GRBL controller 0-10v spindle

I am trying to control the speed of my Chinese spindle from a self built GRBL controller. I have Best VFD and 800w spindle. I had a lot of noise problems initially that were solved when I took off the end of the spindle and connected the ground wire to it. I have added the attached circuit to my controller board and have verified that it is outputting 0-10v when controlled either via bCNC or terminal. My system all works fine when I control the VFD speed from the control panel. But when I connect it to the controller board - connected to COM and AVI - when I start the spindle it works for a few seconds and then slows back down and stops and nothing will work. I have to disconnect and reconnect to it in order for it to work again. I have blown the output on pin 11 on one Atmega328 ic already testing it so something is definitely not right...

All of my cables are shielded and twisted on my CNC machine. And all of the shields, the frame and power supply earth are connected. The Spindle pin 4 and shield are connected to PE on the VFD - as mentioned I had a problem when trying to router a PCB with the machine the hard limits would trigger (but I was able to work on non metal parts). Once I connected the ground on the spindle that problem went away. The COM on the VFD is not connected to PE, and my 12/5v- is not connected to the earth on the CNC either.

I have tested with the output of Pin 11 directly and through the attached circuit and it reacts the same in both cases - the MCU crashes as soon as the spindle is started and I need to disconnect the connection in bCNC and reconnect to be able to do anything.

What is the proper way to control a 0-10 VFD through a GRBL controller?

Your problem is probably ground current from the motor chassis return by using the GRBL connections.

You could start by powering the GRBL controller from the same outlet as the rest of the machine, but that will probably not solve the problem.

Powering the arduino from the PWM converter power supply could probably solve the problem. Check the maximum voltage your arduino board can handle.

The best solution to get rid of the problem is to add an optocoupler (galvanic isolation) between the output of the GRBL controller and the input of the PWM to 0-10V converter. Then you have an isolated PWM output on the GRLB controller and an isolated input on the converter. Add the optocoupler on the PWM converter side. Here is example on how to
https://electronics.stackexchange.co...-arduino-input