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Thread: Powering confusion / sanity check

  1. #1
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    Powering confusion / sanity check

    I need a quick sanity check on powering my Teensy 3.1's and using the Teensy Proto Boards.* I have read the future wiki linked thread 5x, and I am still confused.

    I have a second board with a 24V supply, stepper motor drivers, and a DC-DC converter that outputs 5V (used for opto's & other 5V items). I'm using the 5V from that to power the Teensy and TFT (ILI9341 from Teensy's 3V3). Because the incoming 5V is lower than the 5.2V minimum input for the voltage regulator on the proto board, I want bypass the regulator and route the incoming 5V directly into the 5V (Arduino) header on the proto board, which goes via a trace and jumper, to Vin on the Teensy.

    1) Is there a conflict in having two power sources, e.g. only while I'm programming the Teensy, the 5V feeding Vin and USB? Once programming is done, the 5V into Vin would be the only source.

    2) When *should* I cut the Vin--USB trace on the Teensy? Does that just remove the 5V coming in through the USB cable when connected? I am a bit foggy on the scenarios.

    Thanks,

    --Jon



    * Note that there is an error only on the top of the board drawing that has "5V" and "VIN" mixed up. The silkscreen in the photos of the boards shows VIN and 5V correctly.
    Last edited by epicycloid; 09-14-2015 at 07:17 PM.

  2. #2
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    With no replies I have muddled through this a bit. A while ago I made, and have been using the power-clipped USB cable from the How-To Tips (Option #2) of Using External Power and USB, and will continue with that approach until I read something that more explicitly helps explain other options with Teensy 3.x's.

    Although, I think I have this somewhat figured out, it would be really helpful for us relative beginners if someone could just write an explanatory update for the outdated link above. That hasn't been updated since Teensy 2 and it would be useful to have something specific to the current Teensy 3.x's, the different pads and different voltages.

    Some description of the equivalent diode options and installation would be really useful. E.g. is the hand-solderable Schottky surface mount diode suggested by HWGuy, applicable directly on the pads of the 3.x, with another (1N5817? or axial Schottky?) diode for external power too?

    --Jon

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