I am using 6n137 opto-coupler to take engine tachometer 12v signal from ECU, then send it to arduino nano esp32 that in return it drives rev RGB LEDs. I found in the optocoupler data sheet that the minimum input voltage is 4.5V at Vcc. Is it ok if i supply Vcc with 5V and pull up Vo to 3.3V from the arduino, to get 3.3V pulse output? as shown in below figure.

 

Hello,

As the 6N137 has an open drain output, it should work.
There is no problem to use 3.3 volts on the drain of the output.
The supply voltages are 7 volts max.

Bertus

 

Why do you have a connection between the LED cathode and GND pin? Nothing is being isolated. An opto-isolator is superfluous.

 

Hello,

If you do not need isolation, a simple mosfet will also work.

Bertus

 

Hello,

If you do not need isolation, a simple mosfet will also work.

Bertus

So will a potential divider.