3 position Switch logic

Thread Starter

hupa

Joined May 19, 2011
8
Help please, I am a digital dunce, and not at ease with logic circuits.

I have 3 membrane buton switches each with an associated LED.
Here is what I want....
a) The button pressed dominates (cancels whichever of the other 'positions' was on), and latches.
b) No strange latchups if more than one button pressed accidently.
c) On power up a jumper determines which 'position' is on.
d) Could your idea be extended to N positions with N buttons?
I have supplies of +5, +12, +- 10 & +- 15 available. Load is minimal.
Any ideas please? It seems so straightfoward, but I'm struggling, and I refuse to use a micro.
 

ErnieM

Joined Apr 24, 2011
8,377
Each LED is controlled by a set/reset flip flop. Each button will drive the SET input of it's flip flop, and thru an OR gate RESET all flip flops NOT driven by it.

Using a diode OR scheme would allow this to be extendable to N stages.

The power on set scheme would be similar, OR to the SET of the on device, and to the RESET of all other devices.
 
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