Help figuring out a high amperage PSU/troubleshooting this air pump issue - Page 1
Forum section: electronics / beginners

author: XOIIO
author_rank: Super Contributor
timestamp: May 06, 2014, 11:53:26 pm
content: Hey all, so I used to use a bike pump for my air cannon, and that was a pain (both figuratively and literally), then I got a 12 air compressor for use in cars, and it works fine on the PVC cannon and a 7 pound fire extinguisher, getting them up to 80 PSI in a minute or so, however, this new 33gallon tank is posing an issue.I am unsure why, but the compressor will run fine for a bit, barely getting any pressure, maybe one or two PSI, and then stop dead, when I try to run it again (just manually touching the wires that turn the PSU on) it will run for a couple seconds and then stop.I can't figure out what is causing this, I kind of thought it might be the PSU, but it can run a long time with the compressor drawing much more power no problem, maybe this is another issue? The 12v 12a it can supply seem to work well, maybe it is an entirely different issue, I don't know, maybe you guys have an idea of what is causing this?Aside from this if it is maybe the PSU somehow, I was wondering if there are any decently easy DIY power supplies one could make on a perfboard using salvaged components that could provide more than 12 amps, maybe 20?I think I have a power supply I made from an old UPS, I can't remember if it is 12 volts or not, but that can get decently sized screws white hot no problem, and cause others to get white hot and pop in the middle breaking them or spot welding thin metal somewhat (though the wires get way too hot, and they are mounted to the circuit board, not sure how I could get bigger ones on).I have a feeling it may actually be an issue with the compressor but I have no clue why it would behave like this. Is it possible they put some sort of mechanism that stops it if it does not see a certain PSI rise after a bit? It works fine not connected to anything though. This is quite the head scratcher.Also a tip, if you are pressurizing a tank that has sand build up and metal shavings from drilling and tapping a hole, slowly open the valve. I cranked it open and even though the pressure was minimal, the 1 inch pipe shot a spray of sand and metal bits into the corner of my ceiling , it made me jump

author: Stonent
author_rank: Super Contributor
timestamp: May 07, 2014, 12:11:14 am
content: Many of those have a thermal cut-off so if the motor overheats it will cut the power. Look for anything attached directly to the motor that has wires.

author: Skimask
author_rank: Super Contributor
timestamp: May 07, 2014, 12:12:27 am
content: Are you talking about one of those cheap 12v compressors that plugs into a cigarette lighter adapter?Those things generally have aluminum pistons/cylinders, and they're non-oiled as well.Heat them up good one time (eg. trying to fill a 33 gallon tank) and they're basically fried. Either the piston/cylinder gets worn and won't pump air or the piston/cylinder gets warped and will seize itself up in a matter of seconds. If it doesn't seize up, it'll bind bad enough to cause it to draw a lot more current than it would normally pull.Regardless, trying to fill a 33 gallon tank with one of these cheap compressors isn't the way to go. You'll keep burning them out. Sure, they'll do 200 psi, if you're filling a 1 liter pop bottle or air shocks or something small. But the long run time will wipe out the piston/cylinder even if you add really good cooling.

author: XOIIO
author_rank: Super Contributor
timestamp: May 07, 2014, 12:18:46 am
content: Well it didn't even have time to warm up, this one is supposedly capable of 100 PSI, but filling smaller air tanks can get I decently warm (it has a metal section similar to this onehttp://c.shld.net/rpx/i/s/i/spin/image/spin_prod_245439701) and still runs no problem, this one hasn't warmed up a bit before it stops running.I do plan on cracking it open, the LED's stopped working for some reason, somehow they shorted I think, but yeah, overheating wouldn't be the issue for this. This one has gotten uncomfortably warm when I didn't give it a long enough break but still ran fine, it's pretty reliable, but I do really need to get a proper plug into the wall type, problem is used ones never pop up on classifieds when I have money, and do pop up when I don't, and I'd also like one capable of at least 150 PSI.edit: popped the end off, the whole thing is the actual compressor, and it's fully metal under the plastic cover, I figured they just made it bigger to look good.

author: XOIIO
author_rank: Super Contributor
timestamp: May 07, 2014, 01:19:28 am
content: god damnit, the stupid magnets that hold the center shaft in place (Same construction as a drill) are lose, I've been working since my last post on getting this damn thing back together with the stupid springed contacts to pass the power on, it's driving me nuts.This thing also has no protection or temperature detection but I don't know if I can get the damn thing together. Two little plastic spacing pegs already broke.

author: XOIIO
author_rank: Super Contributor
timestamp: May 07, 2014, 01:50:31 am
content: Well, got it together, sheeesh putting these things together for a living would drive me nuts, I had to hold the motor/magnet assembly together as I put on the cap with the spring contacts, slide that into the metal surround, fit that back in, bolt it in, found out the motor just spun loose, so I opened the back, found a small crankshaft like in a weedwhacker engine (was going to make a whacker bike, but those are illegal here and the engine was faulty, think I still have it somewhere though), so tapped that on with a hammer, working now, however the problem is still there, and the actual crankshaft doesn't even get warm before it stops. I'm going to crack open the top if I can find an allen key that fits, my screwdriver kit might have an end that fits.At least I know how these work now.

author: XOIIO
author_rank: Super Contributor
timestamp: May 07, 2014, 02:03:37 am
content: Damnit, now it does it even with nothing connected, whatever it was I made it worse somehow, so now I'm out of luck until I can save $100+ for an actual compressor.Sure was worth the $30 in parts and damaging my tapping bit to do this

author: Vgkid
author_rank: Super Contributor
timestamp: May 07, 2014, 03:07:14 am
content: Have you tried hitting up Kiji for a used full size air compressor?

author: XOIIO
author_rank: Super Contributor
timestamp: May 07, 2014, 03:12:09 am
content: Quote from: Vgkid on May 07, 2014, 03:07:14 amYeah, that's what I meant for local classifies. Nothing on right now and for decent ones it's usually $75+It especially sucks since it's been a while since I have seen one around that price, and computer work is really slowing down, and I have this tank all set up for testing just sitting there(pink is the only stuff the store had at the time lol)

author: Vgkid
author_rank: Super Contributor
timestamp: May 07, 2014, 03:50:59 am
content: What about looking for scratch&dent/ returns at Canadian Tire.Princess auto would work as wellhttp://www.princessauto.com/pal/Electric/Powermate-1-Gallon-Portable-Air-Compressor/8515082.p

author: rexxar
author_rank: Frequent Contributor
timestamp: May 07, 2014, 06:25:51 am
content: Could it possibly have a pressure switch meant to keep it from running with nothing attached? Maybe your big tank just has so much volume, there's not enough time to build pressure before the switch cuts out?

author: Magicmushroom666
author_rank: Contributor
timestamp: May 07, 2014, 06:48:58 am
content: What you've taken apart there is a DC motor. The magnets are there to provide the rotating force along with the coils. The bearings in either end are resonsible for holding the rotating part (rotor) central inside.The spring contacts at the end are called brushes, usually there is a hole that goes through to the outside so you can put a paperclip or something through with the brushes pushed fully into their housing, enabling the end to easily be slipped on. When you then pull the pins from the outside, the brushes spring into place.If there's no thermal safety etc, its likely it stops because of a mechanical issue with the pump, or if that's free spinning, something may be wrong with the brushes. They wear into shape so should be fitted back the same way they came out.Maybe try putting the power direct to the motor terminals, bypassing that internal wiring.

author: Skimask
author_rank: Super Contributor
timestamp: May 07, 2014, 03:29:48 pm
content: Quote from: XOIIO on May 07, 2014, 12:18:46 amFor comparison, I've got a Craftsman 33 gallon compressor with a 2HP motor on it. 120VAC, pulls about 1,400watts when it gets near it's 150psi maximum.1,400 watts is about 116 amps at 12volts.I don't think that little compressor is up to the task...at least not for very long.

author: XOIIO
author_rank: Super Contributor
timestamp: May 08, 2014, 06:45:12 pm
content: Quote from: Skimask on May 07, 2014, 03:29:48 pmI got a little air compressor for $40 yesterday, seems like it can run a long time no problem, need to put it on my power meter to see how much power it uses but it works much better. Takes around 15 minutes to get the tank to 50PSI, though I didn't record the test of that.