Established in the 1970s as a provider of undersea communications equipment, Deep Sea Electronics has become a leading supplier of control and monitoring systems to the power generation industry.
Based on the UK’s North Yorkshire coast, the company designs and manufactures all its own products. And recognising that the ability to remotely monitor control systems is becoming increasingly important within the industry, it saw an opportunity to exploit the power of the 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.
The solution was built around a Siemens S7-200PLC, linked to a CP243-1IT module. The SIMATIC S7-200 micro system delivers a range of compact yet powerful CPUs and a modular expansion potential that enable the user to build up 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 possible via Ethernet, and with communication based on TCP/IP, the same protocol that powers the internet, that remote location could potentially be anywhere. Adding web-server capabilities to the S7-200 PLC, the system enables standard browser 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 is collected by the S7-200PLC, programmed by Ruddock, and fed in turn to the CP243-1IT module. Java programming technology is used by the company to build an HTML overview of the generating set system and its mains supply usage (Fig.1). 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.”