Need help designing a laser trip alarm receiver.

[ItsMike]

Hey guys,

I'm trying to make a laser trip alarm but i'm having problems designing the receiver.

I want to ASK modulate (with constant '1') the laser beam on some frequency so the receiver's input signal should look like a "clock" signal when the beam hits the sensor and obviously nothing when it doesn't hit the sensor.

I though of using a notch pass filter on that frequency but I'm thinking there must be some better way.
I was thinking of using an oscillator on the receiver and sampling the input signal with it, but what happens if the frequency isn't dead even ?

How do all those IR receivers do it ?

Thanks in advance,
Mike.

 

[ericgibbs]

hi,
Whats the distance of light path.?

 

[ItsMike]

I don't know, I think at least 25 meters.
Why is that relevant btw ?

I want to break the light with mirrors though, so the actual distance between receiver and transmitter is about 5 meters (I already though of using same clock for both circuits).

 

[ItsMike]

BUMP, anyone knows ?

 

[ericgibbs]

BUMP, anyone knows ?

Why not modulate the IR laser with say 38KHz or 40KHz and use an off the shelf TSOP receiver.

I cannot see why you think you need a clock for simple beam break detect.??

 

[blueroomelectronics]

A simple CDS cell would work, trick with a laser is at 25 meters through 5 mirrors it'll probably be hard to keep on target.

 

[ItsMike]

I couldn't find an IR Laser anywhere, so I thought I'd use a plain red one.

I wanted to modulate it so random light won't trigger the receiver sensor.