Well as the title states I am thinking of hacking in a relay to fire up an air compressor only when the mill is on. The compressor is the GMC/California Air unit that Tormach recommends and is dedicated to the mill for power draw bar and incidental blow gun use. I have a separate 20gallon compressor for the rest of the shop. So why the relay? Well I located the compressors and a dedicated 20A circuit at the far end of the shop under a workbench. So far it has worked out really nice. Its super quiet, even standing next to it but being 40' away under a bench and behind a wall its even more so. The issue is I always find myself wanting to get going and its like Oh shoot, got to walk over there and flip the switch. Then when I'm done working for the day the bigger issue is I forget to go and turn it off. Theres enough small leaks in the line and fittings to where it will fire up once every 45 minutes or so. Not a big deal but I'd rather not waste the electricity and wear on the comp. Sometimes I quit then and dont get back to the shop for 3-4 days. To the hack part. I have several options. One is to run a box over to the machine and switch the whole 20A comp circuit. That would still require me to remember to turn on/off and i don't like the idea of switches activating outlets in other rooms or out of sight. The other is to power a relay from within the mill control panel. I have 2 relays on hand, one is a solid state relay. 25A "contact" rating but the control input is 3-32v DC. The DC board in the Tormach is 48v So unless I put a resistor in line that wont work and Im not key on messing with that part of the control. Who knows if noise or other flakyness might occur. The other way I tried that actually works is I chopped the connector off an old phone charger wall wart and an old plug from a sump pump pressure switch. Wall wart is 120 ac/5vdc. Plugged that into power strip under machine that has the monitor and pathpilot pc on it. I could run some low voltage bell wire over to compressor mount the ssr in a box and be done. Issue I have is the weird readings across the output. Getting like 50vac across output when the wall wart is unplugged and relay is supposed to be off. Not sure but Is this leakage??? The other issue is running an inductive load not sure if thats cool on an ssr. 2nd relay is mechanical ice cube type has a 240 coil and contacts rates for 12A/120v which is very handy. So happens theres a 240v transformer fed by a contactor C1 thats only energized and held when the start PB is pressed. I am leaning heavily to go this route with the only reservations being running 240v coil wires over to the relay by the compressor without a raceway or conduit. Not in the mood to run more pipe. And by rights I should fuse it somewhere close where I'm tapping the transformer at. Thus "hack" in my title Sorry for the long description. You guys with Tormach's does this make sense? Am I overlooking anything. Pitfalls?