Imagine you’re at the airport and there’s a critical deadline which has to be met. Can you achieved it? Wireless Application Protocol (WAP) could provide the solution.
WAP phone technology gives PLCs real-time access to the outside world via the World Wide Web and this month, automation leader Schneider Electric has released details of its latest system which puts proven internet-enabled PLCs and Ethernet together with WAP.
So now, if you’re away from the office and perhaps you need to alter a maintenance schedules, you can first check whether there are spares in stock for the work, simply by calling on the WAP phone. If you’re in a meeting when there’s a critical machine failure, the control system will tell you when it detects the fault.
As PLC web servers can now be accessed by a mobile phone or similar wireless device, companies have the freedom to manage process plant and equipment remotely, the instant the need arises.
Schneider Electric’s Transparent Factory concept uses the Ethernet TCP/IP and the internet to link groups of PLCs together and make it possible for control systems to work in close co-operation with business systems. Now the company has made it possible to step outside the factory yet still retain access to control systems by introducing WAP phone access to its PLC-based control systems. Control and monitoring of any process using one of Schneider’s internet-enabled PLCs can be carried out over a digital cellular phone link, which means the engineer can be in the next room, the next town or even the next continent.
“It means you can now get performance and diagnostic data using just a web browser,” said Chris Holt, Automation Marketing Manager at Schneider Electric. “Instead of having to go to the Scada system, you dial into a WAP gateway which after authentication connects you to the web server in the PLC. Software in the web gateway called ‘servlets’ read information from the PLC and pass it out to the WAP phone. Similarly information can be sent from the phone via a servlet to the PLC. And this happens in real time.” A servlet is the server-side equivalent of the applet, written in Java and portable between a selection of web servers. The purpose of the servlet is to connect to the PLC and either update information it from information it has been sent, or take information it reads and create a dynamic page which can be sent through WAP to the mobile phone. When logging in to the control system, the caller is asked for username and password, and the calls themselves, being digital, are extremely secure. Should it ever prove necessary, additional levels of security are available within the servlet architecture.
As well as two way communication between PLCs and the mobile phone, it is also possible for the control system to raise alerts in the event of equipment distress, service disruption or on a timed basis. This can be done either by sending an e-mail or using the simpler mobile phone Short Messaging Service (SMS), which will carries messages of up to 160 characters.
“This is not just relevant to process control systems in factories,” claimed Holt. “Wherever control systems are used, for example in building management, this principle can be applied. To turn off the lights or turn the heating down, here is open technology which will do that job. In the water industry it can be used by the engineering staff to monitor pump status, adjust settings and call out repair teams in the event of failure.” Chris Holt, Schneider Electric, Tel 01203 416255