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Entry type: Application example Entry ID: 81066268, Entry date: 10/21/2013

Realization of a Fault-Tolerant Tunnel Lighting System With S7-400H

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The lighting system in tunnels and subways is not only relevant with regard to traffic safety, it also plays an important role for the smooth flow of traffic. A high illumination quality helps to increase the driving safety, as the driving speeds can be kept more constant, and thus conduces to a better and more harmonic traffic flow.

This application example is aimed at compensating the abrupt change between bright and dark light at the tunnel entrance and exit zones. The solution shall be realized with a fault-tolerant system, as is mandatory for tunnel applications, and meet the following requirements:

  • A light sensor measures the light intensity outside the tunnel. Depending on the result of measurement, the light intensity in the entrance and exit zones shall be adapted accordingly.
  • The values measured by the light intensity sensor shall be verified with the help of a plausibility check, so as to take account of environmental influences (fog, clouds, etc.).
  • The core functionality shall be implemented with a function block.
  • Visualization shall be effected on a local operator panel which is used to display information about the sensor plausibility check and the S7-400H system, to define the light intensity values and to choose between manual or automatic mode.


With the SIMATIC S7-400H system (STEP 7 V5.5), Siemens offers a fault-tolerant controller which meets all of the above-stated requirements.

The figure below provides a schematic overview of the solution and its main components:


The solution realized in this application example offers the following advantages:

  • The use of two control rooms enables the local distribution of redundant systems. If a fire breaks out in one control room, the redundant system will take over and vital functions such as ventilation, lighting and traffic signaling will remain operative.
  • The redundancy-specific functions and configurations require no further assignment of parameters, as this is effected by the optional package “S7-H-Systems” (integrated in STEP 7 Version 5.3 or higher). The project engineer can fully concentrate on the control of the process.
  • All components can be exchanged while the system remains running (hot swapping). Likewise, any changes to the configuration can also be performed during operation.
  • The tunnel lighting control system can be realized with the configurable function block FB100 (without know-how protection).


Content of Downloads


Description related to the application example.
81066268_Tunnel_Lighting_System_V10_en.pdf ( 2007 KB )
STEP 7 V5.5 project for SIMATIC S7-400H CPU, WinCC flexible projects.
81066268_Tunnel_Lighting_System_V10.zip ( 4684 KB )

Further Information



How do you connect a panel to a SIMATIC H station? Entry ID:

Security Notice
The functions and solutions described in this entry predominantly confine themselves to the realization of the automation task. Please take into account furthermore that corresponding protective measures have to be taken up in the context of Industrial Security when connecting your equipment to other parts of the plant, the enterprise network or the Internet. Further information can be found under the Entry ID 50203404.

Additional Keywords
WinCC flexible, S7-400H, H-system, light sensor, tunnel lighting

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