CD4051 Single 8-Channel Multiplexer/Demultiplexer IC (DIP-16)

When a project has more analog signals to read than it has free analog input pins, the CD4051 offers a practical workaround: it acts as an eight-way analog switch, routing any one of eight separate input signals through to a single shared output based on a simple three-bit digital selection code. That lets one precious analog input pin effectively serve eight different sensors or signal sources by switching between them in software, which is a common trick for reading large sensor arrays or multiplexing several potentiometers through a microcontroller that doesn't have enough native analog channels. It works bidirectionally too, so it can just as easily route one output signal to any of eight different destinations instead.