Can anyone recommend a good laser detector?

Forum 2005-2010 (read only) Hardware Interfacing
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I want to play around with laser detection for alarms, etc. but i'm having trouble using the photo cell I received from Adafruit Photo cell (CdS photoresistor) : ID 161 : $0.95 : Adafruit Industries, Unique & fun DIY electronics and kits

  • probably because it requires direct contact and a specific wavelength.

Can anyone recommend a good spec and supplier of laser detector? I've heard some things about photodiodes but not sure which one would work best.

2

probably because it requires direct contact and a specific wavelength

Not sure what you mean by that - direct contact with what?
CdS cells have quite a broad spectrum, I thought.

[edit]Thinking further, having your detector tuned to the same wavelength as your laser is a Good Thing[/edit]

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Can anyone recommend a good spec and supplier of laser detector? I've heard some things about photodiodes but not sure which one would work best.

I use 12-14mm LDRs and they work great. You really want a red (or green or blue depending on the colour of your laser) filter over it to block out the other colours of the spectrum (so sunlight does not affect it so much). You can use smaller LDRs but the large ones are easier to get the laser to point at (they have a larger area that works)

Ahh you are using a small LDR -I am surprised that it is not working properly, is the circuit correct?

LDRs are really easy to just do analog read from so they are probably the best to use. I have had no issues. If you use a variable resistor as the pull down then you can adjust the sensitivity.

Mowcius

4

Have you tried using a phototransistor?

http://www.allelectronics.com/make-a-store/item/TIL99/PHOTOTRANSISTOR-TO18-PACKAGE/1.html

Basically they are like a regular transistor, except the base is controlled by light falling on the junction (there is a lens mounted to the case by which light can be admitted). Some are wavelength specific (typically in the IR region - because they are sometimes used for remote control applications with IR LEDs), but many have ranges in the visible region (and you might be able to find one sensitive to the wavelength of your laser).

Also note that some have the base lead still connected (like the example above); IIRC, this allows you to bias the base (just like any other transistor) to allow you to change its sensitivity to light falling on it.