okay I ama serious beginner ... go easy on me please

Discussion in 'The Projects Forum' started by n00b, Jun 28, 2007.

  1. n00b

    Thread Starter New Member

    Jun 28, 2007
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    0
    Right

    I have an idea which I am trying to design a circuit for at the moment. I am new to microchips, but can handle easier circuit LED chasers etc

    My basic problem is that I would like to use the 16F84 (given Im new) which only has 13 ports .. Im need at least 30 !

    So Im trying to understand what to do (critisim welcomed)
    a) use three 16F84 in the circuit (communicating with each other -- somehow ) - If this is a valid alternative does anyone have an example for me to look at ?

    b) use some kind of extra circuiryt to explode out the number of ports


    I truely would appreciate help

    Thanks !
     
  2. lightingman

    Senior Member

    Apr 19, 2007
    374
    22
    Hi..If it is outputs only that you require to epand, you can use addressable latches CD4099 or 74HC259....For inputs you can multiplex using CD4067 or CD4051....For both input multiplexing and output addressing you can expand to many I/O's ... (within code limitations).Or use a bigger PIC, as the 84 is now a bit on the old side...The 16F877 or 18F458 has 33 I/O's.....Daniel.
     
  3. n00b

    Thread Starter New Member

    Jun 28, 2007
    4
    0
    Daniel ...

    I really appreciate you taking the time to reply ... Its outputs I want to expand ...

    I think possibly the easiest alternative would be to change the microchip to one of the two suggested ..

    As a matter of interest could you point me in the directions of some sample circuits using the CD4099 or 74HC259

    thanks
     
  4. lightingman

    Senior Member

    Apr 19, 2007
    374
    22
    Yes...No prob's there...Just give me a day or so, and I will post some examples here for you....Daniel.
     
  5. Papabravo

    Expert

    Feb 24, 2006
    10,145
    1,791
    You can also use serial in, parallel out shift registers. It would be best to use the kind with an output latch so the shifting data won't disturb the outputs and they can all change simultaneously. The cool thing is that you can cascade them to any length in increments of four or eight.

    http://focus.ti.com/lit/ds/symlink/sn74hc595.pdf
     
  6. lightingman

    Senior Member

    Apr 19, 2007
    374
    22
    Yes you are dead rite, something like the CD4094.....Daniel.
     
  7. n00b

    Thread Starter New Member

    Jun 28, 2007
    4
    0
    """Yes...No prob's there...Just give me a day or so, and I will post some examples here for you....Daniel.""

    Daniel -- I would be incredibly grateful !!!! Thanks
     
  8. n00b

    Thread Starter New Member

    Jun 28, 2007
    4
    0
    Thanks to everyone for the help !
     
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