I want to use many (about 30) switches as inputs to my Arduino Uno. I've built a circuit using four 74LS30 (nine input NOR gates) to multiplex 15 switches down to 4 pins (16th state is when all switches are off, 0000) which works. However, expanding this to accept inputs from more switches will mean…

Reverse multiplexing

Grumpy_Mike April 29, 2012, 7:18am 9

Well a bit less wiring up but the chip is more than twice the size.

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