Digital Tachometer using Arduino for measuring Motor Speed (RPM)

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Hello friends! Welcome back to ElectroDuino. This blog is base on Digital Tachometer using Arduino for measuring Motor Speed (RPM). Here we will discuss Introduction to Digital Tachometer using Arduino, Project Concept, Block Diagram, components required, circuit diagram, working principle, and Arduino code.

Introduction

Normally we have to think measure the Speed (rpm) of a motor or rotating body is too much difficult. Don’t worry, this project can solve this problem. A tachometer is an electronic device that can measure the rotation speed of a shaft or disk, as in a motor or other machine. It measures the number of revolutions of an object in a given interval of time. Usually, it is expressed in revolutions per minute or RPM and displays the revolutions per minute (RPM) on an analog dial or digital display.

Project Concept

The key components of this project are the IR sensor module, Pushbutton, Arduino, and Display. This project work based on the detection or not detection of the infrared light by the IR sensor module. we will use some sort of reflecting material on the rotating body, which could detect a peak of the sensed infrared light and measure the time between those peaks. The measured time is the time that the rotating body takes to make one full rotation. The RPM calculation by the time measurement process is done by the Arduino. The push-button switch is used to Arduino low power mode enable and disable. This helps to low power consumption. When we measure RPM this time we need to press (on) the push button switch. When we get the reading (RPM value), then we can release the push button, then the Arduino will be in low power mode and OLED Display is turn off. We can see the RPM value on the display.

Block Diagram

Digital Tachometer using Arduino for measuring Motor Speed (RPM) Block diagram
Digital Tachometer using Arduino for measuring Motor Speed (RPM) Block diagram

Components Required 

Components NameQuantity
Arduino Nano1
TCRT5000 IR Sensor Module (You can use the normal IR Sensor Module)1
0.96 inch I2C OLED display1
Push Button Switch1
1 k ohm  Resistor1
Slide Switch1
9V Battery with Battery connector1
PCB Zero board1
Connecting wiresAs required in the circuit diagram

 

Tools Required

Tools NameQuantity
Soldering Iron1
Soldering wire1
Soldering flux1
Soldering stand1
Multimeter1
Desoldering pump1
Wirecutter1

Required Library

Download the Adafruit_GFX.h library here: CLICK
Download the Adafruit_SSD1306.h library here: CLICK

Circuit Diagram of Digital Tachometer using Arduino

Digital Tachometer (RPM Meter) using IR sensor, Display and Arduino Circuit
Digital Tachometer (RPM Meter) using IR sensor and Arduino Circuit diagram

Circuit Wiring

Components PinArduino pin

IR Sensor Module Vcc Pin,

OLED  Display Vcc Pin

Push Button Switch terminal-1

 Arduino 5V Pin

IR Sensor Module GND Pin,

OLED  Display GND Pin

GND (ground) Pin
Push Button Switch terminal-2Connected to GND (ground) Pin through 1k resistor
IR Sensor Module Data pinDigital Pin “D7”
OLED  Display SCL pinAnalog Pin “A5”
OLED  Display SDA pinAnalog Pin “A4”
Push Button data pin is the junction point of terminal-2 and resistorDigital Pin “D5”
9v Battery positive (+) terminalConnected to VIN Pin through a Slide Switch for external DC Power supply to operating Arduino.
9v Battery negative (+) terminalGND (ground) Pin

Working of Digital Tachometer using Arduino and IR Sensor

After connecting all the components according to the circuit diagram, now time to turn on the circuit power supply using turn on the slide switch.

Here we are using the IR Sensor Module, which is works as an obstacle detector. We all know that the IR sensor emits and received Infrared light to detect objects. Also, we know that a black surface can’t reflect light, and a white surface is a good light reflector. That’s why we will use a black & white disc, which we will connect any rotating body. Here we will measure a dc motor RPM so we will connect this disk with the motor shaft.

Diagram of Digital Tachometer using Arduino
Black and White Disc

When the black surface comes in front of the IR sensor, this time infrared light does not reflect back to the sensor. So the sensor does not detect and sensor output is High (1/+5v). When the White surface comes in front of the IR sensor, this time infrared light reflects back to the sensor. So the sensor detects the surface and the sensor output is Low (0/GND). When the motor shaft starts rotating then also this disc starts rotating. This time if we place the IR sensor in front of the disk then the IR sensor generates Output in a particular square waveform. This square waveform output depends on the IR sensor detection time.

Techometer using arduino and IR sensor Time vs Amplitude graph
Tachometer using Arduino and IR sensor Time vs Amplitude graph

The Arduino has to start a counter when the IR sensor detects the first positive edge representing the final of the white surface and counts the time till the IR sensor detects another positive pulse, representing the start of the white surface again. Then the Arduino makes the difference of the measure counters and it checks the motor takes how much time for one rotation in microseconds. Using the Arduino code we divide one minute (60.000.000 us) by that value and Then we get the RPM value. The Arduino print that RPM values on the OLED display.

The push-button switch takes an important role in the project. When we measure RPM this time we need to press (on) the push button switch. When we get the reading (RPM value), then we can release the push button, then the Arduino will be in low power mode and OLED Display is turned off. In this way, we can save power without turn off the circuit by the slide switch.

 

Digital Tachometer using Arduino Code

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