Large Photo resistor

[koossa]

Good day

I need something like a large photo resistor (the size of a credit card)
Is there something else that I can use that can detect light, or can I connect a couple of standard photo resistors together?

[Acetronics2]

Hi,

Never heard of silicon solar panels ???

http://www.selectronic.fr/article.asp?article_ref_entier=11.6926-9999

Alain

[rsocor01]

Koossa,

Yes, you can connect a couple of photoresistors together. However, since most photoresistors decrease in resistance as the light intensity increases it would be better if you connect them in parallel so any changes will be easier to detect.

Robert

[Archangel]

hi koossa,
Just curious, why so large? Photo voltaic cells "detect" light and generate voltage and they are large. LEDs can detect light too . . . How much sensitivity do you need ?

[koossa]

Thank you very much for all the replies!!

It's for a long distance shooting game.
On the gun is a laser and on the target is a photo resistor.

Wouldn't it work if I use something like a fresnel lens on the target?

[mackrackit]

http://www.lasertagparts.com/mtsensors.htm

[ScaleRobotics]

http://www.lasertagparts.com/mtsensors.htm

It is a bit confusing, because "lasertag" is usually really LED TAG with optics. So the sensors you linked are for a broader beam LED tag system. It is going to be a lot harder with a real laser, if that is what koosa is intending, since the beam is so small.

I have never tried it, but I have heard that you can sense light with standard LED's. You might be able to build your own target array with them. Here is a simple single LED on a multimeter. http://mvh.sr.unh.edu/mvhinvestigations/led_emission.htm

And maybe a more interesting example here: http://www.cs.cmu.edu/~ehayashi/projects/lasercommand/
(http://www.cs.cmu.edu/%7Eehayashi/projects/lasercommand/)

http://vimeo.com/10819322

[mackrackit]

I gave the link for an idea on how to build the sensor. Besides that, pretty much the same sensor that detects IR will also detect red laser.

The trick with either one is getting past the ambient light problem, being that it seems for this project data is not involved it is much easier.

The security fences that I setup using real lasers work on the same idea. Make or break. I pulse the laser at a given Hz. If the receiver does not "see" the correct frequency then the alarms are triggered. The sensor also sits recessed so it is not washed out by sun light.

For the sensor a simple photo-diode works well. I use one sitting in the bottom of a reflective cone. The cone is 2 inches in diameter, giving a 2 inch target. If the OP wants something flat and rectangular then a few photo-diodes could be arrayed under the Fresnel as he mentioned.

[ScaleRobotics]

I like your reflector cone idea!

For the TSOP4856 in http://www.lasertagparts.com/mtsensors.htm it looks like the laser would need a carrier frequency of 56 khz. http://www.vishay.com/docs/82090/tsop48xx.pdf .