MEMS Thermal & Fluid Control Lab. RFID tag powered by solar cell was set up and integrated with...

MEMS Thermal & Fluid Control Lab.MEMS Thermal & Fluid Control Lab.

RFID tag powered by solar cell was set up and integrated with multiple sensors, such as temperature, humidity, light and air velocity sensors.Since the sensor nodes are wireless, they can be easily installed for form a RFID based sensor network.

Solar cell

UHF tag insert

Energy harvesting chip

Micro processor for sensor signal processing

RFID Sensor Nodes


Sensor network deployed in a convenience store

Sensor network deployed in a convenience store

The energy harvesting wireless sensor network (WSN) was deployed in a 24-hour convenience store to detect thermal comfort degree from the air conditioning control.

All sensor nodes are only powered by the indoor lightings in the store.

RFID sensor node powered by solar cell

120 mm

100 mm


Energy saving in the convenience store

Energy saving in the convenience store

Constant comfort level control can be achieved and 45% A/C energy can be saved!!

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Data loss of a sensor node powered by harvested energy

Data loss of a sensor node powered by harvested energy

During one month operation, the data communication status in the store was investigated.Analyzing the packet counts record, the PLR is considered low at 2.3%. This data loss percentage value is comparable with those of sensors powered by battery . Data

lost

Immediate response time in 75 – 125 ms

Transmission delay (ms)

28.8%

68.9%

2.3%


Not only for identification but also for detection

Not only for identification but also for detection

RFID is a novel technology for remote identification of goods. The main advantage is the data storage and exchange. In this study, a RFID system was developed for detection of occupant. Through data exchange, the remote reader can get the information of occupancy to adjust the light setting to save energy.


UHF RFID for occupancy detection

UHF RFID for occupancy detection

Alien RFID Host

Alien RFID Tag

Name of the product Alien Multi-Port General Purpose RFID

Reader

Spec of the tag EPC Gen 2; ISO 18000-6c

Frequency 902.75 MHz – 927.25 MHz

Channel Width 500 KHz

RF Power Using Alien Antenna Max 4 Watt EIRP

Transmission interface RS-232 (DB-9 F), LAN TCPI/IP (RJ-45)

Simple Inputs/Outputs

interface4 inputs； 8outputs

Operation: under 24 DCV， 0.5ATemperature -20°C to +50°C

NOTE : Successful operation under the experimental instruction, the valid the distance between Tag and Antenna is 7meter.


RFID and LED integrated controllerRFID and LED integrated controller

RFID Reading Interface LED PWM Controlling Interface

IR Mode

RFID Mode

Monitoring Power Consumption

EXIT.


Characteristics of a LED lamp

Characteristics of a LED lamp

Power : 44W (Low power)Power factor : 0.988(Active Power Supply Design)

Color Temperature:4700K


LED illumination distribution

LED illumination distribution

Unit : LuxLED

Lamps

1.8m

Test condition


Circularly Polarized Antenna

3.2M

3M

RFID Host

4 Antenna Power input

I/O port

Power supply &

PWM controller

ComputerAntenna

LED control


RFID based lighting controlRFID based lighting control

Metal mesh barrier signal transmitter

100% Brightness

Variable brightness modulation

Tag 1. 100% Tag 1. 75% Tag 1. 50%

………..

RFIDdriveLEDcontroller

RFIDantenna

RFID TagbraceletControllable aisle light lighting


Comparison between IR and RFID Occupancy Detection

Comparison between IR and RFID Occupancy Detection

• IR detection can’t detect occupant who stand

still but RFID can get it.

• RFID can determine the moving direction of

a occupant.

IR detector RFID Host

No moving

nothing

IR detector


RFID-based Occupancy Detection saves more energy than IR-based oneRFID-based Occupancy Detection saves more energy than IR-based one

LED LED LED

≧ 500lux ≧ 150lux ≧ 150lux

empty emptyRFID Tag

100% 30% 30%RFID Antenna


ConclusionsConclusions

Based on backscatter coupling, used for RFID, zero communication power of the sensor node can be achieved.Through energy harvesting technology, the sensor and related circuits can be enabled. The whole new RFID based sensor networks was demonstrated and employed to record customers’ comfort degree in a store.The RFID based sensor networks can work as good as the battery powered system.


Conclusions (conti-)Conclusions (conti-)

Comparing with the well known protocol – ISO 802.15.4, or so called ZigBee, the RFID based sensor node communication has the advantage on furthermore reducing the power demands.However, different from ZigBee with routing algorithm, RFID based communication is only suitable for the applications of small scale sensor node deployment such like in a store or in your living room.


Conclusions (conti-)Conclusions (conti-)

A UHF RFID reader can detect occupants over 7 meters away. A LED lighting system combined with RFID can be used to adjust brightness in different zones and to reach the purpose of energy saving.The “deploy and forget” scenario was demonstrated by RFID-based sensor networks with energy harvesting chips. There is no need to worry about the replacement of battery.

MEMS Thermal & Fluid Control Lab. RFID tag powered by solar cell was set up and integrated with...

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