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PLCs start chatting with mobile phones

01 October, 2000

PLCs start chatting with mobile phones

You can now dial up a Schneider PLC from your portable phone to check on its behaviour or to alter its maintenance schedules. Similarly, if the PLC develops a fault, it can call you anywhere in the world to alert you to the problem.

This has become possible because Schneider has added WAP (Wireless Application Protocol) phone access to its internet-enabled PLC systems. Control and monitoring of any process can now be performed over a digital cellphone link, allowing an engineer to keep in constant touch with his or her installations.

"It means you can now get performance and diagnostic data using just a Web browser," says Chris Holt, Schneider Electric`s automation marketing manager. "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", reads information from the PLC and passes it to the WAP phone. Similarly, information can be sent from the phone via a servlet to the PLC in real time.

A servlet is a server-side equivalent of a Java "applet". Its purpose is to connect to the PLC and either update its data or collect data from it to create a dynamic Web page that can be sent via WAP to a mobile phone.

The control system can also raise an alert at regular intervals or in the event of a system fault. This can be done either by sending an email, or using the mobile phone SMS (Short Messaging Service) system which carries messages of up to 160 characters.

To ensure security, the caller is asked for a username and password when logging in to the control system. Additional levels of security can be provided in the servlet software.

Holt sees potential applications for the technology outside the industrial arena. It could, for example, be used to monitor and control building lighting and heating. "It 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 a failure," he adds.

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