The project leader at a large battery manufacturing facility in North America was given a seemingly impossible task. He had to pull data from over 200 devices, and feed it to the company MES system. The problem was, the MES required a fixed, always-present data set, whereas the devices were continually coming online and going offline, and would occasionally add or remove a tag from the data set. Adding to this complexity, the data had to be networked securely on the company network, without the hassles of DCOM.
Addressing the last problem first, the project leader used the Cogent DataHub to tunnel the data from OPC servers for each of the devices, and bring it all to a central DataHub that was connected to Citect. Once all of this was configured and running, it became clear that the DataHub resolved the fixed data set problem as well. When a device goes offline, the tag remains in the DataHub, and the quality changes from ‘Good’ to ‘Not Connected’. So every member of the data set was always present in the MES system.
The only problem remaining was handling the tags that the devices occasionally added or removed. For this, the project leader worked with Cogent to come up with a custom solution. First they modified the devices to limit the time to add or remove a tag. Then they wrote a DataHub script to monitor a few tags, and when these change, the DataHub waits out the time limit, and then refresh the data set. This approach works very well, and the DataHub has become an integral part of the company’s MES system.