13  Digital sensors

13.1 SHT31 Temperature & Humidity Sensor Using I2C communication

In this tutorial you can find a lot more information.

Try it · Sensors sharing two wires

Which sensor answers?

The sensors share SDA and SCL. Choose an address, then ask the sensor at that address to reply.

SHT31 A

ConnectedAddress0x440x45

SHT31 B

ConnectedAddress0x440x45

VL53L0X

Connected

Address 0x29

Ask this address0x290x440x450x50

SHT31 address choices represent the board’s hardware address settings. This page does not change real sensors.

Blue: SDA · Orange: SCLPower connections are not shown

Choose an address and press Ask sensor.

Addresses found

Not scanned yet.

A scan lists addresses. It cannot tell whether two sensors share one address.

Simplified diagram and example readings. Real wiring also needs power, ground and suitable pull-up resistors. Use each sensor’s library to request its measurements.

Change an address or disconnect a sensor, then ask again.

Code for reading the sensor:

Download code

/*
 * This program is a modification of
 * http://www.esp32learning.com/code/esp32-and-sht31-sensor-example.php
 */
#include <Arduino.h>   // Include the Arduino library
#include <Wire.h>      // Include the Wire library for I2C communication
#include "Adafruit_SHT31.h" // Include the SHT31 library from Adafruit

Adafruit_SHT31 sht31 = Adafruit_SHT31(); // Create an instance of the SHT31 object

void setup() {
  Serial.begin(115200);        // Initialize the serial communication with a baud rate of 112500
  if (! sht31.begin(0x44)) {   // Check if SHT31 is connected and start it with address 0x44
    // Print an error message if SHT31 is not found
    Serial.println("Couldn't find SHT31");
    while (1) delay(1);  // Wait indefinitely
  }
}

void loop() {
  // Read temperature from SHT31 and assign it to "temperature"
  float temperature = sht31.readTemperature(); 
  // Read relative humidity from SHT31 and assign it to "humidity"
  float humidity = sht31.readHumidity();

  if (! isnan(temperature)) {     // Check if t is not NaN (not a number)
    Serial.print("temp_deg_C:");  // Print temperature label
    Serial.print(temperature);    // Print temperature value
    Serial.print("\t");           // Write a tab space
  } 
  else {
    // Print an error message if temperature reading fails
    Serial.println("Failed to read temperature");
  }

  if (! isnan(humidity)) {        // Check if h is not NaN (not a number)
    Serial.print("rel_hum_%:");   // Print humidity label
    Serial.print(humidity);       // Print humidity value
  } 
  else {
    // Print an error message if humidity reading fails
    Serial.println("Failed to read humidity");
  }

  Serial.println();    // Break line
  delay(1000);         // Wait 1 second
}

13.2 VL53L0X Time-of-Flight Distance Sensor Using I2C communication

In this tutorial you can find a lot more information.

Code for reading the sensor:

Download code

#include "Adafruit_VL53L0X.h"

// also on http://www.esp32learning.com/code/vl53l0x-time-of-flight-sensor-and-esp32.php
Adafruit_VL53L0X lox = Adafruit_VL53L0X();

void setup() {
  Serial.begin(115200);

  // wait until serial port opens for native USB devices
  while (! Serial) {
    delay(1);
  }
  
  Serial.println("Adafruit VL53L0X test");
  if (!lox.begin()) {
    Serial.println(F("Failed to boot VL53L0X"));
    while(1);
  }
  // power 
  Serial.println(F("VL53L0X API Simple Ranging example\n\n")); 
}


void loop() {
  VL53L0X_RangingMeasurementData_t measure;
    
  Serial.print("Reading a measurement... ");
  lox.rangingTest(&measure, false); // pass in 'true' to get debug data printout!

  if (measure.RangeStatus != 4) {  // phase failures have incorrect data
    Serial.print("Distance (mm): "); Serial.println(measure.RangeMilliMeter);
  } else {
    Serial.println(" out of range ");
  }
    
  delay(100);
}

13.3 DS18B20 Temperature Sensor

Pretty accurate temperature sensor. Each sensor has its own unique address, enabling the connection of numerous sensors to only on pin on the Arduino/ESP32.

In this tutorial you can find a lot more information.

Code for finding the sensor’s address:

Download code

/*
 * Rui Santos 
 * Complete Project Details https://randomnerdtutorials.com
 */

#include <OneWire.h>

// Based on the OneWire library example

OneWire ds(4);  //data wire connected to GPIO 4

void setup(void) {
  Serial.begin(115200);
}

void loop(void) {
  byte i;
  byte addr[8];
  
  if (!ds.search(addr)) {
    Serial.println(" No more addresses.");
    Serial.println();
    ds.reset_search();
    delay(250);
    return;
  }
  Serial.print(" ROM =");
  for (i = 0; i < 8; i++) {
    Serial.write(' ');
    Serial.print(addr[i], HEX);
  }
}