I am using a 12v/8amp power source to supply three servos, two steppers, three dc motors, and twenty LEDs. A DC to DC converter will provide step down, 6v source for the servos, but the DC motors are a problem. I have tried an SN754410NESN754410NE, connecting it as described in http://www.uduino.com/tutorials/11, but the chip overheats immediately. Assuming the current was beyond specs, I used an LM317 in current limiting mode, bringing it down to about one amp with the same results - very hot, very fast. Power supply continues to be an ongoing puzzle. Any advise would be appreciated.