How does air pressure regulator work?

Not sure I understand your question, but I'll take a shot at it.

If the compressor is on and has nothing connected to the outlet then it should allow air to escape since there is nothing there to stop it. If you have a quick-disconnect coupling on the end it should seal when nothing is connected. Otherwise when you connect your airbrush the trigger on it will stop the air flow.

What I am trying to say is to obtain a lower pressure level, I have to turn the screw at the bottom of the moisture trap/regulator on the Smart Jet. This causes the air to bleed off the regulator. When I block the air flow (simulating releasing of air brush trigger), the air continues bleeding so the compressor will never automatically shut off since it will never reach the shut off pressure.

Hm... That doesn't sound right. The regulator will make sure it never reach that pressure level anyway, even with a non-bleed type.

Well, never mind.

Stephan: The regulator will only control pressure downstream from it.
If your auto shut off is set for 125 PSI and the regulator is set for 15 PSI the tank will reach 125 PSI and the compressor will shut off but there will only be 15 PSI at the airbrush.

I don't know why the reg. is bleeding air, it shouldn't be. Are all your fittings tight I.E. is it bleeding directly from the reg. or from one of the fitings at the reg.?

Derek,

Thanks for the explaination. I was thinking about the same after I posted it.

It seems Iwata's regulator is the bleed type:

Smart Jet

Note the description "Bleed valve air regulator to adjust air pressure"

So I guess I can buy a non-bleed one and get the auto on-off working. But I will try to get an answer from Iwata first.

Let me take a stab at it.

Let's say you have your tank at 125 PSI. You then have the regulator set for 40 PSI. After cleaning your airbrush, you crank the regulator down to 15 PSI. The regulator bleeds air off at this point. What it's doing is bleeding air from the 'low side' of the regulator, in other words, the airline from the regulator to the airbrush had 40 PSI in it, when you changed the regulator pressure, the regulator opened it's valve to get the line down to 15 PSI. The 'high side' of the regulator never changed. The auto on-off on the compress should still work just fine.

At least, that is my setup, and what happens with my compressor (and it's an auto on-off too). I can't tell from the picture if that has a tank on it or not.

Dan

OK. It turns out the regulator on Smart Jet is just a bleed off valve. It doubles as the drain of the moisture trap.

So I went to Lowe's and bought a regulator. Put it after the compressor's moisture trap and it works great now. I can adjust the pressure to my liking and when the brush is not in use, the compressor turns itself off. Perfect.

Thanks for the helps guys.

That's great news Stephen.

Mike