Power Distribution Module
The power distribution module provides safe power for all of the robot systems, using the main 12 volt battery as its source of energy. As the name implies, the module "distributes" power, but in doing so, it adds reverse battery protection, additional voltages (5 and 24,) and an additional 12 volt low noise power supply. Power for high power 12 volt devices like motors is routed directly from the battery, but through circuit breakers with fault indicators. The block diagram below shows the power distribution module's systems.
Starting at the top:
- The high current breakers and connectors typically provide power for motor controllers driving high loads. There are eight circuit breaker sockets, each designed for a maximum current rating of 40 Amps. There are four sets of power/ground connectors on each side of the module. Power for this system comes directly from the battery inputs of the module. Each breaker has a sensing circuit that activates an LED at the corresponding connector if there is a load connected, but the breaker is open or not plugged in.
- The low current breakers and connectors typically provide power for lower energy systems like small motors, and work exactly the same as the high current system described above. There are twelve sets of breakers and connectors with six power/ground pairs on each side, and the maximum current of a channel is 30 Amps.
- There are three DC to DC converters (switching regulators) for supplying lower current clean (low noise) power to noise sensitive electronic circuits on the robot. All are protected by the reverse battery protection circuit described below.
- The 5 volt 3 amp supply typically powers the ether-net camera. It is protected by a circuit breaker in its ground line.
- The 24 volt 1.5 amp supply is specifically designed to power the cRIO control system and has a four pin connector that matches the one on the cRIO. At its output, it is protected by a circuit breaker in its ground line. In addition, there is a 15 amp breaker on the regulator's input.
- The 12 volt 2 amp supply is typically used to provide power to the robot's WiFi router. Its design is very similar to that of the 24 volt supply. Though the output of this supply has about the same voltage as that of the battery, using power directly from the battery for electronics like the router is a bad idea because of the high frequency noise and voltage variation created by the motors and motor control circuits.
- The reverse battery protection circuit prevents current from flowing backward through the electronics in the module by disconnecting the internal ground (PSGND) signal from the black battery terminal (GND) if the red battery terminal is more negative than the black battery terminal.