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Please help modified a circuit

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by cannibal, Sep 27, 2007.

  1. cannibal

    cannibal New Member

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    If I used CD4026 all the problems will be solved ??!!
    and how can I test only the counter circuit if it's working or now (Only counter circuit)
     
  2. audioguru

    audioguru Well-Known Member Most Helpful Member

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    A CD4026 also needs to have a pretty fast clock input.

    Use a 555 oscillator or a de-bounced pushbutton to clock the counter.
     
  3. ljcox

    ljcox Well-Known Member

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    That is why I suggested that you connect U1/14 to pin 3 of the 555.

    The output of the 555 will be fast enough to trigger the counter.

    The reason why your counter is counting 0, 1, 0, 1, or 8, 9, 8, 9, etc. may be because it is receiving 9 pulses instead of one from somewhere.

    As Audio said - the LDR may be receiving pulses from a light. But I don't know why there would be 9.

    Alternatively, there could be an oscillation due to the breadboard arrangement.
     
  4. dave

    Dave New Member

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  5. ljcox

    ljcox Well-Known Member

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    You should be able to make it work with the TTL if you can't buy CMOS.

    You could test the counter circuit by using a low frequency oscillator, say 1 Hz. Then the count would increment once every second. But it woulds need to provide a low rise time square wave of at least 3 Volt in amplitude, ie. switch between 0 Volt and +3 Volt.

    Alternatively, you could make a bounce suppressor and use it to incement the counter manually, ie. a push button connected to the bounce suppressor.

    There are various ways you can make a bounce suppressor. (Search this forum for "bounce suppressor")

    Can you obtain a 7414 or a 74HC14?
     
  6. ljcox

    ljcox Well-Known Member

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    Another way to make a bounce suppressor would be with a 7400 Nand gate IC. Do you have any or can you buy one?
     
  7. ljcox

    ljcox Well-Known Member

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    I have just realised what your problem must be.

    Your drawing shows a connection between pins 1 & 12 of U1.

    Is this connection really there? If it is, check if it is a good connection, ie. inspect it visually and, if it looks OK, measure the resistance between pins 1 & 12; it should be a low resistance, ie. < 1 Ohm.

    If these pins are not connected then you will experience what you have described since the Modulo 5 counter won't be being driven by the Flip Flop, ie. only the flip flop will be changing.

    In other words, Qa (pin 12) must be connected to input B (pin 1)
     
    Last edited: Oct 29, 2007
  8. cannibal

    cannibal New Member

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    WOW WOW WOW WOW WOW

    finaly the counter is counting perfectly

    0,1,2,3,4,5,6,7,8,9

    the breadbord hole where wire of pin1 to pin12 was defected
    I used another hole in the breadboard to connect pin1 to pin 12

    and thats it

    counting with no problems :)

    thank you very much ljcox
    also BIG thanks goes to audioguru and all other members who'ed helped me

    all the best
     
  9. ljcox

    ljcox Well-Known Member

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    You're welcome. I'm glad that we were able to help.

    It looks like you need more experience at fault finding.

    The general principles are:-

    Do a visual inspection and look for bad connections, short circuits, etc. and if any joints are soldered, check for dry joints.

    If that does not resolve the problem, make voltage measurements. In your case, you would have measured a different voltage on pins 1 and 12.

    If pin 12 was high, you would have seen a low on pin 1. So therefore there must not be a connection between them. Note that if pin 12 was low, pin 1 would also be low and therefore you would not know that the connection was faulty. So you need to change the state of the counter to check both cases.

    If you have a multimeter with a continuity function, you can check for continuity between points that are purposed to be joined. So if you put one probe on pin 1 and the other on pin 12, there would have been no continuity.

    Finally, when I am building something, I check the components before I insert them. New components are rarely faulty, but if one is and you don't check it, then having to fault find when the construction is finished can waste time.
     
    Last edited: Oct 30, 2007
  10. cannibal

    cannibal New Member

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    Thanks for the tips ;)

    Is it possible to make it count to 99?

    and how the connections can be done?
    by the way I decided to use power supply rather then 9V battery :D
     
  11. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Of course. But most modern circuits use a microcontroller or Cmos ICs.
    I haven't used old TTL since about 1972 when I started using Cmos instead.

    Look in Google for Two Digit Counter Circuit.
     
  12. cannibal

    cannibal New Member

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    Done

    pin14 of 74LS90 from circuit2 goes to pin 6 of 74LS47 from circuit1

    :)
     
    Last edited: Oct 31, 2007

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