I've got a 500W ATX PSU (more info about it here) and I would like to use it as a sort of bench power supply. I know that there are many guides about how to convert an ATX PSU to a bench lab power supply, but I'm not sure about how to connect a potentiometer to make a variable power supply, and on the internet I found many contrasting opinions.
My first idea was to take a 10k potentiometer (or maybe a 5k is enough?) and connect it to the -12V wire on one side and to the +12V wire on the other side, so that I get a maximum output of 24V, and I can use the potentiometer to vary from 0V to 24V. Is this going to work?
I also saw on this website that there is another way to do the same thing:
Find the resistor which goes from pin 14 on the PWM IC to pin 2. Now simply place a 10K potentiometer in series with this resistor and pin 14. What this does is mess with the regulating reference. Pin 14 is the internal regulated +5V from the IC. The resistor we put a potentiometer in series with is part of a voltage divider, which supplies ~2.5V originally. Turning the pot decreases this voltage and the PWM IC thinks the output voltage is increasing, so it compensates by reducing the duty cycle. Reduced duty cycle means less power and less voltage. Regulating the voltage down can be done without modifying other components.
I understand the main idea, but I'm not an expert about this stuff; what is exactly a PWM IC? And where can I find it inside the PSU?
Do you know a better way to do what I'm trying to do? Or which one of these two ideas is better? Thank you in advance.