Counter Circuit

Discussion in 'General Electronics Chat' started by ZKY, Jul 28, 2014.

  1. ZKY

    Thread Starter New Member

    Jul 28, 2014
    6
    0
    Hi all,

    I'm new here and I'm a non-native English speaker, so please bear with my poor English..

    I'm a polytechnic student currently doing a project, I want to make an enhanced counter circuit with some additional features. Please refer to the circuit diagram that I attached, and let me elaborate more on my circuit:

    simple 4033 counter score board circuit.png

    WP_002624.jpg

    Basically for the counter circuit, I took example by the circuit that I've found in this website: http://homemadecircuitsandschematics.blogspot.sg/2013/11/making-electronic-scoreboard-using-ic.html
    But instead of using the IC CD4033, I used CD4026B. The connection between the IC CD4026B and the 7 segment display is done by a NC contact of a 12V relay because I want the 7 segment display to display other pre-set pattern when the relay is activated. And when the relay is de-activated, the 7 segment display will return to the number that it was just counting.

    So here's the problem that I encountered:
    1. the circuit is not stable, sometimes when the relay is deactivated, instead of return to the number that is was just counting, it will return to 0.
    2. when the relay is activated then deactivated, segment 'a' is not working fine (it is very dim, almost unnoticeable).

    So please help me! Thank you very much!

    ZKY
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,638
    2,344
    Hello,

    Why not use pin 3 for disabeling the display?
    That way you would not need the relays at all.
    (see the datasheet)

    Bertus
     
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  3. ZKY

    Thread Starter New Member

    Jul 28, 2014
    6
    0
    Hi Bertus,

    I don't know about this pin, can you tell me what this pin is used for? Thanks!

    ZKY
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,638
    2,344
    Hello,

    When you make pin 3 low, all outputs will go low.

    Bertus
     
    ZKY likes this.
  5. ZKY

    Thread Starter New Member

    Jul 28, 2014
    6
    0
    Hi,

    But actually I want to keep these outputs. I mean, for example, the counter counts 1, 2, 3, then when I activate the relay, it will display a pre-set pattern, when the relay is deactivated, it will return to 3 and continue counting.

    ZKY
     
  6. Retiredguy

    Member

    Feb 24, 2007
    28
    5
    ZKY
    First off I assume that you are using the same voltage source for the relay and the circuit. If you are then a diode must be placed across the relay coil to prevent voltage spikes when the the relay is d energized, second you must make sure that the switch you are using is d-bounced( look under switch Bounce in the digital portion of this site) and it would not hurt to place a .01uF capacitor from VDD to VSS of the IC to smooth out the voltage. However, I would not use a relay at all to do what you wish to do but use another IC, a 4551 would do what you want without all the hassle.

    Retired Guy
     
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  7. absf

    Senior Member

    Dec 29, 2010
    1,490
    371
    Thank you for letting me know that there's a quad 2 to 1 mux/demux chip. I used 4053 triple 2 to 1 mux to design but the circuit looks messy and complicated. So I used OR and NOR gates instead.

    When the "HELP" button is pressed, the LED would display "H" while the counter is still counting.

    Allen
     
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  8. AlphaDesign888

    New Member

    Jul 27, 2014
    189
    10
    Instead of the expensive and bulky relays -- you could use CD4066 ICs. These are quad bilateral switches, which will operate in both analouge and digital systems. ::eek:: they're only worth about USD 20¢ ea on eBay.
     
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  9. ZKY

    Thread Starter New Member

    Jul 28, 2014
    6
    0
    Hi Retired Guy,

    Thank you! Very useful piece of information, yes you are right that I used the same source for the relay and the circuit, I may try your suggestion tomorrow and let you know again! And thanks for suggesting me to use IC 4551 too, but too bad I have already prototyped and soldered my circuit onto the stripboard.. So I may need to find ways to improve instead..

    ZKY
     
  10. ZKY

    Thread Starter New Member

    Jul 28, 2014
    6
    0
    Hi Allen

    Thanks for your circuit, indeed gives me a lot of inspirations! BTW, may I know what program you use to draw and simulate the circuit?

    ZKY
     
  11. ZKY

    Thread Starter New Member

    Jul 28, 2014
    6
    0
    Hi AlphaDesign888,

    Yes, by now I found it is an unwise decision to use relays in such a circuit, but its too late to change because I have soldered the circuit already... Thanks for the advice though!

    ZKY
     
  12. absf

    Senior Member

    Dec 29, 2010
    1,490
    371
    The program is called Proteus from Labcenter.com UK.

    Allen
     
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