Mar 05, 2012, 11:44 AM
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INNERKIP,ONTARIO,CANADA
Joined Feb 2006
339 Posts
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12 Volt +5v Charger Power Suply From Old PC
Quote:
Originally Posted by Rodney
A very nice conversion job. However, most computer power supplies are not quite so elaborate. You can find many write ups on the web on how to convert these power supplys to use with our chargers. In most cases, it is simply done by using the yellow (+) and any of the black leads as (-) for the 12 volt charging leads. You usually have to put a load on the 5 volt bus, red is + and any black lead for -, usually 5 ohm 10 watt resistor will suffice for the load. If you do not load the 5 volt bus, you will not get the full 12 volts out of the yellow leads (internal regulation is all based on the 5 volt bus). There is usually a green wire that has to be connected to ground (any black lead) to force the unit to turn on.
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All the new ATX Power Suplies do not need a 5 Volt load, to stay on, they have a power ON pin #14 that is grounded to activate the unit. A load on the 3.3 (orange) and 5 volt (red) line will often keep the 12 volt (yellow) line higher and more stable. The suply I used is already outdated for most of the Dual or Quad Core MPU's and motherboards in use now. The 24 pin header is now used more than the 20 pin ones. Soon the negative voltages (-5 and -12) will be taken out, as they are no longer needed, as there is NO ISA bus. These voltages were used in Phone Line Modems of the Dail Up type, that are now PCI or External High Speed type.  Some of the new Micro Footprint and Carputers only need +12 volts in, and they use an internal DC to DC converter to get +5 and +3.3 volts.
Gone are the days of the simple transformer, bridge, caps, and some regulators, for a power suply, but the output is all the same !
I will try to get a link posted in the Charger Thread section.....Thanks......
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