Digital Clock using 7490 (RESET Button) HELP!

Discussion in 'Homework Help' started by nephelem, Jan 28, 2016.

  1. nephelem

    Thread Starter New Member

    Jan 24, 2016
    22
    0
    I am working on a 24-Hour Digital Clock project with 7490/74ls90 as my BCD. It should have three buttons. 1.) Hour - Increment button. 2.) Minute - Increment button 3.) RESET button. I am not sure if my schematic is correct but it works okay. The two increment buttons are working but I don't know how to connect the RESET to reset all the 7 segment LEDs to 00 00 00.

    It's my first time working with this kind of ICs. My knowledge on cascading these counters came from the book about digital electronics by A. P. Godse which I have read few days ago and by searching through internet. So you could really say I'm a noob. We were just instructed by our professor to use a 74192/74ls192 or 7490/74ls90. Btw, I have another thread similar to this except I used 74192 (http://forum.allaboutcircuits.com/threads/digital-clock-using-74192-reset-button-help.120129/).

    Can you please help me? Better if you include a schematic/circuit diagram so I could understand.
    Thank you very much. Attached here is my schematic: what2.jpg
     
  2. dl324

    Distinguished Member

    Mar 30, 2015
    3,249
    625
    If this is a school project for which you will receive a grade, you should have your post moved to the Homework Help forum. In the Projects forum, someone might just give you the answers and that could be considered cheating; and I've read that some professors visit this forum...

    Think about what you want reset to do and what you're attempting to do. Do you want reset to display zeros on the display or do you want to reset the counters?
     
  3. nephelem

    Thread Starter New Member

    Jan 24, 2016
    22
    0

    lol don't worry about it. i don't think my professor would just sign up here just to spy. regardless of how you do it, what matters to him is the final result which is the hardware/prototype itself. here in my country, project is different from homework. it is MORE than homework.

    what i mean is all the counters will clear/ start again from 00 00 00 when i press the button.
     
  4. dl324

    Distinguished Member

    Mar 30, 2015
    3,249
    625
    But I do worry about it. It would be unethical for someone to help you cheat on school work.
    Will the circuit that you've started accomplish that?
     
  5. nephelem

    Thread Starter New Member

    Jan 24, 2016
    22
    0
    well, i think so? i'm close but not really sure..
     
  6. dl324

    Distinguished Member

    Mar 30, 2015
    3,249
    625
    You have BL, BI, and LT tied directly to the power supply; all are low active. What will happen if you try to pull them low? Would that reset the corresponding counter?
     
  7. dl324

    Distinguished Member

    Mar 30, 2015
    3,249
    625
    The OP deleted their first post so my post was promoted to TS??

    I don't need help, so don't ask me to post a schematic...
     
  8. nephelem

    Thread Starter New Member

    Jan 24, 2016
    22
    0
    I'm the OP but the admin moved my thread to the other forum. What does TS mean? Or is that reply meant to other thread? wrong post?
     
  9. dl324

    Distinguished Member

    Mar 30, 2015
    3,249
    625
    Thead Starter. I and many others prefer to use Original Poster instead.
     
  10. dl324

    Distinguished Member

    Mar 30, 2015
    3,249
    625
    @Karen Anito Answer my questions and we can continue working on your circuit while waiting for the two threads to be merged.
     
  11. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,347
    Hello,

    I merged the threads that got separated and moved the complete thread to homework.

    Bertus
     
  12. dl324

    Distinguished Member

    Mar 30, 2015
    3,249
    625
    Thanks Bertus. I didn't want a bunch of people trying to help me...
     
  13. hp1729

    Well-Known Member

    Nov 23, 2015
    1,957
    219
    On those 7-segment displays ... do you think one resistor for the whole display is correct? If only one LED at a time were on that would work. But ...

    Clock inputs are low edge clocks? Take a look at your pushbuttons.

    Have you considered building these circuits?
     
    Last edited: Jan 29, 2016
Loading...