Contact-Less Tachometer

Download Full-Text PDF Cite this Publication

Text Only Version

Contact-Less Tachometer

Cariappa P K

Dept. of Electronics and Communication Vidya Vikas Institute of Engineering and Technology

Mysuru, India

Shwetha A

Dept. of Electronics and Communication Vidya Vikas Institute of Engineering and Technology

Mysuru, India

Pooja D

Dept. of Electronics and Communication Vidya Vikas Institute of Engineering and Technology

Mysuru, India

Sudharani B T

Dept. of Electronics and Communication Vidya Vikas Institute of Engineering and Technology

Mysuru, India

Geetha M N

Dept. of Electronics and Communication Vidya Vikas Institute of Engineering and Technology

Mysuru, India

AbstractTachometer is a device used to measure the speed of the any rotating object. The measurement is done in revolution per minute or RPM. In olden days tachometers were completely mechanical, but tachometers have changed due to development of modern technology. This paper mainly focuses on developing a contactless digital tachometer. It is built using microcontroller, an infrared system and LCD module. The infrared system senses the interruption in the beam of rays caused by rotating object and generates pulses which will be sent to the microcontroller and these pulses will be counted; this count will be displayed on the LCD in revolution per minute i.e. RPM. The system is economical and has wide applications in automobile industry and medical field.

Keywords LCD-Display,IR sensor, RPM,USB.


    In this modern era of industrialization most of the industries contain rotating objects such as motor, rotor etc for its proper monitoring its speed has to be measured and controlled. For such measurements, there are many methods and one of such method is use of tachometer. Tachometer is an instrument which measures the speed of any rotating objects in revolution per minute (RPM). There exist mechanical tachometers, where direct contact between motor and the tachometer is needed for measurement of RPM. This kind of tachometers requires regular maintenance and is complicated to use. These instruments suffer from wear and tear. Hence there is a requirement for a contactless digital tachometer which can be easily used with monitoring system. This paper is about contact-less digital tachometer designed using infrared methodology. The sensor unit used for measurement is IR sensor and the processing unit used is Arduino-Uno. The measured value is displayed using a LCD module. This kind of tachometer can employed in the region where speed is unit of measurement and size and precision is a factor. This model can be employed in vehicles and robotic arms. This is also used in aircraft, rails and traffic engineering to estimate traffic speed and volume.


    In this paper the author has discussed about various researches that has been done in the development of contactless tachometer. Here author has used arduino-Uno board for controlling part. The IR sensor consists of LED and photodiode. Motor rotates in front of sensor, this interrupts the light and forms pulse which is given as input to microcontroller. Arduino takes average of 3 consecutive readings and displays it LCD. Also the system has arduino program for threshold value of motor speed and if the speed exceeds this value then the motor will be turned off. [2]

    The paper focuses mainly on digital tachometer which gives output directly i.e. Numeric digital output. The author has made used of the infrared transmission technique; thus the system has a controller sensor and display unit the microcontroller used is At89c52 as the controlling unit. [1]

    This paper presents a new approach for contactless speed monitoring and displaying. Here the tachometer contactless which measures the speed in RPM is designed with the help of microcontroller and diodes. The author uses At89s52 as a microcontroller. This is programmed in c program and complied using keil complier. [4]

    This paper describes the basic construction of a low cost optical tachometer and analyzes its performance. The basic tachometer circuit consists of two stages. In the first stage monostable wired around IC NE555 is used, and in the second stage a digital counter based 4-digit counter IC 74C926 is used for the construction of the tachometer. A 5V regulated power supply circuit and an infrared light source circuit are also used. The instrument can measure speed upto 9999 RPM. [6]

    The paper presents the design of a very flexible, low cost speed evaluation system. The system provides a fast dynamic response and a high accuracy over a wide speed range. The proposed design is suitable for a wide range of applications and can he integrated as part of an existing tachometer assembly. Hardware requirements and appropriate software

    structures for a microcontroller implementation are discussed. [5]

    This paper designs a tachometer which works on the principle of an induction machine. It must have windings on the stator as well as rotor. One of the winding is connected to the supply. When the rotor of this tachometer is coupled to the drive, the frequency of EMF induced in the rotor winding will depend on the speed of the rotor. Since the speed of the drive is very low, the frequency of the induced EMF is in the same range as that of applied voltage. This frequency can be easily measured using counters. [10]

    In this paper a new approach to the digital measurement of angular velocity is presented. This new instrument performs the division by time that has been carefully avoided in the existing instruments. The accuracy and resolution of the transducer does not depend upon the number of revolution. The measurements can be made in a very short time, leading to up to 14,700 samples per second. [11]


    The block diagram of the proposed methodology is shown in Figure1 below. It consists of controller, sensor, display and power supply.

    Fig. 1. Block Diagram of the system

    The hardware components required for the above system is explained below:

    • Arduino-Uno board

    • IR sensors

    • LCD display

    1. Arduino-Uno

      The Arduino-uno is microcontroller which is shown in Figure 2 based board on the atmega328.The board are equipped with set of digital and analog input/output pins that may be interfaced o various expansion boards or breadboard and other circuits. The boards feature serial communications interfaces including USB (universal serial bus) on some models which are also used for loading programs from PCs. The microcontroller is typically programmed using a dialect

      of features from the programming languages c and c++ in addition to using traditional compiler tool chains, the Arduino project.

      Fig. 2. Arduino-uno

    2. IR sensor

      An infrared sensor which is shown in Figure 3 is an electronic instrument which is used to sense certain characteristics of its surroundings by either emitting detecting infrared radiation. In infrared sensors are also capable of measuring the heat being emitted by an object and detecting motion.

      Fig. 3. Infrared sensor

    3. LCD 16×2

      The LCD screen which is shown in Figure 4 is more energy efficient and can be disposed of more safely than a CRT can. Its low electrical power consumption enables it to be used in battery powered electronic equipment more efficiently than CRTs can be a 16×2 LCD display is used in the project which displays the count or number of rotation. LCDs are used in a wide range of applications including LCD televisions, computer monitors, intrument panels.

      Small LCD screens are common in portable consumer devices such as digital cameras, watches, calculators, and mobile telephones, including smartphones. LCD screens are also used on consumer electronics products such as DVD players, video game devices and clocks. LCD screens have replaced heavy, bulky cathode ray tube (CRT) displays in nearly all applications. LCD screens are available in a wider range of screen sizes than CRT and plasma displays, with LCD screens available in sizes ranging from tiny digital watches to very large television receivers.

      Fig. 4. Liquid crystal display (LCD)

    4. Working

    The system works mainly on infrared transmission principle. It has mainly controlling unit, sensing unit display unit and motor. The object of interest I.e. motor is placed in front of sensors. The sensor has IR LED and phototransistor the IR LED emits continuous beam of light rays. When motor starts rotating this light ray will be interrupted. The light ray will be rebound back and will be absorbed by the phototransistor. This interruption of light ray is continuous in each and every rotation. This interruption of light ray is continuous in each and every rotation. This results in pulse of light ray that is fed to the microcontroller. The microcontroller counts the number of pulses and that in turn is the number of rotations. This obtained value will be displayed on the LCD screen.


    We have designed the circuit to work with least error. The testing is done and the designed tachometer is capable of determining the speed of the motor. The obtained result of the designed tachometer is shown in the LCD screen in the figure 5 below.


In this modern world all industries have motors whose speed has to be monitored properly. For this the speed has to be determined properly one such speed measuring device is tachometer. We have tried maximum in bringing up this contactless tachometer. This is low cost and gives proper output. Future scope of these tachometer is in medical field. Thus in future the system can still be minimized in size by using miniature component and by reducing noise it can be developed to be used medical field.


The authors express sincere acknowledgement to Dr. B. Sadashive Gowda, principal VVCE, Mysuru. The authors also express sincere thanks to Dr. D.J. Ravi, HOD, Dept. of ECE, VVCE. The author also expresses gratitude to our internal guides Mrs. Geetha M N, Asst. Professor, VVCE. and Ms. Bhargavi K, Asst. Professor, VVCE. for their helpful contribution in this project work and for their encouragement and support.


  1. M. Ehikhamenle, B.O. Omijeh Design And Development of A Smart Digital Tachometer Using At89c52 Microcontroller American Journal of Electrical and Electronic Engineering, vol 5, No-1,2017.

  2. Prateek Mishra1, Shikhar Pradhan, Siddhartha Sethiya, Vikas Chaudhary Contactless Tachometer With Auto Cutt Off International Research Journal of Engineering and Technology, Volume: 04 Issue: 04 Apr 2017.

  3. Md. Masud Rana , Md. Sahabuddin , Shourov Mondol Design And Implementation Of A Digital Tachometer International Journal of Scientific Engineering and Technology,Volume No.5 Issue No.1, Jan 2016, pp: 85-87.

  4. Soumya Das, Contactless Speed Monitoring And Displaying International Research Journal of Engineering and Technology, Volume:03 Issue:12, Dec-2016.

    Fig. 5. Obtained result

    We recorded the readings of both digital and analog tachometer for a particular voltage value and tabulated it as shown in Table 1.

    It can be observed that for analog tachometer the value obtained was found to be in the range. But for digital tachometer a single value was obtained thus making it useful.


    Voltage (V)

    Analog Tachometer (RPM)

    Digital Tachometer (RPM)










  5. [5]Bonert, Richard, "Design of a high performance digital tachometer with a microcontroller," Instrumentation and Measurement, IEEE Transactions on, vol.38, no.6, pp.1104,1108, Dec 1989

  6. A. S. M. Bakibillah, Muhammad Athar Uddin, Shah Ahsanul Haque Design, Implementation and Performance Analysis of a Low-cost Optical Tachometer ISSN 1813-7733,Vol.-7, December 2010.

  7. Salice Peter1, Naveen N M2, Nidheesh M N3, SwethaAnnu James4, Seril Josepp Design of a Contactless tachometer International Journal of Advanced Research in Electrical, Electronics and Instrumentation Engineering ,Vol. 3, Issue 2, February 2014.

  8. Richard Bonert Digital Tachometer With Fast Dynamic Response Implemented By A Microprocessor IEEE Transactions On Industry Applications Vol. IA-19, No.6, November/December 1983,

  9. R. Smith, M. J. Hajiroussou, and J. F. Miller Precision Digital Tachometer, IEEE Transactions On Instrumentation And Measurement, September 1973.

  10. Mukhtar Ahmad A Digital Tachometer for Measurement of Very low Speeds Proceedings Of The IEEE, Vol. 72, No. 8, August 1984

  11. Barna Szabados, Naresh K. Sinha, Senior Member,IEEE, and Colin D. Dicenzo, Senior Member, IEEE High-Resolution Precision Digital Tachometer IEEE Transactions On Instrumentation And Measurement, Vol. Im-21, No. 2, May 1972

  12. Richard C. Kavanagh Improved Digital Tachometer With Reduced Sensitivity to Sensor Nonideality IEEE Transactions On Industrial Electronics ,Vol. 47, No. 4, August 2000.

Leave a Reply

Your email address will not be published. Required fields are marked *