About LONworks
LONworks has become globally the most popular open standard field network protocol for building control applications. It is used extensively for HVAC and lighting applications. This section aims to answer the many questions that arise when using the LONworks technology.
Q. What is LONworks?
A. LONworks is an open standard message based protocol for peer to peer communications developed by the Echelon Corporation, which was started around 1989. In order to assist faster product development timescales and to ensure compatibility between deveices, the LONworks protocol was originally only available on a custom developed microprocessor called a Neuron chip which was manufactured initially by Motorola and Toshiba. More recently in order to be accepted as a European field network standard Echelon were required to release the source code so the protocol can now be implemeted on other processor platforms if desired. An important aspect of Echelon's initiative was the creation of a free-topoloy twisted pair wiring standard called FTT-10. This required the purchase of a custom developer transceiver chip but had the merit of allowing very flexible network installations, compared to RS485 which is only generally suitable for straighforard daisy-chain style wiring with short stubs. A further innovation was the LPT-10 version which enabled power to be transmitted over the same two wires as the communications.
LONworks devices are intended to work in a peer to peer way on a "flat" network, so each node holds information about the other nodes it is associated with. Creating these associations is known as "binding". After several abortive attempts Echelon developed a network management approach called LNS (LONworks Network Service) which enabled softare tools such as LONmaker for Windfows to be created which allowed installation engineers to set-up and manage the biundings between LONworks devices. However, the LNS approach had some serious limitations, so Tridium developed a completely separate approach to binding and managing LONworks devices, which is far more scalable and robust. This alternative approach has proved to be very successful and is used by all the major controls companies in the North American market for managing their LONworks devices.
One of the key aspects of an open protocol standard is the ability for devices developed by different manufacturers to interoperate and share information. Such interoperability can only be achieved in practice by developing agreed device profiles as just using the same protocol is not enough to ensure compatibility.
To address this, in the early 1990s Echelon initiated the LONMark Association which has sought to bring together manufacturers' to decide on profiles for varous types of equipment, satrting initially with sensors and actuators. This organisation has eventually achieved a measure of independnece from Echelon as LONworks acceptance as an open standard has required less relaince on the originating commercial company, especially in Europe.
LONworks is currently the most popular open standard globally for HVAC related devices such as VAV and fan-coil controllers but increasingly Bacnet MSTP is being used in newer product launches.
Q. What are LON bindings?
A. LONworks is a peer-to-peer message based protocol; there is no master node managing the message timings, so advanced collision detection algoritms are used to avoid message conflicts. In order to enable one device to respond to a message sent by another there is aneed to ensure it is "listening" for that message inparticular amongst all the others flowing on the network. This is achieved by making entires in a binding table held in each LON node. This table (list) identifies all the other devices and points within them that that each device is connected to. This bindling table is configured using a network management tool (see answers below for more on this).
Q. What is the difference between LNS and Niagara regarding the way in which LON networks are managed?
A. Apart from Niagara all the network management tools available for managing LON networks are based on an Echelon developed approach called LNS which uses a central database in a Windows application to hold all the binding data relating to a LON network. The LNS database must be accessed in order to make any network configuration changes, so a copy must be maintained on site or brought back to site when changes are required.When LON was originally conceived the backbone network for asystem was assumed to be LON, but for the last 10 years the backbone network has been an Ethernet IP network, so Echelon iLON FTT to IP routers (or equivalents from other manufacturers) have been used to bridge the floor or plantroom level LON-FTT sub-networks to the IP network. Although the physical architecture uses IP the LON network architecture is the same, so a singel LNS database is used per site.
The Niagara approach is radically different. Instead of having a single (often very large) database, each JACE holds the database for the LON-FTT network connected to it. Any bindings required between LON networks are managed using Niagara Fox communications instaead of LON over IP so there is no central database. The big adavantage of this is robustness. If an LNS database becomes corrupted or lost for whatever reason the whole site will need to be re-bound which is very time-consuming, whereas the most that is lost in a Niagara based system is a single LON-FTT sub-network. Also the Niagara approach scales much better as for an LNS based system the performance is limited by the power of the PC running the LNS tool, whereas there is no change in performance with Niagara even when there are hundreds of JACE and tens of thousands of LON devices.
The other big commercial adavntage of Tridium's approach is that we do not make a charge for the use of our LON binding technology, whereas Echelon charge per node bound for their technology.
Q. Is a JACE required to reamin on the LON network it manages in order to maintain the network bindings?
A. No, NiagaraAX can be used in a similar way to LNS tools in that once the network has been configured with the peer-to-peer network bindings, the Niagara JACE can be removed and the bindings will still work. In practice our partners nearly always permananetly install JACEs to manage LON networks because they perform many other necessary tasks such as data logging, alarm management, scheduling and providing the bridge up to the IP network, but if you really want to Niagara can be used as "free to use" LON network configuration tool.
