Motor Controller placement

[matthewdenny]

Is there a reason to place the motor controllers nearer to either the PD board or the motor itself? The total distance is the same from motor to PD board either way but is there and advantage one way or the other?

[Alan Anderson]

Having your motor controllers all in the same general location can make it easier to do troubleshooting by swapping components.

Distributing the motor controllers closer to the motor can make it easier to find room for them.

Having a long run for the PWM cable increases the chance of something cutting it or pulling it loose.

Putting the controllers electrically far from the power source means that more of the voltage drop is seen by the controller and might result in a brownout. For Jaguars, that can cause issues, especially when using CAN instead of PWM control.

[apalrd]

I used to put the controllers near the PD board to keep PWM cable length short and manageable.

General tips for electrical component placement and wire routing:

Main battery and battery cabling:
-Locate the battery first. It is more critical to CG than anything else, so put it low to the ground.
-Locate the PD board next. Preferable in the center of a rather large area. Face the input lugs to the battery, and face the terminals on the battery in the direction of the PD board (this will minimize the very heavy and lossy main battery cable). Think about wago tool access too. I highly recommend a bent 90 degree small screwdriver for wago use.
-Locate the main breaker in the closest possible easily accessible location to the PD board and the battery connector
-Use the shortest possible length of #6 or #4 wire for the robot side of the main battery cable, leaving enough to connect a battery.
-Zip tie the battery connectors together in every match. A velcro wire tie works also.

Drive and other high current motors:
-Locate the talons or other speed controllers as close as possible to the PD board. The drive controllers should be closest.
-Try to use the shortest wire length possible between the drive controllers and the PD board, and the motors, BUT
-Try to keep the wire length the same between both sides (left and right). This will help with drift caused by electrical voltage drop.
-Use #10 wire for the drive motors and all 40a devices even though you can use #12
-I put the controllers near the PD board so all of the controllers are together, reducing the mess and tracing of PWM cables.

Motors on long appendages:
-Wire becomes heavy here. I frequently use a 30a breaker on rollers (even though I could use a 40a) so I can use #14 wire, which is a bit lighter than #12 or #10. It adds up over long lengths (up to the top of an elevator, for example).

Other motors and controls stuff:
-Use the smallest wire size legal for small circuits which do not require high current. We use very light, thin insulation, fine strand #18 instrumentation wire for some of this.
-cRio, modules, digital sidecar, compressor, lights, solenoids, etc. are all wired with this
-When possible, I locate the solenoid valves close enough to the cRio to use the original wires. Then, crimp a 2-pin PWM type connector (or a block such as 2x4 or 2x8 for all of them in one shell) and don't bother with an intermediate wire.


Layout all of the motor controllers in order of load/current, so the higher current motors have higher priority to be where they need to be for the shortest path. So the drive talons are placed for optimum wire routing and shortest wire length, then the high current motors (40a), then the 30a rollers, then the 20a compressors and radio brick and such.

General wire routing:
-Secure wires and think about how the wire will be stressed as things move. Leave enough slack around moving joints but not enough to get caught.
-Try to run wires in bundles for neatness. Think about some of the main bundles and leave space for them so they aren't going over speed controllers.
-Run all PWM cables first since they are easier to bend, then run high current (thicker, stiffer) wires after on top of the PWM cables

And finally, CAD your electronics. Not the wire, but the components. Make sure you leave room for them. Make sure you can work on them without too much pain (they're never exactly easy to get to, but you can try to make it nice anyway). We usually make block models (cubes of the right size/shape/bolt pattern) to make them easier to assemble and easier on the computer we're working on, since we really don't need fine detail for a motor controller.