On Multiplexers – or input hunger

For a project in December, where if all goes well I will have 45 hand-made sewn buttons to trigger 45 sounds. As I want to trigger real buttons from the physical realm, it is clearly microcontroller time.

I will use an Arduino on the physical computing side of the set-up. An Arduino has a limited amount of digital inputs, inputs that detect whether a button is on or off, in this situation (0 or 1). One way of having more inputs is using a multiplexer chip in combination with the analog inputs of the Arduino. I understand the chip works like this: basically an analog input can have several inputs -> if you connect for example a potentiometer, which is a variable resistor -> each time you turn the knob, the analog input gets another value. The multiplexer works in a similar way, translating your many buttons to several signals which arrive in an analog input. Now, such a chip is limited, because per chip you can have 8 channels instead of one.

Here’s a list of resources I have found with regard to the multiplexer.
The Arduino playground page on multiplexers: it’s a bit cryptic, but I will test this set-up it soon. The most common multiplexer chip seems to be the CD 4051.
– Two multiplexer projects, found on the Arduino blog
A tutorial on the website of ITP on using three multiplexer chips with 16 inputs per chip! The chip used here is: CD4067B.

If all goes well I’ll be able to document further and publish some code for the 45 buttons…

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