Introduction: FRC Robot Wiring
Over the past three seasons I have been a part of FRC, I have yet to find a wiring tutorial I fully agreed with. Everyone has different methods of wiring and this tutorial reflects the wiring methods of the electronics team of FRC Team 1477. The reason we chose a wooden belly-pan was the ease of replication for other teams but any material will work (except acrylic - that stuff is evil).
Step 1: Things You Should Have or Acquire
1. Powerwerx Tricrimp Anderson crimping tool
2. Ratcheting crimper (we have a die set for the Powerwerx crimper)
3. Spade crimps for each size of wire going to a speed control
4. Heat shrink to fit over the crimps (we usually get an assortment)
5. Red and black Anderson Powerpoles along with crimps (you can get sets)
6. Wago tool or small flat-head screwdriver (we have found the Wago brand work best)
7. Wire strippers
8. Tons of zip ties
9. Wire (we prefer zip wire but you have to get the good stuff to not have problems)
Step 2: Plan It Out
One thing that is most overlooked in constructing an electronics board on a FIRST robot is good planning. You will not get good results by "just putting them where they fit", you will end up with problems down the road. The biggest thing to look at is ease of access. As much as I hate to say it, the most common repair needed on a robot is electrical. Through careful planning, you can reduce repair time and make the next match without having to cut corners. The two options for this step are physically laying the components out and marking where each is or with CAD software. When I say CAD you do not have to add all of the wires just figure out where the major components should go. If you are a first year team I would suggest the first option and the more advanced teams go for the second.
Step 3: Mount the Components
Begin mounting the components by following your plan and laying everything out to ensure proper spacing. It is essential to leave enough room to work on or replace components, such as the Power Distribution Board, Digital Sidecar, and speed controllers. After you are happy with the layout, start mounting the components with the necessary tools (bolts, zip ties, etc.) Make sure everything is mounted securely, as electrical components coming loose or detached during a competition could cause big problems.
Step 4: Crimp the Wires
After you have mounted everything on your board, it is time to begin crimping and running the wires. To wire the speed controllers, you will need the materials listed earlier. You will need to use at least 12 gauge wire for 30 amp fuses.
Begin by running wires from the speed controllers to the PD Board:
1. Strip the wires slightly longer than the crimps you are using.
2. Cut enough heat shrink and slip it onto the wire before you start crimping.
3. Place the spade crimp into the crimper, making sure the seam of the crimp is in the concave side.
4. Insert the wire into the crimp and squeeze hard enough to fully crimp onto the wire, and release. Do not crimp onto the insulation of the wire.
5. Push the heat shrink over the exposed wire and crimp and use the heat gun to shrink it enough to be secure.
6. Repeat on the second wire.
After one side of the wire has spade crimps, secure them in place on the speed controller. Next, measure the length of wire required to reach the PD Board. Always measure the length from the side of the wire that needs to be longest, and cut the shorter side later. The wires should take the shortest and easiest path to the PD Board, but should have enough slack as to not be too tight or strained. If there is considerable distance from the speed controllers to PD Board, the wires should be zip tied to each other and the board to ensure they are securely in place. If the speed controllers are very close to the PD Board, like in the pictures, just make sure the wires look as neat as possible.
After you have wired all the speed controllers to the PD Board, repeat steps 1-6 using spade crimps on the other sides of the speed controllers. This time, however, you will need to use Anderson crimps to run to the motors for easy removal. Measure and cut the wires to the right length with the motor wires.
1. Strip the wires to fit the crimps.
2. Place the crimp in the Anderson crimper with the open side facing upward into the V-shape.
3. Place the wire in the crimp and squeeze until fully crimped.
4. With the hook side down, push the wire and crimp into the Anderson housing until it clicks into place.
5. Run the wires neatly and securely to the motors, watching out for chains, gears, or anything else that could damage wires.
This is an extremely helpful diagram:
Step 5: Run PWMs
You will need male to female PWMs from the sidecar to the speed controllers. First, assign and label your speed controllers according to the sidecar and port they will be running to. Next, plug the female side of the PWMs into the "PWM OUT" ports on the sidecar. Fold the wires over to make loops to ensure there is some slack and gather them all together facing in the same direction. If needed, drill holes into the board and zip tie them in place. Then plug the male side into the appropriate speed controllers and find a safe place on the board to secure the bundled extra wire. Neatly fold the wires back on themselves and zip tie in place. Bundle them separately so they are easier to replace if needed. When running, make sure there is no stress or tension placed on the wires as it could lead to damage.
Step 6: Other Wiring
Other wiring includes ribbon cables, wiring for the breaker, and power to the sidecar and cRIO.
For ribbon cables, run them neatly and safely from the digital module of the cRIO to the digital sidecar.
The breaker requires 4 or 6 gauge wire. Use circular crimps to run the wires from the PD board to breaker, and large Andersons for the battery.
Use at least 16 gauge wire and a white connector to run from the sidecar to PD board, and a black connector to run power to the cRIO.