk Monitoring Study UHF Antenna Storage Capacitor Capacitive Fluid Level Sensor Refrigerator WISP-PDL
Milk Monitoring Study Reader Antenna Reader Laptop Refrigerator RFID Reader
Study Results Controlled Experiment Carton Tilted to Pour Temperature Increases When Removed From Fridge Fluid Level Decreases After Use
Study Results Uncontrolled Experiment Level Sensor Detects Nearby Cartons
Future Work / Conclusion • Wirelessly charged power model is feasible • New hybrid devices can improve RFID sensing • Key challenge: Increase runtime / decrease required capacitance • Reduce quiescent current draw • Design custom IC for key hardware blocks • Begin collaborative projects • Come pick up information to get involved! Email yeagerd@gmail.com for information
Prior Work Examples of Active Solutions