Measurement of fan speed with IR and Arduino sensors:-

In this project, we developed a digital tachometer that uses an Arduino infrared sensor to measure the rotational fan speed in rpm. The infrared sensor module was simply connected to the Arduino and the 16 * 2 LCD module for the display. The infrared sensor module consists of a transmitter and a single-pair infrared receiver that can be operated with a digital tachometer. Then, learn how to measure the fan speed using the IR and Arduino sensors.

The speedometer is a tachometer that counts n. Rpm. There are two types of tachometers, one mechanical and one digital. Here we will develop an Arduino-based digital tachometer that uses an infrared sensor module to detect an object for counting the rotation of any rotating body. When the IR sends the IR beams back to the IR receiver, the IR module generates an output or pulse that is detected by the Arduino controller when the start button is pressed. Count for 5 seconds continuously.

Required components
To design a circuit to measure fan speed with an infrared sensor and an Arduino sensor, we need the following components:
1. Arduino UNO Commission
2. 16 * 2 LCD
3. Infrared sensor module
4. breadboard
5. Connection via jumper cable


circuit diagram



IR sensor module


An infrared sensor is an electronic instrument that detects certain characteristics of its environment by emitting and / or detecting infrared radiation.

The wavelength range between 0.75 and 3 μm is called the near-infrared range. The range between 3 and 6 microns is referred to as infrared radiation and medium infrared radiation whose wavelength is greater than 6 microns, and referred to as far-infrared.


An infrared sensor consists of an infrared LED and an infrared photodiode. together they are referred to as photocouplers or optocouplers. As already mentioned, the infrared obstacle sensor has an integrated transmitter and infrared receiver. The infrared transmitter is a light emitting diode (LED) that emits infrared radiation. Therefore, they are called IR LEDs. Although an IR LED looks like a normal LED, its radiation is invisible to the human eye. Infrared receivers are also referred to as infrared sensors because they detect the radiation of an IR transmitter. IR receivers are available as photodiodes and phototransistors. Infrared photodiodes are different from normal photodiodes because they only detect infrared radiation. When the IR transmitter emits radiation, it reaches the object and some of the radiation is returned to the IR receiver. Depending on the intensity of the reception by the infrared receiver, the output of the sensor is defined.


  1. Operating voltage: 3.0V – 5.0V
  2. Detection range: 2 cm to 30 cm (adjustable with potentiometer)
  3. Power consumption: at 3.3V: ~ 23mA, at 5.0V: ~ 43mA
  4. Active output level: Produces a low logic level when an obstacle is detected
  5. LED display for obstacle detection on board

Source Code/Program:

LiquidCrystal lcd(12,11,10,9,8,7);
float value=0;
float rev=0;
int rpm;
int oldtime=0;
int time;

void isr() //interrupt service routine

void setup()
lcd.begin(16,2); //initialize LCD
attachInterrupt(0,isr,RISING); //attaching the interrupt

void loop()
detachInterrupt(0); //detaches the interrupt
time=millis()-oldtime; //finds the time
rpm=(rev/time)*60000*3; //calculates rpm for blades
oldtime=millis(); //saves the current time
lcd.print( rpm);
lcd.print(” RPM”);
lcd.print(” “);