The PWM is that kind of a wave in which the ON time and OFF time can vary in a cycle but the sum of ‘ON time + OFF time’ remains constant for every cycle. Duty-cycle is the percentage of time period for which the logic1 voltage exists in a cycle (ON time), starting from the beginning of the cycle. The period of the wave is the sum of the ‘ON time + OFF time’. A simple example of the of waves generated at this pin is shown below Īs shown in the above figure the ‘Period’ of all the wave remains the same but their ‘Duty-cycle’ varies. The P1A is the PWM channel in this particular project. In this project only one of the PWM channels are using. All of them are capable of generating PWM waves at a time. The PIC18F4550 has four PWM output channels and they are P1A, P1B, P1C and P1D. Generating a sine wave has a great deal of importance since the sine wave is the most natural waveform and all other kind of waves can be generated as a combination of sine waves with different frequencies and amplitude. This project explores the PWM module of the PIC18F4550 and tries generating a sine wave with the help of a filter circuit. ![]() The PIC18F4550 has an inbuilt PWM module which can generate continuous PWM waves. ![]() This feature of the PWM wave is making use in so many digital systems like DC motor control, audio devices, simple decoration light controls etc. ![]() Hence the PWM wave is always associated with a filter circuit. The filter circuits are used for generating the voltage corresponding to a modulated wave. With the help of the modulation of the width of a pulse in a period of the wave, they can generate any required voltage with the help of a proper filter circuits. PWM is a digital wavethat can be generated using digital circuits which are not capable of generating analog voltages. The ON time and OFF time can have any different values in the wave cycles, but the sum of the ON time and OFF time remains same for the entire cycles. Pulse Width Modulation ( PWM) is a technique in which the width of a pulse is modulated keeping the time period of the wave constant.
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