Motor Controller 29 On Fire

  1. 4 years ago

    During the meeting today, my team was wiring the robot and one of the motor controller 29s quickly overheated, started smoking, then eventually caught on fire, melted the plastic case (I thought the fire was going to stop eventually but our coach thought differently and told me to unplug the wire, and as far as right now, he seems to be correct since the fire only grew bigger before I unplugged the wire).

    Did this ever occurred to any other team? Or is this an isolated case?

    The motor controller 29 is connected to a power expander, along with 3 other motor controller 29s that's connected to other motors. There shouldn't be any issue with the motors / power expander ports since they had been used in competition without failure previously.

    After putting a new motor controller 29 on there, everything work fine. There was no overheating, smoke, or fire.

    What might cause this incident?

    Also, this brings up another question, what action should be taken if a robot started on fire in the duration of a match?

    I'll attach the pictures tomorrow.

  2. Rick TYler

    29 Nov 2011 Teachers/Coaches, Event Partner Redmond, Washington None

    @TRWSHSHLX Also, this brings up another question, what action should be taken if a robot started on fire in the duration of a match?

    If something like this happened during a match at a tournament that I was running, the match would be stopped and the issue would be dealt with. Safety is far more important than any other consideration.

  3. devinc

    29 Nov 2011 Murrieta,CA 569C

    Did you ever have to do any wiring repairs on it? That's all that I could think may have happened.

  4. fretless_kb

    29 Nov 2011 Parker CO 1166

    @TRWSHSHLX Did this ever occurred to any other team? Or is this an isolated case?

    Can't say I've heard of it in Vex competitions, but I saw several failed motor controller 29s in the BEST competition. - No fires thankfully but the controller seemed to overheat and fail.

    Cheers Kb

  5. RampantFang

    29 Nov 2011 Redmond, WA 10B

    Yes, last year this happened to our team. Not quite certain about the exact cause, but we were pushing our 393s pretty hard when one of the motor controller 29s started smoking. After we replaced it, though, all was well... gave us quite a scare though.

    And just some additional information, it was attached to the power expander and we had filled up all the motor ports on the Cortex while using the maximum legal amount of power (6 269s, 4 393s).

    Hope this helps.

  6. I was still in the testing stage of determining where the motors are running the correct direction when the incident happened. So there shouldn't be any power problems.

    Also, I noticed the motor with the motor controller 29 that caught on fire "locked Up" when the controller was overheating itself.

  7. murdomeek

    29 Nov 2011 SFU (Ex 1107B)

    this happened to one of our motor controllers as well
    the motor wasnt working properly and when we touched the motor controller, it was very hot!
    luckily it didnt melt, smoke, or catch on fire
    when we replaced the motor controller, the motor worked and everything was fine.

    at that time, we had a single battery, old pic, crystal/radio,and only 4 motors hooked up

  8. hwilson

    29 Nov 2011 Event Partner Auckland, New Zealand MESS

    We had this happen a few months ago with the Cortex H-Bridge instead of the motor controller. A similar situation occurred in which a smaller fire started, however this was stopped before it got out of hand (and the cortex still works fine now except for the 2 wire ports)

    We believed it was caused by a large draw of current on the H bridges (which are also present on the motor controllers) as is what seemed to start the fire with the large draw of current from 2 heavy duty motors

  9. jgraber

    29 Nov 2011 Dallas Texas metroplex

    I've seen a number of Cortex H bridge burnt out, particularly by rapid forward/backward changes with BEST Large motor loads.
    Sometimes a puff of smoke, but no fires.
    Two years ago, there was (reportedly) a firmware problem that allowed "shoot-through" current on the H-bridge in the Cortex.

    US consumer electrical plastic compounds are generally required to be "self-extinguishing", so removing the heat source by unplugging the battery, pulling the wires, etc, should put out the fire.

    My understanding is that there are thermal breakers in the motors to keep them from over heating, and PTC current limiters supplying a branch of 4-5 H-bridges.
    Worst case condition would seem to be two heavily loaded motors on a Y cable to the one H-bridge, with no other motors in use.

    I don't understand the description "Lock Up", please use other words, eg:
    "motor stops, doesn't respond to commands to move,"
    vs "motor keeps spinning, doesn't respond to commands to stop".

    Other good reporting practices:

    • What is motor application? lifting an arm or mech? drive train?
    • What is motor hook up? Y cables? motor port? expander port? battery type?
    • What serial number, revisions, other markings (if still readable) on mc#29, motors, power expanders, Cortex/Pic?
    • What type of code is driving motors? EasyCv4 Tank4, Custom PID RobotC arm potentiometer feedback?
    • What exact (not just "latest") version of EasyC or RobotC is in use?
  10. I've seen a number of Cortex H bridge burnt out

    I'm surprised to hear that. Aside from the firmware problem that you mentioned, I've seen very few controllers in the cortex burn out.

  11. Eli Osornio

    29 Nov 2011 Moderator, VRC Q&A, OLC Q&A, League Play, Teachers/Coaches, Event Partner, Worlds Q&A, VEX Tech Support, ROBOTC Tech Support, VEX News Greenville, TX

    TRWSHSHLX,

    Personally I have only seen a few motor controllers with damaged H-Bridges, when they overheat they simply smoke a little and sometimes the plastic melts around the H-Bridge... but no fires.
    Also as a general rule of thumb, is recommended to shut off the power supply on any electronic device if it starts smoking or smells like smoke.

    If the Motor Controller 29 is still under the 90-Day Warranty , you should be able to get a replacement by sending an email here: support@VEXrobotics.com

    Sorry about the inconvenience.
    Thanks.

    -Eli

  12. mbrunn

    29 Nov 2011 Syntax_Error 1200

    i had this experience last year. we plugged the controller into our robot directly from the package (as our previous one had broken) and then we saw black smoke come out of it. we unplugged it immediately and the problem appeared to stop.

  13. jgraber

    29 Nov 2011 Dallas Texas metroplex

    @magicode I'm surprised to hear that. Aside from the firmware problem that you mentioned, I've seen very few controllers in the cortex burn out.

    Its easy to burn out H-bridges if you let the motor leads short together.
    So "Don't do that."

    We changed the rules for BEST for 2011 season to

    1. require face-mounted motors. Clamp mounts can fail and let the motors spin which twists the wires, increasing likelyhood of shorts.
    2. require avoid Cortex ports 1,10.

    Now failures will be in #29 motor controler, which is a $10 part, no $150.
    Plus we can keep using Cortex with burnted out ports 1,10....

  14. Count us in to the fun too. Our motor controller lit on fire at a recent local tournament :-)
    It was plugged in to a 269 motor powering half of a 3:1 geared down lift on one end and plugged into the power expander on the other end. We were nudging the lift up and down with the joystick, and I saw smoke coming from where the motor controller was bundled with some other wires underneath some anti-slip mat, and I turned off the robot and unplugged stuff as quick as I could. Sure enough, there was a big hole melted through the side of the motor controller, and it was right over a black chip about 1/16" square or so.
    We had 10 motors plugged in (4 393's and 6 269's , but two of the 269's weren't being told to move by the software). The Power Expander had four motors on it including the burnt out controller and one non-active 269.

  15. conradev

    28 Mar 2012 United States 2616B

    This happened to me as well. I turned on the robot, and began to drive it, and I noticed one side of the drive was working intermittently. I then noticed smoke coming from the robot, and immediately yanked the battery out. Turns out the motor controller for one of our high strength motors on our chained drive had burned out. It melted two holes in the plastic.

  16. devinc

    28 Mar 2012 Murrieta,CA 569C

    We have had 2 in our club catch on fire and a 3rd almost went up until we unplugged it.

  17. diegohuyke

    29 Mar 2012 San Juan, Puerto Rico 2243B

    @devinc We have had 2 in our club catch on fire and a 3rd almost went up until we unplugged it.

    I really don't know what it is you guys do to your motors for this occur. This has never happened to me.

  18. devinc

    29 Mar 2012 Murrieta,CA 569C

    The second one we believe it may have been caused by a pinched wire on the teams lift. We are still unsure of what caused the 1st fire.

  19. 1412A

    29 Mar 2012 Galveston,TX 2587z

    i was at Nationals okay NATIONALS!! and my cortex caught on fire not once.. not twice.. but three times and my teammate controller caught on fire too

  20. devinc

    29 Mar 2012 Murrieta,CA 569C

    @1412A i was at Nationals okay NATIONALS!! and my cortex caught on fire not once.. not twice.. but three times and my teammate controller caught on fire too

    Your cortex did? As in the "brain"? or a motor controller?

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