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Thread: can you power a load from the 5V pin of the teensy 4.0 such as a sensor

  1. #1

    can you power a load from the 5V pin of the teensy 4.0 such as a sensor

    the above question sounds foolish because what else is the 5V pin for? but if i power a sensor's VCC and ground with 5V, its communication pins (trigger and echo) with output greater than 3.3V back to the teensy's GPIO pins, (i measured this from a voltmeter) This would go against the rule that you cannot supply greater than 3.3V back to teensy pins (except for Vin and Usb port)

    This is correct right?

    I did this and found smoke coming from somewhere. I think it was the sensor which I accidentally reversed the ground and VCC pins on, but it could also be from the teensy which was receiving greater than 3.3V in to its pin 11 and 12. i quickly unplugged everything but 5V power vs 3.3V power is something I wanted to clear up.

  2. #2
    Senior Member+ defragster's Avatar
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    The 5V is there to use - but is a valid concern to keep in mind : if it powers something sharing pins with a non 5V tolerant pin, will it ever put more than 3.3V to that pin.

    That is device dependent - some just need 5V to convert and run at 3.3V without loading the Teensy 3.3V. Others take 5V and manage 3.3V levels perhaps, while some take 5V that could be a problem as they will present 5V on their shared pins.

  3. #3
    that is good confirmation thanks. so the smoke i am assuming was probably from the reverse polarity on the sensor. i will try to test the pins of my teensy to make sure they are not burned out. and i suppose i will have to use a birdirectional logic converter if the >3.3V is the only thing that the load will put into the shared pins

  4. #4
    Senior Member+ defragster's Avatar
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    This pin test sketch may be useful : pjrc.com/threads/66771-MicroMod-Beta-Testing

    Even has some notes on use posted there.

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