Digital clock using 74LS family

Discussion in 'The Projects Forum' started by Mbrubaker, Nov 1, 2011.

  1. Mbrubaker

    Thread Starter New Member

    Nov 1, 2011
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    Hello I'm new to all about circuits and am making a digital clock using the 47LS160 4-bit synchronous decade counter along with other chips of the 47LS family. I'm doing this project for my Digital Devices II class and do not want to change the components drastically I would like to use the ICs in my schematic. can anyone please check my schematic and let me know if the connections are correct or what I need to change.

    Things to note:
    1) all chips are assumed that VCC and GND are connected.
    2) The unlabeled resistor on the 7-segment display is 330R
    3) The clock generator portion of the circuit is not done haven't decided what i want to use to generate my 60Hz pulse.

    This is my first real circuit that I'm designing and I have checked the forums but haven't gotten the answers I'm looking for. Any positive criticism is welcome and any help provided is appreciated.

    Thank you,
    Michael Brubaker

    Edit: The bottom row of Resistors connected to the common anode are connected my picture got cropped in transfer.
     
  2. MrChips

    Moderator

    Oct 2, 2009
    12,449
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    I have not checked your logic. I assume you are using a simulator to check this. The 1K resistors on the 7-segment displays should not be necessary. Pin 9 on U18 should be tied high.
    Pin 7 on U21 appears to be missing it's connection.
     
    Last edited: Nov 1, 2011
  3. Mbrubaker

    Thread Starter New Member

    Nov 1, 2011
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    0
    Yea I'm trying to use multisim 11 to test this but it isn't working properly I'll modify the schematic and take out the 1k resistors and I'll pull those pins high. Everything I read in my digital book says the logic should be correct for the chips and gates but couldn't find much information on the web. I'll respond after work with those changes and post the new schematic.
     
  4. MrChips

    Moderator

    Oct 2, 2009
    12,449
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    One thing you overlooked. How are you going to set the time?
     
  5. elec_mech

    Senior Member

    Nov 12, 2008
    1,513
    193
    Hi Mike, welcome to AAC.

    I think you have a handful of connections that need correction, but before I dive too far into this, what is this circuit supposed to do?

    It looks like you're making a count up timer but you mentioned clock. So I see a two digit seconds display, a two digit minutes (?) display and a single digit hour(?) display. Is this correct?

    Are you only displaying time up to 9 hours?
     
  6. Mbrubaker

    Thread Starter New Member

    Nov 1, 2011
    3
    0
    I've changed some of the connections that I found out were wrong. This is suppose to be a digital clock there are 6 7-segment displays on the schematic. I plan on having a toggle switch on the load to pull it low and will have switches to set the time off the data inputs mechanically using BCD for the hours and minutes and leave the seconds as is. So far in Multisim 11 the seconds portion of the clock works correctly but its after that I'm having problems. I think it might be something to do with the logic but I'm not to sure will work on it more tomorrow.

    Attached is the updated schematic.

    Thank you for feedback so far,

    Michael Brubaker
     
  7. elec_mech

    Senior Member

    Nov 12, 2008
    1,513
    193
    Look at the datasheet for the 74160. There is an example schematic for ripple and cascading multiple 74160s together. I suggest the cascading one. Use the example to wire your tens and ones together for seconds, minutes, and hours. It shows which pins to tie from one to the next IC and which to Vcc.

    Also, unless I'm missing something, I think your clock should be 1Hz, not 60Hz. 1Hz = 1 second, 60Hz = 1/60th second.
     
  8. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Take it in small sections, the hours counter is the hard one, especially if you want to do 12 and 24 hour options.

    I have a basic block diagram, along with some ideas you can dip into...

    Digital clocks

    I also came up with a basic block diagram (besides the one in the article under construction).

    [​IMG]
     
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