Electronics upgrade for an existing machine.

[JAZZCNC]

Question, I'd like to use a relay with e-stop to cut power rather than relying on Mach and the PC.

Can anyone recommend a suitable relay and is a solidstate relay best for this application?

Wouldn't use soild state because they can and do fail "ON" as been said by like Ptjw7uk says.

Also when wiring for a star ground do you wire the earth cable for the mains cable to this and all other earths from PSU's, cable shields etc. into the star ground? I'm really trying to avoid ground loops but am unsure if this is good or bad practise.

Easist way is to do it like this pic shows. One cable to the main ground point back to a bus bar type connector that all others take from. There are other ground type connectors but this shows it well.