Preface: USB is now very popular, not only as a data transmission and peripheral control standard, but even as a power supply, things like fan, cup heater, light, vacuum cleaners, etc are available. I found that it's nice to have USB power (i.e. 5V DC) anywhere so that we can charge up our devices, and to power them, in case a notebook is not always very convenient.
Some mounts like my TG-SP II is driven by 6V DC and thus USB can even serve it, and when a notebook is not available, such a USB power box would be useful. It can even re-charge a mobile phone or other devices with rechargeable batteries.
These kind of battery box is available at $59 HKD (7.7-7.8) or as high as $15 USD in ebay. It's pretty expensive for a simple battery box with USB socket, and so I come up with an idea to DIY, here's the information that we need for DIY, however, do it at your own risk:-
In order to provide power via USB socket, we need to give ~+5V (1) and ground (4) according to the pin-layout as above. So, the next question is, where can we find a USB socket. USB extension cable immediately comes to my mind, but that could be a real waste. I searched around my drawers and I found some PS/2->USB mouse adapters lying around, useless, then I know they're what I wanted, and then we will want to know its pin-layout as well:-
Very simple, right? So basically we're just connecting the +5V of the PS/2 plug (4) to positive terminal of a 4AA battery box and the ground (3) to the negative terminal. In order to play safe, we need a multimeter to check if the connection is correct, and to check the polarity of the USB port of your PC:-
Then, it's time to do the hacking and soldering job. I found removing the outer sleeve of the PS/2 plug would make the job far easier. Unused pins can be bended, or removed to avoid unwanted contact. If power is provided to the unused pin, most probably data pins, undesirable results could occur, or even damage the device, so be careful.
And here's a final product, not very beautiful but quite elegant. Testing could be done with a cheap USB hub first, instead of using your expensive device.
Finally, I tested it with my phone and it proves the DIY work is correct. Since USB port has 5V, and so it's better to use AA rechargeable so that the total voltage will be 4.8V, instead of 6V is your use alkaline batteries.
After all these work, suddenly I realized that maybe we can simply made a simple power plug for the AA battery box to provide power to a USB hub? Will the USB hub then provide power to the USB ports cleanly? I think yes, but I didn't try. That would be a cleaner solution to the problem. Anyway.