What optocoupler has the lowest led diode input current
that brings the output transistor to saturation?
CNY17 has 10mA.
I am connecting the input to 220V 50Hz so I need
low input led current to save watts of the input
resistor.
Try a 4N25 or 4N35 and ground the base of the o/p transistor.
I think they will operate reliable with currents below 10 mA.
Put 2 x 18 k.ohm 1 Watt in series. and use a 1N4007.