How to add variable voltage to an ATX based bench power supply

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Adding variable voltage to an ATX based bench power supply is a cheap way to give yourself a power supply for powering various devices. With knowledge of soldering and electronics, you can add variable voltage to an ATX based bench power supply.

Skill level:
Easy

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Things you need

  • Bits and drills
  • Screwdriver
  • Soldering iron
  • Project box
  • 12V switch (lighted)
  • Banana jacks
  • Strain relief (3/4 inch)
  • ATX connector
  • Heat shrink tubing (various sizes)
  • 14-20 gauge wire (try to match the wires of the ATX)

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Instructions

  1. 1

    Separate an ATX motherboard connector from a motherboard by desoldering it when you are adding variable voltage to an ATX based bench power supply. The motherboard does not have to be a functioning one. You can also buy an ATX extension cable or a 20 to 24 pin adaptor for an ATX if you don't wish to desolder the part from the mother board. Desolder the motherboard by heating it evenly with a "flood" of solder.

  2. 2

    Plug the ATX connector to the power supply. Carefully note the colors of the wires, and then cut the other end of the power supply and solder the wires in this order: "Orange Orange +3.3V," "7 Black Black GND," "10 Yellow Yellow +12V" (you might want to solder two wires to the pin), "Blue Solid Grey -12V," "Black Black GND," "Green Green Switch on," "18 White Grey/Red -5V" and "Red Red +5V." Protect the wires by bundling them into some heat shrink tubing when you are adding variable voltage to an ATX based bench power supply.

  3. 3

    Use a project box (it doesn't have to be very big) that will allow you to use dual banana plugs that are standard in size. Designate one plug as the ground, and the other the voltage you desire. You will probably have to add a hole for the lighted switch.

  4. 4

    Drill a hole in the back of the case large enough to fit the ¾-inch strain relief.

  5. 5

    Place the hardware in the box, and then solder the posts and the leads. The posts should be in this order (as viewed from the front of the box): ground for the center post, -5 volt for the post on the far left, +5V for the post on the far right, 3.3V for the post on the bottom, -12V post on the top left and +12V for the post on the top right. The switch itself should have three terminals: ground, +12V and the "switched contact." Only when the switch is on and the contact grounded will the light turn on. Connect the yellow wire to the +12V on the switch. Connect the black wire to the switches ground, and the wire of the power supply to the contact on the switch.

  6. 6

    Label each of the terminals so you remember which is which. You can do this with a label-maker or a marker. This is the final step of adding variable voltage to an ATX based bench power supply.

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