Digital Clock using 74192 (RESET Button) HELP!

Discussion in 'Homework Help' started by nephelem, Jan 27, 2016.

  1. nephelem

    Thread Starter New Member

    Jan 24, 2016
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    Hi. I'm working on a project. A 24-Hour Digital Clock using 74192/74ls192 IC.There should be three buttons. 1.) Hour Increment Button 2.) Minute Increment Button 3.) Reset Button.

    The schematic diagram is fine but I don't know how to connect the RESET button so that it will reset all 7 segment LEDs to 00 00 00. I did connect the RESET button (push-to-make switch) to VCC and the other pin to GND. Also the CLR/MR (Pin 14) of all the 74192 ICs but it output an incorrect display. Attached is my schematic diagram. Please help me. Thank you.
     
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  2. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    I applaud you wanting to go old school with TTL, but the schematic is not fine.

    ALL unused inputs must be connected to something, usually Vcc or GND, whichever renders them inactive.

    SW1 and SW2 apply Vcc directly to the output of a 7408 gate. If you want to combine the button press with the output of a gate, you have to do it by either connecting the button signal to one of the gate inputs or by running the button signal and the gate output to the inputs of another gate. In your case you want to take the output of the gate and OR it with the button to drive the next stage clock.

    All button signals need pull up or down resistors so the pins they are driving are not open circuits when the buttons are not pressed.

    All LED segments need current limiting resistors.

    You want to separate resetting each counter group from the master reset. You can do this, for example, by using the load input to load a value of zero into the tens-of-seconds counter when a 60 is detected. You have to change the three AND gates for NAND gates for this to work because the load input is active low.
     
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  3. dl324

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    Mar 30, 2015
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    Welcome to AAC!

    You have a similar post in the Homework Help forum. Is this homework?
     
  4. nephelem

    Thread Starter New Member

    Jan 24, 2016
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    This is a project. It was there because I posted a reply from a post in the Homework Help forum. It's already moved here.
     
  5. dl324

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    Your definition of project is different from the norm. If your project will be graded, it's homework.
     
  6. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    You have stated in a post elsewhere that you have successfully pre-loaded the device. What do you think you can do with this knowledge to pre-load a zero into the counter? Effectively, this will clear the counter.
     
  7. nephelem

    Thread Starter New Member

    Jan 24, 2016
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    Yes, sir. CLEAR. Like the whole circuit will start again. 00 00 00 when i press the button
     
  8. nephelem

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    Jan 24, 2016
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    Sir, what I mean is CLEAR. Like the whole circuit will start again from 00 00 00 when i press the button.
     
  9. djsfantasi

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    Apr 11, 2010
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    You didn't answer my question. What can you do with the knowledge you have, that I pointed out?
     
  10. nephelem

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    Jan 24, 2016
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    i have applied that knowledge as you can see in the circuit. a very very little knowledge. what this knowledge i'm talking about is how to make the Tens of the seconds and the Tens of the Minutes be in Mod6 instead of Mod9. That's all the knowledge i knew.
     
  11. nephelem

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    Jan 24, 2016
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    i have applied that knowledge as you can see in the circuit. a very very little knowledge. what this knowledge i'm talking about is how to make the Tens of the seconds and the Tens of the Minutes be in Mod6 instead of Mod9. That's all the knowledge i know.
     
  12. djsfantasi

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    What do you do when your mod 6 counter reaches 6?
     
  13. nephelem

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    Jan 24, 2016
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    what happens is it resets to 0.
     
  14. AnalogKid

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    Aug 1, 2013
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    Where are you located, and what is your native language?

    What you don't seem to understand is that you need four separate Clear or Reset circuits: Seconds, Minutes, Hours, and Master Reset. You have three of them done already, and they look OK. Normally, adding a master Reset would require several logic gates, but you are fortunate and do not have to do this. Because the counters have a preset function built in, you can use this as a master reset by loading 0000 into each counter. Connect together the LD pin of all of the counters, connect this net to a pull up resistor to Vcc and to one side of the Reset switch. Connect the other side of the Reset switch to Ground. After you have made this change to your schematic, post the new version for us to review.

    ak
     
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  15. nephelem

    Thread Starter New Member

    Jan 24, 2016
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    Country: Philippines
    Language: Filipino (Tagalog) - Primary, American English (Secondary)

    There is no device such called Pull-Up Resistor in Circuit Wizard. But according to google, i need to build it. I don't know if I constructed it correctly. Connected all the LD pins. IT WORKED O.O.. But i'm not sure.

    Here it is:

    74192revised1.jpg
     
  16. nephelem

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    Jan 24, 2016
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    Sir, Do I need to connect the LT, BI and BL pins of all 7-segments to Vcc?
     
  17. thumb2

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    Oct 4, 2015
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  18. AnalogKid

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    You do not have all 6 LD pins connected together, and the DN pins are connected incorrectly. The 7447 datasheet describes how to connect all of its pins.

    ak
     
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  19. nephelem

    Thread Starter New Member

    Jan 24, 2016
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    Ah, yes. I missed one LD pin.
    But did I build the pull up resistore correctly?
    Where would I connect the DN pins of the Unit Counters? I only know how to connect DN pins of the Tens Counters.
    I'll take a look of 7447 datasheet
     
  20. nephelem

    Thread Starter New Member

    Jan 24, 2016
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    the post moved.
     
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