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IEC 61131-3 Function Blocks support remote application programming via modem

Ralf Wohlschläger, EURO-Matsushita Electric Works AG

Remote control applications are relatively new and the number of applications has rapidly increased since 1992 when Matsushita entered this market and began to develop expertise with this type of product.

Remote control and monitoring of programmable controllers can be achieved via different telephone network technologies and since typical PLC programmers are not experts in telecommunications, the automation systems suppliers have to offer ready-made solutions for both hardware and software communication components. The Function Block (FB) concept is typical of the type of solution offered by automation systems companies. The IEC 61131-3 supported Function Blocks allows all the special telecommunications know-how to be incorporated in to Function Blocks so that the end-user can integrate the ready made software block without any telecommunication knowledge.

Depending on the application and the environment, several communication methods based on the following connection options can be offered :
  1. Analogue modem (TC-networks) meeting the new CTR21 European standard - (see the picture below)
  2. Multi-Drop modem networks
  3. GSM networks for mobile communication
  4. ISDN digital adapter (TC-network)
  5. Radio modems (see picture)
All of these technologies require ready made function blocks that cover device initialisation, dial-up and disconnection, communication and handshaking, password protection to avoid unauthorised users and the management of the priority / Master-Slave hierarchy.

To cover the different hardware architectures and software options for each concept, Matsushita offers an extensive software library with many IEC 61131-3 Function Blocks for easy integration into user programs - the largest FB in the Matsushita library has 1,200 program steps. The FB MODEM shown below is an example from the Matsushita Library.

(Screen dump of Function Block – not drawn here)

Remote control applications are the best example of the advantages of the IEC 61131-3 and the easy reusability of available software. It would be almost impossible for the traditional PLC programmer to collect all the knowledge and detail about telecommunications and then use it in an efficient way. However, with the IEC 61131-3 Function Block concept, this has been achieved since telecoms experts have investigated and programmed the required tasks in to ready made blocks which can be reused without knowledge of the complex contents.

The use of remote control is increasing and there are many applications examples:
Building Technology / Facility Management : In warehouses, office buildings, hotels, freezers, swimming pools, high rise buildings etc., there is a need for security/ fire alarm systems, elevator control, heating control and tank level inspection, temperature and humidity control and much more.
Power Generation and Energy Distribution : For power plants (fossil, wind, water), transformer stations, solar panels and distribution stations there is a need for error/ alarm information, data monitoring, security control, error location, short circuit location/ protection, emission control, remote service and much more.
Water and Sewage Technology : For water supply, waste water treatment and water distribution there is a need for data monitoring, alarm handling, remote process control, data transmission and storage, security control a. s. o.
Traffic and Environmental Technology : For park houses, park tickets, traffic control, traffic statistics, weather analysis and measurement stations there is need for data transmission, remote control for free parking lots and traffic speed, emission measurement and storage and much more.
Supply Mains for Oil, Gas, Water and so on : For pipelines, tanks and public supply services there is a need for remote control, remote distribution, data transmission and storage, level inspection, security control and much more.
Mobile Data Transmission: For refrigerated trucks, trains and ships there is a need for temperature control/air conditioning, alarm handling, security control, data measurement and transmission a. s. o.
The advantages of modem remote control for the industry are significant:
very short repair/ response time as the PLC can inform about alarms immediately. No human inspection/ delay needed
Detailed error location/ information enables the service engineers to bring the correct tools/ spare parts at the first time
Reduced costs for inspection
Flexible, independent communication for each application through wired or radio transmission
Communication with moving objects
Fixed connections can be replaced by event established communication
Wide available product range and ready made software enables the easy use