RESET button to MCU

Discussion in 'Programmer's Corner' started by Jaden5165, Sep 18, 2011.

  1. Jaden5165

    Thread Starter Member

    Sep 9, 2011
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  2. t06afre

    AAC Fanatic!

    May 11, 2009
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    Are your programmer connected. It take control over the MCLR pin. Try to disconnect the programmer. And see if that help
     
  3. upand_at_them

    Active Member

    May 15, 2010
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    Is it running from 5V? I use a 4.7K or 10K pullup resistor on MCLR, 1K is a bit strong.
     
  4. Jaden5165

    Thread Starter Member

    Sep 9, 2011
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    ya.from 5v.but what do you mean 1k is a bit strong?not 10k stronger than 1k?
     
  5. Jaden5165

    Thread Starter Member

    Sep 9, 2011
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    my programmer is not connected.how?
     
  6. Jaden5165

    Thread Starter Member

    Sep 9, 2011
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    nobody can help?oh no!
     
  7. AlexR

    Well-Known Member

    Jan 16, 2008
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    It would help if you posted your code (use the "Go Advanced" button and wrap your code in the code tags "#" so that it easier to read. Without the code its hard to say what is going wrong.
     
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  8. stahta01

    Member

    Jun 9, 2011
    133
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    An 10K resistor only needs 1/10 the current of an 1k resistor to pull the voltage down to a low voltage.

    Note: No idea if that is the cause; I would guess I code issue; but, I am mainly a programer instead of a hardware person. So, I always look to eliminate what is easier for me to check. After checking the normal hardware things on PICs.

    Normal hardware Items to check.

    Note: I have seen PICs partly work without one of Power or Ground Pins connected.

    Ground to PIC
    Power to PIC
    MCLR properly connected; the proper connection can vary some per configuration options.
    If using external Crystal is it connected with the recommend capacitor(s)
    Check the rest of the schematic connections.

    Tim S.
     
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  9. chejian6

    New Member

    May 22, 2011
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    I think there're 3 things to do:
    1. change the pull-up res from 1k to 4.7k
    2. add a 1uf cap between MCLR and GND
    3. Make sure the load cap of the crystal is correct. Most load caps of crystal are from 10 to 20p. 30p may be a little bigger.
     
  10. upand_at_them

    Active Member

    May 15, 2010
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    Think of it this way: If you have a 1 ohm resistor tying a pin to 5V you will not be able to pull it away from that 5V. But if a 10K ohm resistor is used you can easily pull it away from the 5V. Therefore, 1 ohm is "stronger" than 10k ohm.
     
  11. debjit625

    Well-Known Member

    Apr 17, 2010
    790
    186
    The circuit is ok,it will work properly but your switch might cause the problem so buy good quality switch.I did the same mistake when I was starting with these stuffs...

    You can use this circuit for reset...
    [​IMG]
     
  12. nigelwright7557

    Senior Member

    May 10, 2008
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    I connect my /mclr to 5 volts !
     
  13. t06afre

    AAC Fanatic!

    May 11, 2009
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    Thenever I can (working with PICs) I disable the MCLR function.
     
  14. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    Is it on a breadboard? It can be common to get a problem where the PIC xtal oscillator does not re-start after MCLR reset. Usually caused by long wires and/or too much capacitance near the xtal caused by the breadboard.
     
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