Here I will explore what kind of switches to use to turn the machines in the workshop ON and OFF.
It’s possible to use a normal switch on turn machines ON and OFF. For example like the ones used to control lights but that’s not a good idea for stationary machines that can be dangerous for people.
Why not? Imagine you’re working on the table saw and it suddenly turns off. You wonder what’s wrong and start taking a closer look at the machine and it unexpectedly turns on again (dangerous restart)
What happened? Someone tripped over the cable of your saw and pulled the plug out of the socket. Then he inserted the plug again.
How can we avoid such a situation? Use a switch that doesn’t turn the machine back on when power is lost and then comes back. There can be multiple reasons for the power to go away: Pressing the emergency stop, a power outage or someone tripping over the cable are a few common examples.
2 phase - 230V machines
For 2 phase devices we can use an NVR (No Volt Release) switch.
An NVR switch can be wired to an emergency stop in the following way:
Post on hackaday about NVRs
3 phase - 400V machines
For 3 phase devices it’s common to use a motor starer box that includes a contactor that acts like an NVR switch.
3 kW DOL starter with integrated emergency stop
It should be possible to buy an emergency stop separaterly and wire it to a DOL starter which doesn’t have one.