Hi all,

Last few weeks I've have been busy installing and wiring a PlanetCNC MK3/4 controller board to convert my mini lathe to CNC.
It is a Optimum 180x300 like lathe (like many others) and it has a potentiometer to control the spindle speed manually.
I would like to replace the potentiometer and control the spindle speed with a PWM output of the MK3/4.

The potentiometer is generating a 0-10V signal. I tried to generate this signal by switching the 10V+ with an optocoupler(driven by the spindle output) with 40Hz and feeding it through a low-pass filter.
Unfortunately this does not seem to work.

How could I connect the MK3/4 to the potentiometer wires?
There are quite some people who retrofitted these Chinese machines but I cant find how they managed to control the spindle .
Hopefully you can give me some insight!

Thanks in advance and kind regards,
Patrick