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ware if the values being pulled from the PLC are raw. A spreadsheet was developed for all of the specified addresses in the PLC and used to create a comma-delimited file (.csv) that was imported into the software. The spreadsheet is a time saver for set- ting up the addresses and provides a refer- ence document for future updates. Once the tags have been created and configured with the correct address from the PLC, the data can be viewed in real time with a built-in OPC Quick Client to ensure prop- er setup and configuration of the data tags. Pi Interface on Remote Server The next piece of the communications puz- zle is the interface between the remote serv- er and the central Pi server. The Pi software comes with configuration utility software to set up and configure this interface. This piece of software essentially allows the user to create and modify the service to handle the transfer of the data from the tags written in the OPC database from KEPServerEX. The point source (remote server OPC database) is defined so the central Pi server can be configured to accept data from the specific data points listed in the central database tags. Figure 2 shows the general interface configuration options with the server descriptions and point source identifiers. Another important piece of the interface is the buffer service. This service allows the data from the OPC database to be stored locally if communications with the central Pi server are lost. The data will con- tinue through the OPC database until communications is restored. The data is then processed through the queue and sent to the central server until the current data is transmitted. Normal transfer oper- ations will begin at this point. Pi OPC Client Once the tags have been created in KEPServerEX, the Pi OPC client software can be used to ensure that the Pi system can access the OPC database and read the val- ues from the tags created in KEPServerEX (Figure 3). The Pi OPC Client software allows the user to navigate through the devices, in these cases the PLCs, select indi- vidual or multiple tags, and add them to a customized group for viewing. After data access is confirmed, the customized group of selected tags can be saved as a comma- delimited file, which makes creating tags in the Pi system on the central server much quicker and more efficient since all tags can be imported at once. The Central Pi Server The central Pi server consists of a virtual s e r v e r r u n n i n g W i n d o w s S e r v e r 2 0 0 8 R 2 S t a n d a r d c o n n e c t e d t o t h e c o m - p a n y ' s i n t e r n a l n e t w o r k v i a E t h e r n e t . Configuration of the server and Pi soft- ware installed on the server can be per- formed remotely from anywhere within the company's internal network. Remote Server Trust Before anything can be pulled into the Pi system from the remote server, Pi has to give permission to the remote server's interface for data transfer. The Pi System Management Tools (SMT) software allows the trust to be created based on both the IP address and network path based on the computer name of the remote server (Figure 4). Setting the system up in this manner allows the remote server to communicate with the central Pi server regardless of any networking issues on either of those meth- ods. A static IP address was also given to the remote server to prevent any issues with IP address changes if the computer was restarted for a power loss. This also allows the trust to be applied to the static IP address. p l a n t o p e r a t i o n s c o n t i n u e d July 2014 www.coalage.com 43 Figure 2: Screenshot of general interface configuration in the Pi interface configuration utility software. Figure 3: Screenshot of tag values in the Pi OPC client software.