power source from a computer question

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power source from a computer question

Postby ferslash » Sat 25. Aug 2012, 20:18

Folks:

I am building a seat mover using wiper motors, i would like to power them using a computer power source,

i have two questions

1. what amperage should i feed to the motors (i cant find the specific amperage for my wipers so an aproximation would be nice)

2. how can i know if the computer power sources i can buy would work, i have seen and the power sources are measured in Watts not in amperes... is there a way to conver watts to amperage?
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best regards from mexico

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Re: power source from a computer question

Postby tronicgr » Sat 25. Aug 2012, 20:44

Here is a calculator for watts ans amperes:

http://www.sengpielaudio.com/calculator-ohm.htm

Enter voltage and watts and will give you Ampere rate.
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Re: power source from a computer question

Postby floriske » Sun 26. Aug 2012, 00:00

I'd go for a dedicated switched 12v supply instead.

A pc power supply devides it's total power over multiple voltage lines (12v, 5v,3.3v etc) a dedicated psu uses all its power for one voltage and is a lot cheaper as well, for example:

http://www.ebay.com/itm/High-Quality-12 ... 231bd2ab98
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Re: power source from a computer question

Postby motiondave » Sun 26. Aug 2012, 02:24

Depends on the motor size, I suggest 20 amps per motor for wipers and 30 amps or more for anything bigger. More power for just in case.
http://www.ebay.com.au/itm/12V-40A-500W ... 885wt_1139 yes I know its big, but look for a similar power supply. They are better and unless you have computer psu's lying around, I would not suggest buying a new one to chop it up.
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Re: power source from a computer question

Postby motiondave » Sun 26. Aug 2012, 02:26

tronicgr wrote:Here is a calculator for watts ans amperes:

http://www.sengpielaudio.com/calculator-ohm.htm

Enter voltage and watts and will give you Ampere rate.



watts divided by volts = amps
300 / 12 = 25 for example
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Re: power source from a computer question

Postby ferslash » Sun 26. Aug 2012, 02:44

guys you are awesom!!! thanks for the information o will consider all the options...

i will compare the dedicated power supply vs the pc power sorce (i have access to a computer junke, so if used good power supplys are in budget i will getterm, but i will also check for prices in mexico for the dedicated ones)


thanks!!!

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Re: power source from a computer question

Postby Roadster2 » Sun 26. Aug 2012, 04:24

You will need to choose the PC power supply carefully. You'll need the full output specification in order to know what current the +12V line is capable of providing. The output current available on the +12V line will be limited to this regardless of the maximum output of the psu, even if you're not drawing anything off the other voltage lines.

If there is a choice of power supplies then go for one with the highest output current available on the +12V line. Later power supplies may have Dual or even Quad +12V volt rails (outputs) available but again, check the maximum output current available on each line. Don't be tempted to join two or more of these +12V lines together thinking that you'll increase the current available as your power supply will go up in smoke if you do The acrid smell hangs around for days !
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Re: power source from a computer question

Postby motiondave » Sun 26. Aug 2012, 04:55

Yes, I know what you mean about a smoking power supply. I usually manage to inhale the smoke into me before it gets too far... :lol:
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Re: power source from a computer question

Postby floriske » Sun 26. Aug 2012, 10:18

motiondave wrote:Depends on the motor size, I suggest 20 amps per motor for wipers and 30 amps or more for anything bigger. More power for just in case.
http://www.ebay.com.au/itm/12V-40A-500W ... 885wt_1139 yes I know its big, but look for a similar power supply. They are better and unless you have computer psu's lying around, I would not suggest buying a new one to chop it up.

That's why I use one psu per motor indeed, should have mentioned that. Else you might just get magic white smoke out of it ;)
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Re: power source from a computer question

Postby motiondave » Sun 26. Aug 2012, 10:47

floriske wrote:
motiondave wrote:Depends on the motor size, I suggest 20 amps per motor for wipers and 30 amps or more for anything bigger. More power for just in case.
http://www.ebay.com.au/itm/12V-40A-500W ... 885wt_1139 yes I know its big, but look for a similar power supply. They are better and unless you have computer psu's lying around, I would not suggest buying a new one to chop it up.

That's why I use one psu per motor indeed, should have mentioned that. Else you might just get magic white smoke out of it ;)


Well currently I am, still using one psu and one car battery......
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