Micro PLC finds its sea legs in monitoring role

When generator control system manufacturer Deep Sea Electronics wanted a simple, elegant solution for the remote monitoring of its control systems, it turned to Siemens Automation and Drives.

When generator control system manufacturer Deep Sea Electronics wanted a simple, elegant solution for the remote monitoring of its control systems, it turned to Siemens Automation and Drives for a web-enabled, browser-driven solution.

Established in the 1970s as a provider of undersea communications equipment, Deep Sea Electronics has evolved to become a leading supplier to the power generation industry, internationally recognised for its innovative control and monitoring systems.

From its UK base in the picturesque rural village of Hunmanby on the North Yorkshire Coast, Deep Sea Electronics operates at the forefront of control technology, designing and manufacturing all its own products to meet the emerging needs of the power generation industry.

Recognising that the ability to remotely monitor control systems is becoming increasingly important within the industry, Deep Sea Electronics saw an opportunity to exploit the power of the worldwide web with its control systems.

"More and more generators are being installed in remote locations, so being able to monitor their control systems remotely is very important from a maintenance point of view", explains Deep Sea's John Ruddock.

"Even when the generators are not on remote sites, they are often being installed at companies which don't have the in-house expertise to maintain them, so again the ability to monitor the control systems remotely is of huge benefit".

"The requirement is also greater when there are multiple generators on any one site".

"So we were keen to develop a simple solution that would facilitate remote interrogation of the control systems at multi-set sites".

Looking for a fast solution to integrate with existing products, the company chose to source the Ethernet gateway externally.

"We received lots of proposals based around multiple PLCs, but they all implied levels of cost or complexity that we could never have passed on to our customers", says Ruddock.

"But Siemens was the first to come up with a single-box solution".

"Not only was it the most elegant solution, it was also by far the best from a technical point of view".

The solution was built around a Siemens S7-200 PLC, linked to a CP243-1 IT module.

The Simatic S7-200 micro system represents the pinnacle of micro PLC design, delivering a range of compact yet powerful CPUs and a modular expansion philosophy that enable the user to build up tailored, cost-effective solutions to the most demanding of applications.

Four models are available offering standard I/O counts from 10 up to 40, and with expandable user-memory to handle the most complex machine control programs.

The modular I/O expansion system enables up to seven digital and analogue input and output modules to be added, bringing the maximum possible I/O count to 248.

The addition of the CP-243-1 IT module provides a simple bridge between the data in the PLC and the outside world.

Remote configuration, programming and diagnostics of the S7-200 are all possible via Ethernet, and with communication based on TCP/IP, the same protocol that powers the internet, that remote location could potentially be anywhere in the world.

Effectively adding web-server capabilities to the S7-200 PLC, the system enables standard browser technology to be used in remote HMI applications.

The generator control systems manufactured by Deep Sea Electronics communicate using the Modbus RTU protocol.

Under the Siemens solution, the Modbus data are collected by the S7-200 PLC, programmed by Ruddock, and fed in turn to the CP243-1 IT module.

Java programming technology is used by Deep Sea Electronics to build an HTML overview of the generating set system and mains supply usage.

These pages can then be interrogated remotely, either via a company's local area network or via the Internet using a PC web-browser.

"This simple solution has given us total flexibility, enabling our control systems to be interrogated from anywhere", says Ruddock.

"All that is needed is access to the web, and the relevant user passwords".

"Because the operator interface is built on standard browser technology, there is no learning curve and no software licences to pay".

"And the single box PLC solution has kept costs down and complexity to a minimum".

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