PIC driven 7 Segment displays

Discussion in 'The Projects Forum' started by Joe Lavery, May 21, 2009.

  1. Joe Lavery

    Thread Starter New Member

    May 21, 2009
    3
    0
    Greetings all,

    I'm trying to build a small circuit that simply lights 3 or 4, 7 segment displays using a PIC and controlled by an encoder. All it has to do is increase the value of the displays up or down as the encoder is rotated.

    I wonder in anyone here has come accross such a design, it's to simulate a frequency display on a radio.

    I have the facility to program the PIC but I ned help with the circuit design.

    Thanks in advance

    Joe.
     
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    Connect all the segments in parallel and then connect them to the one port of the PIC via resistors. Then use a transistor on each common pin of the displays to switch them on/off.

    If you switch fast the displays in sequence and light the right LEDs on each one each time it is selected you will think that all displays are on all the time due to the persistence of vision phenomenon.
     
  3. lightingman

    Senior Member

    Apr 19, 2007
    374
    22
    Hi,

    Have you got the encoder?

    If so, it is quite simple to do this. Basicaly the encoder has two outputs. Output "A" pulse occurs before "B" output in one direction and "B" before "A" in the other.

    As for the display driving. You just use a CD4511 to drive the segments that are all connected together I.E: a to a, b to b and so on... You then drive each display from the output of the PIC (through a transistor). After reading the pulses from the encoder and storing the result in PIC RAM. You then send the segment data as a 4 bit binary output to the 5411 and output to the display to display that digit. You do this one digit at a time.

    Daniel.
     
  4. Joe Lavery

    Thread Starter New Member

    May 21, 2009
    3
    0
    Thanks guys,

    I understand the theory but would you have a circuit diagram?

    Regards

    Joe.
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
  6. Joe Lavery

    Thread Starter New Member

    May 21, 2009
    3
    0
    Brilliant,

    That's exactly what I was looking for, thanks again all.

    Regards

    Joe.
     
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