Volume 3, Issue 2, February – 2018 International Journal of Innovative Science and Research Technology ISSN No:-2456 –2165 IJISRT18FB157 www.ijisrt.com 584 DC Motor Speed Control Using PWM K. Priyanka 1 , A. Mariyammal 2 1,2 Department of Electrical and Communication Engineering, Vivekanandha College of Engineering for Women(Autonomous), Tiruchengode. Abstract:-Dc motor are mostly used in industries so we used to control the speed of the motor by using PWM. In this paper, to control the speed of DC motor using Pulse Width Modulation (PWM) method. Microcontroller AT89S52 is used to generate PWM. L293D IC is used to drive the motor which is made up of two H-Bridge. 555 IC is used with opto coupler to sense the speed of DC motor. Rectifier circuit is used for power supply to circuit and motor. This paper shows that precise and accurate control of small DC motors without using costly components. Keywords:-PWM , Microcontroller, DC Motor. I. INTRODUCTION In our project we use PWM to control the speed of the DC motor and Using Atmel AT89S52 microcontroller generate the PWM wave for speed control of DC motor, we need a variable-voltage DC power source to control the speed of the DC motor. When the DC motor is on, it takes certain time to reach at full speed. Then, the power source is on, the DC motor starts gaining speed and if we switch off the power source before it reaches at rated speed, it starts to goes down. In quick Way switching on and switching off are done, the motor rotate at a lower speed between zero and rated speed. we used PWM method so it switches the motor „on‟ and „off‟ with a pulse wave. The main objective of this paper is to become easy with the implementation of hardware of Atmel AT89S52 microcontroller based speed control of DC motor, L293D IC is used to provide to motor and infrared sensor is used to count the speed which are interface with 555 IC, it give senses of occurring overload to the operator at overload condition and speed display on LCD screen. For the required speed the speed controller takes signal represent and to drive a motor at a constant speed. II. DESCRIPTION A. Pulse Width Modulation pulse width modulation is a modulation technique used to encode a message into a pulsing signal. The average value of voltage fed to the load is controlled by turning the switch between supply and load on and off at a fast rate. The longer Switch is on compared to the off periods, the higher the total power supplied to the load.fig:1 represents the PWM. Figure 1. PWM Wave B. Power Supply Power supply is the major source of the electrical base and we use step down transformer from 230v AC to 12v DC and after we use full wave bridge rectifier to convert AC to DC source for the components.fig:2 represents the power supply and bridge rectifier. Figure 2. Power Supply With Bridge Rectifier