Odd Electrical Problems at The Championship

[Gocho]

I am aware of some of the teams at the championship (including my own) are experiencing extremely odd electrical failures/controller flashes. My team came and after making the necessary repairs after damage from our regional, we were pretty confident that we had a functioning robot and would be able to make and play our matches today. After the first of our rounds this morning (Friday) we started experiencing a problem that made our voltage on our robot drop from around the normal 12 operation volts to between 4-8. This caused our robot in two consecutive matches to go around about 3/4 of the track and then lose power to our drive base so that when we tried to drive, even though when idle it showed a steady 12V, it would drop and we could not move. We saw from the OI that this in turn made the main battery power to the RC stop. The first logical choice was the battery. We checked and retightened every one and made sure nothing was lose after the first round that it happened in. After the problem insisted in the second around we started to look deeper in the electronics. I am going to be brief here and say that we basically either bypassed/changed every single componet in the system from the 120A breaker to the RC and the 6 gauge wire that ran through our main input part of the circuit. Over the 3.5 hours that this problem persisted we had most of the mentors and some team members from Team #1511 Rolling Thunder in our pit helping us look at the problem and trying to find a solution followed by mentors and team members from team #16 Bomb Squad and Team #111 Wildstang. With almost 15 extra people about 4 people deep crowed around our pit trying to help and use their brain power we still could not find an issue in the electrical system. Finally from with the help of the Lead Inspector we pinpointed the problem to not in the electrical system which we had just torn apart and rebuild in the past 3 hours but in our drivetrain. The chain inside of the boxed aluminum that we used to chain together our six wheel drivetrain had come loose and was throwing a link in the chain when we made sharp adjustments (ei. turning or speeding up fast or stopping fast). this in turn was causing our drive system that is powered by two CIM Dewalts on either side to stall and pull an amount of current that the whole electrical system was not near capable of handling thus making the voltage drop. So for 3 hours we worked trying to find and electrical problem only to find that all the trouble was mechanical. Just another day at the FIRST Robotics Championship.

I would like to thank all the teams that helped us or offered to help as i know i did not mention all of them. I would especially like to thank all of the team members/mentors from 1511, 16, 111 that helped with the problem and thought the thing through with us it made the pain so much better than it could have been.

We are now in the process of taking the chain in the boxes off as our drivetrain and move without them and we are hoping that that was the only problem. I will post an update tomorrow either way. Hopefully we can get it fixed and have fun in our other rounds. I believe we also have a picture of all the people standing in the pits which i will post tomorrow also.

[Chaos in a Can]

We had a similar problem. Our datalogger stopped working, so we couldn't check the voltage during a match, but during our last two matches, our robot would suddenly stop responding to the drive controls.
It looked like it was trying to move, but didn't have the power to move.
We're going to see if we can reproduce this behavior once we get back home, (we were going to test the bot on the practice field after a match where this happened, but it was being taken down) so we have no idea what is causing the problem.

Also, our robot seemed quite sluggish on the competition field compared to when we ran it on the practice field and barely comparable to when we built it. The problem may only appear after the robot runs for a while, which may explain why it worked fine on the practice field, but the problem almost seems to be related to the competition field.

We'll definitely for voltage drops and chain problems.

[RyanN]

We had similar problems as well... When we would drive from forward to reverse real quickly, it would reset the controller, even though the backup battery was charged and present. I checked all electrical connections, and everything seemed good, but it kept on doing it. We never did solve that problem, we just avoided the problem.

Another issue we had was in our last match, our right drive was not running at full performance, and we found that one of the motor leads going to the victor was lose.

Our IR board never did work in Atlanta. We couldn't get it to work very well even with our remote only an inch or so from the sensor, however it would sometime work, but never in a match...

Oh well... Thanks for a good year FIRST.

[JesseK]

Our "electrical" problem turned out to be a mechanical problem as well. We had replaced the AM SuperShifter shroud with nylon spacers and lexan. We also attached our chain tensioners to the bolts that bolt together the top of the supershifter. As we tightened the bolts for the tensioners, the top of the transmission would decrease its gap between the plates. It turns out the gap at the top of the transmission was a whole 1/32" too small, causing the main gear the CIMs turn to bind up. We loosened the tensioner bolts on either side and immediately noticed a 3-4fps increase and much longer battery life. We did all of this right before our 2nd match of the day on Friday and nearly gave 1114 a heart attack by almost missing our match

Lessons learned: when trimming off weight from your drive train, some things just simply cannot be replaced.

Surprisingly enough, the AM hubs and flat AM aluminum sprockets that served as our main drive sprockets off the transmissions came away from 3 competitions completely unharmed!