I was just reading the post about the AC wall adapter USB charger. I have 2 PC’s at home for charging my Clip on the USB port. I wanted a charger to use in my pickup. I found a couple USB lighter plug style car chargers at Best Buy. I think one was $20 and the other was $25.
I did some research on USB specifications. All you need for charging is 5.0 volts DC, that is the standard voltage from a USB port. I checked my Clip and it only draws about 65mA (0.065 amp) while charging. All you need to do is provide 4.75 to 5.25 volts DC to the red and black wires on the USB cable. Of course red is positive, black is negative.
I made up a little charger with stuff at had at home. I used a lighter plug from an old cell phone charger. I opened the plug and installed a 7805 intergrated circuit linear voltage regulator. The regulator is very easy to use. It has 3 pins, voltage in, ground, and 5.0 volts DC out. Just connect the ground from the lighter plug to the center ground pin on the 7805. The +13.8 center pin from the lighter plug connects to pin 1 on the 7805 (voltage in). My lighter plug had a 3 amp fuse, so I left it in for added safety. This voltage can be anything from 7.5 to 35 volts, so 13.8 is fine. Cut the USB cable, feed it into the lighter plug, connect the black wire to ground and the red wire to pin 3 on the 7805 (+5.0 volts DC output). Don’t connect the other wires from the USB cable, you only need the black and red for charging. I had a mini USB cable from a cheap digital camera that fits the Clip. I also installed two 0.1uF 50 volt capacitors for stability. One cap from pin 1 to ground, the other from pin 3 to ground. This probably isn’t necessary, but won’t hurt.
The 7805 is available from Radio Shack for about a dollar. I had a few in my parts drawers. The 7805 doesn’t need a heat sink, it will only dissipate about 1/2 watt of heat while charging the Clip. MIne works like a champ and only cost me about an hour of time I would have wasted watching TV anyway. Go ahead, build one, it’s fun!