Siemens is a leading electronic and automation product manufacturer in the world. Based on its advanced human-computer communication technology and brand development concept, Siemens provides a variety of high-quality HMI products, solutions and services in the field of production automation and process automation.

In recent years, whether in simple families or complex buildings, users' demand for the convenience, energy saving and functionality of building management system is increasing. Therefore, we need to install more sensors and controllers to achieve intelligent monitoring, which means that users must increase the configuration cost of complex wiring in the existing system environment.

In addition, users need more and more appliances to interact with each other. People require home appliances to be automatic, intelligent and even able to sense the user's emotions.
For example, when the sensor detects you have entered the home, the light is turned on. When the sensor detects that you are away from home, all lights, air conditioners and other electrical appliances will be automatically turned off.

intelligent building management system allows people to control appliance away from home

Figure 1: A cartoon showing how user controls appliances away from home.

Due to the increasing demand of users for smart home and intelligent building system, the Internet of things technology is becoming more and more mature.

1. KNX Standard Protocol

In the early 1990s, EIB, batibus and EHS, the three major residential and building control bus protocols in Europe, were exploring their own market and standardization. Although they have made achievements in different areas and fields, their prospects are still difficult to predict.

Later, the three organizations decided to work together to develop the smart home and building market. They established the Konnex Association in 1995 and launched the KNX standard in the spring of 2002. KNX (short for Konnex) is an officially approved open international standard in the field of residential and building control.

The standard is based on EIB, takes into account the physical layer specification of batibus and ehsa, and absorbs the advantages of configuration mode in batibus and ehsa, and finally provides a complete solution for home and building automation.

2. Siemens Intelligent Building Solutions

The Research & Development team of Siemens integrates the communication between HMI and KNXnet / IP protocol, and proposes a set of intelligent building solutions.

KNXnet / IP is an international standard communication protocol for building control, which can integrate building equipment of different manufacturers, such as large household appliances, lighting, air conditioning system, etc. It can help users quickly build a more convenient, energy-saving and multifunctional building management system.

3D model of Siemens intelligent building system

Figure 2: 3D model of how Siemens HIM and KNXnet system controls the internet connection of a workplace.

The 2 key features of KNXnet are as follows.

2.1 Multicast Communication with HMI as Central Control Computer

In the past, if building equipment needed to connect or exchange data, it had to transfer data through HMI or switch.

This defect is that each brand of different models of equipment has its own way of communication. In addition to increasing the complexity of on-site equipment installation, users often can not effectively integrate and monitor all the on-site equipment. Now, the man-machine integration of KNXnet / IP protocol is a central control computer, which brings you solutions.

For example: the network shown in the figure includes a backbone and three line couplers. Each device on the line has a KNX address and is connected to the corresponding KNX PLC.

Please note: the KNX architecture can use 15 domain backbones, and each domain backbone can set 15 coupling lines. Each coupling line can reuse 1-63 addresses for practical application, for example, 1.1.1 - 1.1.63.

Illustration of Siemens HMI + KNXnet system

Figure 3: Illustration of Siemens HMI + KNXnet system

In this network, the domain backbone of KNXnet / IP system adopts Ethernet, all KNX PLCs point to the same multicast website (default:, and the field devices are connected to the I / o point of KNX PLC in the way of line coupler.

For devices that need to be linked, the common address is used, such as line 2's device address 1.2.1. The user only needs to act on the device with the same address to trigger the linked device with the same address. For example, when the sensor detects that the user enters the conference room, it will trigger all the lighting devices in the conference room to turn on at the same time.

In this network, the Siemens HMI only needs to connect to KNX PLC on the multicast website to display the operation status of KNX PLC and monitor all equipment on site by means of multicast communication.

2.2 Simple Wiring and Increased Flexibility

The wiring architecture of traditional building equipment is more complex (figure a), and the interconnection between equipment must be wired separately. Whenever users add new serial devices, they need to rewire, which is very troublesome.

Using KNXnet / IP communication architecture wiring (Figure b) is very simple, all devices are in the same domain. The user only needs to set the KNX address of the device, and HMI monitor of Siemens can be easily realized, which will not only reduce the cost of purchasing additional communication gateway equipment, but also make the field wiring easier.

comparison of traditional wiring and KNX wiring

Figure 4: Comparison of traditional wiring and KNX wiring.

Wiring engineers no longer need to find the one that belongs to you in the cluster. Wiring becomes very simple now.

Building automation management system is the most widely involved subsystem in intelligent building, with the largest amount of design tasks and engineering construction. Its design level and construction quality have a direct impact on the realization of intelligent building functions.

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