Digital RPM Meter Using IR Sensor With Arduino

Today in our project, we have designed and built a Digital RPM Meter using an infrared sensor and an Arduino to measure the number of rotations of the motor in RPM. We have interfaced the IR sensor module with Arduino and the 16×2 LCD as the display module. The IR sensor module consists of an IR Transmitter and Receiver in a single pair that works as an RPM meter for measuring the speed of any rotating object.

The RPM meter works as an RPM counter which counts the number of rotations per minute. In general, we get to see mainly two types of RPM Meter one is mechanical and another one is digital. In this project, we are going to design a digital RPM meter which is based on Arduino by using an IR sensor module to count the rotation of any rotating body. IR transmits IR rays which reflect back to the IR receiver and then IR Module generates an output or pulse that is detected by the Arduino controller when the start button is pressed. It counts the rotation for 5 seconds.

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Digital RPM Meter Using Arduino

Circuit Diagram

Digital RPM Meter Circuit Diagram

Components Required

  • Arduino UNO
  • 16×2 LCD Display
  • IR Sensor Module
  • Tact Switch
  • Connecting Wires
  • Breadboard
  • 3.7V Lithium-Ion Battery

Circuit Connection for Digital RPM Meter

Now then, after assembling the above-mentioned components we have to do the following connection to design the digital RPM meter which uses IR Sensor with Arduino to measure the RPM.

Arduino PinLCD Display Pin
Arduino PinIR Sensor Pin

About Parts of a Digital RPM Meter

Infrared Sensor

An infrared sensor is an electronic instrument which is used to sense certain characteristics of its surroundings by either emitting and/or detecting infrared radiation. Infrared sensors can also measure the heat being emitted by an object and detect motion.

Infrared Sensor

The wavelength region which ranges from 0.75 to 3µm is known as the near-infrared region. The region between 3 and 6µm is known as the mid-infrared and infrared radiation that has a wavelength greater or higher than 6µm is generally called far-infrared

An IR sensor is made of an IR LED and an IR Photodiode; together they are called Photo–Coupler or Opto–Coupler. As we know, the Infrared Obstacle Sensor has a built-in IR transmitter and IR receiver. An infrared Transmitter is a light-emitting diode (LED) that emits infrared radiation. Hence, they are called IR LEDs. Even though an IR LED looks the same as a normal LED, the radiation emitted by it is invisible to the human eye.

Infrared receivers can also be used as infrared sensors because they detect radiation from an IR transmitter. IR receivers come in the form of photodiodes and phototransistors. Infrared Photodiodes are a whole other thing than standard photodiodes as they detect only infrared radiation. When the IR transmitter emits radiation and it reaches the object, some of the radiation is reflected back to the IR receiver. Based on the intensity of the reception by the IR receiver, the output of the sensor is defined.

For how to build your own Infrared Sensor Module, please visit this link.

Working Principle of Digital RPM Meter

In this circuit, the IR sensor module is interfaced with Arduino so that it can measure the fan rotation speed in RPM. It does the calculation on this basis. After 5 seconds Arduino calculates RPM through a minute using the given formula.

RPM= Count x 12 for a single object rotating body

But here we present this project on a 12V DC fan. So we made some changes that are mentioned below.

RPM = Count x 12 / Objects

Where object = number of the blade in a fan

Arduino Code

To run and compile the below code you have to install this library to the Arduino IDE software.

LiquidCrystal I2C Library

#include <Wire.h>#include <LiquidCrystal_I2C.h>LiquidCrystal_I2C lcd(0x27, 16, 2);#define ir_sensor 3#define start 12int delay1(){  int i, j;  unsigned int count = 0;  for (i = 0; i < 1000; i++)  {    for (j = 0; j < 1000; j++)    {      if (digitalRead(ir_sensor))      {        count++;        while (digitalRead(ir_sensor));      }    }  }  return count;}void setup(){  pinMode(ir_sensor, INPUT);  pinMode(start, INPUT);  pinMode(2, OUTPUT);  lcd.init();  lcd.backlight();  lcd.print(” RPM Meter ”);  delay(2000);  digitalWrite(start, HIGH);}void loop(){  unsigned int time = 0, RPM = 0;  lcd.clear();  lcd.print(” Press Button “);  lcd.setCursor(0, 1);  lcd.print(“ To Start “);  while (digitalRead(start));  lcd.clear();  lcd.print(“Reading RPM....”);  time = delay1();  lcd.clear();  lcd.print(“Please Wait...”);  RPM = (time * 12) / 3;  delay(2000);  lcd.clear();  lcd.print(“RPM = ”);  lcd.print(RPM);  delay(5000);}

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