One and only one circuit

[ADWSystems]

Yes it is a possibility that someone could push two buttons at once. It would only produce a minor non-serious result. Which should be fixed by pushing the button again in the circuit designed so far in this thread. I would prefer that it didn't happen but I think the circuit for detecting more than one button pushed while also meeting the requirement of being expandable would be quite substanial. The circuit could easily interrupt the "clock" sign if it was implemented. Can anyone think of a circuit that has multiple inputs such that if only one is high then the output is also high and if there are zero or multiple inputs high the output is low? (hence the name of the thread...one and only one; but I got side tracked by the rest of the circuit)

 

[KMoffett]

Untried, but I think this would detect more than one output high and is expandable. If no outputs are high, the input to the comparator is 0V. If one output is high, the input to the comparator is 2.5V. For both states the comparator's output is low. If two or more outputs are high, the input to the comparator is 3.3V or more. and the comparator's output is high. Not sure what you would do with that.

Ken

 

[crutschow]

You could perhaps use some variation of a game-show type circuit that responds only to the first button pushed. But that would obviously increase the complexity of the circuit.

 

[ADWSystems]

Interesting. Basically a summing opamp. I was trying to figure out how to do that but I forgot about that setup. I was thinking too much in one's and zeroes.

Unfortunately I forsee two problems, both easily fixed I believe.
The first is that the input would need to be reversed (0 or 1 to be high and 2+ to be low).
That leads to the second, Where you implemented it would be too late. The outputs would already be set. If it was implemented using the '573 input signal and the comparator output ANDed with the switch diode OR gate and then fed to the '573 LE.

 

[KMoffett]

Since we don't know what the whole project involves, we're just guessing what will work. I'd just go with a microcontroller to scan matrix'd buttons and addressable outputs.

Ken

 

[ADWSystems]

The whole project to is control air flow gates in an pneumatic blower system.

I'm trying to stay away from programmables as I don't have access to a programmer and not really in the mood to create another project to build one. I know I should but I'm trying to keep my eye on the prize. Microcontrollers and PLDs depending on the methodology aren't really expandable. I need to do some sketching myself based on the circuit ideas provided, but not only do I think where the design is now is expandable, but perhaps with the right layout and implementation...modular, meaning I could cascade the boards to expandable the circuit.