Detecting Laser Diode?

by iBucky on Wed Jan 16, 2013 2:44 pm

I'm going to make a Laser maze with a couple lasers, mirrors and a photo cell to sense if the laser has been broken.

My question is - can I use the Photo cell (CdS photoresistor) to detect the laser light or will the laser burn the photoresistor out? If not the Photo cell what can I use to sense the laser light?
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Re: Detecting Laser Diode?

by adafruit_support_mike on Tue Jan 22, 2013 4:27 pm

If you stick to class-1 lasers (the average banned laser pointer), you shouldn't have any problems. Those don't have enough power to damage a human eye with extended exposure, even when run through a focusing lens, so they shouldn't hurt a photosensor.

As for sensors, you have a range of options. A CdS photoresistor will work, but so will photodiodes, phototransistors, and the everyday red LED. CdS is losing popularity because it's toxic, so I'd suggest going with silicon unless you already have the CdS on hand.

Silicon devices will definitely stand up to a laser because they use the photoelectric effect. All silicon devices are photosensitive, and sensors are just designed to take the best advantage of it. LEDs make decent sensors because the math works both ways.. putting current through the junction generates light, and putting light into the junction generates currrent. They work best for wavelengths close to the ones they emit, so if you have a red laser pointer, try shining it on a red LED and see what kind of response you get.
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Re: Detecting Laser Diode?

by iBucky on Thu Feb 07, 2013 1:28 pm

Thank you for the suggestion on the LEDs - I'm going to try that! Didn't think of it in reverse - very nice.
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