Re: Banebots RS-775 Case Short
 

Basically our arm was run by the bb775 which shorted out when it hit a certain spot ... Disconnecting communication. At the time we couldn't figure out what was happening we even tried rotating the arm between matches and it worked but we musn't have tested it's full range of motion. So when our auto mode raised the arm we lost comms. After champs we found out that many other teams had the case short problems so we decided we probably won't use banebots for a few years. We also have had problems with banebots before that (2007 I believe) and last year we thought they had been improved so we would try them again.

Having said that the only problem we had with the banebots motors last year was in those last few matches at champs and we went to three competitions before champ.

Re: Banebots RS-775 Case Short
 

J,
What you describe is exactly what will happen with the Crio shorted to frame. It will only occur when the motor is run in one direction. What occurs is that the motor drive signal is opposite polarity to the power input to the Crio. When the motor is turned on in that direction the motor voltage bucks the Crio power supply through the #18 AWG wiring causing the Crio to reboot. The resulting voltage is less than the Crio minimum power input of 19 volts. If the Crio didn't reboot (disabling all outputs) the resultant current path would eventually burn open the #18 wiring. If you had mounted the Crio on an insulated mount, it may have shifted so that the chassis contacted robot frame or something was pushed against the Crio mounting hardware from underneath. When another official I looked into your robot during finals, I did not see anything obvious. I did not turn it over and look at it from underneath. It is also possible that when your arm moved, a wire was pinched in the mechanism and it was not the fault of the motor at all.

Re: Banebots RS-775 Case Short
 

the main reasonwe thought it was the motor was because after we switched it out everything worked. We actually cover the entire bottom of the crio with Velcro and that's how it is attached. It also wasn't the directin but every time it happened the arm was in the same spot

Re: Banebots RS-775 Case Short
 

The motor spins many revolutions as it moves the arm, right? Which means the motor is in it's same spot many times as the arm moves. So it was most likely a wire being pinched by the arm at that spot, or something that moved on the robot as the arm moved

Also the short I found on dissecting a motor, was continuous, it would not change as the motor turned.

Re: Banebots RS-775 Case Short
 

781: How many RS-775 motors were on your robot in total in 2011? What we ultimately found to be the cause of our robot dying on the middle of the field at the Florida Regional was that we had a pair of RS-775s that became case-shorted at a certain spot in their rotation over the course of competition. It was frustratingly hard to reproduce in the pit. Our theory was that when both motors were case shorted at the same time (e.g. bad luck), current was able to flow between them. This added draw lowered the battery's voltage and caused reboots.

Since this thread has been bumped in 2012, it is a good time to ask: Has anyone run into case short issues with the 775 motor purchased this year?

Regardless, thanks to the best motor rules in years, we will be avoiding using RS-775 motors for the foreseeable future.

Re: Banebots RS-775 Case Short
 

Everyone,
I was informed that the manufacturer of last year's motor is no longer supplying those motors to Banebots. Whether there are any still in the supply chain is something for each team to determine. Please check any you plan on using, with an ohmmeter and rotate the shaft during your checks.

Re: Banebots RS-775 Case Short
 

We got our 4 Banebots 775's in last night and 3 out of the 4 have issues.

One motor had about 2M ohms of resistance between the terminals and the case. After running the motor for a about 5 minutes the motor must have cleared whatever debris was causing the reading.

The second motor read 13 ohms between the terminals and the case. We started by "zapping" the debris as was recommended last season to clear case shorts. After zapping the motors we had a 1M ohm resistance between the terminals and the case. We are still working with this motor to clear the debris causing the resistance.

The third motor was the best of them all. It had no case short and the resistance between terminals was good, but only one minor problem...the shaft doesn't spin at all. The motor is completely locked up.

I have a call into Banebots and will post their response to our issues.

I just hope other teams are having better luck with these motors then we are. The 775s are a nice motor when they are working properly.

Re: Banebots RS-775 Case Short
 

Cliff I think you just confirmed for us our total avoidance of the 775 this year. I don't know if I could make it through another failure in a finals match again :cool:

-Brando

Re: Banebots RS-775 Case Short
 

We're kind of ignoring the existence of bb motors this year....

Re: Banebots RS-775 Case Short
 

Seriously??
Completely ignoring BB motors is like not informing your students of the scholarships available to them through FIRST.

Sure, ignore the 775, that I agree with 100%, but the 395, 540 and especially the 550 are great motors in the right application.

Re: Banebots RS-775 Case Short
 

Yeah, seriously.

I don't get the analogy.

Re: Banebots RS-775 Case Short
 

The existence of what? I have never heard of a Banebots 775. I could have sworn they only went up to 550. Oh well, it must have been a mistake from banebots, there's no way they could make a 775.

Yeah, we're staying clear of 775's this year. One that we ordered was so bad, we got every team member around it, told them how terrible it is, and then proceeded to hit it with a hammer. Then it broke, and we danced on the parts.

We're definitely using 550's this year, but we prefer to think that 775's, like 2009, didn't exist. :)

Re: Banebots RS-775 Case Short
 

I'm still waiting to see what they do to make things right before we ban the 775 from our machine. If we do use them on our bot I will be keeping a close eye on them.

We managed to have good luck with the 775 last year. We had a single one on our lift last season that still works just fine after 4 competitions and lots of demonstration time.

Re: Banebots RS-775 Case Short
 

WE have 550 sized motors from FP and AM.

Re: Banebots RS-775 Case Short
 

The set of 775 motors we've gotten this year have performed flawlessly so far, just like every other 775 motor we've gotten. By luck of design we haven't had an electrical connection between the case and any main part of the robot, or the other motor, and everything has been fine.