This paper discusses the structure and features of the modern day Building automation system (BAS). Building automation describes the functionality provided by the control system of a building. The control system is a computerized, intelligent network of electronic device designed to perform the maintenance of the mechanical systems in a building. The field technology used in this is a distributed control system with Lonworks technology. This paper gives a detail review on a building automation system for a 3-storey building with 120 light fittings, 26 air handling units, 2 central heating and cooling systems. The design of Lon maker and intelligent node which uses Lonworks technology are also discussed in this paper. INTRODUCTION
Building automation system is most widely used technology which is mainly used in commercial areas like shopping malls, hotels etc. The core functionality of the BAS is to maintain the building climate in a specified range, monitors system performance and device failures, provides lighting based on occupancy schedule. The BAS functionality reduces building energy and maintenance costs when compared to a non-controlled building. A building controlled by a BAS is often referred to as an intelligent building system. These days, with the high cost of energy, labour, and contract services, it is even more important to put an emphasis on implementing a system that not only automates building equipment and functions, but also improves on the efficiency and effectiveness of a facilities department. It is therefore critical that when implementing a building automation solution it is not done in a commodity fashion. A comprehensive design is
required to maximize the benefits of a building automation system. Otherwise, all you may get in return is a high tech time clock, and that is not good for the bottom line. The primary and secondary bus can be BACnet, optical fiber, ethernet, ARCNET, RS-232, RS-485 or a wireless network. Automatic control has a lot of advantages. First, the use of a building automation system makes it easier to maintain the systems in the building. Additionally, it is possible to modify the system behaviour even if the installation of the system has been finished. For example, in an intelligent building it is possible to change the configuration of the lighting system without changing the physical wiring. The system operator can simply reassign the binding between the light switch and the ceiling light without changing the electrical wiring.
FIELD BUS TECHNOLOGY
For about 20 years now, the word "fieldbus" has been very widely used. Its common meaning is a network for connecting field devices such as sensors, actuators, field controllers such as PLC’s, regulators, drive controllers, etc., and man-machine interfaces. But this is only an informal definition and needs more in-depth analysis. Fieldbus technology represents a wide domain of problems which are similar, but not exactly identical in nature. Fieldbus technology involves a variety of solutions and techniques which, although frequently seen as closely related, are different from each other. Fieldbus technology is a kind of technical, political and human adventure, which for more than 20 years has led to a lot of articles in journals, a lot of announcements, a lot of so-called scoops, a lot of conferences and workshops, and a lot of products and standards. Fieldbus works on a network structure which typically allows daisy-chain, star, ring, branch, and tree network technologies. Previously computers were connected using RS-232 (serial connections) by which only two devices could communicate. This would be the equivalent of the currently used 4-20 mA communication scheme which requires that each device has its own communication point at the controller level, while the fieldbus is the equivalent of the current...