Wednesday, November 16, 2011

How To: DIY PC Power Supply for RepRap

Over the last couple of days I have been cannibalizing a PC power supply to work with my (future) RepRap. I spent quite a while reading and rereading the wiki post for the DIY power supply trying to decipher what was the simplest way of putting the power supply together. I found that the wiki didn't really have any clear instructions for a simple +12V power supply, so after getting one working I decided to share how I did it. I figured out a (somewhat) elegant way of wiring that hid most of the unused wires within the power supply box. The following is a brief simplified how-to on assembling a reprap DIY power supply.

  1. Wire Strippers
  2. Wire Cutters
  3. Soldering Iron
  4. Solder 
  5. Electrical Tape
POWER SUPPLY: Any computer power supply will work that has a rating of at least 16amps on the +12V line. It should say the amperage on the side of the power supply, more than 16A is fine as the RepRap will only draw as much power as it needs.

STEP ONE: Cut all the connectors off the wires and group them by color, the four wires you are interested in are the black, yellow, green and brown ones.

STEP TWO: Select about five of each of the black (ground) and yellow (+12V) and cut them off about 2 inches outside of the power supply box.

STEP THREE: If your power supply has a brown wire (3.3V sense) solder it to an orange wire (+3.3V) and wrap it with electrical tape as shown in the image:

STEP FOUR: The green wire is a power on wire, it must be wired to a ground wire in order for the power supply to turn on. You can either wire them permanently together, similarly to step three, or run them out of the box and connect a switch to them so you can have a power switch right next to your reprap electronics.

STEP FIVE: Solder the five yellow wires together and all the black wires together in two separate groups. Then solder two black wires to the black soldered connection and two red wires to the yellow connection. After the solder connections have cooled, thoroughly wrap them in electrical tape. These wires will feed into your screw connects on your RAMPS (or similar electronic) board. I braided the all the wires including the power on wire together to keep everything clean and tidy.

STEP SIX: Cut all of the rest of the wires down to about an inch and tape them using the electrical tape in groups of similar colors (Example: all the orange together and all the black together)

FINAL TESTING: Put the power supply back together and turn it on, remember to connect the green and black wires together! If your power supply does not turn on, there may be another sense wire for the other voltage rails, look for any wires that are lighter gauge than the rest and wire them to there corresponding colors as done in step three and four.

I hope this helps!