PIC16F84A Matrix LED Display


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  1. #1
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    Cool PIC16F84A Matrix LED Display

    Hi Friends,

    This is a PIC16F84A Microcontroller based matrix LED Display. It uses 7x15 (or 8x16) LED Matrix to display characters.
    The circuit uses two 4017 IC s to move the characters.

    Use the following link to download schematic, source codes and compiled hex files -
    Documentation is also added with details of how to display your own message.

    http://www.manelsoft.com/projects/pi...d_display.aspx

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    Good Luck.!

  2. #2
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    Default Re: PIC16F84A Matrix LED Display

    Did you hook up your matrix exactly like the schematics out of the PIC Programming handbook? If so, I don't see how they work. I've been shown up many times in electronics and it might happen again here so here goes.

    On the 7 x 15 schematic the left hand CD4017 pin 6 is hooked directly to ground along with the base of the first column transistor. On either schematic I don't see how any diode is positively biased. None of the LEDs have a positive voltage applied to the anodes. If a high is to come from the PIC it's blocked by the right most column LEDs.

    I haven't had a chance to look at the code and frankly I wouldn't know an error in assembly if it had a prompt. I do plan on using your code in a project when I get some time. Thanks and let the schooling begin.

  3. #3
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    Default Re: PIC16F84A Matrix LED Display

    I don't understand why column 15 is wired differently than the others.

    Robert

  4. #4


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    Default Re: PIC16F84A Matrix LED Display

    I think this is how it should be wired. The original had all the pic outputs shorted?



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  5. #5
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    Default Re: PIC16F84A Matrix LED Display

    I think you're correct in wiring the rows to a port pin on the pic.

    After looking at the datasheet I see the 16F84 can sink/source 25mA per pin. Now I see why you'd want to use that chip. How would you do it with a 16F877A where the pins are not as robust? That was the chip I was planning on using is the reason I'm asking.

  6. #6
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    Default Re: PIC16F84A Matrix LED Display

    Hi Friends, There was a mistake in the schematic. Thank you all for showing it. I fixed it. Please see the corrected one.
    http://www.manelsoft.com/projects/pi...d_display.aspx
    Last edited by dineshwick; - 22nd November 2013 at 06:31.

  7. #7
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    Default Re: PIC16F84A Matrix LED Display

    @mark_s : Yes you are correct, There was a mistake in the Schematic, I fixed it. Thank you very much, Please see the corrected one.
    http://www.manelsoft.com/projects/pi...d_display.aspx
    Last edited by dineshwick; - 22nd November 2013 at 06:34.

  8. #8
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    Default Re: PIC16F84A Matrix LED Display

    Quote Originally Posted by AvionicsMaster1 View Post
    I think you're correct in wiring the rows to a port pin on the pic.

    After looking at the datasheet I see the 16F84 can sink/source 25mA per pin. Now I see why you'd want to use that chip. How would you do it with a 16F877A where the pins are not as robust? That was the chip I was planning on using is the reason I'm asking.
    I'd sink via transistors; cheap and simple.

    Robert

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