Multiplexeur

How to use a multiplexeur CD74HC4067 with ultrasonic sensors HC-SR04

Objective:

Implement an Arduino code in order to handle several ultrasonic sensors HC-SR04 (max 8).

Requirements:

• a multiplexer CD74HC4067
• an Arduino board
• 2-8 ultrasonic sensors HC -SR04

Steps:

1. Build the circuit with the Arduino, the multiplexer and the ultrasonic sensors.

Multiplexer/Arduino connections :
SIG on 2
s3 on 3
s2 on 4
s1 on 5
s0 on 6

Sensors/Multiplexer connections:
Sensor1:
pin trigg on C0
pin echo on C1

Sensor2:
pin trigg on C2
pin echo on C3

2. Initialize the pins of the multiplexer

const int SIG = 2;
const int s0 = 6;
const int s1 = 5;
const int s2 = 4;
const int s3 = 3;

void setup() {
  pinMode(SIG, INPUT);
  pinMode(s0, OUTPUT);
  pinMode(s1, OUTPUT);
  pinMode(s2, OUTPUT);
  pinMode(s3, OUTPUT);
  Serial.begin(9600);
}

3. To access to the channels of the multiplexer you have to send a number on 4 bits to the multiplexer.
   For example, if you want to access to the channel C0, you have to send 0, which is "0000" in binary, so s0=LOW, s1=LOW, s2=LOW, s3=LOW, if you want to access to the channel 4, you have to send 4 to the multiplexer, whixh is "0100" in binary, so s0=LOW, s1=LOW, s2=HIGH, s3=LOW;
   (LOW = 0, HIGH = 1).

Example with 2 ultrasonic sensors using channels C0,C1,C2,C3 :

void loop() {

//sensor1

  long duration1, distance1;
  digitalWrite(s0, HIGH);
  digitalWrite(s1, LOW);
  digitalWrite(s2, LOW);
  digitalWrite(s3, LOW);
  delayMicroseconds(2);
  digitalWrite(s0, LOW);
  digitalWrite(s1, LOW);
  digitalWrite(s2, LOW);
  digitalWrite(s3, LOW);
  delayMicroseconds(10); 
  digitalWrite(s0, HIGH);
  digitalWrite(s1, LOW);
  digitalWrite(s2, LOW);
  digitalWrite(s3, LOW);

  duration1 = pulseIn(SIG, HIGH);
  distance1 = (duration1/2) / 29.1; 
  
  Serial.print("Sensor_1");
  Serial.print(distance1);
  Serial.println("cm");

  delay(500);

 //sensor 2
  
  long duration2, distance2;
  digitalWrite(s0, HIGH);
  digitalWrite(s1, HIGH);
  digitalWrite(s2, LOW);
  digitalWrite(s3, LOW);
  delayMicroseconds(2);
  digitalWrite(s0, LOW);
  digitalWrite(s1, HIGH);
  digitalWrite(s2, LOW);
  digitalWrite(s3, LOW);
  delayMicroseconds(10); 
  digitalWrite(s0, HIGH);
  digitalWrite(s1, HIGH);
  digitalWrite(s2, LOW);
  digitalWrite(s3, LOW);

  duration2 = pulseIn(SIG, HIGH);
  distance2 = (duration2/2) / 29.1; 
  
  Serial.print("Sensor_2 : ");
  Serial.print(distance2);
  Serial.println("cm");
  
  
  delay(500);
}

Tips:

Make sur that all your sensors and connections are functionals. (lol)