ABSTRACT
For several reasons, invisible electromagnetic signals in the RF and infrared frequency spectra are preferred for the remote control of consumer electronics. However, a niche exists for the use of visible light for the remote control of domestic electrical fittings which require simple power control operations. Electrical fitting controllers like light switches, light dimmers, power sockets and ceiling fan regulators can be remotely controlled by an ordinary flashlight focusing its light beam on the detector for the fitting. The remote control signal detector compares the luminous intensity on a light beam detector with that on an ambient luminous intensity detector and, given a sufficient difference, initiates a cyclic controller output sequence. The output cycles, changing the state of the controlled fitting from OFF to ON (at different ON states if applicable) and back OFF. The design of a simple and sufficiently sensitive light beam detector that can function properly and reliably in all indoors ambient lighting conditions was the main focus of this thesis. The luminous intensity difference detector designed uses two light dependent resistors (LDRs) in special enclosures which increased their sensitivity to a focused light beam in high levels of ambient illumination. A UA741C Op-Amp IC based comparator is used to detect a difference in illuminance between the ambient illumination and the extra illuminance as a result of a focused light beam on the light beam detector. The light remote controlled ceiling fan regulator realized using the luminous intensity difference detector has a control range which competes favorably with infra-red remote controlled systems. The luminous intensity difference detector can be used in security systems, motion sensing, robotics, sunlight tracking systems and many emerging applications of optoelectronics.