using common WPD for 2 pics ??? What happens


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  1. #1
    xnihilo's Avatar
    xnihilo Guest

    Smile using common WPD for 2 pics ??? What happens

    Hello,

    In my deseign, I've connected two PIC16F690:
    RC0 is set as output, default low, with 100K WPD (because I need to set it as input low sometimes).
    On the second pic, RA5 is set as input, default low, with 100K WPD (because I need it to react to a positive pulse).
    RC0 from first pic is connected to RA0 of the second pic while both these pins are tied to GND with their respective WPD.
    Is it allright or should I use only one 100K WPD connected to the link between these two pins?

    I don't know if my topic is clear enough to understand???

  2. #2
    skimask's Avatar
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    Put a 1k resistor inline with the wire. If one pin goes output high and the other pin goes output low and both chips are run from 5 volts, without the resistor, the PICs will try to pass XX amount of current, possibly damaging the pin drivers. With the inline 1K resistor, the max current that could pass between the 2 PICs on said line would be limited to around 5mA....well within the PICs limitations.

    Unless you have this line connected to the heating pad that is set up to burn somebody's skin...then you may want to run both PICs at 100VDC and let that unlimited thousand amps of current flow...

  3. #3
    xnihilo's Avatar
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    Isn't there a limiter for the current a pic pin can sink (25 mA)???

    When you say "inline", you mean between the two pins, right? Sorry english is not the language I'm fluent with.

    Pics will grill if I use 100v and what is the "burn skin" stuff?

  4. #4
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    Quote Originally Posted by xnihilo View Post
    Isn't there a limiter for the current a pic pin can sink (25 mA)???
    Yep, it's called 'smoke'. You try to pull much more than 25mA thru a pin on a PIC and you'll get smoke. That'll limit the current permanently...

    When you say "inline", you mean between the two pins, right? Sorry english is not the language I'm fluent with.
    Yes, inline, as in

    Pin -> Resistor -> Pin

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    I got it. Thank you.

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