8 Dec
2007
8 Dec
'07
1:37 p.m.
From: cclist at sydex.com
How about this?
8 74xx30's (8 input NAND) with each output feeding one of the inputs
of the other stages. The remaining input of each gate is connected
to a pushbutton whose other side is grounded and the gate side pulled
up to Vcc through an appropriate resistor (say, 2.2K). The circuit
is self-debouncing and the last button released governs the output.
Basically an 8-stable flip-flap-floop...-flop. Initial state is
theoretically random, but probably could be forced with a small
capacitor across one of the buttons.
If you expand much beyond this, note that fanout issues may rear
their ugly heads.
Cheers,
Chuck
Hi Chuck
Essencially the same as I described. I think is best meets the
general design criteria. I just used a single throw switch as
the circuit would be more than fast enough to ignore an bounch issues.
If there was a fan out problem, one could do a ripple ring for clearing
but that might require some timed circuits to keep from racing.
Dwight
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