You may have seen many different LED chaser projects. Simple LED chaser can be built using IC555 and digital counter chips. Many LED chasers are built using micro controllers. Micro controller based LED chaser have variety of different chasing effect. One can generate awesome LED chasing effect using micro controller programming. There may be 8 or 10 or 16 or even more LEDs connected with micro controller and it will turn LEDs ON/OFF LED or vary its brightness or blink them to create wonderful effects.

All the micro controllers have built in timer-counter. Timer means counting internal clock pulses and counter means counting external pulses. It can be used to generate time delay or PWM or counting. AVR micro controllers ATMega16 and ATMega32 have also three timer-counters. They have one 16 bit (T1) and two 8 bit (T0 and T2) timer-counters. Today we will learn how to use these T0/T1/T2 as counter – means how it can count external pulses or any other event. This article explains how to use T0 as counter. It counts frequency of external pulses connected to T0 pin (1). 

All of you may know about many different single chip audio amplifiers,  some of which are very popular like LM384, LM386 from National Instrumentation (NI). You will find these chips in many easy-to build audio amplifier circuits  which need additional components like resistors, capacitors as well as some time inductors.They require additional components like resistors, capacitors and some time inductors also.

In many applications it is required to precisely control speed of DC motor to an exact RPM. In such application it is required to control as well as measure DC motor speed. In close loop control system speed of DC motor is controlled at the same time its actual speed is also measured and given as feedback. The system compares require speed and actual speed and takes necessary action if deviation is found.

DC motors are widely used in different machines, mechanism and motion control in manufacturing and processing industries. In these machines/mechanisms it is required to control speed of motor or number of rotations of motor or may be both. As shown in figure, the circuit is built using AVR micro controller ATMega32, darlington chip ULN2003A, 16×2 LCD, opto-interrupt sensor MOC7811 and other few components like push buttons, resistors, crystal etc.

Stepper motor are used in CNC (computerised numerical control) machines, industrial robotic arms, 3D printers and in many such applications where precise motion/movement is required. The stepper motor controller controls mainly three parameters of motor – speed, directions and number of rotations.

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Phase lock loop is one of the most essential building blocks of any communication system. It locks to particular frequency and generates output. It is used in electronics frequency control like in satellite communication, air born navigation, radar and FM communications.