|Project - Elonics - DEFY
CMW Automation was recently subcontracted by Elonics in Durban to create a data logging system for their client, DEFY.
The brief was to create a system that could gather, display and log specific data from 19 machines in the plant. The communication protocol chosen was an OPC server connecting the various machines to the monitoring system. CMW had to find a suitable package to perform the required functions.
Our choice was the OPC Trend program from Eldridge Engineering, which displays data on-screen in the form of a graph. This program is highly configurable, and has a very high sampling rate, without taxing the CPU.
However, although it has the ability to perform logging and various other features (reporting, alarming, etc) the requirement from Elonics were such that OPC Systems - OPC Trend just wasn't enough. The solution was a Visual Basic program which uses an ActiveX control from OPC Systems to gather PLC data from the PLC OPC server. The program then performs various calculations with this data, and has an in-depth logging operation. Thus the OPC Systems program is used only for trending, all the logging operations have been taken over by the Visual Basic application.
A second program was requested, also written on the VB6 platform, which would display a summarised version of the data received from the PLC's on a 40" LCD screen on the production floor. This screen is entirely dependent on the first program. When the first program runs, the second one runs. When the first program closes, the second one closes. The activeX controls from OPC Systems are so designed that running multiple OPC Clients is possible, and full use of that feature is made here, as both programs gather data seperately, even though they are executed at the same time on the same computer. In addition to an extensive logging system, the Visual Basic application also has an integrated security system. This prevents unauthorised users from viewing sensitive data, and also keeps an eye on the user logons.
Future developments include even more detailed logging, and the ability to connect to the server from remote clients. In conclusion:
In comparison to traditional, costly SCADA/HMI products on the market, VB6 and VB.Net have the ability to integrate with activeX controls that perform almost anything. These activeX controls are cheaper and more specific than the general SCADA and HMI products on the market, and thus if a company has a specific need that should be addressed, this may be the way to go.