Apparently Monday is DIY day here at CrunchGear, as we have another project for you. Battery powered USB chargers are nothing new — but building one yourself, that’s something different. Using a few components from your local electronics store and a 9v battery, you too can solder together your own little frankencharger.
It’s a pretty easy build. Solder the battery connector wires to a regulator, and then from the regulator to the female end of a scavenged USB cable to the regulator, and you’re set. The hardest part will be finding a female end of a USB connector, unless you want to just chop the end off of a cable. You can read about the whole process here (there’s a little more to it then I’ve described).
One thing to be aware of: I contacted an electric engineer friend of mine, and he advised me to be very cautious with this build. It is a strong possibility that this device could short out and destroy the device you are trying to charge. In this case, it might be better to spend the $20 and buy one from your favorite retail outlet.
[via Gizmodo]
I wouldn’t plug anything of value into this.
It *might* for devices that don’t follow the USB specification exactly (like cheap cell phones, for instance) but it certainly would not charge something like an iPod and could quite possibly damage it.
The use of a 7805 is old school. Four AA or AAA batteries and a Low Drop Out (LDO) linear regulator would perhaps be better. If memory serves the USB specification limits current to 500mA max. There’s no current limit here; but that shouldn’t matter IMHO.
possibly a life saving moment, if need be you are stuck in an area where your phone is dead, gather together some parts hopefully u can find them lol,
These regulators generally like some capacitors involved. Check out the app note from the manufacturer.
http://www.national.com/mpf/LM/LM78M05.html
This will not work with any iPod or iPhone because the USB-Datalines are not wired to anything telling the device to switch to charging mode.