Hi All,

I found this thread
https://forum.allaboutcircuits.com/...o-a-ucontroller-with-an-opto-isolator.159447/

and I am trying to something very similar: connect the tach wire from balmar mc-614 to a raspberry pi.

I am curious why the original poster decided to use an optocoupler? Do you think I can connect the wire directly to GPIO pin through a voltage divider.

Thanks,
A.

 

NO. Not unless you want to fry it.
The optocoupler is to isolate the vehicle electrical system from the Rpi.

 

Use an optocoupler it's better for isolation against blowing up your micro,
do you want to measure the alternator rpm ?

 

The stator connections used to drive tachometers are actually AC signals to begin with that are connected before the rectifier and will take more than a simple voltage divider. It never really seemed to get answered in that thread. The charging output is DC of course. Besides that little bit there are a number of other reasons to use an optocoupler.