The following work has been designed to analyze the pulse-width modulation system of a 555 timer in astable operation and implement this property to design blinking LED circuit. The frequency in which LEDs blink, can be easily changed by controlling the output signal from 555 timer. Pulse-width modulation uses a rectangular pulse wave whose pulse width is modulated resulting in the variation of the average value of the waveform.
Pulse-width modulation is regularly used in the field of digital communication and as well as in robotics. Its duty cycle has been used to convey information over a communications channel. This can be used in precise time controlling device and thus it has the ability to control delicate instruments at ease.
Introduction.
Pulse width modulation is a process of generating an analog signal originated from a digital source which allows to encode the amplitude of a signal into the width of the pulse (duration) of another signal. This will make it easier and cost-efficient to apply adjustable power to devices where only partial power is needed. [1].
The Pulse Width Modulation (PWM) plays an important role in controlling the circuits. If we want to control the speed of a dc motor, or direction of a servo motor, PWM is the key.[2] The width of pulse is used to regulate power to a device. If the pulse width can be controlled, then it will be possible to control that device too. In this project, PWM generated through a 555 timer is used to blink LEDs. .
In the past, when only partial power was needed (such as for a sewing machine motor), a rheostat (located in the sewing machine's foot pedal) connected in series with the motor adjusted the amount of current flowing through the motor, but also wasted power as heat in the resistor element. It was an inefficient scheme, but tolerable because the total power was low. This was one of several methods of controlling power. There were others, some still in use - such as variable autotransformers, including the trademarked 'Autrastat' for theatrical lighting; and the Variac, for general AC power adjustment.
