Tachometer using Arduino

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.

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


object = number of blade in fan.

Arduino Tachometer Block Diagram

Components Used

  1. Arduino
  2. IR sensor Module
  3. 16x2 LCD
  4. Push button
  5. Bread board
  6. 9 volt battery
  7. Connecting wires


Circuit Diagram and Explanation

Arduino Tachometer Circuit

As shown in the above tachometer circuit, it contains Arduino Pro Mini, IR sensor module, buzzer and LCD. Arduino controls the whole the process like reading pulse that IR sensor module generate according to object detection, calculating RPM and sending RPM value to LCD. IR sensor is used for sensing object. We can set sensitivity of this sensor module by inbuilt potentiometer situated on IR module. IR sensor module consist an IR transmitter and a photo diode which detects or receives infrared rays. IR transmitter transmits infrared rays, when these rays fall on any surface, they reflect back and sensed by photo diode (You can understand more about it in this Line Folloewr Robot). The output of photo diode is connected to a comparator, which compare photo diode output with reference voltage and result is given as output to arduino.

IR Transmitter and Receiver

IR sensor module output pin is directly connected to pin 18 (A4). Vcc and GND are connected to Vcc and GND of arduino. A 16x2 LCD is connected with arduino in 4-bit mode. Control pin RS, RW and En are directly connected to arduino pin 2, GND and 3. And data pin D4-D7 is connected to pins 4, 5, 6 and 7 of arduino. A push button is also added in this project. When we need to count RPM we press this button to start this Arduino Tachometer to count RPM for five seconds. This push button is connected to pin 10 of arduino with respect to ground.


Program Description

In code we have used digital read function to read output of IR sensor module and then calculate RPM.

Counting RPM in Tachometer


#include <LiquidCrystal.h>
LiquidCrystal lcd(3, 2, 4, 5, 6, 7);

#define sensor 18
#define start 10

int delay1()
  //unsigned int long k;
    int i,j;
    unsigned int count=0;
    return count;

void setup() 
  pinMode(sensor, INPUT);
  pinMode(start, INPUT);
  pinMode(13, OUTPUT);
  lcd.begin(16, 2);
  lcd.print("Circuit Digest");
  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.....");


Comments (14)

  • angel's picture

    nice project

    Oct 01, 2015
  • Ray's picture

    What if I flipped the direction switch on the fan to make it spin backwards? How could you sense direction as well as RPM?

    Oct 21, 2015
  • John's picture

    You would need to IR modules connected to the Arduino, and code that would detect which one is "tripped" first.

    Jun 27, 2017
  • binduni's picture

    Great project! I'm curious as to what the double count loop is doing, and what the 1227 count has to do with. I suspect it's related to the processor speed of the board... but how?

    Jan 17, 2016
  • PUNEET KUMAR's picture

    Sir please tell me which arduino (3.3V or 5V) is used in arduino based digital tachometer

    Feb 03, 2017
  • John's picture

    The project uses an "Arduino Pro Mini" If you look that up on Google, you will see that it has an onboard voltage controller and can accept up to 12v (this project is using a 9v battery) when connected to the "RAW" terminal. For 5v or 3.3 v, connect to the appropriate 5v or 3.3v terminal

    Jun 27, 2017
  • Raj's picture

    Is it possible to count 300rpm

    Feb 09, 2017
  • John's picture


    Jun 27, 2017
  • sahu sravani's picture
    sahu sravani

    in code ,rpm = count *12/3 ,what it is indicate?(12???)

    Feb 15, 2017
  • John's picture

    If you read the instructions, you will see that the code runs for 5 seconds. Multiply the revolutions found after 5 seconds by 12 to get revolutions per minute.

    Jun 27, 2017
  • n.jae's picture

    can you please tell me what's the PinMode(13,OUTPUT) means? there seems to be nothing connected to the 13 pin

    Apr 27, 2017
  • John's picture

    Pin 13 connects to the onboard LED on the Arduino, and so the code will flash that.

    Jun 27, 2017
  • Arthur's picture

    I get a bunch of errors while trying to upload the code,. Such as expected initializer before int

    Jul 20, 2017
  • Arthur's picture

    Mine keeps reading the rpm forever and then gives wrong values

    Jul 21, 2017

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