What is this project?
This project is a simple use of an ATX power supply to make a variable bench supply. However instead of converting the ATX supply itself as seen in many other projects, I instead use a 24 pin ATX cable to connect it to an ATX supply which makes it smaller, lighter and more adaptable.
What is needed?
It is not a particularly hard power supply to make, but it does however require some time and soldering skills.
I used the following tools:
- 3D Printer
- Soldering iron
- Screw driver
- Flush cutters
- Shrink tubing
- Hot glue gun
Bill of Material
- 12V Fan
- Fan Dust Filter or Guard
- 24 Pin ATX cable
- Power switch
- Red and black banana jack
- Colored banana jacks
- 10 turn potentiometer
- Volt and Ampere display
- Step down converter
- M16x1.5 Cable gland
- 8 x M3 nut
- 4 x M3x15mm bolt
- 4 x M3x25mm bolt
- 2 wood screws
- Some wire
The casing I made for the supply is a simple 3D printed case which provides all the needed holes an mounts for the parts. I had to drill out the holes afterwards to make the bolts run through more smoothly.
All the needed parts can be found on Thingiverse here
Wiring it all together
First I started by soldering some wires to all of the banana jacks. I used some wire from an old broken ATX supply to ensure that it is a thick enough gauge and in the correct colors. I strongly recommend using shrink wrap around ALL of the connections as the small size of the casing means that the wires will be pressed together risking a short if not properly insulated.
The predefined jacks I simply connected directly to the ATX supply and can therefore be soldered and shrinked before being mounted in the casing. The yellow, green and blue plug is used for the predefined 3v3 (Orange wire), 5 (Red wire) and 12 (Yellow wire) volt supply and the black plug is used for the ground connection.
The black jack used for the variable supply’s ground needs to be connected to the display which made it necessary for me to mount the jack before all the wires were solder to it. I then soldered a black wire and the thick blue wire from the display.
The red jack used for the variable supply’s positive also needed to be mounted before soldering. I then connected a red wire and the thick AND thin red wire from the display.
To finalize the display’s wiring the thick AND thin black wire was soldered to one black wire which should be connected to the ATX ground.
The step down module needed to have the potentiometer used to regulate the voltage removed and replaced with one mounted on the front of the case. I used three jumper wires to connect the step down module and the new potentiometer adding a bit of glue to secure the wiring on the step down.
I then screwed the black and red wire from the variable supply jacks in the step down modules positive and negative screw terminals. Then I added a blue wire (-12 volt) to the negative input and a yellow (12 volt) to the positive input giving a total range of ~ 0-24 volt.
The power switch was a matter of simply adding a green wire to one of the pins and a black wire to the other.
The 12 volt fan I wired to be one always and therefore extended the red wire with a yellow wire and its black wire with some more black wire. I am planning to add a 40 degree Celsius, temperature switch to activate the fan when the step down would get to hot. I was considering using a KSD-01F switch to do this.
Once everything is wired and shrinked, guide the wires through the cable gland on the side of the casing and cut them all to an equal length. I then soldered all the wires to the ATX cable which is a lot easier if the wires coming from the supply match the color codes on the ATX cable. I decided to add a cable sleeve to add a bit of style.
Now all that there was left to do was screwing the two case parts together and verifying that everything was working as it should.