24 vdc question

[greasefingers]

Ok I have to test a 24 vdc solenoid valve, in the field. I cannot figure out if the electronics board driving the actuator is failing or the solenoid itself is failing. I need an external 24 volt power supply so that I can isolate the solenoid valve from the electronics.

I have a couple of old computer power supplies lying around. I usually gut a computer of good stuff before I toss it in the bin. I know PC power supplies have a 3v, 5v, & 12v output. Has anyone ever wired two 12 volt lines together, from two of these power supplies, to get a 24 volts output. It seems fine in theory?

 

[alpha]

in theory, if you put the two voltage sources in series, you should get a 24V output. not sure if those power supplies necessarily output 12V nowadays, you could try. they should, check it with a multimeter.

maybe you can ask if the local university has some extra power supplies that they use in they're EE courses that they have replaced and just have laying around unused. its a long shot, but maybe. most of those power supplies, at least the ones used in electronics classes, should go up to 30Vdc. Unless they have one for the Power courses, which shouuld have 120/208V power supplies.. again, its a long shot, but possible.

but the two comp power supplies should work, wired in series.

do be careful though..

disclaimer applies: i'm not responsible for any damage or injury incurred by any of the above information.

 

[greasefingers]

I was thinking that at the very least, whatever voltage one finds on these it should be very clean since the computer components are sensitive to noise.

Thanks for replying. I will wire to supplies up and connect my voltmeter to it and check for smoke

 

[greasefingers]

I am a little worried about the grounds not being isolated?

 

[kglueck]

be careful wiring up two power supplies like that. the 12V outputs need to have what's called a "floating ground" otherwise, you'll have some sparks...

prolly the easiest way is to get two smaller capacity 12V batteries, gel-cells from upses come to mind, I have literally 40 or 50 cells I cycle through for my various ham radio stuff. just hook them up in series and you'd be set. (be sure to use a fuse, just in case...)

 

[kglueck]

I am a little worried about the grounds not being isolated?

heh...read my mind... :

 

[greasefingers]

I do not know about these gel-cells, but they seem interesting. I will see if any electronics type warehouses are near me. Maybe I

 

[kglueck]

gel-cells, a.k.a. SLAs (Sealed Lead Acid) are the same technology found in the optima yellow and red top batteries. it's basically a nonspillable lead acid battery. a couple of 3Ah ones are quite handy now and again...if you were in my area of texas, I'd just give ya a couple.

 

[alpha]

good point. forgot about the ground.