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3D 7 Segment LED Display Using 112 LED's

Discussion in 'LEDs and Optoelectronics' started by Madmax3zero, May 26, 2012.

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  1. Madmax3zero

    Madmax3zero

    6
    0
    May 26, 2012
    Hello All!

    Just joined your community here and wanted to share a project I recently completed for my digital electronics class. This is a
    3D 7 segment display with four levels using 112 5mm led's. As designed, it simply counts from 0 to 9 while switching each level on and off in sequence.

    3D 7 Segment Display.jpg

    Here is the link to the video


    I'm not finished with the schematic yet, but I'll post it as soon as it's done. In the mean time, here is a quick run down on how it works.

    The first stage is a mod-4 ring counter built using a universal shift register. Each of the 4 parrallel outputs are connected to the base of a 3904 NPN Transister. Each Transistor acts as a switch to ground for each of the four levels of the display. The ring counter can be pre-loaded with any sequence of 1s or 0s you want (I went with a 1 0 0 0 pattern in order to activate one level at time). The way it works is; Each clock pulse cycles the high bit through each flip-flop one at a time causing a high logic level to appear on its respective output. This drives the corresponding transistor into saturation which, in turn, switches its corresponding display level to ground.

    The second stage is a simple decade counter built using two 74LS76 dual flip-flops. The clocks of the decade counter are connected syncronously to the Qd output of the ring counter. When the Qd output of the ring counter goes high, it triggers a change in the state of the decade counter. In this case, my counter counts from 0 to 9, then recycles (you can set it up to count in any sequence you like). The output of the counter is connected to a BCD decoder (binary-to-decimal) then routed through a couple of 7408 inverters and sent off to the seven segment display. This provides positive voltage potential to each of the selected segments while the ring counter handles the ground.

    As you can see in the video, the decade counter starts and holds state at 0 while the ring counter cylcles the 0 through each of the four levels. When the 0 reaches the lowest level, the output of the ring counter goes high and the decade counter switches from 0 to 1 on the next clock pulse. The cycle repeats until the counter reaches 9. After that it's just rinse and repeat.

    Of course, a lot more functionality can be added to this circuit through the use of a microcontroller. Alas, my instructor made it clear that we needed to use hard logic. Future designs will, however, incorporate a few Arduinos.

    Thanks for looking. I'll get a schematic posted as soon as it's done.
     
    Last edited: May 26, 2012
  2. timothy48342

    timothy48342

    218
    1
    Nov 28, 2011
    Welcome to the forum MadMax!

    That's looks pretty cool.

    I'm curious how you got the LEDs to all stay lined up so nicely. Is there a clear structure there holding them or is it just the leads keeping them in place.

    --tim
     
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,489
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    Jan 21, 2010
    Very cool.

    Now for a question... Do you know what it's called when you get each level to display a different number, AND you switch through them very quickly, AND you have them next to each other rather than on top of each other? (you'll note that the only fundamental change is that the number changes between levels)
     
  4. Madmax3zero

    Madmax3zero

    6
    0
    May 26, 2012
    Thank you for that. The entire structure is supported by nothing other than the leads of the LEDs. It's actually quite sturdy. I will admit though, that it was very difficult and time consuming to get them to line up properly.
     
  5. Madmax3zero

    Madmax3zero

    6
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    May 26, 2012
    LOL. You've got me on that one. Answer? I'm curious...
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,489
    2,830
    Jan 21, 2010
    Google "multiplexing 7 segment displays" :)
     
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