Jonestown

USB Wall Wart

Here is a quick and easy way to make an USB charger/power supply.

This can be used to charge/power a PSP, iPod or any other USB device.
First you need to acquire a regulated 5 vdc wall wart rated at 500ma or higher. The one I used is from an IoMega Zip drive. It has a switching regulator with an output of 5vdc @ 1 amp.

Other parts needed:

• 330 ohm 1/4 watt resister
  
• 10k ohm 1/4 watt resister
• 3mm LED (red, green or yellow)
• USB-A jack, female

This is the IoMega wall wart/power supply I will be using:

The case is held together by a drop of glue in each corner. Prying gently with a small screwdriver removes the top.

A picture of all the parts.

And a schematic for the parts we will be adding to the wall wart.

Pin 1 on the USB jack is bent over and soldered to the case of the jack. The case of the jack is then connected to the wall wart ground.
Pins 2 & 3 are connected together then soldered to one end of the 10k ohm resister. The other end of the 10k ohm resister is connected to +5vdc.
Pin 4 is connected to +5vdc. One end of the 330 ohm resister is also connected to +5vdc. The other end connects to the anode of the LED. The cathode of the LED is grounded.

The 10k ohm resister is used to pull the USB data lines high. Some devices require these lines to be at +5vdc before initiating charging.
The LED functions as a power indicator and supplies the switching regulator with a minimum load.

The hole that the power cable came out of is enlarged for the USB jack and a 3mm hole is drilled for the LED.

The USB jack and LED fit snuggly in their holes when the case is closed but I have added some epoxy to make sure they stay put.

The unit with its LED lit.

And powering sound-sensitive USB lights.

All posts by Jim Jones