Air Compressor 12 volt pressure switch

[zuiko]

A well switch would do the job, but the trick is finding one with the right on/off pressure. I'm not sure I've seen one higher than 60psi cutoff. For air I'd want something like 125.

They are also a lot bigger and in my experience a lot less reliable than you generally want for that kind of application (they aren't even all that reliable inside the house... in a vehicle they'd be that much worse).

I need a 12v pressure switch too but I'll end up mail ordering a $20 12v air suspension one rather than going the well switch route. It would be nice not to have to mail order it, but I've never seen anything like that locally. In my case I picked up the 12VDC compressor from harbor freight... works fine but it has no pressure switch. It'll just keep running until something breaks I guess. Nice design.

 

[Soundguy]

I don't know why I even bothered to make a reply in this thread.... I already stated that there was difference between DC and AC.. but for the most part.. the simple math will be fine.. duty cycle aside. The difference is almost 4-fold.. if that's not a safety factor I don't know what is.. you usually don't even see that kind of a safety factor in burst ratings on hyd hose.. etc.

sheesh...

First no more civ-eng advice.. and now I think no more electronics opinions...

My stock answer to those questions will now be to go take a college/community ed course or courses in the field in which you have questions!

soundguy

 

[DavidPerry]

I looked around again and found a pressure switch on e-bay. It's not adjustable, but it will do quite nicely. For 99 cents I can't beat the price.

Campbell Hausfeld air compressor switch Pressure NICE!! - eBay (item 230291450680 end time Sep-21-08 18:07:43 PDT)

I also got a guage, pop-off valve, and some other stuff from the same guy. so shipping is real reasonable.

For $0.99, I hope you got a warranty.

 

[DavidPerry]

I don't know why I even bothered to make a reply in this thread.... I already stated that there was difference between DC and AC.. but for the most part.. the simple math will be fine.. duty cycle aside. The difference is almost 4-fold.. if that's not a safety factor I don't know what is.. you usually don't even see that kind of a safety factor in burst ratings on hyd hose.. etc.

sheesh...

First no more civ-eng advice.. and now I think no more electronics opinions...

My stock answer to those questions will now be to go take a college/community ed course or courses in the field in which you have questions!

soundguy

Are you saying I've missed my chance to ask you about converting my tractor to 24 VDC and building a bridge out of a flat bed rail road car?

 

[Matt_Jr]

::Kilby Enterprises::

I know you said you don't want mail order but this switch is perfect for what your looking for. Not sure the amperage rating on it but if hooked up to a relay will probably last forever.
As for this ohm's Law discussion switches are rated by the amperage they can handle. Not wattage. Though your formula is correct the application is not. For instance, when I do a 6-12v conversion you don't have to change the switches 'cause the lower voltage switches are twice as heavy duty as a 12 volt switch. For instance, lets say a starter motor is rated at 300 watts. At 6 volts that's 50 amps of current. At 12 volts the same starter motor only draws 25 amps of current. Find out how many amps the pto clutch draws you'll know whether the switch will work or not. I know some clutches pull more than others but I'd bet that it doesn't pull 20 amps. My well is on a 20 amp 240 circuit meaning my switch is capable of 20 amps. That doesn't matter if it's a/c, d/c, 5 volts or 1000 volts. 20 amps is 20 amps. The reason Allenr hasn't had any trouble with his switch is it's only pulling 4.7 amps. That switch is running well under capacity and will probably work forever.

 

[Soundguy]

Are you saying I've missed my chance to ask you about converting my tractor to 24 VDC and building a bridge out of a flat bed rail road car?

Yes!

For the record.. I'm not fond of native 24v industrial equipment.. or the 12vr/24v start stuff.


soundguy

 

[allenr]

For instance, when I do a 6-12v conversion you don't have to change the switches 'cause the lower voltage switches are twice as heavy duty as a 12 volt switch. For instance, lets say a starter motor is rated at 300 watts. At 6 volts that's 50 amps of current. At 12 volts the same starter motor only draws 25 amps of current. Find out how many amps the pto clutch draws you'll know whether the switch will work or not. I know some clutches pull more than others but I'd bet that it doesn't pull 20 amps. My well is on a 20 amp 240 circuit meaning my switch is capable of 20 amps. That doesn't matter if it's a/c, d/c, 5 volts or 1000 volts. 20 amps is 20 amps. The reason Allenr hasn't had any trouble with his switch is it's only pulling 4.7 amps. That switch is running well under capacity and will probably work forever.

Thanks Matt, you've described the importance of Amps in the equation very well!
I guess it's the same reason electricity companies transmit power over long distances at much greater than 240 or 120V.

 

[Matt_Jr]

Allenr, you are correct.