In our rookie FRC team, I have filled the position the electrical coordinator. We need to order some electrical components that are not included in the kit of part and that are easily breakable/fragile. Being a first-timer, I am genuinely clueless as to the course of action to be undertaken. Can anyone please recommend some necessary parts that we should add to our list? Thanks!
The things I can think of that are most “fragile” would be the non-resetting fuses on the PDP for the roboRIO and VRM. My team hasn’t had one blow yet, but we definitely don’t want to be left without a backup if they go out.
Luckily, a lot of FRC electrical components are designed to not break easily. However, you should certainly still look into getting backups of the main control system components in case one dies on you in competition.
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One of the most fragile things we’ve had issues with is the OM5P radio. There’s a couple of failure points, the first being the power connector. A barrel connector does not lock, and has no way of keeping it on there. Some teams have resorted to hot gluing the connector in, which works fairly well. I would strongly recommend using the supplied PoE cable and the barrel hot glue method to prevent it from rebooting or shutting down completely in game.
The next issue is the metal shield on the inside can bounce and touch components, causing the radio to reboot at what seems like random times. Here’s a link on how to fix that. I STRONGLY recommend following this procedure with all your radios. We’ve had no issues with the device since we did both of these things.
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A lot depends on how well funded your team is. I have seen pretty much every electrical component on the robot break. Even the robust ones,
As others have mentioned a spare radio. Spare motors especially if you are using redline or 775 pros. Fuses and resetable fuses. sensors and limit switches. Anything that is on the perimeter of the robot. spare motor controllers.
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I’ve never seen a good application for hot glue in electrical connections on a FRC robot.
POE with a barrel backup, with strain relief and a piece of electrical tape gives you reliability plus easy swap field-side. Make sure you are using the correct sized barrel connector - not something snipped from the nearest spare wall wart that happens to fit.
Helps avoid being bypassed if a quick radio replacement is required.
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Sounds like a good idea, to have replacements for stuff that has a significant probability of failure.
In addition, you might want to have someone on the team investigate ways to prevent failure. For the electronics, the most important thing you can do might be to protect all electronic components from being contaminated with metal filings. If you drill a hole in piece of aluminum on the robot, and this procedure happens above or near the electronic part, little pieces of metal will fall onto, and enter, the electronic part, and cause failure at some inopportune time. To prevent this happening, your team can do several things, including having procedures about careful workmanship, or housing all electronics in a safe enclosure, or applying some covering over all the parts, or some other ideas.
Being prepared for failures is great, but preventing them is even better.
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Congratulations. I imagine that you have a steep learning curve and a short time-span to acquire the education. Below is a few of my must have spare parts:
SRX Mag Encoders from CTR: http://www.ctr-electronics.com/sensors.html
Versa Planetary Encoder: https://www.vexrobotics.com/217-5046.html
Adafruit IR Break Beam Sensor - 5mm LEDs [ADA2168] from Amazon.
Use these with the FWD/REV limits on the Talon SRX or the SparkMAX motor controllers to protect your robot from destroying itself.
Sentinel Interface boards for the Talon Motor Controller form AndyMark:
This also works with the Talon SRX and SparkMax motor controllers and the IR Break beam sensors.
Good luck with the build and competition.
Very useful. Thank you very much
Will convey this to the safety/construction team. Thanks for the advice, as rookie team all the help is greatly appreciated
One thing we learned a few years ago was that your RoboRio can be very fragile. Make sure that you put electrical tape over every opening on your Rio. If you don’t metal shavings and other stuff can find their way in there and short your Rio. So buy an extra one of those and use electrical tape.
If you use them improperly they are very easy to break. Roborios hate metal shavings, PDPs hate not using a proper wago tool and hot glue, and the VRM can get messed up if you push to hard on the pins. Finally the router needs to be modified to prevent shorting (https://www.mentorbuilt.com/2018/12/how-to-repair-your-frc-radio-to-avoid.html)
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No connection in the FRC control system requires the use of hot glue. A fully-seated PDP branch circuit is plenty strong and should survive any hits the robot will take. As long as you’re using an imperial barrel jack (not metric) and backing it up with POE, there really isn’t any reason to hot glue the radio barrel jack either. Adding hot glue can get inside the connection and increase its resistance (hot glue is a good insulator), and make it unnecessarily hard to remove the connection if you need to swap something between matches.
The router can be modified to prevent an internal shorting problem, but it doesn’t need to be. Modifying the radio requires opening the case, which puts the fragile antennas at risk to be damaged. It’s not something I’d recommend just anyone to do, and certainly not something I’d “STRONGLY recommend” to a rookie team. The shorting problem only arises when you press with a decent amount of force on the top/bottom of the router case. If you design your mounting solution so it doesn’t apply pressure to the case (which is probably a good idea anyway), you really shouldn’t need to modify the radio. In Israel, the CSAs have been recommending that teams do not modify their radios because the risk of damaging an antenna is greater than the cost of redoing your mounting.
roboRIOs certainly don’t like getting metal shavings inside them. But I wouldn’t call them “very fragile.” It’s actually fairly difficult to destroy a roboRIO compared to your average piece of electronics. And in the event that you do break your roboRIO, NI has amazing customer service to repair/replace it at minimal cost. That being said, you should always cover your electronics while drilling on your robot. Just lay some piece of plastic, fabric, or even clothing over the electronics to catch the metal shavings as they fall. When you’re done, be sure to lift the covering straight up so you carry the shavings away instead of dumping them right back into your electronics.
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To the OP:
The components of the FRC control system in general are built pretty robustly. If you treat them with care and aren’t reckless with them, they should last you a while. For a rookie team, the only thing that you will probably need to get more of are motor controllers; everything else (roboRIO, radio, PDP, VRM, PCM, main breaker, RSL, and a few motor controllers) should come in your kit of parts. That being said, it’s a very good idea to get a second set of electronics. Having a second set means you can build a test platform for programmers to test code while waiting to get the real robot, you can build a spare robot (or even just a drivetrain) for driving practice if you have the resources, and you have spare parts if anything breaks.
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We’ve never done the hot glue trick since the PoE cable has been extremely reliable. But other teams have in the past. But my point was don’t rely on just the barrel connector, that is a well known point of failure many teams have experienced.
As for the tape insulator mod, I’m putting our experience out there - we had nothing applying pressure to the case of our radio and had several failures at NEDCMP in 2016. It ruined our event, and was something so trivial to fix that I can’t imagine not doing it. If a rookie team isn’t comfortable with the process, talk to a team that has done it. We’re more than willing to help any team since our electrician has done it many times. If WPILIB Screensteps has gone out of their way to document an unusual procedure to modify a radio, I would guess it happens often enough to be an issue.
I am mentioning that I have seen teams use a screwdriver on the PDP, break it, and then use hot glue. Thus they destroy the board. It is always a good idea to have a replacement if you do not know how to properly use the PDP.
We gave our router to a Freshman with instructions and it came out fine. It is not that hard. You just need to make sure that you are careful and slow. Also our practice bot (until it was modified) would have the router reboot when we jumped off of L2. And our electric board was shock mounted. It is a good idea as it can ruin your season.
Agreed.
If you see that this problem is specifically causing your radio to be sensitive to shocks, then you can consider doing the modification. But to do it to every radio in advance just doesn’t make sense to me. Your teams were careful/lucky that you didn’t damage the radio antennas, but they’re very fragile and in a place that makes them easy to be damaged when you open the case. I’ve heard from a number of teams that have damaged theirs. I wouldn’t recommend a rookie team to do it without a good reason to.
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The electrical components that we’ve broken the most of are probably some of the smaller motors (775 pros and BAGs), and potentiometers which don’t always last long with our super accurate™ +/- .030" machining. We’ve had VRMs fail on us in the past, but not often.
Make sure you have double the amount of wire you think you need, and double the number of connectors. You’re going to make mistakes that you need to fix (everyone does, don’t sweat it but be prepared). We use four types of connectors on our robots:
These PWM connectors for digital and analog IO connections to the RoboRio
These 0.1" latching polarized connectors for the CAN bus
These Anderson Powerpole PP-45 connectors for motors
These Anderson Powerpole SB50 connectors for batteries
You’re also going to want to stock up on ferrules for the VRM and PDB.
https://www.andymark.com/search?q=ferrules
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Leg lamps aside, we burn Talons regularly. Would very much like to know if they can be repaired?
So far since the OM5P was introduced, and not counting it being ripped out by another bot or snagging something on the field itself (yes, I’ve seen the PoE adapter destroyed), I have witnessed a SINGLE time on the field where the barrel connector was the actual problem when a robot disconnected and the radio was rebooting (the connector turned out to be the wrong size). Every other time I have found a power problem somewhere else in the path, more often than not, at the breaker itself (battery, VRM, PDP VRM ports - being the probable order after that). Since the breaker lugs are normally covered with tape and whatnot, teams forget that it is there when they are checking connection points.
To secure the barrel connector, simply put some tension on the wire and tape it back onto the radio itself. It will stay secure. Don’t really pull it, as you can cause internal damage, just a light tensioning will work.
By all means, use the PoE adapter as well (please make the port the roboRIO is plugged into easy to get to though for troubleshooting without having to power cycle the bot), but please don’t just think the barrel connector is the sole cause of radio reboots without looking into the rest of the power path from battery forward.
As an FTA that is a HUGE fan of this program, I REALLY want to see 6 robots running on my field for the full 2:30 every match. Power path problems are something that is entirely avoidable and I even have it in my driver’s meeting notes for teams to please ask myself, my FTAA, a CSA, the LRI, to come take a look at the power on the robot and see if there is anything standing out that we can spot. We haven’t been looking at that robot since January, so we may spot things that are obvious, but not necessarily to you since that thing is your baby. Practice day (I’m Regionals) is not just practice time for your robot/drive team on a real field, but it is also practice for us field people to “get back into the game”. Troubleshooting is a huge part of that game from my point of view.
It also gives me a chance to thank teams for letting me into their world.
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One thing I haven’t seen mentioned that we have had problems with is the main power switch.
Because they are required to be easily accessible, it’s easy to make them overly accessible and damage them.
We also used to have them just die on us after a few competitions for no clear reason, so we started replacing them at champs each year.
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