Best placement for electrical components

If you do this, make sure that both sides is accessible for inspection, troubleshooting, repair and modification.

A ratcheting crimper will give the most reliable crimps.

Solder only if you know how to solder properly. Otherwise, you can actually make things worse. Not all soldering irons/tips are capable of soldering on 12~10 AWG wire.

The strip length Al gives sounds about right for the power wires going into the WAGO connectors on the PDP. The PDP Users Guide recommends a strip length of 3/8" for the smaller wires that go into the Weidmuller connectors.

This previous year, my team had somewhat of spread out electronics. We CADed some of it, but just general making sure its gonna fit. We placed the PDP in the center of the robot and located the VRMs (one for POE, one for barrel jack) right in front of the PDP. Located between our drive gearboxes in the rear, we had 2 sets of Talon Blocks as we called in. We have been doing this for a couple years but attach SRXs on a piece of sheet vertical sheet metal (3" tall probably) and attach 2 to each side to create little blocks that allow us to still see the lights but in a compact space. We located one of these blocks up front near our elevator also. This moves the electronics away from the center but allows for room around the electronics for easy reach (messing with data cables, resetting, etc.). Finally, we stacked our roboRio over our PDP on a hinge to save space, and allow us to open it for inspection. Incase the roboRio needed removed to get better access to the PDP, there were 2 screws located under the robot that would release it.

EDIT: Pictures
The Rio over PDP shown is from stripped practice bot. Comp bot is in better shape so harder to get picture, but same layout.

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Above the Waterline. :yikes:

If the breaker still allows a CIM to draw 131 A of current, then what exactly is its function?

It’s designed to protect the wiring on the circuit. During use, wire heats up from the current travelling through it. Based on the gauge of the wire, there’s a certain amount of heat that can safely dissipate. If you push too much current through the wire, the amount of heat build up exceeds the amount dissipating, eventually leading to the insulation and wire itself burning up.

Hereis the datasheet for the 20A snap action breaker. At 133A (665% of rated current) it takes something like 1/2 second to trip. During that time, the wire would heat up… but then the breaker tripping, and cutting off all power, allows the excess heat to dissipate safely while there is no additional heat being generated (no current travelling through the wire).

So the CIM motor can pull 133A. The breaker tripping breaks the circuit for a short period, until the breaker resets. Once it does, the motor can pull 133 A again instantly, tripping the breaker again. So it doesn’t change how much current the motor can draw, only the length of time it can draw it. Since breakers are temperature based devices (they use a build up of heat to cause a physical movement to disconnect the circuit, then upon cooling down physically move back to reconnect the circuit), after tripping and resetting the temperature is already elevated and it’s quicker to trip if the current draw is still exceeded.

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If the motor draws over the breaker’s limit*, it breaks the circuit, stopping the motor. Since these are self-resetting breakers, they will re-close the circuit after some time. If the CIM motor is still stalled, it will go back to drawing 131A, and the breaker will break again. And so the cycle continues.

  • for a certain amount of time, see the datasheets

edit: sniped

The “Melting Integral”, “Time vs Current Curves” and “Surge and Pulse Current Characteristics” sections of this fuse application note explains why currents higher than the rating of a protection device can flow through the device. The thermal breakers used in FRC operate (trip) in a similar fashion. I tried to find similar documents for breakers but they were all for thermal-magnetic breakers which are a bit more complicated in how they work.

In a simple explanation, the breakers are chosen to protect branch circuit in the event of a short. Fire on the field is a bad thing.
Due to the trip characteristics of the breaker they can withstand the 600% over current for a short period of time. This does not prevent a driver from pushing the robot against an immovable object for several seconds. In general, with all of the other losses on the robot, even a stalled CIM motor is unlikely to draw 131 amps. However, there are conditions where the breaker may not fully protect a speed controller max current specifications. The breaker is not intended to protect devices connected to it, merely to prevent fire in a catastrophic failure.
Likewise the 120 amp breaker has a similar 600% over current response except, it is not auto-resetting.

Ah I see thanks a lot fellows.

As someone who had this problem before, our 2018 year I went with an upside down electronics design. This allowed us to have plenty of space for components and wire placement, and we never had a major problem the whole year. However if this is not an option for you, here are some basics that I follow to make anything work well.

  1. Place your PDP as close to the center of your robot as possible, this is to decrease wire lengths to all areas of the robot and have less extremely long wires, which can cause some voltage drop.

  2. Group motor controllers close together, and put power wires from them directly into the PDP. Putting them directly into the PDP will have less resistance, and Grouping them together is extremely important for maintenance, as having to look around your whole robot for light codes is a pain.

  3. Group wires that are going to the same places together. The easiest way to make it more manageable (and good looking) is to group wires together along set paths. For example, if you have a 6 CIM drive system, six of your motor controllers are going to those CIMS, so you can route all of their wires togther. The best example of this is from team 1538, whose electronics layout you can also learn a lot from.

Bonus tips: PROTECT EVERYTHING. Please don’t run wires near an exposed gearbox without protection, it’s just a really bad idea. Also make sure that nothing outside of your robot is able to take down your electrical or pneumatic system.

Pneumatics is another beast to tackle, but hope those help out!