KNX Protocol

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 KNX Protocol

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What is KNX? What are its applications? Whats Special about it? Lets see:

• KNX is a network standard, basically OSI-based network communications protocol which is extensively designed and developed for building/home automation.
• KNX is an abbreviation for the word Konnex
• KNX is based on three technologies: EIB (European Installation Bus), EHS (European Home Systems Protocol) and BatiBUS.
• The KNX is not constrained by hardware compatibility, a KNX device could be controlled by anything from an 8-bit microcontroller to a PC, based on the level of implementation and application.

Communications that support KNX:

• Twisted pair (Most commonly Implemented, Avg. bit rate: 9.6Kbits/sec)
• Radio frequency
• Infrared Power line
• IP/Ethernet

KNX is used in residential and commercial building automation for HVAC, lighting, security, remote access, blind and shutter control, visualization, and energy management.

KNX Model

Here is how KNX provides the ideal introduction to the world of bus technology:

• Many of the problems that can be solved by KNX occur in our everyday lives. This makes it easy to become familiar with how to solve automation-related problems using KNX.
• Many professional training schools teach bus systems, particularly KNX, as part of their syllabus.
• KNX is simple and straightforward to plan, program and implement. Approximately 10% of companies in the electrical and electronics industry can plan and install KNX systems. Many engineering companies take on KNX projects, which mean that their energy and building system engineers need to have a good working knowledge of KNX.
• Using IP Gateways, KNX systems are increasingly being integrated into the network infrastructure of buildings (TCP/IP networks), allowing them to be accessed externally via the Internet. KNX also enables you to connect electrical installations to the Internet. In this respect, learning about KNX provides a sound in-depth introduction to modern automation technology.

Typically KNX network consists of 3 major set of components: - Sensors (e.g. push buttons, temperature , movement-sensors) - Actuators (e.g. Dimming units, bulb, motors) - System devices and components (e.g. Line-Couplers, Backbone-Couplers) - Operating and monitoring (visualization) devices such as control panels The devices and components are interconnected in any one of the communication medium (mostly being twisted pair) to communicate data between each other to perform the required actions. KNX allows in ease of extending the network in already existing setup. The application program is loaded into the devices together with the project design and commissioning software via a system component called interface (either serial or USB interface) connected to the PC and the bus. The two-wire installation bus is routed in parallel to the 230 V electrical power supply connects all devices and systems of the household technology together and transmits all the control signals. KNX systems can be installed at required places and can consist of several KNX subsystems. - 

It follows a tree topology.

• Nodes (N) are assigned to a line (L)
• Several lines are connected via a main line (ML) and form an area (A)
• Several areas are connected with each other via the backbone line (BL) -

 The basic unit of a KNX TP installation is a line which includes a KNX power supply (including choke), and usually no more than 64 other bus devices. - Branches could be taken out on bus cable to extend more subsystems.

- No more than three repeaters can be operated in parallel in a line, meaning the maximum number of bus devices is 255. - Line Couplers could be used to increase the network further, up to 15 lines can be operated via Line Couplers on a line. Cable Length: - Distance from power supply to device: max. 350 m - Distance between any two devices in a line: max. 700 m - Length of a line segment: max. 1,000 m - Distance between two power supplies (including choke) in a line: as per manufacturers’ specifications. Individual Address: - Every device in a KNX system is assigned a unique, unambiguous number. This consists of three numbers separated by dots. The numbers depend on the position of the bus device in the topology: - The first number denotes the number of the area - The second number denotes the number of the line - The third number is a sequential number indicating the device’s position in the line 

 The KNX Standard includes different Configuration Modes: S-Mode (System Mode):

• S-Mode uses the standard frame format. It needs active Network Management (as

The KNX Standard includes different Configuration Modes: S-Mode (System Mode):

• S-Mode uses the standard frame format. It needs active Network Management (as performed by ETS) with Broadcast and Individual Addressing.
• Controller Mode:
• It uses Group communication with the standard frame format. It needs active Network Management (as performed by ETS) with Broadcast and Individual Addressing. Push button mode:
• For configuration, PB mode relies only on active management from one device directly by another. It uses group addressing with the standard frame, with structured binding. Logical Tag Extended mode:
• LTE defines extended frames for its “native”• run-time communication, with tagged binding on Interface Object properties. 

KNX Software:

• System software: It is particularly responsible for processing data communication over the bus, is saved permanently in the device (in the communication module’s ROM) by the manufacturer.
• Application software (application programs): A device’s application software, on the other hand, is supplied by the manufacturer in an ETS 3 product database. The user must then select the corresponding product software, set the parameters, and then load it into the device using ETS 3 in order to commission the device.
• Engineering Tool Software Version 3 (ETS 3): ETS 3 is an integrated program for designing and commissioning KNX systems. 

KNX monitor:

• A cloud based remote debugging, monitoring and control system for KNX installations, requiring nothing but an off-the-shelf KNX IP-router and an Internet connection by KNX IP tunneling Protocol.
• It records every change to a Group Address and storing that as a time-series in a database, which helps in real monitoring of the network for troubleshooting.