I have a project that is very similar to the tripwire project. Where a photoresistor detects a laser beams existence or lack of...
My problem is, when setting the threshold of the photoresistor to detect the laser, the photoresistor also detects ambient lighting and doesn't see the Laser.
My question is; How can I exclude the ambient light and only have the photoresistor see the green or red laser?
FYI the photoresistor is not a constant distance from the laser source nor will it be in the same enviroment. So I can not expect to set certain values and fine tune them. I need to have my photoresistor be strictly sensitive to the laser.
Do we really talk about a photoresistor? A photoresistor will react slowly to changes in light intensity. It is not possible to use a carrier frequency to dinguish the laser light from ambient light.
Maybe a photodiode is more adequate for your ( still unknown ) usage.
And the spectral sensitivity of your detector should fit to your laser.
I looked into IR transmission a little and realized that IR laser is neither safe nor legal. However if you could elaborate on how I could filter out a green or red laser, other than using lenses, that'd be apreciated.
Are you SURE you want to filter out those colors. Don't you want to only pass those laser colors? Trouble is your ambient light also includes the color you are interested in. That is why you need a different way to recognize your particular light and a modulation, on and off, pattern is necessary.
Both parts are wrong for a tripwire.
The laser is hard to aim exactly onto the photoresistor,
and a photoresistor is also sensitive to ambient light.
You should have used a (narrow-beam) IR diode and a 38kHz 3-pin IR receiver (without AGC).
With that combination you can bridge 50+ metres in bright daylight.
Leo..