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Automatic Air Compressor Relay For 1100

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Cheeseking

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#1
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[emoji53]. 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?
ImageUploadedByTapatalk1473537995.499117.jpg
ImageUploadedByTapatalk1473538013.513735.jpg ImageUploadedByTapatalk1473538026.132252.jpg ImageUploadedByTapatalk1473538034.383034.jpg ImageUploadedByTapatalk1473538044.648919.jpg
 

JimDawson

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#2
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.
Yes that is leakage. If you measured it with a light bulb in the circuit, the voltage would read about zero. The impedance of most modern DMMs is so high that it only takes a few microamps of current flow to read voltage.

The SSR will run an inductive load just fine. I do it all the time.
 

GLCarlson

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#3
110 or 220 AC relay (ie, a contactor) wired to either the main power switch or the computer switch, with a separate circuit to power the compressor as you already have. One component and a couple wires. Anything beyond that is adding complexity without benefit. If you follow Tormach's procedure for start-up/shut-down, wiring to the computer power switch sets up time for the compressor to charge before you power the machine.
 

tq60

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#4
Avoid long load circuits and never risk your equipment.

First confirm you can get a dry contact closure out of your machine.

This must always be first choice as it is usually a simple relay isolated from the rest.

If no output exists then look for something inside the machine that powers on when you need compressor control then confirm the voltage that it requires and get a relationship with coil voltage that matches it and slave from that.

Now yiu have dry contact.

At compressor end it does not look like it has magnetic starter so you need to get a contactor or motor starter to control it.

Get a contactor rated twice the compressor load as cost is not much more.

Also get control voltage low like 24 vac.

Also get a power source to match.

Place contactor and power source at compressor and run a pair to machine.

Relay in machine controls low voltage low current that controls higher voltage high current.

Safe.

Sent from my SAMSUNG-SGH-I337Z using Tapatalk
 

Cheeseking

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#5
Yep. Compressor is on its own, separate 20A 120V circuit and the relay is essentially in series with the pressure switch on the compressor. It pulls 6-7A so the 12A mechanical ice cube style relay shown above should be adequate. Until I get a proper box, I mounted it temporarily on a wall stud next to the compressor under the workbench. Inside the machine control cabinet I mounted a fuse holder utilizing a standoff and a longer screw and took 240 power off the transformer. Also very temporary hack I made the 50' run from machine to relay with some 14/2 speaker wire but my concern is the insulation rating. I see no markings but my guess is 30v. Current capacity on 14ga is way more then the puny little coil will draw but the 240v has me a bit worried. So on my list are a box to enclose the relay and maybe 2 conductor SJ cord to replace the speaker wire. For the time being tho it works great. As soon as I press reset then the green power on button the compressor kicks on.
Heres my fuse block and where I mounted it.
ImageUploadedByTapatalk1477959826.696978.jpg
 

Cheeseking

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#6
Thought I'd post an update to this project- so far it has been working out great. No more waking up in the middle of the night to compressor racket cuz I forgot to shut it off and one less step at machine start up. Very happy with it.
 
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