In this project we have designed Digital Tachometer using IR Sensor with Arduino for measuring the number of rotations of rotating Motor in RPM. Simply we have interfaced IR sensor module with Arduino and 16*2 LCD module for display. The IR sensor module consists of IR Transmitter & Receiver in a single pair that can work a Digital Tachometer for speed measurement of any rotating object.

Tachometer is a RPM counter which counts the no. of rotation per minute. There are two types of tachometer one mechanical and other one is digital. Here we are going to design an Arduino based digital tachometer using IR sensor module to detect object for count rotation of any rotating body. As IR transmits IR rays which reflect back to IR receiver and then IR Module generates an output or pulse which is detected by the arduino controller when we press start button. It counts continuously for 5 seconds.

Components Required

For designing Digital Tachometer using IR Sensor with Arduino & LCD we need the following components:

1. Arduino UNO Board
2. 16*2 LCD
3. IR Sensor module containing both transmitter and receiver
4. Tact Switch (Reset Switch)
4. Breadboard
5. Connecting Jumper Wires

Digital Tachometer using IR Sensor with Arduino for measuring RPM

Now after managing this components do this following connections for designing Digital Tachometer using IR Sensor with Arduino for measuring RPM
LCD Pins 1, 3 ,5 ,16 ——— GND
LCD Pins 2, 16 ————— VCC (+5V)
LCD Pin 4 ——————– Arduino pin D7
LCD Pin 6 ——————– Arduino pin D6
LCD Pin 11 ——————- Arduino pin D5
LCD Pin 12 ——————- Arduino pin D4
LCD Pin 13 ——————- Arduino pin D3
LCD Pin 14 ——————- Arduino pin D2
IR Sensor Module Pin -GND —— GND
Humidity Sensor Pin +VCC —— VCC
Humidity Sensor Pin OUT — Arduino Pin D9
Tact Switch one end ————- Arduino PinD12
Tact Switch other end ————-GND
A connection diagram is given below as well. Simply assemble the circuit as this

IR Sensor Module


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 are also capable of measuring the heat being emitted by an object and detecting motion.

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

An IR sensor consists of an IR LED and an IR Photodiode; together they are called as Photo–Coupler or Opto–Coupler. As said before,the Infrared Obstacle Sensor has builtin IR transmitter and IR receiver.Infrared Transmitter is a light emitting diode (LED) which emits infrared radiations. Hence, they are called IR LED’s. Even though an IR LED looks like a normal LED, the radiation emitted by it is invisible to the human eye. Infrared receivers are also called as infrared sensors as they detect the radiation from an IR transmitter. IR receivers come in the form of photodiodes and phototransistors. Infrared Photodiodes are different from normal photo diodes as they detect only infrared radiation. When the IR transmitter emits radiation, it reaches the object and some of the radiation reflects back to the IR receiver. Based on the intensity of the reception by the IR receiver, the output of the sensor is defined.


1. Operating Voltage: 3.0V – 5.0V
2. Detection range: 2cm – 30cm (Adjustable using potentiometer)
3. Current Consumption:at 3.3V : ~23 mA,at 5.0V: ~43 mA
4. Active output level: Outputs Low logic level when obstacle is detected
5. On board Obstacle Detection LED indicator

Working Mechanism

In this circuit the IR sensor module is interfaced with Arduino to measure fan rotation speed in RPM. The calculation is done on this basis.
After 5 seconds arduino calculate RPM for a minute using given formula.

RPM= Count x 12 for single object rotating body.
But here we demonstrate this project using ceiling fan. So we have done some changes that is given below:
RPM=count x 12 / objects
Where object = number of blade in fan.

Arduino Source Code

So here is a source code for designing Digital Tachometer using IR Sensor with Arduino. Simply copy the code and upload it to your Arduino Board using Arduino IDE.

#include <LiquidCrystal.h>
LiquidCrystal lcd(7, 6, 5, 4, 3, 2);
#define sensor 9
#define start 12
int delay1()
  //unsigned int long k;
    int i,j;
    unsigned int count=0;
    return count;
void setup()
  pinMode(sensor, INPUT);
  pinMode(start, INPUT);
  pinMode(2, OUTPUT);
  lcd.begin(16, 2);
  lcd.print("   Tachometer");
  digitalWrite(start, HIGH);
void loop()
     unsigned int time=0,RPM=0;
     lcd.print("  Please Press  ");
     lcd.print("Button to Start ");
     lcd.print("Reading RPM.....");
     lcd.print("Please Wait.....");

Video Preview & Explanation