As we know Arduino has 6 analog input channels. But what if we need more of them – like 16? The best way to do so is to use an analog multiplexer like CD4067B which has 16 digitally selectable channels. aggaz used one Arduino’s ADC to accept incoming signals from multiplexer and he used next four analog pins to control multiplexer itself. This way he preserved digital pins for other general purposes.

This technique was used in 8 step sequencer where sample rates are controlled via 16 potentiometers.

ADC expander can be used in other great projects where more than 6 ADC channels are needed.