Today, we are going to create a reverse sensor simulator, the kind that is used in cars. For this, we will make an assembly that uses the ESP32, a buzzer, four indicator LEDs, and an ultrasonic sensor, plus a 4-digit display (with 7 segments).

So, let's read the ultrasonic sensor and play with the distance on the display. As the distance reaches a "dangerous" space, the LEDs gradually light up from blue to green, yellow, and finally red, according to the shortening of the distance. An alarm goes off when reaching the space limit.

Step 1: WiFi NodeMCU-32S ESP-WROOM-32

Step 2: Display

As for the display, in this assembly, we show how to use the I2C, which enables the sending of vast information by only two wires.

Step 3: Ultrasonic Sensor

We explained that the HC-SR04, the most common ultrasonic sensor and widely used with Arduino, is cheap and easy to find. Remember the minimum distance that it can measure is from 2 inches away, and the maximum is 4 meters. Another detail is that 5 volts power it.

Step 4: Continuous Buzzer

Step 5: LEDs

There are 4 colored LEDs with 220 ohms resistors.

Step 6: Assembly

The principal details of the HC-SR 04 is that it has power and uses two pins, the trigger and the Echo, which appear in the source code.

Step 7: Libraries

In this assembly, we used two libraries: TM1637Display and Ultrasonic. The PDF file contains the links to download both, on: http://www.fernandok.com/2017/12/sensor-ultrassonico-com-esp32.html

Step 8: Source Code

In this part, you can see a demonstration about the operation of the project. Already in the code, we declare TM1637Display and Ultrasonic, with a reading range of 250 milliseconds. This was the chosen time to avoid extremely fast number changes. Next, we define the pins used for the LEDs and the buzzer. I declare yet another variable, the "unsigned int", which will save the distance of the device.

//Biblioteca responsável para comunicação com o display de 7 segmentos
#include <tm1637display.h> //Carrega a biblioteca do sensor ultrassonico #include < ultrasonic.h> #define INTERVALO_LEITURA 250 //(ms) //definição dos PINOS que utilizaremos para os LEDS e o BUZZER #define PIN_BLUE_LED 16 #define PIN_GREEN_LED 17 #define PIN_YELLOW_LED 18 #define PIN_RED_LED 19 #define PIN_BUZZER 21 //variável responsável por armazenar a distância lida pelo sensor ultrassônico unsigned int distancia = 0;

Sensor and Display

In this step, we define the pins and the constructors of the objects that we use to control the ultrasonic sensor and the display.

//conexão dos pinos para o sensor ultrasonico
#define PIN_TRIGGER 4 #define PIN_ECHO 5 //Inicializa o sensor nos pinos definidos acima Ultrasonic ultrasonic(PIN_TRIGGER, PIN_ECHO); // Module connection pins (Digital Pins) #define CLK 14 #define DIO 13 //Inicializa o display nos pinos definidos acima TM1637Display display(CLK, DIO);

Setup

In this function, we initialize the serial with a speed of 9600, configure the pins, and then configure the brightness for the display.

void setup()
{
  Serial.begin(9600);
 
  configurarPinos();
 
  //configura o brilho do display com valor máximo
  display.setBrightness(0x0a);
   
  Serial.println("Setup...");
}

Pin Configuration

Here, we set both the four LEDs and the buzzer as pinMode, all OUTPUT, because they are outputs.

/*
  CONFIGURA O MODOS DE CADA UM DOS PINOS QUE UTILIZAREMOS COMO SAIDA
*/
void configurarPinos()
{
  pinMode(PIN_BLUE_LED,   OUTPUT);
  pinMode(PIN_GREEN_LED,  OUTPUT);
  pinMode(PIN_YELLOW_LED, OUTPUT);
  pinMode(PIN_RED_LED,    OUTPUT);
  pinMode(PIN_BUZZER,     OUTPUT);  
}

Loop

In the Loop function, we have the distance and delay check, that is, the reading interval.

void loop()
{
  verificarDistancia();
  delay(INTERVALO_LEITURA);
}

Get Distance

Now, we are going to read the current distance calculated by the sensor.

/*
  FAZ A LEITURA DA DISTANCIA ATUAL CALCULADA PELO SENSOR
*/
int getDistance()
{
    //faz a leitura das informacoes do sensor (em cm)
    int distanciaCM;
    long microsec = ultrasonic.timing();
    // pode ser um float ex: 20,42 cm se declarar a var float 
    distanciaCM = ultrasonic.convert(microsec, Ultrasonic::CM);
  
    return distanciaCM;
}

Check Distance

We check the distance that will be shown on the 4-digit display. Then, we erase the 4 LEDs and silence the buzzer. This type of situation can be used in many applications.

/*
  VERIFICA A DISTANCIA ATUAL QUE O SENSOR ULTRASONIC ESTA LENDO
  E EM SEGUIDA, IMPRIME O VALOR NO DISPLAY, E ACENDE O LED CORRESPONDENTE
*/
void verificarDistancia()
{
 
    //recupera a distância atual lida pelo sensor
    distancia = getDistance();
 
   //imprime no display o valor lido
  display.showNumberDec(distancia);
 
//esse FOR tem como objetivo apagar todos os LEDS que estejam acesos.
  for(int i=PIN_BLUE_LED; i<=PIN_RED_LED; i++)
  {
    digitalWrite(i, LOW);    
  }
 
  //desliga o BUZZER
  digitalWrite(PIN_BUZZER, LOW);
 
 
//caso a distancia lida seja menor ou igual a 5, tomaremos como uma distância de perigo
  //então acenderemos o LED VERMELHO e ligaremos o BUZZER
  if( distancia <= 5 )
  {
    digitalWrite(PIN_RED_LED, HIGH);
    digitalWrite(PIN_BUZZER, HIGH);
  }
  //caso a distancia seja maior que 5 e menor ou igual a 20,
  //tomaremos como uma distância de atenção, e ligaremos o LED AMARELO
  else if(distancia <=20)
  {
    digitalWrite(PIN_YELLOW_LED, HIGH);
  }
  //caso a distancia seja maior que 20 e menor ou igual a 40,
  //tomaremos como uma distância segura, e ligaremos o LED VERDE
  else if(distancia <= 40)
  {
    digitalWrite(PIN_GREEN_LED, HIGH);
  }
  //para distâncias maiores que 40, tomaremos como uma distância sem perigo
  //acenderemos o LED AZUL para indicar
  else
  {
    digitalWrite(PIN_BLUE_LED, HIGH);
  }
}