Prepared By :Amar pandey

Pulse width modulationwith using dc fan

&pulse genertor

INTRODUCTION Pulse width modulation (PWM) is a method of changing the duration of a pulse with respect to the analog input. The duty cycle of a square wave is modulated to encode a specific analog signal level. This pulse width modulation tutorial gives you the basic principle of generation of a PWM signal. The PWM signal is digital because at any given instant of time, the full DC supply is either ON or OFF completely. PWM method is commonly used for speed controlling of fans, motors, lights in varying intensities, pulse width modulation controller etc. These signals may also be used for approximate time-varying of analogue signals. Below you can see the pulse width modulation generator circuit diagram (pulse width modulator) using op amp. PWM is employed in a wide variety of applications, ranging from measurement and communications to power control and conversion. Pulse width modulation dc motor control is one of the popular circuits in Robotics.

What is modulation ?OR

What is modulation of a signal In electronics and telecommunications,

modulation is the process of varying one or more properties of a periodic waveform, called the carrier signal, with a modulating signal that typically contains information to be transmitted.Modulation Signal = Original Signal +

Carrier Signal

What is Carrier Signal ?

How to Generate a Carrier Signal ?OR

A method of generating a triangle waveform is to first use a clock oscillator to produce a square wave and then use an integrator (low pass filter) to integrate the square wave into a triangle wave it’s called carrier signal .

Types of modulation There are three types of modulation.

I. A.M (Amplitude Modulation)II. F.M (frequency Modulation)III. P.W.M (Pluse

widthmodulation)

A.M (Amplitude Modulation)

In amplitude modulation, the amplitude (signal strength) of the carrier wave is varied in proportion to the waveform being transmitted.

F.M (Frequency Modulation)Frequency modulation (FM) is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave.

What is PWM (Pulse Width Modulation)

Pulse-width modulation (PWM) is a digital modulation technique in which the width of a pulse carrier is changed according to the instantaneous value of the information signal.

CIRCUIT DIAGRAM

Fig. CIRCUIT DIAGRAM OF PULSE WIDTH MODULATION

Advantages

Average value proportional to duty cycle, So variation in pulse width leads change in output which can be easily control.

P.W.M give output in terms of digital signal which reduction noise.

Less heat dissipated versus using resistors for intermediate voltage .values

Disadvantages

Complexity of circuit Radio Frequency Interference Voltage spikes Electromagnetic noise

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