HVAC Control in the New Millennium.pdf - HVAC.Amickracing

Computer Networks and SecurityPure PC-based control will grow while blending traditionalforms of control like programmable logic control with PCs will decreaseas the range of PC software expands to cover more diverseapplications.PC-based control runs on a standard operating system such asWindows NT. Off-the-shelf application programs continue to improve.Control systems can be built on Windows with real-time extensions.PC-based control offer improved options in programming software.Systems can utilize popular languages such as Visual Basic, VisualC++, C, or even ladder logic. Applications programmed in differentlanguages can reside simultaneously on the same system.The methods used to simplify program control continue to growand improve. These include sequential function charts, function-blockdiagrams, structured text and flowcharts. A system may use a combinationof several languages and program control methods.In PC-based control, the information sharing between programscontinues to grow and become more simplified. Tools like ActiveXcontrols allow small, specialized software components to be createdthat can be reused to develop customized applications.I/O independence is another characteristic of most PC-based engines.It allows users to choose the I/O and network solution bestsuited for the application instead of using a proprietary solution. Thisis being fueled by open, multisupplier network technologies such asDeviceNet, ControlNet, and Ethernet.Open Systems GrowthToday, there is a trend towards open computer systems for commercialand industrial control. These applications include boiler andchiller controls, heating and air conditioning and fire alarm systems. Inthese control and monitoring systems, a critical element is the method ofcommunication that links the individual components into an organizedsystem.Most modern control components are capable of connection tosome type of communication network. There are many choices availableas these open control systems compete for attention.The elements in these systems need to pass information amongthemselves in order to execute their assigned tasks. An example is an©2001 by The Fairmont Press, Inc. All rights reserved.