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Industrial Ethernet Book 103

Lift stations can be monitored in real time, with map overlays to give operators real-time situational awareness. version of the system, posting large amounts of data from the controller to the cloud server proved to be slow and processor intensive. In addition, the cloud server didn’t have a reliable method for ensuring configuration changes, such as HMI setpoints, were sent back to the controller. “This posed a problem,” said Chris Parish, senior application engineer at Perceptive Controls. “The controller would often check for configuration changes, only to have the server respond back saying that no changes were needed. It wouldn’t work to have the controller check less frequently, because we wanted the controller to be able to respond in a timely manner.” “We decided to consider alternate options for transferring data. So we investigated the RESTful API capabilities built into Opto 22 SNAP PAC controllers,” Parish added. SNAP PAC controllers come with a built-in, secure HTTP/S server with an open, documented API, effectively creating a RESTful architecture. RESTful architecture and its technologies, like HTTP/S and JSON (JavaScript Object Notation), are intrinsic to the Internet of Things and paramount to web, data, and mobile-based application development. With their RESTful API and secure server, the SNAP PACs offer valuable alternatives for application development. Through the RESTful API, developers can gain secure, programmatic access to data from new or legacy physical assets wired to the PAC.Developers can use any programming language that supports JSON to access control variables and input/output (I/O) data. “After switching to the new RESTful API method, we now have a cloud-based software application running on a dedicated server that uses the SNAP PAC’s RESTful API to request data directly from the controller,” Parish said. “Requests are made over a private cellular network to avoid cyber security-related concerns and avoid opening ports in firewalls,” Finkler added. “We store data in float tables on the PAC (about 44 indexes per table) and the software can grab up to 100 tables of data per request without slowing down communication performance.” The cloud application then uses the RESTful API to write back how many tables were retrieved, so the controller can delete the old data and move everything up in the table, with new data again at the top. This ensures that all data was received into the cloud application. “It’s more efficient to make the cloud application process large amounts of data, instead of making the controller do the work in addition to its normal operations,” noted Finkler. “This method saved an average of 5.8 KB per data set transmitted, which ended up saving us about 250 MB per day, adding up to significant savings in cellular data charges.” Using the RESTful API, Perceptive engineers can also send configuration changes on demand. Since configuration changes rarely occur after the initial setup, 99% of the previous configuration traffic has been eliminated, and data is transmitted only when necessary. The cloud application also monitors for alarms and sends out notifications to operators if necessary. Using the Perceptive Polaris solution, water and wastewater customers can monitor their lift stations and SCADA network in real time, with advanced map overlays that provide operators with real-time situational awareness of the SCADA system. Operators can view and respond to alarms through the website, and authorized users are alerted to alarms via email and/or text messaging. Operators who receive an alarm can acknowledge it by replying to the text message. Historical data is stored on cloud servers hosted by Perceptive Controls and backed up regularly. Looking ahead The engineers at Perceptive Controls are currently developing a mobile app that will communicate with the Perceptive Polaris server and allow users to respond to alarms and change setpoints as needed. “In the future, the entire SCADA system will be able to be managed from almost any authorized mobile device,” Finkler said. Application article by Opto 22. 11.2017 industrial ethernet book SOURCE: OPTO 22


Industrial Ethernet Book 103
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