Main Site Documentation

Drive opto coupler from fez pin



can I drive an opto coupler straight from a Fez pin? (opto coupler = 4N35)

Thanks in advance


May be this can help


Note that at 10mA I believe you’re at the limit. I’d probably avoid it, because I don’t like living on the edge (of a dead pin, or worse…).


It is 8mA, showing on page 668

forward voltage (TYP) is 1.18V
forward current (TYP) is 10mA
voltage supply is 5v (Arduino)

Results in 390Ohm resistor. (even with MAX forward voltage rating of 1.5V)
(why did they say on that arduino forum that 330 ohm was enough? Did I miss something?)


only had a 560 ohm available and it works.

Thanks guys


I got away with driving an optocoupler directly… for a little while. Then I ended up with a crippled Panda. I went through several data sheets before finding out (with the help of someone here) that 6ma is the recommended limit for the an out pin. I am using a simple emitter follower transistor current amp with good success (no crippled Panda’s) but the output is not fully linear at the bottom end.