pic: Recycle Rush Re-design Part 2

[GeeTwo]

Originally Posted by Ari423

Also for the OP, if you do decide to go with pneumatics as GeeTwo suggested, you can move the PCM onto the tethered bot. Then you can decrease the tether to two wires (power and CAN). The power wire has a pretty low amperage when not running a compressor, so if you make it a big-ish wire you shouldn't see too bad of a voltage drop.

I wanted to share my reasoning for putting the PCM on the robot side. Either way has benefits and costs relative to the other.

• The way I set things up, all of the wires carried simple DC signals that switched on the order of a second. CAN carries rather faster switching, so I wanted to leave it just on the main hull. I've since checked CAN lengths, and you should be OK running from one hull to the other, and even back. However, to simplify things and reduce losses, I would use an external terminator on the stacker end rather than bring the line back to the robot for termination at the PDB as most teams usually do.
• I didn't want to run CAN down the tether, because it's inherently more vulnerable. I was worried that if something happened to the tether, the whole robot might freeze up. If you are using PWM for motor control, this may not be an issue for you.
• I didn't want to run compressor power down the tether. There are workarounds, including a spike relay on the main hull side, and using a "tether bypass" when filling the tanks*. Still, much less current is required to power a compressor than some CIMs.
• Note that even with the PCM on the stacker hull, any limit switches or other sensors (except the pressure switch) still have to go back to the 'RIO. Limit switches and thoughtful design can significantly reduce the amount of air needed.

* I haven't found any rules in 2015 that would have prohibited making internal electrical changes (e.g. disconnecting the tether and wiring directly across it using molex or Anderson power poles) during pressurization process. Just make sure you put things back! The more steps in a checklist, the more likely something will get missed.