5 switches and a 7seg

Thread Starter

raffter

Joined Feb 28, 2008
113
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
 

jpanhalt

Joined Jan 18, 2008
11,087
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
 

beenthere

Joined Apr 20, 2004
15,819
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?
 

Thread Starter

raffter

Joined Feb 28, 2008
113
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
 

Thread Starter

raffter

Joined Feb 28, 2008
113
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
 

Wendy

Joined Mar 24, 2008
23,415
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.


 

Norfindel

Joined Mar 6, 2008
326
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.
 

Thread Starter

raffter

Joined Feb 28, 2008
113
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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Wendy

Joined Mar 24, 2008
23,415
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?
 
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