Archive for the ‘IEEE 1473-L’ Category

Lonworks – Control Network for Building Automation

Saturday, June 13th, 2009

 An introduction to Lonworks

Lonworks networks really describe a complete solution to the problem of control systems. Like the computer industry, the control industry was, and in many cases is, creating centralized control solutions based on point-to-point wiring and hierarchical logic systems. This meant that you had a “master” controller, like a computer or programmable logic controller, physically wired to individual control, monitoring and sensing points, or “slaves.” The net result worked, but was expensive and difficult to maintain, expand, and service. It was also very expensive to install.

Lonworks networks started out with some very simple notions – control systems are fundamentally the same regardless of application; a networked control system is significantly more powerful, flexible, and scaleable than a non-networked control system; and businesses can save and make more money building control networks over the long term than they can with non-networked control systems.

Where and how is Lonworks used?
Lonworks networks can be found in all key building automation sub-systems including heating, ventilating, and air conditioning, lighting, boilers, air handlers, security, elevators, fire detection, access control, energy monitoring, irrigation control, and window blinds. In factories, Lonworks technology can be found performing a multitude of industrial tasks — from running wastewater treatment plants to checking paint colors to monitoring the arrival of parts at assembly stations. Lonworks is supported by Echelon.

Background

LonMark is a proprietary protocol developed by the Echelon Corporation in conjunction with Motorola in the early 1990s. The LonMark standard is based on the proprietary communications protocol called LonTalk. The LonTalk protocol establishes a set of rules to manage communications within a network of cooperating devices. To simplify implementation of the protocol, Echelon chose to work with Motorola to develop a specialized communications microprocessor called the Neuron. Through the use of this chip and its supporting software, the protocol establishes how information is exchanged between devices. Because much of the communications protocol is contained on the chip, system designers and installers can focus on other aspects of the system.

While LonTalk addresses the issue of how devices communicate, it does not consider the content of the communication. A second protocol, known as LonWorks, defines the content and structure of the information that is exchanged. LonWorks is a distributed control system that operates on a peer-to-peer basis, meaning any device can communicate with any other device on the network or use a master-slave configuration to communicate between intelligent devices. The LonWorks platform supports a wide range of communications media.

LonWorks-compatible devices communicate with each other through what is known as a Standard Network Variable Type or SNVT. While a SNVT defines a device just as an object does for BACnet, its approach is somewhat different. For a SNVT to function, both the sending and the receiving devices must have detailed knowledge of what the SNVT structure is. Therefore each SNVT is identified by a code number that allows the receiving device to properly interpret the transmitting data.

Initially, LonWorks did not define what a particular SNVT code meant. This resulted in confusion between vendors who used the same code to mean different things. To eliminate the confusion and to standardize SNVT codes, the LonMark Interoperability Association was formed in 1994. Made up of hundreds of manufacturers and integrators, one of its primary goals was to lay out standard methods for implementing the LonWorks technology.

To ensure that any device installed in a LonMark system will work properly with other devices, LonMark requires that in order to carry the LonMark logo, products must have been verified to conform to the LonMark protocol. LonMark uses a Web-based tool to reduce the time and cost for certifying devices.

One of the more recent innovations made by LonMark is the network profile. The idea behind the network profile is that no matter who makes a particular device used in a building system, such as a variable speed drive, all like devices will perform a similar function. To ease and speed system installation, LonMark then defines how a particular device should function on the network, from the points included to how they are named. This predefined network profile is the minimum profile for any connected devices. Manufacturers can add additional items to the predefined profile based on their particular product, giving them flexibility while maintaining simplicity and interoperability.

LonWorks has been accepted and adopted by the international standards organizations (ANSI/CEA 709.1 and IEEE 1473-L).