Our team uses 9 motors and we face a problem which shuts down the robot every time we run it.
We figured that the high number of motors consumption of voltage decreases the voltage of the RoboRio to under 10V which apparently shuts the robots voltage.
Any tips on how to solve this problem?
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How does it shut down the robot? Does the robot’s main breaker (the main on/off switch) pop (Turn Off)? That switch is also a 120 amp circuit breaker.
I believe what’s he referring to is that the roboRIO is browning out. Specifically described on page 7 of this pdf.
As for how to fix it, likely at least 4 (probably 6?) of those motors are drive train related, you can reduce the load that those motors are under when your turning by adding a or increasing your center wheel drop, or by switching from traction to something lower traction (Omni-wheels maybe?) on the outer wheels.
Describing which motors you are using and what they are doing would probably help others here help you more.
We have 4 CIM motors for the drivetrain(west coast drive), 4 AM-775, two in a gearbox with 1:45 ratio for a lifring mechanism , two with 1:30 gear ratio each for a cube intake mechanism, and a snowblower motor for another lifter
I may have not explained the situation properly.
each time we drive our robt and/or activate our mechanisems,the voltage drops to under 10v (which we figure) collapses the RoboRio and leads to a communication breakdown. the ampbraker does not pop.
we really need help!
If you have all of those motors geared correctly, that really should not brown out your roborio. Especially since you’re probably not using all of those at once. If you post the gear ratios and expected loads you have for each motor, we can help you figure out if one is drawing too much current. Also check to make sure that all of your wiring is tight (especially the wires between your battery and PDP). If you can wiggle the connector, it’s too loose. Also, feel free to PM me and I can send you my phone number if you would rather talk instead of writing online.
Make sure one of the motors isn’t wired backwards and fighting the others.
Remove all the PDP Breakers except one. Test that motor. Move the breaker to the next motor. Test that. Test each motor independently. This is easiest to do in the Shuffboard Live window under TEST mode on the driver station.
Make sure each motor is spinning in the right direction.
Can you confirm that the Roborio is wired to blue VBatt/Controller side on the PDP and not on the green/PCM/VRM side? The green side is not protected against voltage drops.
We’ve had far more motors than that on a robot before and we didn’t have any voltage issues until the end of a heavily defensive match. My guess is a failing electrical component.
Another thing that isn’t explored: how many motors are running at one time, and how much current are they drawing? If your strategy requires running a 6-motor drive while also running a really heavy worm-driven arm, maybe that’s a problem.
That can be solved by going with a numerically higher gear (or sprocket, or pulley) reduction, which will allow the motor to work at a higher speed (which means less current draw) at the expense of time to accomplish the task.
I’d check those other things above first though. Hope you shake it out!
FYI, neither is the blue side. The only difference between the blue and green sides is the blue side is on a 10A breaker and the green side is on a 20A breaker. The only regulated voltage in the control system comes from the VRM.
Another way to find the culprit is to put the robot on a block then run a few motors for 5 seconds. Which one(s) gets noticeably hotter?
If your battery is properly charged that energy is going somewhere.
A hot motor won’t tell you what exactly is wrong, but it does narrow lens.
It’s possible I’m wrong. I was trouble shooting a brownout issue on our robot at competition. I had noticed that the Roborio was on the wrong side and the only change we made was to move the RoboRio from the green to blue side. I was standing next to one of the control systems people and he said that might be our issue. I had mentioned that the documentation doesn’t say either side is regulated and that it shouldn’t matter. He said let me find out and came back and said it was.
We had already eliminated loose wiring, poor connection and the radio as possible issues. In the end we never had an issue with the Roborio browning again.
Try disconnecting the CAN between the PDP and roboRIO. You will still get the battery voltage readout on the driver station, which leads me to believe that the roboRIO has some method of measuring the VIN internally. I’d suspect that this means that the PDP doesn’t regulate voltage to the RIO. Also look at the PDP User Guide. On page 6 it says that the output on the VRM, PCM, and Controller Weidmullers are all VBat. None are 12V regulated or similar.
Anyways I second the idea to test motors individually and confirm that they spin the same way. We had this issue earlier on in the season with Talon SRXs on the drive. If you are using Talon SRX with the new Phoenix library, where you have 1 master and 1 follower (slave) per side, make sure you are inverting BOTH the master and the follower on the inverted side. I just had the master inverted, but the slave stayed uninverted so it would instantly brownout the battery as the two motors fought each other.
None of the PDP outputs are boosted. The boosting is inside the roboRIO.
Another possibility is that there is more electrical resistance than there should be in the circuits with the big 6-gauge wire. Connections being tight is necessary but not sufficient. Think about the difference between a shiny penny coin and a darker, oxidized one. Oxidized copper doesn’t conduct electricity as well as clean, shiny copper.
Choose a good, charged battery - do you have a AM Battery Beak or another tester? Checking the battery voltage, under no load, with a multimeter isn’t good enough because the multimeter draws so little current.
Take the connections off the battery and clean the battery lugs with sandpaper. Do the same with the lugs which bolt to the battery, and only then reattach them to the battery. Make sure the fasteners are good and tight.
Any chance you are using the copper lugs like shown here:https://www.chiefdelphi.com/forums/showpost.php?p=1583148&postcount=7 (Thanks to Al from 111 WildStang), as connectors to the battery lugs? One of my teams had only these. I asked them to take the #6 cable out and sandpaper its end and ALL the copper areas that contact the cable or battery lugs. Put the cleaned end of the #6 wire into the clamp and tighten it as TIGHT as you can get. Before attaching to the battery, we used a propane torch and electrical solder to solder the cable+clamp assembly together to become one piece. It wasn’t pretty but it was going to conduct really well and never get loose. Tape or heat-shrink over the soldered assembly and don’t worry about how it looks. Attach it to the battery’s cleaned lugs and tighten its fasteners well. Insulate then too.
Sandpaper the lugs of the #6 cable that go into the PD board clamps AND the ones that go into the main breaker too. Tighten everything tight.
Sandpaper the ends of the wires that go from the speed controllers into the PD Wago connectors. Clean the other ends if they aren’t integrated into their speed controllers. Make sure the wires going into your crimps are clean and shiny first before you crimp.
A general rule: we want all electrical connections to be good and conduct well, but the bigger the wire is, the more critical its connection, because it carries more current.
Ohm’s law, paraphrased: a tiny electrical resistance times a lot of current turns into a bigger voltage drop. The power lost is power that never makes it to our motors, sensors, and roboRIO.
Have you reviewed the driver station logs when this occurs? It will allow you to see the actual battery voltage, as 10 volts is too high for a brownout to be occurring. It will also allow you to see the current draw of each motor/speed controller connected to the PDP and see what the heavy hitters are.
The roboRIO is labeled (right next to its power connector) as accepting 7-16 VDC, so if the logfiles show the robot voltage as >= 7 it’s probably not dropping out.