Short  Description  Of  Projects

Automatic Sensor and Illuminator

Submitted By:                                  

                                                 Anoop Jayadevan 94038

                                                        Chandan 94073

                                                        Siddhartha Ghosh 94282

Project guide:                  Dr.Manjunath

Introduction: 

The main motivation for this design was its relevance in today's world. In our day to day life, we come across umpteen situations where lights, or for that matter any electronic gadget is switched on for a very long time, when it is needed only for a very short while.

A very simple situation is that in a library. There are many remote corners in the library where the lights are kept on all the time and people go there only for a very short while, if any do. So if we have some mechanism by which we can switch on the lights sensing the presence of a human being then we are done. We can find more examples like the case of a long corridor where only very few lights need to be kept on all the time and when ever somebody passes by, within a reasonable distance we switch on the light.

The device has two modules viz. the sensing circuit and the lighting system.

Underlying Principle

Here we discuss the various options we had for making the sensor. The choice of the second module viz. the lighting circuit is not that important.

Infrared sensors: These are sensors which have an infrared source and a sensor. When the infrared rays emitted by the source are obstructed by any object, then the 'circuit' that was completed is now broken. Thus the object is sensed. Here, the main drawback is the directionality of the sensor. It cannot sense a human being if he comes from any arbitrary direction. Moreover, these are sensors that consume power always, as the source has to transmit the rays always.

Ultrasonic sensor: This is also functionally identical to the above sensor except for the fact that Ultrasonic waves are used instead of infrared rays. The disadvantage are the same as that for the above.

Capacitive sensor: In this case sensing is done by making use of the body capacitance of human beings. Here, we do not have the problem of directionality. Also power is consumed by this sensor only during its functioning.

So finally, in this implementation we chose the third option, ie. , use of a Capacitive Sensor (also called a proximity switch).