Sensor to detect Laser Diode?

by iBucky on Thu Jan 17, 2013 3:25 pm

(I might have posted this in the wrong area of the form.)

I want to make a laser maze with a couple lasers, mirrors and a photo cell to sense the laser and when it has been broken, i.e. someone got infront of the light beam somewhere.

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?

Thank you in advance.
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Re: Sensor to detect Laser Diode?

by adafruit_support_bill on Thu Jan 17, 2013 3:58 pm

A cds sensor will probably work. But they do have a fairly strong 'memory effect' so the response time tends to be fairly slow. Photodiodes or phototransistors are more commonly used in that application.
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Re: Sensor to detect Laser Diode?

by Arctic_Eddie on Sat Jan 19, 2013 1:30 pm

How much of an aiming problem do you anticipate? The laser pointer beam size and photodiode/phototransistor active area are quite small. If you need a large area detector, you can use a reverse biased solar badge. Put a piece of red photo filter over the face to block other colors, assuming a red laser. Here's a good choice of solar panel.

http://www.adafruit.com/products/700
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Re: Sensor to detect Laser Diode?

by iBucky on Thu Feb 07, 2013 1:25 pm

Wasn't going to aim with the Laser pointer. It is going to be setup as a maze so you try to make your way across the room without breaking the laser light beam. Anyone know of a sample with a phototransistor. I picked one up tested changes with my multimeter, but cannot figure out how to set it up with the Arduino. I usually work off samples and didn't get far on the phototransistor.
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Re: Sensor to detect Laser Diode?

by Arctic_Eddie on Thu Feb 07, 2013 1:58 pm

Simplest method is to use the phototransistor as a pull-down on a digital pin. Emitter goes to ground and collector to digital pin with base open. Connect a 4K7 - 10K pull-up resistor from digital pin to Vcc. The signal on that pin will be high if there is no beam striking the detector and low if the beam hits the active area. The beam will likely be many times large than the sensor active region. The room lighting may trigger the sensor so you may have to put some kind of attenuation filter over the sensor. A piece of red plastic will work, assuming your laser is red.
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