I was wondering about other teams ideas of where the put their power distribution panels, voltage regulator module and so forth because on our 2018 robot. Most of the robots electrical objects were in extremely hard to reach and hard to access areas of the robot, it was helped someone with the addition of anderson connecters but was still quite difficult. Thanks from team 107s wiring team.
Our electronics were all mounted to an acrylic panel that was mounted against the diagonal support structure of our elevator. We didn’t use pneumatics at all so that eliminated a lot of the usual electronics mess. I have a hunch that the diagonal mounting of everything caused some issues with our gyro in autonomous, but I’m not positive that’s what it was. Either way we will probably be mounting everything horizontally in the belly of our robot in 2019. Having our electronics open and up out of the bottom of the robot was great for fixing anything that went wrong. Fortunately, no electric components failed all season so there was really no point anyways.
Put your electronics where it is most easily kept well organized, accessible, and protected. Where on your robot that is won’t matter for 99% of FRC teams.
On 319, we put our electronics panel 6" above the ground, mounted upside down in 2018. I was initially worried about trying to keep it as low as possible for CoG reasons but that ended being a rather silly concern.
The easiest way to succeed in accessible and maintainable electronics is to plan them along with the design of the rest of the robot. Don’t try to wedge them in after the bot is built / designed.
That was are problem last year was our cad department designed our robot with wiring as a afterthought and that created the suffering of not enough space to work well and also fast.
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Provide them with the cad models for each electronic component (battery, rio, motor controllers, VRM, etc) before build season and make sure they work them into the CAD.
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Please, please, please use polycarb, not acrylic. Acrylic has a much higher tendency to crack and shatter, and when it does it leaves very sharp edges and points. Polycarb is much easier to work with, and doesn’t have that same risk.
For my team, we typically try to put the electronics as low as possible. It’s a good chunk of weight, so it helps with your center of gravity, and often there’s room in the bottom of the robot, leaving space higher up for game piece manipulation. For access, the electrical board can be hinged. Tip the robot on its side, remove a couple of bolts, and swing it down. You have to be careful to design your service loop appropriately - you don’t want wires stretched tightly when you lower the board, or risk unplugging anything from it.
This is the first example I found, from back when we were alpha testing the new RoboRio control system on our 2013 robot (They didn’t even have a case for the RoboRio or PDP, just the bare board with connectors!). The older cRio control system we competed with that year was set up the same way. You’ll notice the service loop in this picture - everything goes from the electrical board to the rest of the robot through a path that runs it near the hinge - no stress on the wires when the board is lowered.
Oops, I had a brain fart. We had this exact discussion with a mentor regarding the panel. We did use polycarb, not acrylic.
In my opinion, this is an unnecessary restriction for most teams. I’ve seen too many teams get stuck on shoving the electronics as low as possible and making sacrifices in robot design where they shouldn’t.
It certainly shouldn’t be seen as a restriction on the robot design. This year, for example, our electrical board was higher up on the robot, mounted to our elevator supports. Between drive train, pneumatics, battery, and our elevator winch, there wasn’t room at the bottom of the robot. BreakAway was another year with a different design - electronics were scattered throughout the robot due to other constraints we placed on ourselves. In Logomotion, we had a 2 level electrical board. It could be removed as a unit, and the top level hinged to give access to the lower level while on the robot. In Stronghold our electrical board was above the frame as well, to assist with getting over the defenses.
But despite those examples, many years the bottom of the robot is the best spot for it. You need a large hopper up high to hold balls, or you want to shoot from higher up or have an arm that takes up a lot of room above the chassis. That limits your options for placement higher up. Having the ability to hinge an electrical board to improve access lets you put it in places, like the bottom of your robot, that would otherwise limit accessibility. It’s just one possible solution for your design.
For the past two years we’ve mounted most* of our electronics upside down underneath the robot. This way we can tip our robot on it’s side and get access to everything.
*We ran out of room this year for everything under the robot so we ended up mounting to the top of the bottom panel as well.
We like this approach, though it’s been flat fields the past two years. Terrain games will likely have us mounting upside up in the belly pan.
+1
If you can get your CAD team to work with the electronics team during week 1, try designing a bellypan electronics board with all of the electronics and battery on it that can be mounted at the bottom of the chassis. The electronics team can help organize the components to minimize wire lengths/spaghetti effect. If you have access to a CNC router, waterjet, etc., use that to cut the bellypan. If not, just measure and mark holes on your material where holes need to be drilled for mounting the various components. If you are able to access a large printer (for posters/big paper), you can even print out the CAD sketch of the bellypan, tape it to your sheet, and punch the centers of all the holes that need to be drilled.
You can also just lay out the physical components on your bellypan sheet and mark the holes directly without even doing CAD, but that’s boring.
Several people have suggested putting in all the electrical components when designing the robot. This is great if your CAD people are proficient and can work quickly.
I suspect that an important step many teams miss is for their electrical team to look at the CAD and give feedback on the layout (see below for some guidelines). This needs to be done frequently (and sometimes forcefully). They end up with a lousy layout that is perfectly represented in their CAD model. Remember, a robot where the electronics is not accessible for repair and/or modification may make the fancy scoring mechanisms useless.
A “shortcut” is to ask for sufficient real estate in an accessible place with some part near where the battery will be mounted. The area should be large enough to install all of the electrical components you will need. It may be acceptable to use different shapes. It would also be best if the area near the battery is large enough to install the PDP and your motor controllers.
Remember to have the CAD people put the main breaker in an easily accessible location that is still protected. I inspected several robots last year that had the main breaker right on the outside where a loose Cube could hit it and shut them off.
Make sure the battery is also easily removed and somewhat protected, including the cables to it. You don’t want someone else’s input to catch your battery cable.
Design your electronics panel(s) so that the components can be pre-assembled on to a panel, pre-wired and pre-tested. It can then be quickly installed into the chassis. This allows work on the chassis and the electronics to proceed in parallel. The panel can be thin polycarb or coroplast. Most of the electrical components can be attached with Velcro or Duo Lock.
A way to make a good electrical layout is to look at the “power flow”. Start at the battery, then go to the main breaker, then the PDP, minimizing the lengths of the wiring. From there, the best is to fan out from the PDP to the motor controllers without crossing over the wiring.
Lastly, the RoboRio, VRM and PCM can be installed a little further away. If absolutely necessary, these components can be in a separate area. I have seen people making posts here about folding electronics panels and multi-layer electronics panels. It is easier to do a poor job with such schemes than it is to do a good job. We avoid such designs at work unless absolutely necessary.
Someplace where you can get to them easily and see all the flashing lights.
As far as CoG is concerned, try to keep the battery low and centered (or counter-balancing other heavy items), but otherwise not a big deal since 2015. (The cRIO was much heavier than the RoboRIO.) Assuming the robot design allows, my favorite place to put the control board is on the side or back of the robot in a vertical orientation covered by a removable sheet of polycarbonate. Oh… if you have pneumatics and an on-board compressor, you may want to try to keep the compressor low.
In addition to placement, consider your wire routing before doing component layout. Try to keep wires carrying large currents (the 6AWG main lines and your motor power lines) short to reduce the amount of your battery energy that gets turned into heat rather than useful robot activity.
There’s always a tension between having the motor controllers near the PDP and roboRIO vs having them near the motors. Unless you’re using sensors wired to the controller, and can’t get the cables long enough, I prefer to have the controllers close to the RIO, because having all your diagnostic lights in one place simplifies troubleshooting. If you’re having that problem I mentioned with short SRX data cables, you may also want to consider putting the encoder on a CANifier and programming the SRX to utilize the external sensor as described here.
Edit: forgot this: put your radio where your metal members won’t drown it out. If you put the radio where you can easily see the lights, you’re probably OK here, but over and above visibility of lights, make sure the radio is able to receive and transmit; don’t enclose it in a Faraday cage of robot structural members.
Edit2: The worst thing is to make the controls fit in “whatever space is left after mechanical stuff is designed”. This is what 3946 did in 2013, The chief wiring guy called the job “playing five dimensional tetris”. Just don’t. This is the year we suffered from TRS “Twitchy Robot Syndrome”. Just don’t.
Another thing to consider when planning electronics is drivetrain resistance. If your PDP isn’t centered on the robot, your drivetrain motor wires will be uneven lengths. If the difference is bit enough, that can cause a noticeable difference in voltage at the motor, meaning one side of the drivetrain will move faster than the other. We made that mistake in 2015 putting the PDP all the way on one side of a wide robot, and our robot drove in circles all season. We went through all of the normal diagnostics and couldn’t figure out the issue. I didn’t realize this was the problem until a few years later.
I’ll second (or third or fourth) the idea of putting the electronics vertically and easily accessible, especially as a CSA/FTAA. When your robot is having connection problems on the field, being able to see the diagnostic lights on the electronics can help us get your robot out of the pits and back working on the field faster. The robots I least enjoy working on are the ones where plugging in a wire takes an endoscope and a pik stick.
Finding space for electronics on the robot is not an easy thing to do… Our 2017 robot had its electronics buried and tucked away in various different spots. However, in the previous 2018 season, the size of the robot allowed for greater space for electronics. Our team mounted our electronics around the base of our robot on lexan panels that spanned the width of our robot and was bordered by the cross members and front of our frame. For the radio, I would say you don’t want it hard mounted to the base in case of a large hit that could knock wires loose on such a valuable component. For the radio, our team uses a shock mount in a location where mobile components of the robot cannot hit it (this is key to keep in mind for mostly all electronics). Id say the dimensions of the robot depending on the year have a huge influence over the placement for electrical components. A picture of our electronics panel that was put in the front of our 2018 robot can be seen below. The electronics were then covered by a 1/8 inch detachable lexan panel to avoid game piece or component interference.
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Figuring out where to put the electronics on a robot, is an exercise in dealing with conflicting requirements.
GeeTwo has a pretty good explanation of what to do, as I see it.
It really helps if someone who’s been around robots a while, is overseeing the design of the whole thing. If you don’t have that person on your team, you’re probably going to learn some lessons the hard way…and as a result, you will get some of that necessary but costly experience!
have fun
One idea I’ll throw out is that if you can put the PDP and RoboRio back to back on opposite sides of a board and keep power and control separated it really helps keeps things clear.
In a perfect world you’d be able to disconnect the actuators and lift it out of the robot.
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WildStang has conflicts with mechanical over placement of electronics most years. We deal with it creatively and with lots of discussion.
- Center your PDP so that drive train wiring is nearly equal length. (See post above, you will have a very difficult time getting auto to work because the robot will not drive straight)
- Make high current wiring as short as possible. That is all #6 AWG wire. The more #6 you add, the greater the risk of brownout. All robot current passes through this wire and it has resistance.
- Low current items like the PCM, VRM, and RoboRio can be placed where they fit. However, the PCM, PDP and compressor should be close. The compressor draws maximum current when starting.
- Using lower current rated breakers does nothing to limit current. A
CIM motor in stall will draw 131 amps through a 20, a 30 or a 40 amp breaker. - Use short, large diameter wire for high current loads. #12 AWG for drive motors, #10 AWG is better.
- If you use crimp terminals make sure they are crimped properly. Every crimp will add resistance, a poorly crimped terminal will add more resistance. Consider soldering crimped connections to insure low resistance connections.
- Be sure to strip wire insulation as recommended by the manufacturer. Wire for the PDP should be 1/2-5/8 inch.
Quack, sometime in the future, perhaps I can visit and explain this further.
In 2010 we built a “control box” that had all the expensive stuff in it… solenoid valves, all the electronics… and screw terminals for connecting the heavy stuff… the motors and such, to the box.
This let us build two robots, practice with one, and then carry our control box in to the competition as part of our withholding allowance. It took about half an hour to install the box and then we were up and running with a mostly identical clone to the machine we had been practicing with.
It’s a good strategy for teams who want the benefit of a practice robot without the expense of two control systems. Here’s a photo of the two of them… unfortunately it doesn’t show the box. https://www.chiefdelphi.com/forums/showthread.php?t=83530&highlight=1346
Jason
For those considering such a design, please keep in mind inspectability and maintainability. Inspectors need to be able to see breaker values and wire gauges. We need to be able to trace certain wires, like those powering the RoboRio and the VRM that powers the radio, to ensure devices are being powered from the correct locations. As a team, you want diagnostic LED’s visible during operation - those on the RoboRio should be visible to the FTA or CSA on the field, and you’ll want to be able to see those present on your speed controllers when something isn’t working right. When designing a control box, these considerations are often the first team’s forget about in their rush to make it as small and compact as possible.
I’ll share a few stories to help illustrate how important the above considerations are.
This past year, a team at one of my events had such a control box. Very small and compact, but it was impossible to see the breaker values in order to properly inspect it. They proceeded to spend over an hour disassembling the box so the inspector could look at it, and then reassembling it. That’s valuable time at an event where their robot wasn’t operational. Later in the event, they ran into an issue (with their CAN bus, I believe) that forced them to call in a backup robot during the playoffs - it simply took too long to disassemble the box and find the issue.
This year my team had an unfortunate issue with some crossed wires - we miss-wired our intake and one side of our drive train. One of the drive motors was being controlled by an intake speed controller, and one side of the intake was being controlled by one of the drive speed controllers. In the end, we identified the issue by looking at the diagnostic LED’s on the speed controllers and realizing they weren’t doing what we expected. After that, the fix was easy.
At an off-season event just this past weekend a robot died near the end of the first finals match. It was near the edge of the arena, and myself, the FTA and a CSA were able to observe that the radio and speed controllers were just fine, but the RoboRio had no power. After the match we helped with some additional diagnostics, and after removing the RoboRio discovered that it was internally shorted by some robot debris. After cleaning it out, they got back up and running. They missed the second match, but were able to come back in for the tiebreaker match - and that was only possible because their RoboRio was easily accessible!