Opto-couplers and Arduino

Projects General Guidance
1

Hi, I wonder if anybody can help me please.

I'm hoping to make a trigger unit for my DSLR.
Eventually, I want it to do all sorts of complicated things but for now, I just need to know that the hardware works.
I will be controlling focus and shutter from two Arduino pins. I would like to isolate the camera using optocouplers. I have never used them before so would like a little help please.

They are ILD74 optocouplers.
Here is the data sheet http://www.farnell.com/datasheets/6513.pdf.

I'm not great with data sheets but, I assume I'll need a current limiting resister, is this correct?

Thanks in advance for any help.

Paul

2

I assume I'll need a current limiting resister, is this correct?

Yes. About 180 Ohms on the input/LED side should do it.

With 5V out of the Arduino, and 1.3V across the opto's LED, that leaves 3.7V across the resistor. 3.7V / 20mA = 185 Ohms.

(I don't know what the camera-side needs.)

3

That's brilliant, thank you very much.
I think I should be fine on the output side, I just didn't want to feed the optos anything they couldn't handle.

Thanks again.
Paul