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Thread: Voltage regulator on Teensy 3.5 and VESC simultaneously failed

  1. #1
    Junior Member
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    Nov 2019
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    Voltage regulator on Teensy 3.5 and VESC simultaneously failed

    Have recently been using the Teensy 3.5 (such a great little board) to control a fairly complex robotic vehicle. Some of the hardware in the vehicle includes 3x VESC's and motors, 2x Dynamixel servos, RC receiver, relays and other bits and bobs. Have been integrating the hardware bit by bit, ensuring that everything works correctly before adding the next piece of hardware. My last successful test included all of the hardware elements working together and everything appeared to be functioning fine.
    So fast forward a couple of hours after doing some cable management, fastening down lids on the teensy's shielded enclosure and mounting electronics to vehicle chassis, and... the vehicle won't startup.
    After hours of troubleshooting I have identified the following issues:
    - Voltage regulator on teensy has failed. (Board won't turn on and regulator gets burning hot when teensy is plugged in. Also 3.3v pin appears to be shorted to GND)
    - Voltage regulator on one of the VESC's has also failed. (Has the exact same symptoms as above.)

    So the crux of my question is: Are there any common causes for the voltage regulators on multiple devices to fail at once?
    Has anyone had something similar happen?

    Heres some more info about my setup:
    - Teensy and VESC's are all connected over UART
    - Vehicle is powered by 12cell LiPo and has a dual output PSU (5v and 12v) to power teensy, servos and relays
    - Everything was initially working prior to failure.
    - The VESC which failed was connected to a long power cable (approx 600mm to battery)
    - Nothing is visibly damaged (have looked closely at teensy and Vesc for burn marks etc)
    - I accidentally connected 5v to the analog only pins on the teensy a few days before the failure occurred
    - The grounds of the two power supply outputs are internally tied together. (After the failure I noticed that I had been channeling current from the 5v output of the PSU through the GND cable of the 12v output. Not sure if this may have caused the issue?)
    - Happy to post pics of hardware/wiring if needed

    I'm keen to hear any of your thoughts and thanks in advance!

  2. #2
    Junior Member
    Join Date
    Apr 2021
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    Quote Originally Posted by davey View Post
    Have recently been using the Teensy 3.5 (such a great little board) to control a fairly complex robotic vehicle. Some of the hardware in the vehicle includes 3x VESC's and motors, 2x Dynamixel servos, RC receiver, relays and other bits and bobs. Have been integrating the hardware bit by bit, ensuring that everything works correctly before adding the next piece of hardware. My last successful test included all of the hardware elements working together and everything appeared to be functioning fine.
    So fast forward a couple of hours after doing some cable management, fastening down lids on the teensy's shielded enclosure and mounting electronics to vehicle chassis, and... the vehicle won't startup.
    After hours of troubleshooting I have identified the following issues:
    - Voltage regulator on teensy has failed. (Board won't turn on and regulator gets burning hot when teensy is plugged in. Also 3.3v pin appears to be shorted to GND)
    - Voltage regulator on one of the VESC's has also failed. (Has the exact same symptoms as above.)

    So the crux of my question is: Are there any common causes for the voltage regulators on multiple devices to fail at once?
    Has anyone had something similar happen?

    Heres some more info about my setup:
    - Teensy and VESC's are all connected over UART
    - Vehicle is powered by 12cell LiPo and has a dual output PSU (5v and 12v) to power teensy, servos and relays
    - Everything was initially working prior to failure.
    - The VESC which failed was connected to a long power cable (approx 600mm to battery)
    - Nothing is visibly damaged (have looked closely at teensy and Vesc for burn marks etc)
    - I accidentally connected 5v to the analog only pins on the teensy a few days before the failure occurred
    - The grounds of the two power supply outputs are internally tied together. (After the failure I noticed that I had been channeling current from the 5v output of the PSU through the GND cable of the 12v output. Not sure if this may have caused the issue?)
    - Happy to post pics of hardware/wiring if needed

    I'm keen to hear any of your thoughts and thanks in advance!
    Hello! I keep having the same issue with several teensy boards. Please let me know if you sorted out the cause of the problem since then!

  3. #3
    Senior Member
    Join Date
    Jul 2020
    Posts
    977
    Quote Originally Posted by davey View Post
    So the crux of my question is: Are there any common causes for the voltage regulators on multiple devices to fail at once?
    Has anyone had something similar happen?

    ...


    - The VESC which failed was connected to a long power cable (approx 600mm to battery)
    This immediately suggests rail bounce (inductance of the wiring causing a spike or ringing on sudden current changes)

    There should be decoupling at both ends of a power cable to quell this tendancy - if this is lacking it might
    suggest a failure mechanism.
    - Vehicle is powered by 12cell LiPo and has a dual output PSU (5v and 12v) to power teensy, servos and relays
    Thats 40 to 50V, which is higher than many power supplies can handle - you haven't mentioned what the supplies are.

    If there's a mechanical switch at those voltages there will be arcing and some very high dV/dt values when the
    switch closes, which can capacitively couple to other signals if run alongside them. The inrush current to charge decoupling
    capacitors will also be very high from such a string of LiPo's - as high as 100's of amps is easily possible, which is bad news
    for several reasons including stressing the capacitors, mechanical shock on the conductors, and welding switch contacts
    together.

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