technology upgrade – cellphone part 3

The USB cable, car charger, and wall charger I ordered from amazon showed up today. I popped the installation CD in for the usb cable and installed the drivers. I then plugged my phone into the cable and fired up bitpim. I am finally able to transfer custom ringtones to my phone!  Now I just need to make a few more ringtones.

On to the car charger. I bought a bluetooth headset with the intent of using it while driving. This means that my headset will end up living in my truck. No big deal, except that it only came with an AC charger. The charger plugs into the headset via a usb cable. I checked the output of the transformer and it’s a 5V output. My phone also uses a 5V output to charge, but it is a proprietary plug. The car charger outputs 5V, but only for the phone. If I wanted to charge my headset, I’d either have to buy a car charger ($20 from verizon) or make my own. If I bought one, I would only be able to charge my phone or my headset, not both, at any one time.

I happened to have an extra USB cable lying around, so I grabbed it, my wire cutters, my soldering iron, some electrical tape, my dremel, and a soda and sat down at my desk. I cut the end of the USB cable that plugs into a computer off as it will not be used and threw it away. I stripped the insulation back to reveal 4 individual wires: red, black, green, and white. A quick google search turned up the following pin-out for the wires:

• red: Vcc
• black: Ground
• white:  Data -
• green: Data+

I stripped back the insulation on the red and black wires, then taped off the white and green wires. I then disassembled the cigarette lighter portion of the car charger. Inside was a fuse and a small circuit board with a couple resistors, a couple capacitors and a voltage regulator. I followed the ground input from the cigarette plug to the ciruit board, around the edge of the board to the output wire. I soldered my black wire to this wire. I then soldered the red wire to positive output of the voltage regulator. I used the dremel to carve out a new opening for the usb cable to exit. I wrapped some tape around the portion of the usb cable that would be housed inside the cigarette plug so that if you pulled the cable, it wouldn’t directly pull on the circuit board.

I reassembled everything, taped the two charger wires together in a couple places to make it neat and clean and headed downstairs to the garage. The moment of truth had arrived. I put my keys in the ignition, turned it to on, then plugged in my modified charger. The LED on the side of the device lit up. I then plugged in my phone. A familiar beep meant it was charging. I then plugged in my bluetooth headset. The LED flickered on. Success! I now had one charger to charge both of my new devices, all for under $8.