Current for the 4N25
4N25 CTR 50 %
I dont understand very well your formulas, but:
if indicator LED current is choosen to be 10mA (maybe lower as i dont need it to be bright)
LED current x CTR = phototransistor current.
LED current (10mA) x CTR 50% = possible phototransistor current 5 mA
If you use 10kohm pullup = 0,5 mA from optocoupler you only need 1 mA LED current.
I dont understand this last phrase.
as they are in series, if 10mA go through the status led, arent there going to be the same 10mA through the optocoupler led?
