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

system April 25, 2012, 5:57am 2

Yes, I believe the correct IC for this job is the 74HC165N: the parallel to serial shift register. Sparkfun sells them but probably for 1000% markup.

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