Mod 60 counter with start/stop button reset or skip

Discussion in 'Homework Help' started by Alfred Pang, Jan 9, 2016.

  1. Alfred Pang

    Thread Starter New Member

    Jan 8, 2016
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    Hi guys, I'm doing a mod 60 counter with start/stop button and reset button like how others works. But during the doing process in multisim everything works fine until i start to connect up the circuit with the components provided 74ls93 x2, 74ls08, 74ls32 and 74ls00. With all this components i follow closely to my multisim but one thing failed on my physical connection is the start/stop button, when i press the start/stop button it will start normally then when i want to stop the counting i press the button it can either reset my counting to 00 immediately and continue counting or jumping of counting number ,example when it count until 23 i press the stop button it will jump to 47 and stop at there instead of stopping at 23. snap.PNG
     
  2. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    More than likely, your problem exists because your switches for start/stop is floating (not connected to anything ) during the reset. That is not the same as connecting to ground (0V). You really need zero volts. Even if it is through a resistor. So, a "pull down resistor" is used in your case to keep the pulse low.

    You can use anything from 1k (as shown) to a 100k. Normally 10k to 100k range is used.

    Make sure the same is true for your Reset. If you need the reset to be high instread of low, you can do the reverse (pull up resistor). Just make sure that + power rail is never connected directly to the - power and you get a short circuit. Always make sure power flows through a resistor from plus to ground.


    image.jpg
     
  3. Picbuster

    Member

    Dec 2, 2013
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    Use a pic 16f690 write a few lines of code. you have this within a few hours operational cheaper and easy to modify.
     
  4. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    He could also do it with one of these but I am not sure it meets the constraints he set upon himself or the constrains set upon him by someone else. Let's stick with the 7400 logic they he started with.

    image.jpg
     
  5. dannyf

    Well-Known Member

    Sep 13, 2015
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    60 = x * y or x * y * z, depending on the counters used.

    So all you need is to find counters that count to x, y or z, and chain them together.
     
  6. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Did you even read the question?
     
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  7. crutschow

    Expert

    Mar 14, 2008
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    Those higher values will work with CMOS logic but this is LS TTL.
    Those circuits generate an input sink current of a couple hundred microamps or so at a logic low, thus you would want to keep the pull-down resistor to not much more than a couple kΩ. 1kΩ is good.
     
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  8. Picbuster

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    Dec 2, 2013
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    He put this into the project form so I react to help him to get a proper, easy, cheap and maintainable solution.
    Ok, lets stick to the 74xx series
     
  9. sailorjoe

    Member

    Jun 4, 2013
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    I see two problems I think you should change. Your schematic seems to show you create an open circuit on InA when you press the start/stop switch. Instead, use a pull-up resistor on the InA line, and use the switch under the resistor to pull the line to GND. Second, add a capacitor from InA to GND to denounce the switch.
    Consider similar changes for the reset switch.

    Edit: on second look, there is no reason that the start/stop switch should have any reasonable effect the way it's connected up. Use the switch to inhibit the clock signal getting to the units (M10) counter.
     
    Last edited: Jan 10, 2016
  10. dl324

    Distinguished Member

    Mar 30, 2015
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    That isn't helpful. OP is asking for assistance debugging his circuit; not for alternate solutions.
     
  11. dl324

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    Mar 30, 2015
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    The way I interpreted the post is the OP is asking for help with start/stop, not counting.
     
  12. dannyf

    Well-Known Member

    Sep 13, 2015
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    Then all he needs is counters with reset -> many of them do. The same logic applies.
     
  13. Alfred Pang

    Thread Starter New Member

    Jan 8, 2016
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    Hi, guys I deeply appreciate all of your replies, but I don't think i can add in a resistor to the circuit as this is one of my school assignment which it says we can use the IC we had with us and the provided IC given by our tutor, so we are not suppose to add in resistor in this circuit. As one of you said that you notice my button is connected to high instead of low, because i followed the physical circuit board provided by the school. The button is on high output when it is not press, only goes to low output when it is pressed. We only need to design the Mod 60 counter circuit . So i'm kind of confuse what's going on. Is there any other alternative guys?
     
  14. dannyf

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    Sep 13, 2015
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    Most buttons follow that convention. the otherway around would have been rare.
     
  15. dl324

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    Mar 30, 2015
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    Connect the two switch terminals on the right together.

    In the future, you should post homework in the Homework Help forum. In any other forum you might be given answers, which could be considered cheating.
     
  16. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    And the same question applies. Did you read the question, look at the schematic, and consider the problem within the OP's context?

    ak
     
  17. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    Late to the thread, agree with dl. But while that looks good on paper and will work in a sim, it doesn't solve the real-world problem of switch bounce (the cause of the magical jump from 23 to 47 in post #1). If adding a capacitor is out, then the question is - are you limited in the number of other logic gates you can use? If not, use two 74LS00 gates to form a set-reset flipflop that is driven by the start/stop switch, and use the Q- output to drive the counter input. This will work with TTL, but not with CMOS gates. TTL gates have an inherent weak pull up current source on the inputs. It is very bad design practice to rely on it, but if added passive components are out, we go with what we got.

    At the start/stop switch, both left-side pins are tied to GND. Each right-side pin goes to a set/reset flipflop input. Whichever flipflop gate has it's input grounded by the switch in the rest position, that gate's output drives the counter. Also, in this circuit the start/stop switch is not starting or stopping anything; it is incrementing the counter. A better name would be COUNT.

    ak
     
    Last edited: Jan 11, 2016
  18. dl324

    Distinguished Member

    Mar 30, 2015
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    @Alfred Pang You have some problems with counter wiring/logic. As this appears to be homework, you should do as much work as you can before asking for help.

    When asking for help, include what you have attempted to solve the problem and why it didn't work.

    If Multisim is showing correct counting, there is either a problem with the 74LS93 model or the simulator. You're not the first who has come here with a counter circuit with logic problems and Multisim showed correct operation.
     
  19. WBahn

    Moderator

    Mar 31, 2012
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    I agree with ak that the description of the problem (count jumping from 23 to 47) indicates a switch bounce problem. This is particularly indicated if the anomaly is erratic (goes to 47 this time and some other value next time).
     
  20. Alfred Pang

    Thread Starter New Member

    Jan 8, 2016
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    What you said are true, but impossible you're asking me to refer to my friend works isn't it? Because I recheck already everything seems fine even my friend can't find out what's wrong with it too. When the circuit is off for some time and on back it works fine on the start stop button, but after a few press on the start stop button, issues start to come in like auto rest and skip/jumping of number. :D And i did a IC testing on 74LS93 and it went fine.
     
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