breadboarding


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  1. #1

    Default breadboarding

    Hello all
    I am working with a Pic 16f628A, and can program it ( albeit I am primitive). I have a problem now where I am using the development board and writing a simple "Blink" program to flash an LED on Port RB0 and it works perfectly, until I breadboard it. When I put it on a breadboard, the LED will flash for about 15 to 20 seconds and then stop. When I turn the power off to the breadboard, the LED resumes flashing for about three seconds as the unit powers down, and then ceases. Then I can power up the breadboard again, and the LED flashes again for 15 to 20 seconds before stopping. Anyone have any thoughts on why the LED stops? The only hardware in my circuit is the PIC, an LED, and a 470 ohm resistor.

  2. #2
    Join Date
    May 2013
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    australia
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    1,610

    Default Re: breadboarding

    reset/mclr pin no pullup?
    This is more entertaining than Free to Air TV

  3. #3
    Join Date
    Apr 2014
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    Northeast
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    313

    Default Re: breadboarding

    Quote Originally Posted by richard View Post
    reset/mclr pin no pullup?
    ...or possibly Watchdog Timer nipping your butt. Somehow it sounds like you are getting a Reset condition, or maybe a Brown-Out. Check your VDD supply voltage when it quits. If it isn't what you want (especially if it's below about 2.5 volts), you are getting a Brown-Out Reset Hold condition.

    You should have a 4.7k (up to 10k) pull-up resistor on MCLR to prevent inadvertent hardware Reset. In your CONFIGs, turn WDT (Watchdog Timer) off. You can do this at program time with PBP.

    Since it works on the Dev Board, you have something (or lack something) not the same as the Dev Board. Do you have a capacitor on the power supply to your PIC? Data sheets suggest a 0.1 uF cap RIGHT AT your VDD-to-VSS pins.

    Hope this points you in the right direction.

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