Turning LED's into photodiodes?

[petitericeball]

I think that's what they're called. I was guessing that you just put them in backwards, but I'm betting its more complicated than that?

 

[mgb_phys]

In theory, although you would be better off with real photodiodes.

 

[berkeman]

In theory, although you would be better off with real photodiodes.

You will connect the LED or photodiode up to a current-to-voltage converter circuit, in order to convert the photocurrent to an output voltage. See the example opamp circuit on this page, for example:

http://sales.hamamatsu.com/assets/html/ssd/si-photodiode/index.htm

Using a high reverse voltage across the photodiode or LED will help it to operate faster (detect higher frequency signals), because the high reverse bias decreases the capacitance across the depletion region.

 

[petitericeball]

how would i go about sending these "impulse" type things into a computer?

 

[bassplayer142]

People who have green 532nm lasers have been known to try to test the output power by using green LED's. It works but it is not a very accurate way of approaching this problem.

 

[berkeman]

how would i go about sending these "impulse" type things into a computer?

What impulse type things?

 

[petitericeball]

Sorry that was very vague.. bad day.. Okay, so how would i hook up the photodiodes up to a computer so that the computer can understand the signals that the photodiodes are sending out?

Okay, so I'm trying to create some sort of a computer targeting system (nothing fancy) with lasers and photodiodes. I want to be able to be able to "track" the movement of the laser using the photodiodes. Later on I hope to somehow make the laser track movement.

I know this is a terrible explanation, but I don't totally understand how I am suppose to do this..

 

[berkeman]

The traditional way would be with some data acquisition and motion control modules, connected via RS-232 or USB to your PC. Here are three companies that make such modules:

B&B Electronics http://bb-elec.com/

Omega http://www.omega.com/das/index.html

National Instruments http://www.ni.com/

You can also "roll your own" modules, but you need to be fluent in RS-232 or USB interface hardware, and comfortable programming your own uC and data acq and motion control hardware.