[Don] had some Serial RFID readers that he needed to work and be powered by USB. He went out and purchased a simple serial to USB converter, but was left with the problem of the operating voltage. He supplies the schematics on his site for his solution. Basically he gutted the converter and integrated it all with the appropriate voltage broken out. The final project is nice, using the serial to USB convert as the project box and even including a nice LED to show when an RFID tag has been read.