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problem with my PCB pro2

2017-07-16
2017-07-16
  • Markus Bieringer

    Hello,

    at first let me say thank you Mr. Brown for this great project.
    I built the pcb and uploaded the firmware in the Nano (it´s a clone). So far everything works.
    But when the Nano is mounted on the pcb and I turn the power on, the LED on the Nano stays dark.
    The L7808 gets hot so I switch the power off after a few seconds.
    What could be the problem? The 10A10 Diode is a very thick one. Hope, this is correct???
    One of the ceramic capacitors is a Tantal, because I couldn´t get another one. Push-Buttons, LEDs, IR, BT, LCD and the motor are not connected at the moment. Seems the circuit get´s no power...maybe the wrong diode?

    Thanks a lot for your help!

    Best regards,

    Markus

     
  • brownrb

    brownrb - 2017-07-17

    Sounds like you have a short somewhere on the VIN to GND or 5V to GND rail.
    There is NO way the LM7808 should get hot, let alone warm,
    Check for solder that may be bridging more than one connector
    Look closely at all your soldering - use a magnify glass
    Check all the wires to make sure thay they go to the right pins

    It does not matter about the capacitor, thats fine.
    There has to be a short - this stops the nano getting power and causes the LM7808 to get hot.

    if you just use a USB cable to connect to the nano - do any lights come on?
    If no, then you have a short probably between 5V and GND (but can also be VIn to GND)

    Are you sure you connected to the right pin number for VIN? I would probably disconnect the VIN pin from the LM7808 to VIN.
    Then try - the LM7808 should be cool. If not there is a short before that.
    If cool, then I would try connect with USB cable = if that works then I would be checking connections to VIN

     

    Last edit: brownrb 2017-07-17
  • Markus Bieringer

    I´m nearly sure the short is in the 5V circuit.
    I took the LM7808 away and there is no short between Vout and GND.

    And yes: When I connect USB there are no LEDs coming on.
    When I take the Nano away, there is a short between 5V on the pcb and GND (there should only be the three 1,2k resistors in between, right?). When I give 5V on the pins on the pcb it makes a short. Unfortunately I can´t localize it. I checked all the soldering several times...I have at the moment no LEDs and no buzzer on the board. Does that matter anything?

     
  • brownrb

    brownrb - 2017-07-17

    the leds and buzzer will not make much difference

    Did any of the jumpers get put on the wrong pins?

    If you can take a hi-res picture of both sides of the board and post it I will take a look

    Cheers
    Robert

     
  • brownrb

    brownrb - 2017-07-18

    Looks ok
    Did you cross over any wires between LCD connection on PCB and the header of the LCD
    The PCB goes GND/VCC/SDA/SCL
    The LCD1602I2C header is VCC/GND/SCL/SDA
    Note different order so wires need to be crossed

     
  • Markus Bieringer

    No, the LCD isn´t even connected. It´s only the wires you can see in the picture.
    Is there any possibility to delimit the short? I mean there is a connection between GND and 5V because of the three resistors with 1,2 k. I have only a simple multimeter to test it...
    But the Driver board is connected to GND and 5V too. Is there a possibility of a mistake? The soldering looks ok to me. But on the driverboard maybe?

     
  • brownrb

    brownrb - 2017-07-19

    Yes.
    See attached. This is a stuff up on my part.
    Email me at brown_rb at yahoo dot com please
    I have updated the files on Aisler and here

     

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