FrankenPower! Building a 12V Power Supply

[rcpilot82]

just bought one of these from e-bay: http://cgi.ebay.com/Powmax-SlienceBl...QQcmdZViewItem
I already have the resistor and binding posts so hopefully this will work well! I plan on using it to run a polycharge 4 and hobbico mkII charger, I will also put the 5V tap on a set of plugs justin case i need em!

[Doc]

	Quote: Originally Posted by Boulder
	You can't get a much cleaner voltage than a computer power supply.

that makes sense, but is the 5 volt rail as clean as the other rails? (it is not a high current rail, so i guess it doesnt power much in the computer and may not need to be clean if it just powers LED's and motors - anyone know what it powers?)

i also worry about AC spikes and other interference getting thru to the receiver. wouldnt do much harm to a battery on charge - the charger may even cut off if too much tried to get thru.

might be safer just to use an old battery?

[DesertHucker]

	Quote: Originally Posted by Doc
	that makes sense, but is the 5 volt rail as clean as the other rails? (it is not a high current rail, so i guess it doesnt power much in the computer and may not need to be clean if it just powers LED's and motors - anyone know what it powers?) i also worry about AC spikes and other interference getting thru to the receiver. wouldnt do much harm to a battery on charge - the charger may even cut off if too much tried to get thru. might be safer just to use an old battery?

5v rail powers things like HDD controler on the HDD and various other components on the MB

[Mike Bargman]

I would tend to think that it would be a fairly clean voltage. I'll try it and let you all know. I'm not worried about it spiking. It must be pretty well regulated.

[betheballdanny]

Mike, what 5V line did you put the sandbar resistor on?

AC INPUT

115V/230V 10A/6A 60/50Hz

DC OUTPUT

+3.3V

+5V

+12V

-12V

-5V

+5VSB

500W

Max
Combined
Watts

28A

30A

34A

0.8A

0.3A

2.0A

500W

If you put it on the 30A 5V line - you should have a very hot resistor - too hot to touch.
I'm guessing its on the 2 A line?

[Mike Bargman]

Yes, it's on the 2A line.

[betheballdanny]

Mike, man, that was a quick reply! Good to know (a must know) - that makes sense - you might want to point that out in your instructions, some may not be aware of that.

Regards

[betheballdanny]

Mike, How do I tell which red wire is the 2A line?

[Mike Bargman]

You can put the resistor on either one of the +5V lines, but if you're charging at more than 10A or so at a time, you have the possibility of burning out the resistor.

[Mike Bargman]

I'm going to pull mine apart tonight and see if I can get some pics of the board. It should say it on the board.

[Mike Bargman]

	Quote: Originally Posted by Mike Bargman
	You can put the resistor on either one of the +5V lines, but if you're charging at more than 10A or so at a time, you have the possibility of burning out the resistor.

Here's something to ponder, guys. Got this PM from my buddy Craig...

	Quote: Originally Posted by ckoerner
	It shouldn't matter how much current you charge at unless the resistor is in series with the charger.You have it from ground to the 5V. So it's in parallel with the 5V supply. It will only draw .5amps unless the voltage changes.

[ckoerner]

	Quote: Originally Posted by Mike Bargman
	Here's something to ponder, guys. Got this PM from my buddy Craig...

If the resisor is across the 5V it shouldn't matter what you charge at. At 10ohms you are going to have a .5A load across the 5V line. The voltage would have to rise for the resistor to get hot. Disregard the series thing.