Design and implementation of a microprocessor based room illumination control system

Abstract

This paper describes the development of a microprocessor based room illumination control system that offers advantage of improved efficiency in the use of electrical energy and reduced cost of electricity over manually controlled lighting systems. This system is developed to regulate the intensity of light from direct current (DC) bulbs when the presence of a person(s) is detected in the room so that ambient light is always maintained between 135 lux and 300 lux. Lights are however completely turned OFF if the ambient light level is beyond this range. At the heart of this system is an Intel 8085 microprocessor which controls all operations of the system. The infrared and the passive infrared (PIR) sensors are used to detect the occupancy status of the room while the visible light sensor is used to detect the ambient light level in the room. The PIR sensor is mounted at a height of about 2 m which prevents the system from detecting the presence of animals like cats and dogs in the room and therefore avoids turning the lights ON falsely. Analog signals are produced as outputs from the three sensors and are fed to the microprocessor unit (MPU) for processing through the analog-to-digital converter (ADC). The MPU is then capable of controlling all operations and automating the system. The entire hardware functioning is coordinated by a software program written in low level 8085 assembly language and stored in the erasable programmable read only memory (EPROM). Implementing this system improves efficiency in the use of electrical energy and reduces the cost of electricity.