The 74HC4051; 74HCT4051 is a single-pole octal-throw analog switch (SP8T) suitable for use in analog or digital 8:1 multiplexer/demultiplexer applications. The switch features three digital select inputs (S0, S1 and S2), eight independent inputs/outputs (Yn), a common input/output (Z) and a digital enable input (E). When E is HIGH, the switches are turned off. Inputs include clamp diodes. This enables the use of current limiting resistors to interface inputs to voltages in excess of VCC.

The Multiplexer Breakout provides access to all pins and features of the 74HC4051, an 8-channel analog multiplexer/demultiplexer. The 74HC4051 allows you to turn four I/O pins into eight multifunctional, individually selectable signals, which can be used to do everything from driving eight LEDs to monitoring eight potentiometers.

The 74HC4051 can function as either a multiplexer or a demultiplexer, and it features eight channels of selectable inputs/outputs. The routing of common signal to independent I/O is set by digitally controlling three select lines, which can be set either high or low into one of eight binary combinations.

A multiplexer, commonly abbreviated down to "mux", is an electronically-actuated switch, which can turn one signal into many. It routes a common input signal to any number of separate outputs. Similarly, a demultiplexer routes any number of selectable inputs to a single common output.

The 74HC4051 can function as either a multiplexer or a demultiplexer, and it features eight channels of selectable inputs/outputs. The routing of common signal to independent I/O is set by digitally controlling three select lines, which can be set either high or low into one of eight binary combinations.

One half of the board breaks out the control signals (E, S0-S2) and common input/output (Z). The other side provides access to all eight independent I/O's (Y0-Y7). Both sides include supply and ground connections (VCC, VEE, GND). The table below summarizes each pin and its function.

One half of the board breaks out the control signals (E, S0-S2) and common input/output (Z). The other side provides access to all eight independent I/O’s (Y0-Y7). Both sides include supply and ground connections (VCC, VEE, GND).

One half of the board breaks out the control signals (E, S0-S2) and common input/output (Z). The other side provides access to all eight independent I/O's (Y0-Y7). Both sides include supply and ground connections (VCC, VEE, GND). The table below summarizes each pin and its function.

Power Supply Limits

The 74HC4051 supports a wide supply range, but the presence of the optional negative voltage supply -- VEE -- has the potential to make things a little complicated. Here are the basic rules that govern the 74HC4051's power supplies:

VCC must be at least 2.0V (above GND).

VCC must not exceed 10V (above GND).

VEE must be less than VCC -- anywhere between 2.0V and 10V below VCC.

The operating area graph below -- figure 7 in the datasheet -- represents those ranges visually:

For example, the 74HC4051 supports standard 3.3V, 5V, and 9V supplies, as well as bipolar supplies, like ±5V (but not ±9V).

JP1 -- Connecting VEE to GND

We expect that the majority of multiplexer-equipped projects may not need the 74HC4051's bipolar supply support. So, to make the board easier to get quickly up-and-running, we've added a jumper to the top side, which shorts VEE to GND.

Connect the Multiplexer Breakout up to eight photocells to create a single-octave, touchless keyboard!

In lieu of a collection of eight analog input devices, you can just use jumper wires to short the input pins to either VCC or GND. That way you can at least prove to yourself that it works.

COPY CODE

/******************************************************************************

Hardware Hookup:

Mux Breakout ----------- Arduino

S0 ------------------- 2

S1 ------------------- 3

S2 ------------------- 4

Z -------------------- A0

VCC ------------------- 5V

GND ------------------- GND

(VEE should be connected to GND)

The multiplexers independent I/O (Y0-Y7) can each be wired

up to a potentiometer or any other analog signal-producing

component.

Development environment specifics:

Arduino 1.6.9

SparkFun Multiplexer Breakout - 8-Channel(74HC4051) v10

(https://www.sparkfun.com/products/13906)

******************************************************************************/

/////////////////////

// Pin Definitions //

/////////////////////

const int selectPins[3] = {2, 3, 4}; // S0~2, S1~3, S2~4

const int zOutput = 5;

const int zInput = A0; // Connect common (Z) to A0 (analog input)

void setup()

{

Serial.begin(9600); // Initialize the serial port

// Set up the select pins as outputs:

for (int i=0; i<3; i++)

{

pinMode(selectPins[i], OUTPUT);

digitalWrite(selectPins[i], HIGH);

}

pinMode(zInput, INPUT); // Set up Z as an input

// Print the header:

Serial.println("Y0\tY1\tY2\tY3\tY4\tY5\tY6\tY7");

Serial.println("---\t---\t---\t---\t---\t---\t---\t---");

}

void loop()

{

// Loop through all eight pins.

for (byte pin=0; pin<=7; pin++)

{

selectMuxPin(pin); // Select one at a time

int inputValue = analogRead(A0); // and read Z

Serial.print(String(inputValue) + "\t");

}

Serial.println();

delay(1000);

}

// The selectMuxPin function sets the S0, S1, and S2 pins

// accordingly, given a pin from 0-7.

void selectMuxPin(byte pin)

{

for (int i=0; i<3; i++)

{

if (pin & (1<<i))

digitalWrite(selectPins[i], HIGH);

else

digitalWrite(selectPins[i], LOW);

}

}

After uploading the sketch, open your serial monitor and set the baud rate to 9600. Here you'll see the analog values from all eight independent I/O (Y0-Y7) read and printed out once a second.

Toggle your inputs, or switch out some jumper wires to see the values change.

This example uses that same selectMuxPin function to set the S0, S1, and S2 pins. But instead of writing out to the Z pin, we read from it.