DIY USB Charger
Rachel wanted an external charger to charge up her iPod nano but Apple sells iPod one for $30! I wanted to see if I can cook something with the stuff in my miscellaneous electronics closet.
Disclaimer: This info is provided with no guarantees. If you don’t know what you’re doing, do not try to put this together.
I found a 5V (1A) power supply that I purchased to use for microcontroller projects. I bought it from allelectronics (part number: PS-513) and it was only $4.50.
I didn’t have a female USB plug, so I bought a USB extension cable from Target for $8.
You’ll also need a multimeter, a soldering iron and some heat shrink, 1/4″ diameter. (You can use electrical tape, too.)
- Cut the male phone connector off of the power supply. Remove an inch or so of the the outer insulation and you should see four wires. Red/Black => +5 and Yellow/White => GND. Strip the Red and White wires. I plugged in the power supply and the voltage measure 5.2V. The USB specs indicate that USB hubs will supply voltages in the range of 4.4V to 5.25V (more specifically 4.7V to 5.25 V for High power devices and 4.4V to 5.25V for Low power devices.)
- Cut the USB extension cable. I just cut my 6′ cable in half. One should haver the male connector and the other should have the female connector. We’re going to use the half that has the female connector. Remove some of the insulation, the metal foil, and shield, from the cut end and you’ll see four wires. Red is +5 and Black is GND.
- Now, connect (just twist together for now):
- Red (power supply) to Red (USB cable)
- White (power supply) to Black (USB cable)
- You can do a little test before plugging in a real device. Take the other section of the cut USB cable (the one with the male connector) remove the insulation, and strip the red and black wires. Plug the male USB connector into the female USB connector. Plug the power supply into the wall. Take a voltage reading from the red and black wires you just stripped. If you see +5V then you’re set! If you see -5V then you’ve misconnected the wires between the power supply and the USB cable(w/ female connector)
Now you’re ready to plug in your USB device. I have a “broken” mobiblu MP3 player. It doesn’t play music anymore, but it still responds to charging. I plugged my power supply into the wall. I plugged my mobiblu into the female connector of my homemade charger…and voila the mobiblu shows that it’s charging from a charger! If you don’t have a device that you can test on, make sure that you check all the voltages before plugging in something expensive…like your iPod. If you have a USB light or something try that first.
So now all you have to do is tidy up your work by soldering the connections you made and heat shrink (or tape up) the section of exposed cable and you’re project is complete.
You can do this with any regulated 5V power supply. There are lots of places you can get them. Jameco has them.
Some more info on USB specs (including pinouts and voltage specs).
Good Luck!