SFX Bench Power Supply (Variable Voltage)

thingiverse

After looking at many guides on how to convert an ATX power supply to a variable voltage power supply, I decided that most of them were too complicated for a novice to follow and included circuit diagrams that I couldn't decipher. My aim here is to provide instructions that anyone can follow. Please be aware that you are working with ELECTRICITY here and as such you need to be VERY careful. Make sure you unplug everything before attempting to cut and solder wires. Also be aware that the capacitors inside a power supply can hold high voltages long after the power supply is switched off. Make this thing at your own risk, I will not be held responsible for any accidents. There is actually no need to open the power supply for this build so as long as you unplug it before tinkering, you should be fine. Remember to cut the wires that you don't need and insulate them properly. Regarding the circuit: It is the simplest way I have found to output a variable voltage of 0-24v (or close enough) using a 12v line and a -12v line from the power supply. I am not an electrician, I am a designer and a maker. If anyone knows this to be dangerous, or they know a more simple and safe way to achieve what I have here, then please do comment and make suggestions for changes. Make sure your power supply has a -12v line for this to work. The variable voltage banana sockets give a voltage difference of 1.2v to 22.7v which is adequate for most Arduino projects and alike. It also includes a USB socket that delivers 5v, a banana socket that delivers 3.3v and another that delivers 5v. Bill of materials: Printed: 1 x CASE MAIN 1 x CASE FACE Bought: 5 x Banana sockets of different colours (https://item.taobao.com/item.htm?spm=a1z09.2.0.0.67002e8dUgkbaW&id=561956389062&_u=52q9f1426ddc) 1 x Potentiometer 50k Ohms (https://item.taobao.com/item.htm?spm=a1z09.2.0.0.67002e8dUgkbaW&id=13300625190&_u=52q9f1423320) 1 x Knob for the Potentiometer (https://item.taobao.com/item.htm?spm=a1z09.2.0.0.67002e8dUgkbaW&id=546066796422&_u=52q9f1422257) 1 x Switch (https://item.taobao.com/item.htm?spm=a1z09.2.0.0.67002e8dUgkbaW&id=560730371702&_u=52q9f1425c4f) 1 x Female USB Socket (https://item.taobao.com/item.htm?spm=a1z09.2.0.0.67002e8dUgkbaW&id=14422856956&_u=52q9f1428c5a) 1 x LED Voltage Display (0.28") (https://item.taobao.com/item.htm?spm=a1z09.2.0.0.67002e8dUgkbaW&id=544408516843&_u=52q9f1423bb7) 1 x SFX Power Supply (Bought a second hand one on the street) 4 x 10-16mm M4 Screws for the face 7 x 10-12mm M4 Screws for the feet and the back of the SFX power supply 1 x LM317T Voltage Regulator 1 x Heat Sink for the regulator (I used the heat sink that came with the stock Anet A8) 1 x 120 Ohm resistor 1 x small protoboard Circuit: Assembling the components should be fairly straight forward except for the wiring. Check the images for a wiring diagram I made in illustrator. I decided to show the circuit in this format rather than a circuit diagram in Eagle CAD as it's a lot easier for a novice to understand. Make the circuit first and test it before assembling everything. If you are resting the protoboard on top of the power supply case, then make sure the circuit is insulated from the metal case (I used hot glue for this). The circuit I made does not light up the switch when it is on, as I couldn't figure out how to do this. I think my switch needs 250v AC to light up, I'm not sure. The LED display lights up when the unit is on, so that is good enough for me.