Possible FMS problems.

[G_rupp]

Originally Posted by Canon reeves

There has been a lot of mention of a frame short, could we test for this by testing the frame with a multimeter? we did that and it wasn't conducting anything, we checked the battery and all the connections to the pd board with it and got a consistent 12.5 volts. After the testing when the robot drove forward and shut off, we tried turning it back on, it took a few times but after it did turn back on we had no connection whatsoever, we tried rebooting, reset the radio, re-deployed code, exited the driver station then came back in. Under the diagnostic page on the driver station there was no light for the bridge, but there was a red light beside "robot". I've been trying to get it to shut off by shaking and dropping, and it still isn't rebooting like it is when I drive it. Is there anything else in the driver station we can use to diagnose the problem? Thank you guys so much, the team really appreciate's your help and GP!

Are you using any of the DIO connectors? I have seen instances where the +5V wire from the PWM cable will short intermittently to ground. This is normally seen when the White and Black wires are used for a Limit switch. The RED wire is cut and left hanging instead of being cut back and taped. The end of the wire will come in contact with the Black wire causing the 5VDC in the Digital Sidecar to turn off.

[Al Skierkiewicz]

Canon,
You can use a multimeter to check for continuity between the frame and each output terminal of every speed controller with the power off. You will likely find a short on one of them if this is related only to driving. It is normal for motors to have some resistance (2k-10k) to frame as the brush dust builds up inside. It is not normal to have a reading under 100 ohms. I am thinking you are going to find a shorted wire(s) in one of those outputs. There are two things that are known shutdown issues for the cRio. That is the cRio tied to the frame with another path somewhere, or a simple short on the output of a controller. If you are using Jags, the short should show up as a fault on the Jag that is affected even without motion I think.

[Canon reeves]

Originally Posted by Al Skierkiewicz

Canon,
You can use a multimeter to check for continuity between the frame and each output terminal of every speed controller with the power off. You will likely find a short on one of them if this is related only to driving. It is normal for motors to have some resistance (2k-10k) to frame as the brush dust builds up inside. It is not normal to have a reading under 100 ohms. I am thinking you are going to find a shorted wire(s) in one of those outputs. There are two things that are known shutdown issues for the cRio. That is the cRio tied to the frame with another path somewhere, or a simple short on the output of a controller. If you are using Jags, the short should show up as a fault on the Jag that is affected even without motion I think.

So the output from the vector to the CIM motors? we are running 4 CIM motors as well. So we need to put the hot wire to the output and the ground on the multimeter to the frame and if we get a reading of 100 ohms we need to replace the motor controller? or is it the wire from the PD board to the Vector? Thank you so much for your help!

[Al Skierkiewicz]

Canon,
You need to check each Victor output screw to robot frame. The fans on the Victors are legal to be wired to the input terminals of the Victor to which they are mounted. They do not need to go back to the PD. Since you can only put one wire into a WAGO terminal, and it must be #18 or larger, wiring the fans to the PD is not practical. It is possible for metalic debris to enter a Victor in such a fashion that it will show a short in only one direction. However, that usually shows up in a very spectacular fashion.

[Canon reeves]

I tested the output screws on each side, on one side I got .3 resistance, on the other .4, is this ok? I am also getting a 12.5 volt reading on the input to the victors. I'm not sure how to test to the frame. I connected one part to the screw and the other to the frame and get zero everytime.

[Al Skierkiewicz]

Canon,
You put one meter probe on each of the output screws and one on a metallic part of the frame with the power off. You should read something higher than 2000 ohms. If you are reading the same value (~zero ohms) as when you touch the two probes together, then you have something shorted to the frame.

[Canon reeves]

Ok, thank you for sharing you wisdom with us! I am relatively new to FRC and wiring in general, so if these questions seem very basic please bear with me. Why do we want to have 2000+ ohms from the frame to the vector output? Why does the short happen when it isn't running through the frame? You do mean the drivetrain frame correct? here is the link to the multimeter we have, https://pioneers.berkeley.edu/wiki/H...e_a_Multimeter from what you have said we do need to set it to the ohmmeter setting correct? So when we discover the short, what would be the proper steps to fix the problem and ensure it doesn't happen again?

[RobotKnight2014]

Originally Posted by Richard Wallace

Our team is in Michigan -- the issue I mentioned occurred at the Southfield District in Week 1. The intermittent chassis short was caused by some wiring that had previously provided power to a custom circuit (LED string), which had been removed after it was damaged during a practice match.

What was the issue seen at Utah?

There was a team at Utah who lost communication sporadically during teleop, the mentor who I saw talking to the FTA about it looked like your profile picture. I also thought there was a team called the average Joes there, must have been mistaken.

[Al Skierkiewicz]

Canon,
The short to the frame is an issue due to wiring errors, bare wire or lack of insulation. The 2000 ohms to frame is a normal condition with CIM motors that have been used for a while. The carbon dust worn from the brushes collects on the end bell of the motor inside and causes some leakage currents. When they get below 2000 ohms I start to worry. I speak to the drive train because you seemed to indicate the issue occurs only when driving. On the meter you show, if you set it to the position just below ohms, it will beep when you have a low resistance connection. If you find anything that beeps when one probe is connected to the frame, you have a serious problem.

[Canon reeves]

I do believe we located 1/2 of the problem. I did the tests with the multimeter and it was fine, I then turned on the robot and began checking the converter for the radio, when I did I heard this high pitched whining noise, and I noticed this happened when I tugged on the Wago for the converter on the PD board. I could cause the entire robot to briefly shut off by slightly tugging on the connector. When I checked the connector it was charred black around the wire, and when I pulled the wire out it was as if all of the individual strands had been saughtered together. I replaced the wago and pulled on it and it didn't shut off. We then tried to run the robot, but got no communication or code, but it did when we tethered it to the clamshell. I then drove back and forth and when I went forward then jerked back the entire robot shut off, the main breaker had been tripped. I pushed the red button on it then tried to turn it back on and it wouldn't turn on then I had to leave. It did this as well yesterday, and ever since then we hadn't gotten any communication or code unless we are tethered? Any probable causes?

[geomapguy]

Originally Posted by Canon reeves

I do believe we located 1/2 of the problem. I did the tests with the multimeter and it was fine, I then turned on the robot and began checking the converter for the radio, when I did I heard this high pitched whining noise, and I noticed this happened when I tugged on the Wago for the converter on the PD board. I could cause the entire robot to briefly shut off by slightly tugging on the connector. When I checked the connector it was charred black around the wire, and when I pulled the wire out it was as if all of the individual strands had been saughtered together. I replaced the wago and pulled on it and it didn't shut off. We then tried to run the robot, but got no communication or code, but it did when we tethered it to the clamshell. I then drove back and forth and when I went forward then jerked back the entire robot shut off, the main breaker had been tripped. I pushed the red button on it then tried to turn it back on and it wouldn't turn on then I had to leave. It did this as well yesterday, and ever since then we hadn't gotten any communication or code unless we are tethered? Any probable causes?

Has the radio been reset since competition??

[Canon reeves]

Originally Posted by geomapguy

Has the radio been reset since competition??

Yes, I reset it and made sure it as in ap 2.

[Al Skierkiewicz]

Canon,
What you describe is typical when the wire strands come out of the WAGO and contact the other polarity. What you are doing is shorting out the power supply on the PD. I would check that you have wired the WAGO correctly when you replaced it. If that is not an issue, then you may have killed the PD power supply. The only repair is a replacement.