photoresisitor/ counter project

josh739

I have a project I have to complete to pass a course in microprocessors, I want to use a photoresistor with a laser light as a counter. i need help with the programing aspect because i have found programs with counters and some using photoresistors, just not a combination of the two.

Mike Green

One way to do a project like this is to start at the highest level ("I want to use a photoresistor with a laser light as a counter") then get more and more detailed a piece at a time. So, first describe how you're going to use the photoresistor and the laser light to count. I don't mean for you to describe this yet from a programming standpoint. What do you mean by "photoresistor" and "laser light"? What do you mean by "counter"? What do you plan to count?.

Leon

I'm not sure if a photo-resistor is suitable for use with a laser, due to the small area of the incident light. A photo-diode might be better.

josh739

its just to count simple objects that travel down a conveyor we have built, after a preset count, the motor will stop for a set time and begin moving again and start counting again. the laser light was to have something to hit the photo resisitor in order to keep it high so when the object passed in fron of it, would go low and count it and move on.

erco

Photo resistors (CdS cells) are typically more sensitive to yellow/green light, FYI. Per Leon, a phototransistor is a better spectral match for a laser (and safer yet is an IR LED instead of a laser).

PJAllen

I had a flashback:
http://forums.parallax.com/showthread.php?83402-photoresistor&highlight=photoresistor+matrix