[sdiy] interlocking switches

[Scott Gravenhorst]

I don't have a circuit, but I think it can be done with CMOS flipflops (D or JK
wired like D) and a one-shot or two.  Each switch should be debounced.  The
debouncers each feed a multi input OR gate.  The OR output starts a one shot
intended to time out prior to when you could release the switch but after the
debouncer's output has stabilized.  The one-shot clocks all of the flipflops
simultaneously.  Each debouncer output also feeds the D input of it's flipflop.

What I have described will have the flaw that it's possible to set more than one
flip flop at a time.  However, it's very simple.  If I were building this to use
myself, that's how I would do it.  For someone else, maybe not.

This could also be done with a PIC very easily and with more/better features
such as not allowing more than one output to be set on.

"Roy J. Tellason" <rtellason at blazenet.net> wrote:
>I *know* I've seen this in some service manual or other,  but can't remember 
>where...
>
>Say you have a row of buttons,  and you push one,  an LED lights up.  When you 
>push another,  that light comes on and the first one goes out.  Sort of like 
>the old mechanically-interlocked switches I remember from ages ago.
>
>Posted about this elsewhere,  and have of course the immediate suggestion to 
>throw a processor at it,  which I'm not inclined to do,  and some more that 
>discuss using lots of logic.
>
>Can any of you guys point me toward a circuit like this?  I know there were a 
>fair number of commercial keyboards out there that used such stuff,  rows of 
>momentary-contact switches with LEDs and some toggled on/off,  while others 
>"interlocked" like I'm talking about here...
>
>
>
>
>
>

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