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Thread: Design Problem?

  1. #1

    Design Problem?

    I seem to have just messed up my second Teensy. I can no longer upload to it. This one is a Teensy 3.2. My order was "211407" on 9/29/2015.

    I had asked before whether or not I was placing too much load on the board. I am unable to attach a copy of the documentation for my project. It is a lengthy word document. You can get a copy off my github https://github.com/mboroff/Repeater_Controller.git.

    Page 7 has the wiring diagram. The construction section is a step by step following of how I put it together. Figure 15 on page 14 is missing. I forgot to make it. But simply the Teensy 3.2 is sitting on 14 pin female headers solder to the board.

    Adafruit is suppose to replace the first Teensy 3.1, if they get one in (I have told them they have been replaced but they don't list the 3.2 yet). You advised me on a previous post on this one getting very hot when I plug in the usb cable.

    The Teensy 3.2 for this issue does not get hot just a little warm. It just won't upload.

    So my question is do I have a design flaw in my design that you can determine? I have used this design with an ATMEG2560 and not experienced any problems with voltages or heat.

    Thanks for looking.

  2. #2
    The only potential issue I can see (from a very quick scan of your doc) is the lack of any over-voltage protection for the Teensy; the 3.1 and 3.2 are 3.3 volt compatible (man, that looks confusing). As I understand it, they'll tolerate up to 5V on their I/O pins but you have to have a series resistor in there to limit any potential current.

    And the one thing in your circuit that could cause a problem is the servo - I haven't used RC servos enough to be sure of this, but I suspect they may introduce voltage spikes on the power lines (being motors, and all that). Could be that a chunky capacitor and or a diode or two sprinkled in the right places may help... anyone? Anyone? Bueller?

  3. #3
    You reversed the voltage input. Check the wiring on the breadboard, you connected the Teensy's ground to the red wire of the battery and the Teensy's plus to the ground. The wire colors are correct in your diagram but you placed them in the wrong rows of the breadboard. See the annotated figure, you basically used a black wire to connect the positive lead of the battery to the ground of the Teensy, and a red wire to connect the ground of the battery to the Teensy Vin.
    Click image for larger version. 

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  4. #4
    Senior Member PaulStoffregen's Avatar
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    The fritzing diagram does seem to have the power connected wrong. It also shows the I2C signals on the wrong pins.

    But those look ok in this photo, so I really don't know if this was the problem or not.

    Click image for larger version. 

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  5. #5
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    How do you power the project? do you have the battery and USB connected at the same time? i.e. programming downloading debugging while using a battery to power the circuit? is the USB power trace still connected or cut?

  6. #6
    Thanks so much for all the replies. This is a terrific forum.

    howiemnet - Thank you for point out my input Vcc mistake. I have updated the Fritz document to add two 1N4001 diodes in series with the 5Vdcc positive bus. This drops the voltage to 3Vdc and adds reverse protection. Something I haven't down with my ATMEGA2560 or Uno R3 project but should. The relays are opto-isolater relays which switch AC or DC. I may put a filter cap on the input power supply.

    inwanders - Thanks for catching the Fritz wiring error. I didn't actually do that when I constructed the board as PaulStoffregen points out. Updates to the document ar in the github. Photos to follow.

    fretless_kb - Currently I am using a 13.8 Vdc @ 15 Amps switching power supply when I am running the project. USB when uploading. I occasionally have left the power supply on when uploading which I I shall not do in the future. The battery in the Fritz diagram is symbolic for the power used by either the UV-RS3 or a fan.


    I think that covers. Again thanks so much for taking the time to assist me.

  7. #7
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    I'm still not following how your '13.8 Vdc @ 15 Amps switching power supply' gets brought down to 3.7 - 5.5 or 3.6-6.0 v Vcc for a teensy.

    cheers

  8. #8
    I use a UBEC to drop the 13.8Vdc to 5Vdc. https://www.hobbyking.com/hobbyking/...dProduct=62873. I was running the Teensy and all 5v peripherals off that. The 1N4001 has helped. Does this now make sense?

  9. #9
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    yes, good luck getting to the root of the issue.

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