Detect someone in front of a computer using the smallest available sensor.

Hello,

I'm trying to create my first project using a tiny arduino but I still don't know how am I going to accomplish that...

I need to be able to detect a person in front of a computer. PIR is out of the question because I need to be able to detect the person as long as he keeps in front of the computer. I though of using the Parallax's Ping but it is too big for my project.

So I'm not really sure of how am I going to do this so I'm asking you: What is the smallest sensor that I can use to detect someone in front of a computer? Something with the size of a 10 cents coin (euros) would be nice.

Thanks!

For those of us that don't use the Euro, 10 Cent coins are 19.75mm in diameter, according to Wikipedia.

There are single element ultrasonic sensors around that size, like http://www.dfrobot.com/index.php?route=product/product&product_id=291.

dxw00d: For those of us that don't use the Euro, 10 Cent coins are 19.75mm in diameter, according to Wikipedia.

There are single element ultrasonic sensors around that size, like http://www.dfrobot.com/index.php?route=product/product&product_id=291.

Yes this one is 19.9mm...just a smidge wider (at the board) http://www.instructables.com/id/Getting-started-with-the-Maxbotix-sonar-sensor-q/

Perhaps you could measure the change of lighting as they arrive and leave, using a photocell which are far smaller again http://www.instructables.com/id/Getting-started-with-the-Maxbotix-sonar-sensor-q/

Or hide a force sensitive sensor in the seat cushion?

Lots of options, Geoff

You could use an IR led and an IR receiver. These are very small and will be able to detect if something is in front of it.