LED Matrix with transistors damaging pics

Discussion in 'Embedded Systems and Microcontrollers' started by ozirock, May 6, 2011.

  1. ozirock

    Thread Starter Member

    Jan 13, 2011
    44
    0
    Hi,

    I was trying to control an 5x7 LED dot matrix using a pic 16f627 with transistors. I was able to light the LED's by directly connecting transistors to ground and +5v so I'm pretty confident that side of things is okay. However when I connected a 1k resistor between each transistor and a pin on the pic and ran some simple code my pic broke and could not be reprogrammed. I think too much current was drawn through the pic but I don't know why, I'd be very grateful if someone could explain my mistake.

    I had it wired like this:

    [​IMG]

    Parts:

    Thanks
     
  2. debjit625

    Well-Known Member

    Apr 17, 2010
    790
    186
    Provide a proper schematic diagram of your circuit and the simple code that you ran........

    Most Microchip's PIC range use Vdd,Vss,RB7,RB6 and MCLR pins to get programmed now RB7 and RB6 are one of the ports pin also, that can be used for general I/O operations.

    If any pin is damaged that might not stop the programming,but if its one of the RB7 or RB6 then it might be.....

    Good luck
     
  3. trixheim

    Member

    Apr 1, 2009
    10
    0
    There should be a serial resistor to the LED for current limiting. I think the base resistors are too small, they should be around 10K.

    Regards
    Tor
     
  4. mehtadhaval

    New Member

    Sep 21, 2007
    9
    0
    What is the current limit for the PIC 16F627 pins ?
    if it is below (5 - 0.7)/1k ~ 4.3 mA, then you might have damaged the MCU.
     
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