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Thread: T4 killing board

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  1. #1
    Junior Member
    Join Date
    Feb 2020
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    17

    T4 killing board

    I built this little board to control a little robot with a T4. It's mainly a puzzle of various pre-made modules.

    It has one big switching voltage regulator to provide power to 12 tiny servos, 5.5V. That voltage (should) never get in contact with the Teensy.

    It has one small switching voltage regulator that provides 5V to VIN to the Teensy and feeds a LDO to make 3.3V that powers a NRF24 radio module and an MPU6050 module. I have cut VIN from the USB port power.

    The thing works fine for a few minutes but eventually kills the teensy. The first Teensy it killed ended up with a shorted 3V rail, stone dead. And the 2nd it killed had the USB stop working. That teensy still works and it is possible to make it load the built in blink program. It still runs perfectly fine, as seen in the attached picture.

    I have measured all I can with the partially working Teensy in place. Scoped all signals. Hooked up an old Arduino UNO to it to test the radio and MPU (those modules are 5V compatible). Everything looks fine and works as intended. No 5V signals I can see reach the Teensy.

    The PWM pins for the servos are connected straight into the Teensy, I should add some series resistors to be safe. But all testing have been done without servos so far. Other I/O are 4 pins with 10k pull up resistors (to teesy 3.3V) for attaching some pressure sensitive resistors.


    Anyone have ideas for what might be wrong? I am out of ideas, and soon out of cash to buy new Teensies
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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