How to power a fan through a USB port

Written by rebecca burdick
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How to power a fan through a USB port
It's possible to power a computer fan through the USB port with modifications. (cooling fan image by dinostock from

Computer fans run off of 5 volts DC. USB ports provide 5 volts DC and 500 milliamps of power and most computer fans will run at less than 500 milliamps. It makes sense that you should be able to connect a computer fan to the USB port of your computer in order to power it. This is in fact possible, but keep in mind that these are totally different kinds of connections and some custom wiring will be involved. Additionally, a short circuit in your custom wires could burn out your USB port.

Skill level:

Things you need

  • Wire cutter
  • Wire stripper
  • USB cord (male end required)
  • Utility knife
  • Heat shrink tubing
  • Soldering iron
  • Rosin core lead-free silver solder
  • Lighter
  • Electrical tape

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  1. 1

    Cut the wires of the computer fan as close to the connector, not the fan, as possible. Using the wire stripper, strip 3/8 inch of the insulation from both wires. The computer fan needs to be a two-wire type. The three-wire types are made to be able to control the speed of the fan, which you will not be able to do through a USB port.

  2. 2

    Cut off the end of the USB cord. Locate the end that will plug into your computer's USB port and, since this is the end you want to keep, cut off the other end as close to the connector as possible. Using your knife, make a small cut in the outside insulation of the USB cable and peel back the insulation about 2 1/2 inches and cut off the peeled-back insulation. You will have exposed 4 wires: black, red, yellow and green. The yellow and green are useless for this project and can be cut off as close to the outside insulation as possible. Strip 3/8 inch of insulation off of both the red and the black wires.

  3. 3

    Cut two pieces of heat shrink tubing, each about 1 inch long. Slide these over the computer fan electrical wires and make sure they stay as far as possible from the stripped wire ends.

  4. 4

    Cut about three inches of heat shrink tubing and slide it over the black and red wires of the USB cord and continue sliding until you have slid it over the insulation that holds all four of the USB wires. Make sure the tubing stays as far away from the stripped wires as possible.

  5. 5

    Twist together one of the wires from the computer fan and either the red or black wire from the USB cable. Once twisted, solder the two wires together. Bend the soldered connection until it is parallel with the wires and slide the heat shrink tubing over the new connection. Repeat this process for the other wires.

  6. 6

    Using a lighter, hold the flame about 2 inches below the tubing and move it back and forth until the tubing shrinks evenly.

  7. 7

    Slide the tubing that is on the USB cord over the entire new connection, making sure to cover everything. Again, use the lighter to shrink the tube.

  8. 8

    Wrap the entire length of the wires in electrical tape if you want to strengthen the connection.

Tips and warnings

  • Make sure your clipped yellow and green wires are not touching. If possible, put a dab of hot glue onto each to insulate it.
  • Be careful with the lighter, these materials can burn. Hold the lighter as far away from the heat shrink tube as possible and can still achieve results.
  • Never work on a cord that is plugged into any electricity, including your USB port.

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