Variable power supply using an old PSU.

After working with various small phone chargers and cheap 5V transformers I decided to build my own power supply from an old PC PSU and a couple of parts ordered from Ebay. I did documented myself and tried to understand a little bit about the operation principles of a power supplies.

The PSU that I have outputs 12V, -12V, 5V, -5V and 3.3V. The negative voltages are rated with a very low current (0.5A) but they could prove useful sometimes.

300W PSU - Ideal for Pentium IV processors!

A very simple solution would have been to directly build a case with the fixed outputs... but I think having a higher voltage is a must (charging some batteries would require-it). So I have decided to include a buck-boost converter in the design. The 12V is shared between the fix and the variable voltage output providing up to 15A (more than I would ever need).

A switch is necessary in order to power on and off after setting the required voltage and 2 potentiometers to set the voltage/current limit.

Part Price Details
1x LTC3780 10$ LTC3780 DC 1V-30V 10A Step Up/Down Regulator
1x Voltmeter/Ammeter 4$ DC 100V 0-10/50/100A Voltmeter Ammeter
13x Connectors 3$ 20PCS 4mm Banana Plug Jack Binding Post
2x Switch 1$ ON/OFF 2 Position Latching Toggle Switch
2x Knobs 1$ 6mm Black Potentiometer Pot Knobs Caps
2x Power Rezistor 4$ High Power 100W Watt Aluminum Resistor 5%
2x Potentiometer 4$ 200K Linear and 500k Log Potentiometer
Nice 3d printed front

The precision in terms of voltage is ok for my projects (about 0.1V). The current measurement is a little more volatile (~50%).... but this is by no means relevant for what I use-it. Overall I think is quite ok, a little bit loud due to the cooling fan.

Overall result

I have posted the printed parts on Thingivers if someone would need them.