I'm trying to use the signal generator from a DSO Nano v2 to drive an Arduino interrupt for testing purposes. I have measured the output of the signal generator at approximately 13mA @ 2V DC.
I have tried using a 4N28 optcoupler alone but I found that the voltage differential at the output was nowhere near enough to trigger the interrupt (it was ~0.4V), I assume there is not enough input current for the IR LED to saturate the transistor.
How can I make this work? Also, would this solution apply for other comparatively weak signal sources.
Would an opamp be able to boost the output signal?
Best Answer
@Chris it sounds like the circuit is not complete... do you have a pull up like R2?
This is what I expect to be using in this situation. The opto does not exists in CircuitLab but you get the idea. With only a 4N28 with CTR (Current transfer ratio) of 10% assuming R1 is 80 ohmsish and the diode forward drop is 1.2V, 10mA LED current, we should see 1mA sink capacity on the Output to Micro...
NOTE: The grounds will be separate in this type of circuit normally.
I like CircuitLab... just wish generic symbols were available by default...
simulate this circuit – Schematic created using CircuitLab