Design, Construction and Characterisation of Computerised Control Device for Electrical Appliances

Abstract

In this study, a computerized control of electrical appliances such as lighting and other home and office appliances was designed, constructed and characterized. A circuit (switch controller) that controls the “on” and “off” state of lightings and home appliances was first designed and then a computer program capable of sending and receiving signals back and forth the circuit was written using Microsoft visual basic 6.0. The switch controller circuit is implemented with ADC0804 analogue to digital converter which incorporates, by design, LM35 precision centigrade temperature sensor for monitoring temperature-controlled appliances like heater, air conditioner etc. And also light sensor- Light Dependent Resistor (LDR)-to monitor the on/status of the lights is incorporated as feedback mechanism. The ADC0804 is capable of harnessing information from these sensors and communicating same through the parallel port (printer’s port) to the personal computer (PC) which in turn issues command to the switch controller circuit to either switch on or off the appliance. The switching is achieved by means of transistor switch (C3331), which drives directly 5V, 4700 relays to make or break contact with 220VAC power line to the appliances. There are altogether four sockets for four appliances. The system was tested and confirmed to perform according to design specifications.