Author Options:

Need to build a 12 volt 3.2 amp dc power source. Help? Answered

I picked up a nice flat panel monitor, cheap, but seller wouldn't part with the brick he had.(needed it for her monitor) I have pc power supplies and can scrounge with the best for other bits required. Would someone please help. Thanks


4 Replies

jeff-o (author)2009-01-28

Well you've already got almost all you need. A computer power supply will easily supply 12V at 3 amps. All you need to do is rig up the power supply to run without a signal from a motherboard (connect the green wire to ground, as far as I recall). Hook up the +12V to the monitor and you should be good to go.

Select as Best AnswerUndo Best Answer

rocketman221 (author)jeff-o2009-01-28

atx power supplys have a minimum load so you will need a load on the 3.3 and 5 volt lines in order for the 12 volt line to regulate properly.

Select as Best AnswerUndo Best Answer

jeff-o (author)rocketman2212009-01-29

Yep, just rig up some shiny LEDs to take care of the other lines. :)

Select as Best AnswerUndo Best Answer

ac-dc (author)jeff-o2009-02-06

Actually no, it would take far too many LEDs to be reasonable, to provide enough of a load.

The best option is to buy a 12V, 3.2A or higher brick PSU as these are not hard to find now that LCD monitors are common.

IF someone were on Gilligan's island and had to make due with that they had, if it were a computer PSU, in that case they should draw at least 2A from the 5V rail of the PC PSU. Doing the math that is, 5V/2 = 2.5 Ohm resistor
2A * 5V = 10W,
so a 2.5 Ohm, 10W resistor if it were ran at the limits of it's capability, very hot. Normally, a resistor is derated by half meaning a 20W would be used instead.

Large wattage resistors are not cheap and produce a lot of heat, the best alternative is to just buy a 12V, 3.2A or higher switching wall wart. They cost about $15 on ebay, maybe a little more with shipping.

Select as Best AnswerUndo Best Answer