Wiring a Dual Digit Display

Discussion in 'General Electronics Chat' started by kainotk, Mar 31, 2009.

  1. kainotk

    Thread Starter Member

    Mar 31, 2009
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    How does one wire a dual digit 7-segment LED to display different characters, when there is only 1 set of a,b,c,d,e,f,g. :confused:

    For example, how do I display a "0" and a "1" at the same time?

    thanks
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    By multiplexing of the commons pins.
    The display is either common cathode or common anode.

    Find the datasheet for your particular display.
    You'll find something like:
    CC1, CC2
    or
    CA1, CA2
    for the respective digits.
    [eta]
    Here's an example using a PIC uC:
    http://www.picbasic.com/resources/articles/ledart.htm
    It starts out nice and simple, with the basics of powering LEDs, and works up to multiplexing 7-segment displays.
     
    Last edited: Mar 31, 2009
  3. kainotk

    Thread Starter Member

    Mar 31, 2009
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    Is the CD4051 the right chip to use? single 8-ch mux. w/ 3-binary inputs

    thanks again
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    What are you trying to do? Display a count of items?

    If so, look at using the CD4543 and CD4553 IC's together.
    One is a 3-digit BCD counter with a multiplexing output, the other is a 7-segment display driver.
     
  5. kainotk

    Thread Starter Member

    Mar 31, 2009
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    For starters, I just want to display a "0" on the left and a "1" on the right of a dual digit display. Eventually, I'd like to built a counter.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    Oddly enough, it would either require a microcontroller or more parts than just the 4543/4553 IC's, a few resistors and transistors to just display a "01".

    See the attached schematic for a simple project using the 4543 and 4553 IC's. It's using three separate 7-segment displays, but the idea is the same; you would just have one set of abcdefg connections to make instead of three.

    The clock input to the 4553 3-digit BCD counter is a Hall-effect sensor, it provides logic-level pulses. It's a design to count revolutions of a shaft.
     
  7. SgtWookie

    Expert

    Jul 17, 2007
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    If you really just want to display a "01" for starters, then you could begin with just a 4543 and resistors wired up like I show on the schematic.

    Inputs B, C, and D would be connected to ground.

    A 555 timer with some resistors, a cap and some transistors could be used to alternate sourcing/sinking current from the display common anode/common cathode, and changing input A to a logic 1 or 0.

    But you need to know if your display has common anode or common cathode. Pin 6 of the 4543 is the "phase" input. For common anode displays, the phase input is connected to ground; for common cathode it's connected to Vdd.
     
  8. drakkardred

    New Member

    Jan 15, 2010
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    I have a really good question I'm building a timer replioca from the show sliders but I don't know how to wire up the numeric l.e.d. display chips I have 3 dual digit and the ic chips I have 7 CD40110BE and 1 TLC551CP CHIP but no one can tell me how to wire them up I need it to be able to count up/down I'm not sure if your familiar with that show but I'm looking to build all the timers from that show but like I said no one can tell me I have called the place mouser.com where I bought them from to see if they could help me and they were no help at all so I went all the way to the manufacture which is Texas Instruments and they couldn't even help me I'm lost to is what to do I have these parts and can't do a thing cause Idk what to do can you help me please.
     
  9. SgtWookie

    Expert

    Jul 17, 2007
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    Well, the 40110 is a CMOS decade up/down counter with built-in 7-segment decoders, and the TLC551 is compatible with the industry standard 555 timer.

    You might find ST Microelectronics HCC40110B datasheet easier to read.

    Not familiar with the show "Sliders".
     
  10. Wendy

    Moderator

    Mar 24, 2008
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    Sliders was about an inventor/mathematician who solved the theory of everything, and created a device that moved between alternate universes, or earths in this case. It became a lost in time format. Started off OK, and went downhill over several seasons.

    There are several CMOS chips that will do what you want quite nicely, besides the ones Wookie mentioned. How much do you know about electronics in general?

    I like the CD4029 myself.
     
  11. SgtWookie

    Expert

    Jul 17, 2007
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    Bill,
    The 40110 will work just great for what they want to do (I think) - as they want to drive 7-segment displays; the 4029 would require an additional IC, whereas the 40110 would not.

    I don't know what the "Sliders" counter did, though...
     
  12. Wendy

    Moderator

    Mar 24, 2008
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    As I understand the OP wants a BCD counter that you can input the numbers (presetable) and counts down, possibly with the ability to count up also. This describes a 4029 pretty closely. The mod six counters may present a problem though.

    To the OP:

    You may want to put up your proposed control panel and display, it will give people a better idea what you want.
     
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