DESIGN AND CONSTRUCTION OF A PHOTO SENSITIVE AUTOMATIC SWITCH

1.0.INTRODUCTION:

The automatic electric switch is a light dependent resistor as its main sensor. It is preset to trigger a control circuit at a particular intensity of light. This control circuit is built using the 555 timer IC as the basic building block and is ideally suited to the task of switching devices on and off at a preset intensity of light. Thus it can be useful in many applications.

Some prominent areas of application include automatic security lighting, burglar alarm, image detectors, automatic curtain rail etc. light intensity is detected by suitable transducers which converts it into an electrical signal.

A switch is basically any device that is used to interrupt the flow of current in a circuit. Switches are usually binary devices. They are either complementary closed ON or complementary open OFF, we have manually operated switches hand switch and automatic switches.

The manually operated switches are operated manually by somebody whereas; the automatic switches are controlled by a physical stimulus such as light temperature, pressure, magnetic field, liquid etc.

Automatic controlled devices are now sweeping the manually operated devices out due to the comparative advantage of auto regulated devices over manually operated devices

The need for accuracy, sensitivity and reliability in this present day calls for the use of automatic operated devices. The automatic light switch is basically a switch that is operated by light, it is an example of automatic switch which uses light as a physical stimulus. It is a device that is set to a complementary close when light is absent or reduced it responds to changes from light to darkness.

The project is designed in such a way that when light intensity reduces, an LED is switched ON and automatically goes OFF when a source of light is present.

1.1.PURPOSE OF THE STUDY:

It has been observed that places such as schools, factories, hospitals, residential buildings etc need to be illuminated at nigh and the light put OFF once it is day break. But this is often not so because either the operative who would have put ON the light is not there or perhaps forgotten to do so at the right time.

There is need therefore to construct an automatic switch which will complement if not eliminates the human efforts by putting on the light when night comes and turns it OFF when day breaks.