5 switches and a 7seg

Discussion in 'General Electronics Chat' started by raffter, Apr 10, 2008.

  1. raffter

    Thread Starter Active Member

    Feb 28, 2008
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    Guys,

    my brain not working again:rolleyes:

    I have N.O. switches.... labeled 1 through 5.... When I press "4", 7 seg would show the digit "4" and would BE that always, until I depress another switch/digit.....

    any inputs/ideas/tips/suggest(ments):D how???? and NO micros please....


    Ralph
     
  2. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,677
    899
    Do you want to display all 10 digits (0-9) or just "4"? Do you want to allow multiple switches for each digit, such as each switch would represent a binary number (i.e., 0, 1, 2, 4, 8). Thus 4 would be a single switch and 7 would require three switches to be pressed.

    John
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    You will only need 4 switches and BCD to go 0 - 9. You will have to debounce the switches and latch the switch states to feed the decoder. Any logic family you care to use?
     
  4. raffter

    Thread Starter Active Member

    Feb 28, 2008
    113
    0
    guys,

    its like this:

    at startup(dont care state), dont matter what is would display..but you could prime it up pressing ANY of the 5 switches..

    >If I press "1" , display would be "1" and it would stay "1" not unless I press anything else
    > I press "3", display changes to "3" and would stay that way...
    > etc etc.... I hope thats more clear now :)


    digits will only be 1-9... want to make it as simple as possible..

    I was thinking of SCRs(per switch) driving OR-AND(diodes) to light up "1" "2" etc etc.. sort of like those found in game shows...but instead of driving LED/buzzer, I want to use a 7seg for the "display" part...

    I was thinking a BCD->7seg decoder (for the 7seg part, would surely help) but -something- to interpret a bunch of switches -->> BCD is the missing link here...

    im open to ideas....


    Ralph
     
  5. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    How about four JK flip flops with preset and clear, and an array of steering diodes from the switches?
     
  6. raffter

    Thread Starter Active Member

    Feb 28, 2008
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    hmmmm ....

    any other ??

    I think an array of SCRs(1 per switch) + steering diodes(4bit output going to BCD->7seg decoder chip) would do the trick..??! hmmmmm


    thingmaker,
    thats a cool idea too.. JK flip flops(to SET THIS and reset OTHER) + steering diodes to output 4 bit... ok !! :)



    EDIT:
    thingmaker,

    how would I wire this JK flip flop?? I was thinking there would be a clock(10HZ perhaps) to all the CLK inputs, "Set" for the switch input/s, and Q as the output/s(1 JK flipflop per "digit"), and diodes per Q output to reset the other JK flip flops... is this correct?? or is there more simpler approach?


    Ralph
     
  7. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,535
    How about this approach? You use the following button scheme, and feed them into 4 Set/Reset flipflops, which buffer the BCD to 7 Segment Decoder. The clear button feeds all the flipflops, no debounce required.


    [​IMG]
     
  8. Norfindel

    Active Member

    Mar 6, 2008
    235
    9
    What about using a 4 bit latch, and trigger the latch by using diodes from every of the keys, instead of a bunch of flip-flops? (you can also use a four-input OR gate, instead of diodes).
    EDIT: uh, sorry, you don't wanted BCD, so, that is 10 keys to take care about. What about coding to BCD by using diodes? For example, you need to conect switch 1 to the LSB with a diode, switch 2 would be connected to bits 0 and 1 using 2 diodes, you would then use an OR gate with the 4 BCD digits, and trigger the latch with that. Should work :)
    But be aware that things would get strange if someone press 2 switches at once.
     
  9. raffter

    Thread Starter Active Member

    Feb 28, 2008
    113
    0
    Bill,

    nice approach but would be perfect IF pressing "another" switch would reset the other outputs(but NOT the swich I just recently pressed)...

    >>press 1 , output is in 1(reset the 2,3,4,5)
    >>press 2, output is now 2(and reset 1,3,4,5)
    >>press 4, output is now 4(and reset 1,2,3,5)
    >>etc etc something like that...latching and would reset the others...

    now thats what im trying to figure out... :)

    EDIT: something like this(good for 2 only,can be replaced with single RS latch)... BUT I need at least 5 inputs/witches...



    Ralph
     
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  10. Wendy

    Moderator

    Mar 24, 2008
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    There are Data Latch switches that would do exactly what you're talking about, so would the JK varity with a little wiring. You press all the buttons on the BCD side, then press the fifth button (label it "strobe"), is that more what you're looking for?
     
  11. raffter

    Thread Starter Active Member

    Feb 28, 2008
    113
    0
    Bill,

    what particular chip ?? there are many Data latch chips out there...


    Ralph
     
  12. Wendy

    Moderator

    Mar 24, 2008
    20,765
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