Help with Optical sensor

Thread Starter


Joined Feb 16, 2011
Hi guys. I have been working on my project. Something that could detect incoming intruders in the house. is there a way to make an optical sensor to detect as far as 1m? I looked up some of the sensors in the market but a lot of them can only detect as far as 2mm. Or is there a better way? The sensor output should be able to activate a relay in so the output should be approximately 6v min.

i think this works but it functions as a sound/tone detector or something.


Joined Jul 9, 2011
i think this works but it functions as a sound/tone detector or something.
The receiver is tuned to only respond to incoming infrared light modulated at the specified frequency, since he says tone I assume it's audio frequency. It could work like a light barrier. Which brings us to a fundamental question.

Do you want to detect someone approaching or do you want to detect someone passing through a light barrier?

One works with reflection, the other one on interruption of a light beam (pulsed or continuous).

Ambient light sources can be a quite challenging issue to resolve. Is this going to be installed where ambient light changes rapidly? (like direct sunshine with passing by clouds)

Have a look at the SI1102. You might be better off with ultrasound modules.


Joined Dec 26, 2010
I've seen barrier alarms working indoors really well using a sender and receiver pair pointing at a corner reflector (prism type, like the ones on vehicles). I think the optics use collimating lenses though. Security companies must use loads of these things.