Hi Doddy, thanks for coming back.

Unfortunately I next tested the spindle whilst the machine was in the living room being built, however the spindle never caused me an issue in the past so when I swapped it from one machine to the next I thought nothing of it. That was till I blew the power. It's also why I'm ruling out wiring the spindle wrong etc and I have seen it working. I did however run the spindle on a different circuit whilst in the garage and had the same result.

I don't believe it is my RCD as I haven't had any random trips in the past and have been using this VFD and spindle in the past. I do know it has something to do with the arduino board - as really thats the only thing that has changed.

When I initially wired it up I found multiple people who had connected it in the way I describe. I can control the speed to the nearest 1000rmp - from the instructions it does state 'Analog Voltage Frequency Reference Input' I'm not sure it's a true PWM input? However looking at the manual I could also try hooking it into the AI terminal? I'd need to check the current is between - 4~20mA.

I will try feeding a 5v input into it, I like that idea as it should tell me is the issue lies with the PWM/gnd or the DCM/For enable spindle.

Do you think it's worth me grounding the machine earth through an additional power supply? Currently it runs through the laptop power.