One of the great criticisms of the programmable controller (PLC) has always been that its functionality is limited to sequential control. If you want to see what it is going on inside it and to interact with the program, you must add an operator interface. To be sure, a few PLCs with built-in operator interfaces have appeared, but the market in general has not followed this pattern.

Ten years ago networking brought new possibilities for connecting and distributing PLCs with their operator interfaces and the popularity of HTML and web tools has made it possible to take the decentralisation trend one step further: now manufacturers can embed a web server inside a PLC, one that would serve its 'clients' on the network—operator interfaces, in other words—with all the data they need to have. And on the client side, all that's needed is a computer, any kind of computer, that runs a web browser. The web browser becomes the operator interface. You can't get any cheaper HMI software than that.

Web servers embedded in industrial products aren't new, of course, but control manufacturers have taken hold of the concept and have moved it forward.

Recently Hitachi announced its micro web controller, the EH-WD10DR that is in every sense a microPLC (six inputs and four outputs) that fits into the palm of your hand. Its cost is truly micro as well: it will list for £550 in the U.K. and @825 in Europe.

'The new micro controller opens up the possibility of supervising all manner of control systems through the web,' explains Stuart Harvey, managing director of Silverteam, the company that distributes Hitachi industrial products in the U.K.

'As it is a gateway there is effectively no restriction on the number or type of I/O.'

The low cost will be a major factor of its implementation, he believes. 'Factory automation technology periodically undergoes a step change, usually when a technology reaches a price point such that it becomes universally available.

'The uptake of web control of production machinery and industrial systems has to date been restricted to special cases where costs could be justified and special requirements were met,' says Mr. Harvey. 'The micro web controller breaks down this barrier, so that web control becomes a possibility for many new fields of applications.'

He's also keen to push the PLC/web technology out into non-industrial areas. Some new applications he has in mind include vending machines, high performance office printers and other machinery that needs regular refilling or servicing. Because the micro web controller can send e-mails and text messages, it can alert travelling field engineers when their stocks are running low or otherwise need attention.

Researchers could set up automatic monitoring of their experiments. Secure locations could effectively have a robot watchman: sensors would detect intruders and activate the EH-WD10DR to operate cameras and inform a central control officer via an e-mail or text message. In retail the controller can use its bi-directional monitoring capabilities to monitor stock levels plus the status of point of sale equipment, refrigerators, and forward information to both head office and local managers.

And, where else but in the U.K. would they think of this application: protecting yacht thefts. 'We think we have found an effective solution to the massive problem of theft of yachts from the moorings,' says Mr. Harvey.

'A little EH-WD10DR could be secreted into some dark corner of the craft and alert both owner and coastguard if there is unexpected entry or engine start.

It could also set a GPS tracker going and conceivably could cut the engines and electrical power supply after 30 minutes.'

At the heart of the little controller is a 32-bit RISC processor with enough memory to process a 3K step program. All programming is done via standard Hitachi programming software, which runs on a Windows-based machine and handles all five IEC-61131 languages. It is compatible with Hitachi's H and EH series of PLCs.

A built-in auto-detection capability matches communication speed with the device to which it is connected.

As for its web interface, the controller uses HTTP D (hyper text transfer protocol Daemon) and special CGI (common gateway interface) for automatic data read and write by a standard web browser networked to the PLC. The web controller also has SMPT (simple mail transfer protocol) capabilities with the power to automatically send up to 16 different pre-defined e-mail messages to eight different addresses. Serial and Ethernet ports are on the front of the device. Add-on analogue I/O is planned for future release.

The serial port allows expansion by connecting to other Hitachi PLCs, so that the micro controller can function as a gateway module with a control network, to engage with PLCs, HMIs, PCs, or other field devices. In this sense, the micro controller could be viewed as a potential SCADA platform, because it provides high-level control by enabling users to view calculated values, view inputs, outputs, and internal bits. 'It gives you a window into the process,' says Mr. Harvey.

For more information readers can visit www.silverteam.co.uk or use enquiry form on the inside back cover.