A model of windmill is kept in the path of light having a light detecting sensor on the opposite side. The LCD Display starts displaying the speed only after the start button is pressed. When the cardboard blades rotate in the presence of wind, they will block the light and hence light wouldn’t reach the sensor anymore. The sensor will be connected to the microprocessor and speed will be calculated on the basis of the frequency with which the blades block the path of light. The number of times the path of light is blocked is counted and the time in which this happens is noted and both are stored in the microprocessor memory. Speed is calculated by dividing these two quantities. The calculated speed is then displayed at the LCD for the user to note down.
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