How to assemble a basic electronics board:
The diagram below courtesy of team 3128 shows a phenomenal example of how to wire a robot. The battery powers everything on the robot, but to distribute said power, the battery is hooked up to the PDP with 2 very large gauge wires. The PDP powers motors of different sizes through the large ports on the sides. Larger motors (Falcons and CIMS) will be connected through the higher power 40 amp slots on the PDP and smaller motors will be hooked to the less powerful 30 or 20 amp slots (you can change out the fuse to change between 20 and 30 amps). In order to control said motors, between the motor and PDP you need to install a motor controller of your choice, whether it be a Spark, VictorSP, Victor SPX or any other suitable motor controller. There are 4 large places to connect wires on most motor controllers: The side labeled with M+ and M- will connect to the power and ground for the robot respectively and the side that is usually labeled V+ and V- takes in power and ground from the PDP. Do not wire these backwards. The smaller ports at the bottom of the PDP are used to power the RoboRIO, VRM and PCM. There is one set of cable holes outlined in purple and 2 outlined in green. The RIO is wired to the purple ports and the PCM and VRM can be wired to either of the green ports.
The VRM powers smaller devices and will provide 5V 0.5A, 5V 2A, 12V 0.5A and 12V 2A. Usually a quick google search or reading the labeling on the device you want to power will tell you the requirements from the VRM.
The PCM is essentially the hub for all pneumatics. To power your compressor, you plug its leads into the "compressor out" port and next to it, outlined in purple, is the port for the pressure switch. All of the other ports (excluding CAN and power in) are dedicated to wiring solenoids. Most of the time we use double solenoids, which have 4 wires. Referencing the picture above, essentially as long as the wires are starting at the same part of the solenoid and ending at the same part of the solenoid, as long as you plug said wires into the same number on the PCM, it should work.
The Radio is powered either with a black power cable from the VRM or using power over ethernet (an orange wire that connects to ethernet and to the VRM).
The Limelight (not pictured above), is abnormal to wire. It is wired to the PDP into a 20 Amp slot although the wires are of a very small gauge. The ethernet cable is then wired to the switch along with the other ethernet cables from the robot.
Wiring up communication between different parts of the robot is straightforward as long as you keep things organized. We tend to stick to 2 main methods of communication: PWM and CAN bus.
CAN references the green and yellow wires and green and yellow ports found on most of the electrical parts. Essentially you are making a daisy chain of all the components that accept CAN bus, starting from the RoboRIO and usually ending with the PDP. In between the start and end points you include everything else such as the falcon motors, PCM and any CAN based motor controllers. After that just make sure to move the little pin on the PDP that says "Termination Resistor" to the on position.
PWM is much simpler and refers to wires that are black, white and red. They connect to the PWM ports on the RoboRIO, where red goes to power, black goes to ground and white goes to signal. These power Spark motor controllers, servo motors and any other motor controllers that use PWM. There is not much to remember with these aside from the one wire you run from the RIO to the device.
Other things that require some degree of wiring are the RSL which has a dedicated spot on the RIO and requires the power cable to be split into 2 terminals on the light itself and only requiring 1 ground.
Wiring sensors is more complicated as it varies from sensor to sensor...