SpudFiles

Starting to get parts together for my AC compressor, worked out the pneumatic/electrical, just got to finish welding a frame for it. Trying to get a regulated 140Psi output.

Tring to build a cheap air compressor? Use a pressure activated on / off switch before the storage tank and a regulator on the output. That should keep a steady pressure.

For some reason your diagram isn't zoomable so I can't see the detail...

Since you are only going up to 140 psi for simplicity I'd just use a standard air compressor pressure switch. Contacts will be large enough to directly switch that motor and they have a built in unloader vent that opens when the switch does. You will still need the check valve of course.

wdr0 wrote:Since you are only going up to 140 psi for simplicity I'd just use a standard air compressor pressure switch. Contacts will be large enough to directly switch that motor and they have a built in unloader vent that opens when the switch does. You will still need the check valve of course.

Yes, some cheap ones on Ebay

I'm not sure if you folks know, but air compressor switches are far more versatile than you'd think. Recently I was working with a bore pump that was switched with an air compressor pressure switch. Checked out the datasheet on the model (appeared identical to all others I've seen, including the springs). It could be adjusted from 30-250psi. We actually got it running at 12psi cut in, 28psi cut off. With some shimming of the springs, I daresay they'd operate at a much higher pressure without causing problems.

I'm trying one of these first, basically cause that's what I have adjustable up to 200PSI

You may run in to issues with that sort of switch. I've used them before and they are very sensitive, more of a single setpoint. I could see it causing the compressor to turn on and off unnecessarily even from temperature fluctuation. But since you already have it worth a shot.

Yes, it may have a close deadband, maybe if I get 2, one for on and one for off

Painted the frame, it's very orangey

But wait there's more!

It doubles as a traffic cone.

The deadband is a minimum (supposedly) 30psi. With some wee tweaks, we got it down to 15. You can make it much much larger if you want

Looking at the spec. sheet for this pressure switch it has a 30psi deadband at 200psi setting, 3psi at 40psi setting, that might work nicely. I'm hoping for a constant 140psi output from the regulator, and I have a 175psi safety blow off for the tank, so I would like the compressor to run in that range.

If not Automation Direct have a nice electronic pressure switch with set/reset pressure settings, but I would need a power supply for that

Since you're running a pressure tank and regulator, your cutoff pressure shouldn't be critical. I'm sure your safety valve would go down half a twist to bump it up to 190-200, that way your tank should always have well above the regulated pressure.

paint dried enough to put some parts together, oiler on the inlet side.

What's the rating of that tank? A flat ended pressure vessel is a bit atypical.