Hello,
I am trying to make a remote triggering by WiFi for my DSLR camera using esp8266.
I tried to use an optocoupler(4n35) as a relay but apparently it has a large reverse voltage(6V) for the esp8266 (3.3V).
Do you have a suggestions which units/parts can be used as digital switch in low power projects?
Thanks

 

A 4n35 should work just fine..
What value resistor were you using on the output of the digital pin to the LED? (something like a 50 to 150 ohm 1/8W should work just fine)

 

@matabar:
Can you post a schematic of what it was you tried that failed?

 

A 4n35 should work just fine..
What value resistor were you using on the output of the digital pin to the LED? (something like a 50 to 150 ohm 1/8W should work just fine)

I used 200 ohm. I measured the led anode pin (#1) voltage and it was 1.2V.
The problem is pin 4 and 5 are not shorted so I think that the led is not conductive.
I added a pic of my project.

 

The problem is pin 4 and 5 are not shorted so I think that the led is not conductive.

How did you determine that it's not "shorted".
The output doesn't generate a short, like a mechanical relay would provide.
The output should be conducting at least 10mA (collector positive with respect to the emitter) with a 3.3V input through 200 ohms.

 

^^.. yep..
Its probably working just fine you just aren't aware..

Throw a resistor/voltage on the transistor side of the opto and see if its switching as it should..