Generating a pure sine wave has its significance especially with devices like microcontrollers which runs on digital voltages. The sine wave is referred to as the basic of all kind of waveform since the combination of sine waves can produce any required wave. In microcontroller systems the analog output like sine wave is generated with the help of digital pulses itself which are generated in such a way that their width are modulated corresponding to the amplitude variations of a sine wave. The method of modulating the pulse width so as to generate an analog voltage is called Pulse Width Modulation technique or PWM. Most of the microcontrollers have this built-in PWM modules which enables them interface with analog circuits, control devices like DC motor etc. This project explains how it is possible to generate a frequency variable sine weave using PWM method with the help the Arduino board.