Author Options:

RFID/NFC computer lock? Answered

I am curious if any of you have an idea for something that could detect a bracelet from 5-10 feet and when it leaves, issue a sleep command to a computer.  I think it would be relatively easy to issue the command from an arduino, but I'm not very sure on which tags and readers to use for the right range.  The idea would be for the computer to automatically sleep/lock when you leave the room.

 So what frequencies/types of tags and readers should I look into that will offer a decent range, that is close enough not to loose connection reaching across the desk or walking a few feet across the room, but won't work from a few rooms down the hall, and will interface well with an arduino.



3 years ago

I assume a piece of background software to keep awake on mouse and keypad action is not reasonable ?

The idea is to lock my computer when I leave the room, sometimes I forget and my roommates have a ball with it and I send half an hour setting everything back to normal.

Exactly a small program referred to as a watchdog timer is used allow a timer to time out in the absence of a key-press or mouse action resetting it to ONE.

When the timer rolls-over to zero a batch file sleeps your computer which needs a password to restart.

You can certainly put an RFID Tag on the shape of a bracelet or inject one under your skin and make that work but a roll over timer can be the computer itself.


Vs the $60 in hardware for what I sugested, This will be much simpler !

The problem will be the distance from the sensor...

You can easily use a Atmega 328 (Arduino Leonardo and a few others) as whats called a HID, Human Interface Device. If say a input pin is pulled low it will send a keystroke to your computer. You can also easily hook up a NFC / RFID chip to your Arduino that can read a massive selection of tags. I've seen dozens of different styles of tags from a bracelet like you mentioned, to key chains, mounted Disks, Credit cards and even stick on patches like what they use for anti theft.

The problem is many of these won't work from too far away (Aprox 10 - 15cm / 4-6 inches) This is to prevent scanning the wrong tag and to prevent someone from gaining unauthorized access with a scanner. You could try researching what the major car companies are using, personally I haven't delved into it myself >.>

May I suggest you use a Capacitive touch sensor?

You could set an electrode beneath your seat, under your desk or just hook it up as an Occupancy sensor.

I suppose you could also hook up a load cell to you chair?

How to build a HID


and the Capacitive sensor I like to use