Digital Tachometer With Arduino For Measuring Rpm

Photo of hIOTron

Made by hIOTron / Automotive / IoT

About the project

The tachometer is a device utilized for measuring the number of revolutions of an object in a specific interval of time.

Project info

Difficulty: Moderate

Platforms: Arduino

Estimated time: 1 hour

License: GNU General Public License, version 3 or later (GPL3+)

Items used in this project

Hardware components

Ultrasonic Sensor Hc-sr04 Ultrasonic Sensor Hc-sr04 x 1
Momentary Pushbutton Switch - 12mm Square Momentary Pushbutton Switch - 12mm Square x 1
Standard Lcd 16x2 White On Blue Standard Lcd 16x2 White On Blue x 1
Arduino Mkrfox 1200 Arduino Mkrfox 1200 x 1

Software apps and online services

Arduino IDE Arduino IDE



The tachometer is used to measure an RPM counter which counts the number of rotations per minute. The tachometer is divided into two types one mechanical and another one is digital. Here in this project, we are going to design an IR sensor module to recognize objects for count rotation of any rotating body.

IR Sensor Module:

An IR sensor is an electronic instrument that is utilized to genuine certain features of its surroundings by either emitting and/or detecting infrared radiation. Infrared sensors are also able to measure the heat being released by an object and detecting motion.

IR transmits IR rays that return back to the IR receiver and then IR Module creates an output or pulse which is recognized by the Arduino controller when we press the start button. It counts constantly for 5 seconds.

Depends on the intensity of the reception by the IR receiver, the output of the sensor is determined.

Working Mechanism:

In this circuit, the IR sensor module is interfaced with Arduino to estimate fan rotation speed in RPM. The calculation is done as follows.

After 5 seconds Arduino measures RPM for a minute using the given formula.

RPM= Count x 12 for single object rotating body.

But here we describe this project using a fan which was rated 9V/100mA. So the formula will be:

RPM=count x 12 / objects

Where object = number of the blade in a fan.

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