7 seg cycle

Discussion in 'General Electronics Chat' started by duxbuz, Apr 10, 2014.

  1. duxbuz

    Thread Starter Member

    Feb 23, 2014
    133
    0
    Hi

    How could I cycle through the numbers on a 7 Segment LED without using a microcontroller.

    Can anyone give me any clues to get me started please?

    My limited experience is not bringing much to mind.

    I think of counters, shift registers and clocks.... am I on the right track?

    Thanks
     
  2. MrChips

    Moderator

    Oct 2, 2009
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    There are many ways to do this.
    You need to state what you are attempting to accomplish.
     
  3. duxbuz

    Thread Starter Member

    Feb 23, 2014
    133
    0
    I basically want to run through the number sequence on the LED repeatedly.

    No practical reason.

    But i dont want to use a microcontroller, I only want to use ICs.
     
  4. MrChips

    Moderator

    Oct 2, 2009
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    You can choose from TTL or CMOS components.

    You need to know the type of seven-segment LED display. Is it common-anode or common-cathode?

    If using TTL chips, the typical BCD to seven-segment decoder/driver is SN7447 or SN74LS47. This is designed to be used with common-anode LED displays.

    You can select from a number of 4-bit counter chips such as 7490, 74160, 74192 (or 74LSxxx versions).

    For CMOS chips, you can use 4510 or 40192 interfaced to a 4511 decoder/driver.

    For a single chip solution, CD40110 interfaces directly to a common-cathode LED display.

    You can also use HC or HCT versions. There are simply too many combinations and permutations to list here.

    For a list of common TTL and CMOS chips see here:

    http://forum.allaboutcircuits.com/showthread.php?t=65137&page=2
     
  5. Potato Pudding

    Well-Known Member

    Jun 11, 2010
    684
    92
    Clock > BCD (binary converted decimal) counter > 7seg LED decoder driver IC

    In real parts terms.



    555 timer >> CD4026B or CD4033B

    Note that this is intended for a common cathode (ground) 7 Segment LED.

    Common anodes 7 segment LEDs are common and would need an inverter between each output of the counter and the LED segments cathodes. Simple NPN transistors will do fine for this purpose if you don't think wiring up 7 transistors is too much trouble. Simpler is to use an IC inverter. There are several Inverter IC's that will basically put 8 CMOS or NPN darlington transistors and dropping resistors for the inputs in an IC package. Look for inverting buffer drivers.


    EDIT. Always remember to put dropping resistors on the LED segments. You can get convenient R-Packs in chip formats.
     
    Last edited: Apr 12, 2014
  6. duxbuz

    Thread Starter Member

    Feb 23, 2014
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  7. MrChips

    Moderator

    Oct 2, 2009
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    Note that 74160 is 0-9 counter (BCD - binary coded decimal)
    while 74161 is 0-15 counter (4-bit binary).

    If you are going to order parts why not get one of each and experiment.

    If you are flexible with the budget, get 4 or 5 of 74xx160 (sooner or later you will want to show multi-digits).
     
  8. MrChips

    Moderator

    Oct 2, 2009
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  9. duxbuz

    Thread Starter Member

    Feb 23, 2014
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    0
    Thanks a lot

    I was wondering should I get a clock also to step through the counter sequence.

    I have some 555 timers or are they not suitable.
     
  10. MrChips

    Moderator

    Oct 2, 2009
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    555 timers are ok.
     
  11. duxbuz

    Thread Starter Member

    Feb 23, 2014
    133
    0
    Thanks.

    Didn't see the potato pudding reply earlier. Thanks to you both
     
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