Labview Implementation Of On/Off Controller

Abstract

This paper describes an application of LabVIEW to system control which includes data acquisition, data processing and the display of data. The application described in this paper emphasizes the hardware and, perhaps to a greater extent, the software used to control a physical process. The use of the computer in data processing and control applications is a trend that one sees in today’s industrial environment. This application is one of many that is offered to the students in the Industrial Controls laboratory at DeVry, in order to provide them with hands-on experience that they are likely to experience on the job.

Virtual Instrumentation is a current technology that is making a significant impact in today’s industry, education and research. DeVry Institute selected LabVIEW as an good representative of this technology and is using LabVIEW in its curriculum at all DeVry campuses in the United States and Canada. This article is a result of a research project for LabVIEW implementation into the Industrial Controls course. LabVIEW is also used in the communication and physics courses. LabVIEW is one of many skills that the student will need as he enters today’s highly competitive job market.

I. Introduction

LabVIEWTM (Laboratory Virtual Instrument Engineering Workbench), a product of National InstrumentsTM, is a powerful software system that accommodates data acquisition, instrument control, data processing and data presentation. LabVIEW which can run on PC under Windows, Sun SPARstations as well as on Apple Macintosh computers, uses graphical programming language (G language) departing from the traditional high level languages such as the C language, Basic or Pascal.

All LabVIEW graphical programs, called Virtual Instruments or simply VIs, consist of a Front Panel and a Block Diagram. Front Panel contains various controls and indicators while the Block Diagram includes a variety of functions. The functions (icons) are wired inside the Block Diagram where the wires represent the flow of data. The execution of a VI is data dependant which means that a node inside the Block Diagram will execute only if the data is available at each input terminal of that node. By contrast, the execution of a traditional program, such as the C language program, follows the order in which the instructions are written.