This is a follow up to this question, but isn't specific to the other one. This is both an ohm's law question and a 'how does one interpret data sheets' question.
I want to minimize the current I use to hold open a relay via a trigger (which only requires 1.2mA) that I need to isolate. If I use, say, an NTE3083 optoisolator to trigger this relay, how do I pick the proper resistor for the optoisolator's input? The datasheet says the NTE3083 will trigger as low as 1mA.
But the datasheet doesn't give a definitive forward voltage. It gives a 60mA forward current, and then has a table that also mentions 1.15V-1.5V and 20mA as part of its characteristics.
If my source voltage is 12V, and I want, say, 2mA to be conservative, how do I get there from here?
Do I just drop the voltage and current (R of the optoisolator would be constant?) by scaling down current and voltage? So if I want 2mA, divide by 10: 20mA/10 and 1.15V (or 1.5??)/10? And then calculate the resistor?
((12 volts) - (.1 volts)) / (2 milliamperes) = 5950 ohms
Is that the right approach?