I have an ATX power supply (400W) and I want to use make a variable power source for 3-20V using a LM317.
I know that the 4 pins connectors (like the ones for the IDE devices) are +12V|GND|GND|+5V, is it possible to put in series 2 of the +12V outputs to get 24V?
Best Answer
No you cannot. Intern there is only one 12V source.
If you try to put in series 2 of the +12V outputs you created a short circuit ( +12V to ground).
? WARNING ?
As you can see in the comments below @Passerby: sees some dangers in the rest of the answer which I cannot confirm yet.
But inside the power supply there is also a -12V. You can use +12V and -12V to get 24V.
This manual 'Convert a Computer ATX Power-Supply to a Lab Power Supply may be useful for you. Warning: the colors of the cables differe in a lot of ATX Power-Supplies. Always have a look at the connectors to detect which wire is the wanted.
Note from the linked web site:
The voltages that can be output by this unit are:
P.s. Not every ATX Power Supply seams to have the +3.3V and the -5V