Raspberry Pi Pico Analogue Multiplexer Expander on Stripboard

The Raspberry Pi Pico while being a really useful microcontroller has only 3 pin for use with analogue signals. This can be a limitation for some projects, and this small adapter is to expand one of those ADC inputs to eight via a 4051 CMOS multiplexer.

The multiplexer requires three digital inputs to select the input required, and a fourth is used to power the multiplexer as it's power requirements are very small.

The circuit has been assembled on a small piece of stripboard with a PCB socket to ease connectivity.

4051B CMOS 8 into 1 multiplexer IC (MC14051B, CD4051B, CD74HC4051)

16 pin dip IC socket

Small piece of stripboard (12 strips by 13 holes)

PCB pins

PCB header socket

Hookup wire

The stripboard needs to be cut as 12 strips wide and 13 holes long.

Soldering the PCB header socket is achieved by lining up the socket with the strips and soldering one pin before adjusting and soldering the others pins. The holes should be cut as per the diagram. Unfortunately the picture is an example and doesn't quite align with the diagram.

This is the best time to solder the pins to the socket, supporting them with either a breadboard or strips if PCB socket to hold them in place. Once one pin on a strip is fixed, the strip can be adjusted before soldering the others.

Once the pins are in place, the IC socket can be placed and soldered.

An additional pin is shown in the diagram not present in the pictures. This is to allow access to the ADC1 pin on the Pico.

There aren't many wire connections to be made, each being made with bare hookup wire.

Once the wiring is complete and checked, the IC can be inserted into the socket.

The multiplexer is connected to the Pico via the PCB header socket as shown.

The first pin is GPIO19 or physical pin 25

An example program to use the multiplexer is held on github here.