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Thread: Teensy 3.6 and 5v tolerance.

  1. #1
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    Teensy 3.6 and 5v tolerance.

    Hi gang, I've just joined and would appreciate some advice.

    I'm not new to electronics (although my experiences are 30+ years old) but I've just started tinkering with Arduino. I have a few sketches under my belt by now, but I needed something smaller than an Uno for a prop build, and a Nano just won't store the sketch (103% - dammit!).

    So I've come across and invested in a Teensy 3.6 to do the job. There will be three external boards, all of which are 5v logic and powered. Assuming that I have to run these off a separate buck converter due to the Teensy not having it's own 5v (why is that?), I'm asking the experts here:

    Is the Teensy safely 5v tolerant on it's input pins, or am I going to have to use resistors on anything coming in from my external boards?

    I don't really want to blow up the Teensy on my first project, not at these prices.

  2. #2
    Senior Member+ MichaelMeissner's Avatar
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    Quote Originally Posted by Beachcomber_Bob View Post
    Hi gang, I've just joined and would appreciate some advice.

    I'm not new to electronics (although my experiences are 30+ years old) but I've just started tinkering with Arduino. I have a few sketches under my belt by now, but I needed something smaller than an Uno for a prop build, and a Nano just won't store the sketch (103% - dammit!).

    So I've come across and invested in a Teensy 3.6 to do the job. There will be three external boards, all of which are 5v logic and powered. Assuming that I have to run these off a separate buck converter due to the Teensy not having it's own 5v (why is that?), I'm asking the experts here:

    Is the Teensy safely 5v tolerant on it's input pins, or am I going to have to use resistors on anything coming in from my external boards?

    I don't really want to blow up the Teensy on my first project, not at these prices.
    As it says on the back of the Teensy 3.6 pinout card that is supposed to come with your Teensy 3.6, the Teensy 3.6 is NOT 5v tolerant. If any input pin gets 5v, it can risk damaging the Teensy.

    If you need 5v tolerance for digital inputs, only the Teensy 3.2 and 3.5 are 5v tolerant. Note, even though they are 5v tolerant on digital pins, if you feed 5v to one of the pins that can be used either for analog reads or digital read/writes (i.e. A0..A9 and A12..A20) and you do analog reads, the Teensy will clamp voltages over 3.3v as being 3.3v.

    The VIN pin at the bottom left of the Teensy 3.6 (with the Teensy facing up and the USB port on the bottom) can give you the 5v from the USB port. Or if the USB port isn't connected, and you apply 5v power to it, it will power the Teensy. Normally you can draw about 500mA from VIN (assuming your USB power produces more than 500mA of power). There is a solder jumper underneath the teensy that you can disconnect, so that VIN and VUSB are not connected. If you do that, you need to feed power to VIN (possibly by having transistors so that if both power sources are used, only one is fed to the Teensy)..

    Note, you can feed the Teensy 3.6 VIN pin 3.6v to 6v.

  3. #3
    Senior Member PaulStoffregen's Avatar
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    Teensy 3.6 is not 5V tolerant. Applying more than 3.6V to any digital or analog pin risks damage.

    VIN & VUSB (power) is the only place on Teensy 3.6 which can handle 5V.

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    Quote Originally Posted by PaulStoffregen View Post
    Teensy 3.6 is not 5V tolerant. Applying more than 3.6V to any digital or analog pin risks damage.

    VIN & VUSB (power) is the only place on Teensy 3.6 which can handle 5V.
    Thanks for the advice. I guess I'll tread carefully for the first few projects.

    It's really reassuring that I didn't get flamed on here for a really noob question.

  5. #5
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    Thanks for the comprehensive answer. I appreciate any information I can get. I've been building lipo powered props for some years now, and have always sought the lowest voltage solutions to keep me in the 3.7v scope of a single lipo. Looks like the Teensy can now deliver microprocessing that I've been doing up until now with discreet circuits (told you my electronics was 30+ years out of date!)

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    Senior Member+ MichaelMeissner's Avatar
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    Quote Originally Posted by Beachcomber_Bob View Post
    Thanks for the comprehensive answer. I appreciate any information I can get. I've been building lipo powered props for some years now, and have always sought the lowest voltage solutions to keep me in the 3.7v scope of a single lipo. Looks like the Teensy can now deliver microprocessing that I've been doing up until now with discreet circuits (told you my electronics was 30+ years out of date!)
    For lipo batteries and having the batteries recharge when USB power is fed to the Teensy, I tend to like the Adafruit Teensy -> Feather adapter because the JST plug is more solid for connection and disconnecting the battery than the noraml chargers where the plug is just soldered on. However with the Teensy 3.5/3.6/4.1 being longer, you need to make some adaptions. One nice thing is you don't have disconnect VIN from VUSB:


    There is also this board that is made to attach directly under or over the Teensy that provides lipo charging. With this board, you do have to cut the solder jumper. Adafruit also has a charger that is easy to hook up:

  7. #7
    Senior Member+ defragster's Avatar
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    Quote Originally Posted by MichaelMeissner View Post
    For lipo batteries and having the batteries recharge when USB power is fed to the Teensy, I tend to like the Adafruit Teensy -> Feather adapter because the JST plug is more solid for connection and disconnecting the battery than the noraml chargers where the plug is just soldered on. However with the Teensy 3.5/3.6/4.1 being longer, you need to make some adaptions. One nice thing is you don't have disconnect VIN from VUSB:

    ...
    Nice Wiki info on the AdaF Teensy Feather adapter! Just got a pair of those on the 'Feather discount' Black Friday. Was not looking forward to verifying function on 4.0 and 4.1 - nice to see it spelled out.

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