Upside Down Electronics Bay?

My team’s been working on a slew of upgrades for our robot, Rhonda, one of which is changing the current electronics situation. The old electronics sat on some stiff plastic that looked almost like pegboard (may have been PVC) and was zip tied to the sides of the robot. It was very sturdy and didn’t cause any problems throughout the season, but is was disgraceful to have to show folks that this was electronics, so this offseason we set about fixing that problem. As part of the new robot, we have a hopper whose floor is made from aluminum sheet metal with lightning patterns cut out above the WCD gearboxes. We also have the option of adding a proper bellypan on the bottom of the robot. I was wondering if it is a bad idea to mount the electronics in the underside of the hopper (the balls wouldn’t disturb them) or to just go with a proper bellypan? We’re looking to make it as easy as possible to service the electronics, and when we put them on the bellypan in the CAD, it looked like it would be near impossible to service them due to the hopper overhead, hence why I suggested putting it underneath the hopper (so we can turn the robot on its side like 1746 Otto and easily get to them in case of problem)


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You can do it upside down, however you need to make sure you consider how gravity will affect things! Being upside down, it may be easier for things like PWM cables or PDP breakers to work themselves loose.

Instead, consider using a belly pan with a hinge. You can place a piano/continuous hinge down one side of the belly pan, and have a couple of bolts on the other to hold it up. If you run your wires with an appropriate service loop, you can put the robot on it’s side, take out a couple of bolts (rivet nuts/PEM nuts work great for this!) and fold down the board for easy access and maintenance. My team has used this approach across many years.

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Idk if this was specifically what you were talking about but this year 1678 put all of their electronics on the underside of there robot, it allowed them to easily access their electronics. Here is the grab cad link, it has the only image I could find of it.

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We put our PDB and talons under the belly pan (with a thin, removable lexan cover), and we were super happy with that arrangement. Nothing came loose, and we had access to everything (in comparison, everything on top of the belly pan was blocked by our hopper). 10/10 - will do again.

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Makes it impossible to diagnose problems while it’s running or while on the field…

You can’t run the wheels when it’s turned on it’s side? Seriously I get you, but when the alternative is “buried under a giant hopper where we can’t see lights anyway” (as was our practice bot), this was much nicer.

I am personally a big fan of electronics on a board mounted vertically on the side of the robot. It makes them easily visible for diagnostics and repairs (both in the pit and field-side). It also makes it easier to show other people how everything works. There are ways to make it look just as nice as in a bellypan or under the robot. Some spray paint and clean wiring go a long way.

This was our upside down electronics tray that was referenced in the initial post. We didn’t have any gravity related issues. We were also kindly warned by PCH FTAs about limited ability to diagnose any issues, but luckily we avoided connections issues throughout the season. I also included a pic of how we had the robot on the cart to easily access the electronics.

We added a poly-carbonate cover panel to avoid any issues with debris kicking up and getting into the panel.

How do you keep the electrons from falling out?

Installing the electronics on the bottom can be done. It is more a matter of execution than the idea itself that will determine how successful you are with it. In 2014, 2587 put their electronics on the bottom. I enforced a much higher standard of electrical construction that year so we had zero problems with the electronics. The whole electronics panel was assembled outside of the robot chassis and pretested before being installed. The clear protective cover only came off twice the whole competition season. Once, because a Robot Inspector wanted to take a closer look. The only other time was because we found some PWM wires wrapped around one of our axles so we went looking for broken wires. It turned out to be from someone else’s robot.

You hinted that your were not proud of your current electronics panel. Was it workmanship you were not proud of? If so, I would strongly suggest that you do not put your electronics panel on the bottom. If your teams workmanship on the electronics is not very good, you will need more frequent access to fix things. It will be harder to get access to fix things if it is mounted on the bottom.

If your team does put the electronics on the bottom, your designers will have to put some thought into where the wires and cables are going to pass between the top and the bottom so that the wire and cable routing makes sense. It isn’t clear if you will have a protective panel on the bottom. It will save you a lot of heartache if your robot runs over something that catches some of the wires and rips them out. The protective panel should be transparent to facilitate inspection and troubleshooting. Lastly, the radio should be mounted up as high as possible, in a protected location and away from large pieces of metal, never in the bottom of the robot.

Really strong magnets :slight_smile:


Don’t tell Rivet Man… please

This was our third year placing our electronics facing downward. It’s worked flawlessly.

I think only reason we will move away from this arrangement is if we need to have a large portion of the robot open for some type of intake mechanism, like in 2015. Otherwise, the ability to both observe and access the electronics is wonderful.

We’ve mounted electronics on the sides of the robot and didn’t care for it. We’ve had too many instances of intrusion into our robot space with spears, claws, and entire robots. Our electronics go where no one else will ever hit them.

Ditto. We loved the access, but would do a few little things differently to protect the electronics more (better cover, a bit more ground clearance, etc).


I was brought on last year for Electronics, because the old guy who did electronics was a no-show that year. Basically, the thing was as neat as it would have been, but was constrained by the design of the robot to prevent a good electronics bay. We didn’t have a bellypan, so the electronics was mounted via zip-ties to a large PVC pegboard sheet ziptied to the main cross members of the robot. It jiggled a lot, and even tho I spent about an hour on the main board, our solenoids weren’t organized at all because they were essentially tossed in there with no thought, so there was wires everywhere. It was better than electronics during 2016, but it wasn’t optimal, hence why I’m working to make it better this year. I did plan the whole thing out last time as well, but I had to make everything from things in the shop with zero planning except for layout.



Ugh, just going to say it. I hate inspecting hinged/moving electrical panels. They are rarely well executed. Usually a wire gets caught on something while moving the panel and it ends up getting tugged from its socket.

Probably too late to implement this, but our team had our hopper on a hinge, allowing us to access our electronics underneath the hopper. The design worked well and didn’t have any issues with it. We also attempt to design and build the electronic board before mounting it

With the amount of continuous shock that comes from an FRC robot (bumping into things, harsh acceleration, falling, etc), it’s unlikely that gravity will play much of a part with working things loose. The PDP breakers are inserted very tightly and if gravity pulls them out it’s a good sign that it’s time for a new PDP. As for PWM cables, they’re hard to keep in place in almost any arrangement, but gravity alone won’t work them loose. Give the cables plenty of slack or 3D print a holding bracket and you’ll be hardpressed to find any issues.