Is this an easily accessible circuit breaker?

So I put a protective covering on our main electronics board, and in order to comply with rule R43 which states:

“The 120A circuit breaker must be quickly and safely accessible from the exterior of the ROBOT … Examples considered not “quickly and safely accessible” include breakers covered by an access panel or door”

My mentor, however, argued that the circuit breaker can be easily accessible while being covered by the panel (There is sufficient space to press the circuit breaker while covered by the panel from the side, you don’t need to remove the panel). He argued that a panel door and a fixed panel are two different things, but I disagree.

Will putting the circuit breaker under the panel violate R43?

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Would depend on how that panel is mounted on the robot.


Circuit breaker mounting can be tricky, as it needs to be in an easily accessible place where a person can quickly and safely turn off the robot. However, not in a place where a robot or ball can turn your robot off mid-match. We had a stronghold ball shot into our robot so hard that it pressed the breaker button and turned off our robot, so I have no doubt that these balls can do it too.

My suggestion would be to put it under the panel and cut a large hole so you can access it with your hand from that direction.

Inspectors have asked us to put labels pointing at the circuit breaker. So that’s what I would suggest that you guys print a label that indicates where the breaker is.

inb4 acrylic people yell at you.

See those cracks you already have? That’s no bueno. Try replacing this plastic with thin polycarbonate instead. That will actually help protect your electronics. Please make sure that acrylic is not used elsewhere on your robot too. It snaps instead of flexing like polycarbonate.



My rule of thumb with main breaker placement is to ask yourself whether someone with minimal knowledge of the robot (field personnel) would, in the event of an emergency, be able to find the button and hit it quickly without injuring themselves.

Generally, this usually means not hiding it under an acrylic/lexan/etc covering (though a reasonable-sized opening directly above it is usually acceptable).

It comes down to a judgement call on the part of the RI and/or LRI if your breaker is sufficiently accessible.

I have also heard the volunteers around the field say something like “that’s not accessible enough for me to quickly turn it off without getting myself hurt so I am going to let that robot burn”. Large labels as others have suggested would be helpful to the field volunteers since they cannot be expected to be familiar with your robot.

As a new-ish RI, I’d say “probably no, not accessible enough” and ask my LRI.
LRI would either have a fast judgement… or a group of RI’s would debate for a bit.

My recommendation - figure out what you will do if the ruling is NO, and be prepared to fix on the spot.

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I don’t think this is acrylic, I’m pretty sure it’s Lexon glass. It’s actually pretty flexible, but it cracked as I was trying to drill a hole through it for the circuit breaker wire. I’m probably going to recut it if we decide to relocate the circuit breaker

I think that’s a pretty good solution, Thanks for the suggestion!

“Lexon” isn’t a thing as far as I know. You may be referring to “Lexan”, which is a brand name for polycarbonate. The fact that it cracked like this means that it is NOT polycarbonate (Lexan). It looks like acrylic to me, aka “Plexiglas”.

You are going to have a much better competition experience if you use a less brittle plastic, such as polycarbonate.


It is very rare to see polycarbonate in that colour but it is quite common in acrylic. If you can use a large pair of pliers, grab a corner and bend it 90 degrees and have it bend and hold the shape, you have polycarbonate. If it shatters, you have acrylic. As others have stated, you will have a much better competition experience if your protective shield does not shatter upon impact or just flexing of your chassis.

For STEAMworks (2017), we had a part called a scoosh to push the gear onto the peg. The students had the concept, I did the math to come up with the shape, and the students fabricated it. When they handed me the first one, I inspected the curves, nodded, and asked them if they made it from polycarbonate or acrylic. When they responded polycarb, I raised it high over my head and threw it at the floor with all the speed I could muster, drawing gasps and sputters. It bounced. I then said, would you rather have it break here and now or on the floor at Bayou?

Going back to OP, the breaker looks accessible given what is showing. Still, context (nearby moving and/or obscuring parts) could easily render this inaccessible.


Polypropylene and PETG are also acceptable alternatives that will bend-not-break. Not as good as polycarb and not sold in hardware stores, but way cheaper.