SparkFun Forums

[jdebros]

I have recently picked one of these up for a project and it has been working perfectly. I am able to control the on-board LED with no problem.

My question is what do I interface with the GPIOs? For instance, I picked up and Opto-Isolator that works perfectly at low voltages - so the 2.8v is fine, but the problem is that the 1ma can't drive the opto-isolator's photodiode.

Is there a specific opto-isolator that I should be using or some other means of controlling higher voltage/amperage devices such as relays and motor controllers?

Thanks for any advice - I'm a s/w engineer teaching myself about transistors, biasing, base/emitters/collectors, diodes etc. Things are going well, I just don't know how to build a hardware interface to the Sparkfun USB board/GM862.

Thanks!

/jd

[leon_heller]

You seem a bit confused. The photodiode in the opto-isolator is a detector, you don't need to drive it but you will need to amplify it. You should buy an opto-isolator with a photo-transistor rather than a photo-diode, it will be easier to use.

Leon

[jdebros]

You seem a bit confused. The photodiode in the opto-isolator is a detector, you don't need to drive it but you will need to amplify it. You should buy an opto-isolator with a photo-transistor rather than a photo-diode, it will be easier to use.

Leon

Thanks Leon. Here's an excerpt from the docs for the opto-isolator that I've been attempting to work with:

"The NTE3042 is an optically coupled isolator consisting of a Gallium Arsenide infrared emitting diode and an NPN silicon phototransistor mounted in a standard 6–Lead DIP type package." - Source: http://www.nteinc.com/specs/3000to3099/pdf/nte3042.pdf. I guess I mis-quoted the product - sorry about that. I should have stated that 1ma from the I/O's doesn't seem to be enough to drive the infrared emitting diode.

Am I going down the right road or is there a *better* way to accomplish the I/O interfacing?

Thanks again,

/jd

[leon_heller]

That sounds OK, it has an LED (not a photo-diode) and a photo-transistor -it's a standard opto-isolator. You shouldn't have any problems with it.

Leon