RFID Human Motion Alarm SystemChris Hirsch & David Huskey

Introduction to RFID• Automated identification method

• Lightweight, portable

• Tags can be read from several meters away, (sometimes) beyond line of site of reader

• Passive RFID tags have no internal power supply – Small electrical current induced in the antenna by the

incoming RF signal provides just enough power for the tag to power up and transmit a response back.

Objectives• Incorporate RFID into room alarm

systems• Sound an alarm when an unaccompanied

unauthorized intruder is in the protected room

• Transmit data via serial to a computer where it can be monitored by security

• Design an alarm system that is user friendly

• Design an alarm system that is robust enough to detect any intruder using any method of entry

Basic Abstract Design• Inputs:

– RFID Reader– IR Motion

Sensor– 16 Button

Keypad

• Outputs:– Siren– LEDs– RS-232 Port

RFIDTransponder

Controller

Antenna

RFID Reader

Keypad Input

Siren / LEDs

PC Output

IR Motion Sensor

PIC16F877A Microcontroller• Runs program that monitors voltages from

the inputs of the system (keypad, motion sensor, and RFID reader) in an infinite loop.

• Controls all outputs of the system (Siren, LEDs, and PC display) by setting voltages on output pins.

Microcontroller Flow Chart

Siren

Deactivated

Motion Detected

Siren Activated

3. Siren State

Keypad

Deactivated

Correct

Keycode

Keypad

Activated

Correct

Keycode

1. Keypad State

RFID

Deactivated

Tag

Not Present

Keypad

Activated

Tag

Present

2. RFID State

(when Keypad & RFID activated)

SkyeTek M9 RFID Reader• Chosen over the Texas

Instrument RFID Reader for its superior range

• Receives commands from and transmits responses to the controller through an RS-232 port at 34.8 kbps

• Operates at a frequency of 915 MHz and output power of 500 mW

Skyware Software

HyperTerminal Communication with RFID Reader

Grayhill Keypad• 16 buttons – 16

possible interconnections

• 4x4 matrix that can be probed at the 8 output pins

• Extra buttons allow for adding additional features in the future

Microcontroller: Keypad Input• Sets pins 1-4 to high

sequentially and observes pins 5-8 for connections to determine if a key has been pressed.

• Correct sequential Key-Code from the user activates / deactivates the alarm system

6000 PIR Infrared Motion Detector

• Chosen for its long range and low cost

• Requires +12 and –12 volts for power

• Outputs a signal of 1.1 volt when motion is detected

Microcontroller: Motion Detector Input

• The controller monitors the voltage on the motion detector output.

• Microcontroller uses the ADC function to monitor the AC voltage.– Converts a continuous signal to a discreet

digital number from 0 to 1024 (2^10)

• When voltage rises above 50mV or 10 on the ADC scale on this input (and the alarm is in active mode) the alarm is triggered.

Output Components• Sonalert Siren

– Draws little current at 5 volts (~2 mA)– Controlled by the Microcontroller

• LEDs– Red and green LEDs have a voltage drop of 2.1 volts

and are connected to 560 ohm resistors in order to limit the current sourced by the PIC to approximately 5 mA

• RS-232 Port PC Output– Connected to the microcontroller via the MAX-232

chip– 38.4 kbps and only requires a wire for transmitting to

the computer and a wire for ground

Microcontroller: LED Output• Red LED can be turned on and off by

entering correct key-code.

• Green LED is on when the controller considers no tags to be in the room.

• When both LEDs are on, unauthorized personnel are to stay out of the room, because the alarm is in active mode.

Microcontroller: Siren Output• Beeps (voltage high for 150 milliseconds)

once when a tag is seen entering the room and twice when a tag is seen exiting.

• Longer Beeping for a 10 second grace period when the PIC decides that there is an intruder.

• Continuous noise from the siren if the alarm is not deactivated after the grace period.

Microcontroller: Computer Output• Information is sent to the computer as

ASCII characters through an RS-232 port connected to the PIC microcontroller through the Max-232 chip.

• Microsoft HyperTerminal displays the text.– Shows when the alarm is activated and

deactivated.– Shows which ID tags enter and exit the

protected room.

Main PCB Components & Enclosure• PIC Microcontroller

– The brain of the alarm system

• FOX 20MHz Oscillator– Clock input for the PIC

• 5V Voltage Regulator– Steps voltage down from 12 volts to

5 volts

• Max-232 Chip & 0.1 microfarad Capacitors– Converts TTL voltages to RS-232

voltages and vice-versa.

Overall Schematic

RFID READER &MOTION DETECTOR

TESTING & VERIFICATION

Counter Code Implemented• Each user could

only exit and enter after ten iterations of the coded loop

• User held tag parallel to reader at various distances

Null Code Implemented• Each user could

only exit and enter after the PIC had received a null response from the reader

• User held tag parallel to reader at various distances

Both Codes Implemented• User can only exit

and enter after null code is received and after 3 iterations of the loop had passed

• User held tag parallel to reader at various distances

Multiple User Test• Test to make sure

the system could handle multiple users at once

• Tested in single file and side by side

• User held tag parallel to reader at various distances

Wallet & Denim Test• Through a wallet at

under a foot• Through a denim

pocket at under an inch

• Due to the low power output of the reader as well as the orientation of the tag

Testing the Motion DetectorMotion Detection Range at Varying Angles at 10 feet

0

1

2

3

4

5

6

7

8

9

10

0 50 100 150

Degrees

# o

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etec

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/ 10

Testing the Motion DetectorMotion Detection Range at Varying Angles at 20 feet

0

1

2

3

4

5

6

7

8

9

10

0 50 100 150

Degrees

# o

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/ 10

Series1

Testing the Motion Detector

40˚

50˚50˚

40˚

Never

Always

50% Detection Rate 50% Detection Rate

Always

Never

Successes• Project is a success

– Alarm sounds when the system is in active mode and an unauthorized intruder is in the 40’ x 40’ room.

– Information about current ID tags in the room and the state of the alarm system can be transmitted serially to a PC for observation.

– The design is user friendly. Users are able to quickly identify the beeps and LEDs to know if their ID tag has been scanned.

Challenges• RFID Challenges

– Certain materials greatly reduce range of RFID tag detection rate

• In Wallet Range – <1ft for reliable detection rate• In Denim Pocket range - <1in for reliable detection

rate

– Standing just out of range of the RFID antenna (>4ft) can sometimes cause erroneous, unwanted tag scans

More Challenges• More RFID Challenges

– The reader struggles to scan tags when there are large obstructions such as another person.

– Two people walking in the room at once has a poorer success rate.

• Motion Detector Challenges– Poor placement can result in undetected

motion.

Design Alternatives• A computer program could be written to

notify authorities when there is a security breach by sending an E-mail or SMS.

• Extra buttons on keypad could be utilized to add more functionality such as the ability for the user to change the key-code.

• More RFID tags could be added.

Thank YouDavid Huskey & Chris Hirsch