RF 433 Transmitter and Receiver with sensors and OLED displays

In this video I show you how to send data between 2 Arduino Nanos and use some OLED displays to show if something happened. I wanted to use a microphone as a triggering device, but my microphone circuit was not working as I wanted to. The main concept of this circuit is to see something remotely, but you can easily transform this idea into a for example remote controller.

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Wiring diagram

RF433 transmitter (left) and receiver (right). The sound sensor show in the video is substituted by a potentiometer on the drawing. It emulates a signal level. The displays are i2C compatible OLED displays. They are connected to A4 (SDA) and A5 (SCL) pins.

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Arduino source code

Transmitter

#include <RH_ASK.h> //RadioHead Amplitude Shift Keying Library
 
#include <SPI.h> //SPI Library
#include <Wire.h> //Wire Library (I2C)
 
//ASCII-based OLED library
//Its huge advantage that it is _not_ graphical, so it is using much less memory
#include "SSD1306Ascii.h"
#include "SSD1306AsciiAvrI2c.h"
// 0X3C+SA0 - 0x3C or 0x3D
#define I2C_ADDRESS 0x3C //Address
#define RST_PIN -1 //For OLED with no reset pin
 
SSD1306AsciiAvrI2c display; //Instantiating a display
RH_ASK rf_driver; //Instatiating a rf_driver for the transmitter
 
int soundLevel = 0; //variable for the microphone's output
int triggerLevel = 0;
int AVGsoundLevel = 0;
int messageNumber = 0; //1 = triggered, 0 = reset (receiver will wait for a new trigger).
bool triggered = false; //we change this based on the status
 
//PINS
int microphonePin = A6;
int redLED = 5; // On, when triggered (Triggered)
int greenLED = 6; //on when not triggered (Waiting)
int calibratePin = 2; //to save the triggel level
 
void setup()
{
 
  //Initializing the display
  #if RST_PIN >= 0
  display.begin(&Adafruit128x64, I2C_ADDRESS, RST_PIN);
  #else // RST_PIN >= 0
  display.begin(&Adafruit128x64, I2C_ADDRESS);
  #endif // RST_PIN >= 0
  display.setFont(System5x7); //font type
  display.set1X(); //font size (small)
  display.clear();
  //-----------------------------------------------------    
  // Initialize ASK Object
  rf_driver.init();
  //-----------------------------------------------------
  //Pins. By default, green will be on.
  pinMode(calibratePin, INPUT_PULLUP); //use the internal pullup
  pinMode(redLED, OUTPUT);
  pinMode(greenLED, OUTPUT);
 
  digitalWrite(redLED, LOW);
  digitalWrite(greenLED, HIGH);
 
  attachInterrupt(digitalPinToInterrupt(calibratePin), triggerSoundLevel, RISING); //L -> H, button for calibration
 
}
 
void loop()
{    
    PrintScreen();    //Print the info on the screen
   
    MeasureSound();   //Measure the sound
   
}
 
 
void PrintScreen()
{  
  display.clear();  //clear display
  display.setCursor(0, 0); //start in the 0 position  
  //----------------------------
  display.print("Level: ");  
  display.println(AVGsoundLevel);  
  display.println();
  //----------------------------
  display.print("Trigger level: ");  
  display.println(triggerLevel);
  //----------------------------
  display.println();
  display.print("Status: ");
  if(triggered == false)
  {
    //This gets printed if we do not cross the trigger value
    display.println("Waiting");
    messageNumber = 0; //sends a 0 to the receiver
    SendMessage(messageNumber);
    digitalWrite(redLED, LOW); //only green is on while waiting
    digitalWrite(greenLED, HIGH);
   
  }
  else
  { //triggered == true
    //This gets printed if we cross the trigger value
    display.println("Triggered");
    messageNumber = 1; //sends a 0 to the receiver
    SendMessage(messageNumber);
    digitalWrite(redLED, HIGH); //red is on when triggered and green is off
    digitalWrite(greenLED, LOW);    
  }
       
}
 
void MeasureSound()
{
  soundLevel = 0; //Reset it, before filling it up
  AVGsoundLevel = 0; //Reset it, before filling it up
 
  //Let's measure it for some time and create an average
  for(int i = 0; i < 10; i++)
  {
    soundLevel += analogRead(microphonePin);
    delay(200);
  }
  AVGsoundLevel = soundLevel / 10; //calculate average
 
  if(AVGsoundLevel < (triggerLevel-100)) //if there is less value, we flip the value of the variable
  {
    triggered = true; //set the bool to true
  }
  else
  {
    triggered = false; //set the bool to false
  }
 
}
 
void triggerSoundLevel()
{
  soundLevel = 0;   //Reset it, before filling it up
  triggerLevel = 0; //Reset
 
  for(int i = 0; i < 10; i++)
  {
    soundLevel += analogRead(microphonePin);
    delay(200);    
  }
    triggerLevel = soundLevel / 10;  //calculate average
   
    soundLevel = 0; //Reset it, again, otherwise, it goes to weird levels in the measure()    
   
}
 
void SendMessage(int messageNumber)
{
    rf_driver.send((uint8_t *)&messageNumber, sizeof(messageNumber)); //send the message through the RF module    
    rf_driver.waitPacketSent();  
}

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Receiver

#include <RH_ASK.h>//RadioHead Amplitude Shift Keying Library
#include <SPI.h> // SPI Library
#include <Wire.h> //Wire Library (I2C)
 
RH_ASK rf_driver; //Instatiating a rf_driver for the receiver
 
//ASCII-based OLED library
//Its huge advantage that it is _not_ graphical, so it is using much less memory
#include "SSD1306Ascii.h"
#include "SSD1306AsciiAvrI2c.h"
#define I2C_ADDRESS 0x3C //Address
#define RST_PIN -1 //For OLED with no reset pin
 
SSD1306AsciiAvrI2c display;
 
 
// Set buffer to size of expected message
    uint8_t buf[24];
    uint8_t buflen = sizeof(buf);
 
    String receivedString; //String for long messages
 
//REC pin = D11
int redLED = 5; //on, when it is too loud
int greenLED = 6; //on when it is OK
 
 
void setup()
{
    // Initialize ASK Object
    rf_driver.init();
   
  #if RST_PIN >= 0
  display.begin(&Adafruit128x64, I2C_ADDRESS, RST_PIN);
    #else // RST_PIN >= 0
  display.begin(&Adafruit128x64, I2C_ADDRESS);
    #endif // RST_PIN >= 0
  // Call oled.setI2cClock(frequency) to change from the default frequency.
 
  display.setFont(System5x7);
  display.set1X();
  display.clear();
 
   //Managing the LEDs
   pinMode(redLED, OUTPUT);
   pinMode(greenLED, OUTPUT);
 
   digitalWrite(redLED, LOW);
   digitalWrite(greenLED, HIGH);
   //----------------------------
 
  //Serial.begin(9600);
  //Serial.println("Receiver started");
}
 
void loop()
{
   
    // Check if received packet is correct size
    if (rf_driver.recv(buf, &buflen))
    {    
 
      for (int i = 0; i < buflen-1; i++)
      {    
        receivedString += String(buf[i]); //building up a string from the received data            
      }
     
      PrintScreen(); //print to OLED  
      receivedString="";  //reset to zero, so we don't mix the messages
     
    }
   
}
 
void PrintScreen()
{
  display.clear();  
  display.setCursor(0, 0);
  display.println("Status: ");
  display.println();
 
  if(receivedString == "0")
  {
    display.println("Waiting...");
    digitalWrite(redLED, LOW);
    digitalWrite(greenLED, HIGH); //Only green is on, while we are waiting
  }
  if(receivedString == "1")
  {  
    display.println("Check device!");
    digitalWrite(redLED, HIGH); //Red goes on, when the trigger level is crossed on the transmitter side
    digitalWrite(greenLED, LOW);
  }
 
 
}

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