Portable Power Supply

This is a very simple hack. Its more that nobody thought if it that surprises me, maybe people did but didnt share it. Who cares, its here now for those that need.

Most electronics projects that people make run on 5v. Untill now that meant a voltage regulator. A lot of time was wasted making regualtors for AC adaptors or batteries.
Many home projects had 4 AA cells powering them with a 7805 voltage reg IC. This is wastefull because the regulator basically kills the extra voltage off as heat. Not good for battery life. Making a rechargable pack for your own project had its own downfalls, mostly a custom charger. Now, here is the solution, ready made and cheap.

Add a lithium-ion rechargable battery pack to your project!
Buy a PSP external battery pack. Its that simple. Because sony designed the PSP to charge from a clean regulated 5v supply, the external packs output just that, a clean regulated 5v. They are 1800mah and above too, so you get 5v at the right voltage for a long time. You can add the 'standard' 5v connector to your project then use the PSP charger to power it directly or the external pack for portable power.

Since the Sony PSP (and even the Nintendo DS I think! check the pack outputs 5v first) many third party manufacterers are making external battery packs with lithium-ion and regulated 5v. The best part is they use a DC-DC converted for much more efficient conversion so the pack lasts ages. You can get them for £9.99 or so, thats as much as youd pay for a decent pack of rechargable AA cells.

Desktop Power

thats all very well when you are out and about, but if you dont own a PSP, or want to power the project from a clean 5v supply at your desk then how?
USB.
Every PC now has many usb ports, they can output up to 500ma of power. I suggest not taking more than about 300ma anyway though, just in case. Get any USB lead that plugs into your PC, cut the other end off and use the RED and BLACK wires. Its that simple. the yellow/white are USB data, cut them short and make sure they don't touch anything. The RED wire is 5v and the BLACK wire is GND. Plugging this in/out lots can cause a spike on the PC USB port, and sometimes windows will disable power so be carefull. Maybe a soft powerup/down option on your board to avoid the spike is an idea.
The best way is to get a USB charge cable for the PSP, to power the battery pack you just bought. You can charge it via USB, then run your project from the battery anywhere. This is the recommended method as it removes any risk of damage to the PC or USB port.

Ive just solved 90% of 5v power problems for hobby electronics, with a supply for desk and battery. A lot of other people need more amps or 3.3v. For the 3.3v people there is also a solution. Go to Dontronics and buy the USB module. That can provide 3.3v out as well as 5v from the USB port. It also provides a TTL level Serial port into the PC! I have one of these, and they are great. Im not affiliated with Dontronics in any way but can recommend both their products and service.