Help cycling a 7-segment display

Discussion in 'Homework Help' started by Nerfhurter, Dec 11, 2010.

  1. Nerfhurter

    Thread Starter New Member

    Dec 10, 2010
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    For an introduction to seven segment displays we built a circuit that has 3 switches to cycle 0-7 in binary and display our date of birth at each number. (MM-DD-YY) for example. That was easy enough but I'm interested in making a circuit that could automatically cycle through it all but I'm not sure where to start. I'm using NI CDS, thanks ahead of time for any help.
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    What does the schematic for the original circuit look like?
     
  3. Georacer

    Moderator

    Nov 25, 2009
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    Are you familiar with shift registers? We have a section about them on the resident e-book.

    You could load the 3-bit information of the 6 numbers on 3 8-bit registers and replace the switches with the registers' serial outputs.

    As the registers would unload their content, it would act just the same as your 3 switches.

    Is that clear?
     
  4. Nerfhurter

    Thread Starter New Member

    Dec 10, 2010
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    Alright thanks, I've been reading up on shift registers I think it's a little beyond me at the moment, but I'll try looking at it over x-mas break more. Finals...
     
  5. Nerfhurter

    Thread Starter New Member

    Dec 10, 2010
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    Here's my original schematic. http://img219.imageshack.us/img219/761/dateofbirth.png

    After looking a shift register I'm not sure exactly how it works, from what I understand a clock is connected to determine when to send data out, and it "remembers" the last output so it sequentially goes though a set of imputed data. So to use an 8bit out for each switch so I input 5v or gnd for each input and connect clock to clk? What do I attatch to ~CLR, and is D output?
     
    Last edited: Dec 15, 2010
  6. Nerfhurter

    Thread Starter New Member

    Dec 10, 2010
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    Feel like I'm talking to myself but...
    So after looking at it more, I think I have to use what CDS calls Shift_8PIN. I'm guessing A-H I input values for counting, and clock to clk. QH is output? What do I connect to ~CLR, SER, ~SH/LD, and INH?
     
  7. Georacer

    Moderator

    Nov 25, 2009
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    If you need an intro to shift registers, take a look here, up until the end of the chapter. http://www.allaboutcircuits.com/vol_4/chpt_12/1.html

    There are many versions of shift registers. I 'm not familiar with CDS, but ypically, all the shift registers have a clear, shift and load pin. ~CLR will blank the registers if driven to LOW, while, ~SH/LD will shift the content towards the output or load it into the register, whith a LOW/HIGH signal respectively. I 'm not quite sure what SER does in your case, but try using the IC with in on LOW first.

    If you are using Multisim (deducing from your image capture), try using the 74166 shift register, it is incuded. Also read its datasheet to gain a complete understanding of its operation.
     
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