Light Dependant Electronic Controllers for Switching Lamps

The overall objective of the research is to conserve energy through reducing wastage. This particular work involves innovation and fabrication of devices towards the above objective. The subject presentation of this manuscript is in respect of devices, which will enable domestic, factory as well as street lights to be automatically switched ON at sunset (when darkness arrives) and automatically switched OFF at dawn (when light arrives). Literature survey revealed that several such devices are available but they suffer from many draw-backs such as high energy consumption by the device, flicker (ON & OFF oscillations) at the critical light level of switching, poor reliability, high space requirements, circuit complications etc. The research has solved these deficiencies and has come up with suitable solid-state devices having no electro-mechanical relays. In particular, the flicker problem needed positive feed-back of some form to give a Schmitt trigger effect. In one case this was solved by an innovative method wherein the very lamp that is turned on (or a pilot lamp) beams a fraction of its light on to an LDR, which in turn strengthens the trigger ON. This innovation allows the Schmitt Trigger effect without a D.C. power supply otherwise required for traditional feed-back. The reduction of energy consumption by the device itself necessitated novel approaches. Suitable prototypes have been designed, fabricated and have been subjected to a limited extent of field testing.