First E-Stop Test

https://questionable-engineering.com Tonight I wired up the emergency stop button for the CNC router table project. Not sure if this is how it’s conventionally done, but I feel pretty clever for having figured it out. A 24 V, 4-pole contactor lies at the heart of the circuit. If the e-stop button (normally closed) is closed, and you press the enable button (normally open), current flows through the contactor coil, closing the four poles. One of the poles is wired in parallel with the enable button, sustaining the current through the coil. If the e-stop is opened (by pressing down on it), current through the coil is interrupted. The other three poles of the contactor will provide power to the two 75 V supplies (I mistakenly called them servo drives, but they're really just simple power supplies) which will supply the servos. The 75 V supplies are single-phase 240 V, and so one will be powered between L2 & L3, and the other between L3 and L4. The 24 V supply will be on L1 & L2. Or some similar arrangement. For fun, I have the fans being powered by the coil’s 24 V supply, which means they come on when the contactor is on. It also means they turn off when the e-stop is triggered; I haven’t decided if I'm happy with that or not. There are more fans to come in this cabinet, we’ll see which ones get the special treatment, and which ones will be on all the time. I still need to tie the spindle motor’s VFD into the e-stop. I think the VFD should have a 24 V enable input I can use for this purpose. This contactor is only rated for 20 A, not big enough to directly kill the VFD, and frankly I don't want to do that, if I can avoid it. Not sure what the best practice is for safety, though.