Our power distribution system used two 7.2V NiCd batteries to provide 14.4 V to our motors and with three LM7805 5V 1Amp voltage regulators to distribute logic level voltage to our circuits. The motors were powered straight from the 14.4 V of the batteries, while the E128 board, having its own voltage regulator, was powered from one of the batteries. To prevent damage from accidentally plugging the batteries in backwards we included a P-channel power MOSFET (the IRF5305 capable of sourcing over 20Amps) which would only open when the batteries were corrected in the proper polarity.
We also used this transistor to implement a kill switch to quickly power off the robot if it was necessary. An 8amp fuse was used to protect our circuitry in the case of a short. 3 voltage regulators were used. One provided power for the side indicator LED’s which drew on the order of 50mA. A second regulator was supplied to provide power to the servo motor which could draw currents up to 450mA. The rest of our circuits obtained power from a third 5V regulator. Since we weren’t using the tape sensors nor the IR beacon detector, this regulator only has to supply power to our LED display which drew ~100 mA, while the encoders and switches drew very little current. Small power indicator LEDs were used to signal that power was reaching the various circuits.
A large 2200uF bypass cap was placed on the unregulated 14.4V side of the power board to reduce noise on the supply line due to the large current drawn by the motors. As per datasheet recommendations a 0.1 uF was placed on the regulated side of the regulators, to smooth voltage ripple from the regulators.