n00b question about power - Electronic Circuits Projects Diagrams Free

pervertatoid · 30th April 2007, 07:07 AM

If I've got a 500w power supply, but I need more power, could I hook up multiple computer power supplies and get the extra output required?

If I needed 1000w for my computer, I'd buy a 1000w power supply. But for a car audio testing set up, (the project I'm working on) I'd rather use the spare power supplies I've got laying around if it's possible. I figure it's the same theory as multiple batteries since I'm working with DC current, but it is converting from AC, so I don't know if that changes anything.

Sceadwian · 30th April 2007, 07:37 AM

Keep in mind a 500 watt power supply will not supply 500 watts on it's 12 volt line alone I'm asuming that's what you're intending on using. For example, a PC power supply I have sitting on my desk is rated for 200 watts. But the 12 volt line is only rated for 6 amps, which is only 72 watts. I think you need to very carefully analyze what the current requirements of the hardware you're currently using REALLY are and go from there, don't just look at the labels on the devices you're using, actually analyze the voltage and current that's being used.

Do a search in the forums, there was a thread not more than two weeks ago that explained the ins and outs of daisy chaining PC power supplies.

pervertatoid · 30th April 2007, 08:23 AM

Quote:

Originally Posted by Sceadwian

Keep in mind a 500 watt power supply will not supply 500 watts on it's 12 volt line alone I'm asuming that's what you're intending on using. For example, a PC power supply I have sitting on my desk is rated for 200 watts. But the 12 volt line is only rated for 6 amps, which is only 72 watts. I think you need to very carefully analyze what the current requirements of the hardware you're currently using REALLY are and go from there, don't just look at the labels on the devices you're using, actually analyze the voltage and current that's being used.

Do a search in the forums, there was a thread not more than two weeks ago that explained the ins and outs of daisy chaining PC power supplies.

I understand that, but If I've got fifteen power supplies giving me 72 watts apiece, I should hit my 1000w requirement. I just want to know if I'm able to do this.

ericgibbs · 30th April 2007, 08:58 AM

hi,
The problem you going to have, is balancing the 15 psu's outputs.
You could get the situation where one psu trys to supply more than say its rated 6amps and so it shuts down.

You will have to devise a method that limits each 12V output to its maximum rated current,
without causing a voltage drop across the limiter circuit.
This could be difficult, it maybe possible to increase the 12V say to 15V coming out of each supply??

You could consider using a standard 12V 100AHr lead acid battery as your test voltage source
and use a high powered charger to keep it topped up.

Sceadwian · 1st May 2007, 01:55 AM

15 power supplies? I've heard of hacks but that's like a new level. Eric's suggestion of using a lead acid bank is much more sane.
If you need high power audio that you're going to connect to a wall use home audio equipment not car audio equipment, the current requirements drop in a hurry when you raise the available voltage from 12 volts to 120 and it makes things MUCH simpler.

kchriste · 1st May 2007, 02:05 AM

If you isolate the output grounds on the supplies you can put 4 x 3.3V lines (Or 3 x 5V) in series to get around 12-15V. Then you'll get a greater current capability and won't have to worry about balancing current draw between supplies.

Sceadwian · 2nd May 2007, 01:06 AM

kchristie, current doesn't go up with power supplies in series, voltage does, current supply ability stays the same, and in reality actually goes down a bit as the series resistance of the power supply's' add up and oscillation problems increase past 2 power supplies. He wants 1000 watts of 12 volt power, that's just shy of 84 amps. For that you're better off finding a surplus store for high current diodes and a large transformer and make your own; Commercial electronic hardware just was not meant to deal with that much power, aside from perhaps electric heaters, and they're almost purely resistive with possibly an inductive limiting effect. Maybe look for an old single phase tap switch rectifier from a plating surplus store.

kchriste · 4th May 2007, 04:19 AM

Quote:

kchristie, current doesn't go up with power supplies in series,

Sigh.... You really missed my point. Look at any computer power supply and you'll see that the 3.3V line is rated at around 25-40amps where as the 12V line is rated around 4-8amps......

Quote:

For that you're better off finding a surplus store for high current diodes and a large transformer and make your own

Eric's idea is the most sane.....

things · 5th May 2007, 12:41 AM

84 amps

. you could almost weld with that much power

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30th April 2007, 07:07 AM	(permalink)
pervertatoid	n00b question about power If I've got a 500w power supply, but I need more power, could I hook up multiple computer power supplies and get the extra output required? If I needed 1000w for my computer, I'd buy a 1000w power supply. But for a car audio testing set up, (the project I'm working on) I'd rather use the spare power supplies I've got laying around if it's possible. I figure it's the same theory as multiple batteries since I'm working with DC current, but it is converting from AC, so I don't know if that changes anything.

30th April 2007, 07:37 AM	(permalink)
Sceadwian	Keep in mind a 500 watt power supply will not supply 500 watts on it's 12 volt line alone I'm asuming that's what you're intending on using. For example, a PC power supply I have sitting on my desk is rated for 200 watts. But the 12 volt line is only rated for 6 amps, which is only 72 watts. I think you need to very carefully analyze what the current requirements of the hardware you're currently using REALLY are and go from there, don't just look at the labels on the devices you're using, actually analyze the voltage and current that's being used. Do a search in the forums, there was a thread not more than two weeks ago that explained the ins and outs of daisy chaining PC power supplies. __________________ "Because I be what I be. I would tell you what you want to know if I could, mum, but I be a cat, and no cat anywhere ever gave anyone a straight answer, har har."

30th April 2007, 08:58 AM	(permalink)
ericgibbs	hi, The problem you going to have, is balancing the 15 psu's outputs. You could get the situation where one psu trys to supply more than say its rated 6amps and so it shuts down. You will have to devise a method that limits each 12V output to its maximum rated current, without causing a voltage drop across the limiter circuit. This could be difficult, it maybe possible to increase the 12V say to 15V coming out of each supply?? You could consider using a standard 12V 100AHr lead acid battery as your test voltage source and use a high powered charger to keep it topped up. __________________ Eric "Good enough is Perfect" PIC tutorials: Gramo's: www.digital-diy.net/ Bill's: www.blueroomelectronics.com/

1st May 2007, 01:55 AM	(permalink)
Sceadwian	15 power supplies? I've heard of hacks but that's like a new level. Eric's suggestion of using a lead acid bank is much more sane. If you need high power audio that you're going to connect to a wall use home audio equipment not car audio equipment, the current requirements drop in a hurry when you raise the available voltage from 12 volts to 120 and it makes things MUCH simpler. __________________ "Because I be what I be. I would tell you what you want to know if I could, mum, but I be a cat, and no cat anywhere ever gave anyone a straight answer, har har."

1st May 2007, 02:05 AM	(permalink)
kchriste	If you isolate the output grounds on the supplies you can put 4 x 3.3V lines (Or 3 x 5V) in series to get around 12-15V. Then you'll get a greater current capability and won't have to worry about balancing current draw between supplies. __________________ --- The days of the digital watch are numbered. ---

2nd May 2007, 01:06 AM	(permalink)
Sceadwian	kchristie, current doesn't go up with power supplies in series, voltage does, current supply ability stays the same, and in reality actually goes down a bit as the series resistance of the power supply's' add up and oscillation problems increase past 2 power supplies. He wants 1000 watts of 12 volt power, that's just shy of 84 amps. For that you're better off finding a surplus store for high current diodes and a large transformer and make your own; Commercial electronic hardware just was not meant to deal with that much power, aside from perhaps electric heaters, and they're almost purely resistive with possibly an inductive limiting effect. Maybe look for an old single phase tap switch rectifier from a plating surplus store. __________________ "Because I be what I be. I would tell you what you want to know if I could, mum, but I be a cat, and no cat anywhere ever gave anyone a straight answer, har har." Last edited by Sceadwian; 2nd May 2007 at 01:10 AM.

5th May 2007, 12:41 AM	(permalink)
things	84 amps . you could almost weld with that much power __________________ The 3 laws of science.... 1. If it smells bad, It's chemistry. 2. If it's mushy, It's biology. 3. If it doesn't work, It's physics. www.laserpointerforums.com A forum for disscusion of lasers and laser shows! www.laserchat.org IRC chat for laser and electronic related stuff.