Also all port pins are pulled high through external pull up resistors as shown 5 push buttons SW1 – SW5 are connected to PORTA pins PA0 to PA4.The circuit is made up of ATmega32, L293D and few discrete components like LEDs, registers, capacitors, push buttons etc Scans push buttons continuously to get user input.Push buttons – five push buttons are given to run, stop, change speed and direction of DC motor Along with them we need some push buttons for controlling and LEDs for indications. The major building blocks of this system are as shown in figure that are ATmega32 and DC motor driver chip L293D. So this project demonstrates how to vary the speed and change the direction of simple 12V 500 RPM DC series motor using AVR microcontroller ATmega32. In this technique we shall vary the width of applied pulse that will vary average voltage applied to motor and its speed will change. And for varying speed, there are various ways to vary speed of DC motor but the best amongst them is PWM – pulse width modulation technique. The direction of DC motor can be controlled by just reversing the polarity of given supply. Thus we can count number of such applications where there is a need to change direction and/or speed of DC motor. Communication application – rotate dish antenna upward – downward or clockwise – anticlockwise.Defence application – to rotate radar, automatic gun, tank gun in either direction. Domestic application – to vary speed of battery (DC) operated portable fan.Industrial application – to change direction and speed of rotating machinery.Robotic application – to change direction and speed of moving robot.Controlling direction and speed of DC motor is very essential in many applications like
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