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BACnet vs Modbus vs LonWorks

bigstock-Engineer-Or-Architect-Looking--281576422Until recently, there was no standard industry network protocol for building automation, and users had to choose between many different systems from different manufacturers. Proprietary communications were a result of no off-the shelf communication solution.

Today, we have reached a place where there are three inter-operable standard network protocols to choose from: BACnet, LonWorks and Modbus. All three are widely used, and according to a Building Operating Management survey in 2011, 62% of respondents had at least one BACnet application; for LonWorks the percentage was 40%, while for Modbus the number was 30%.

Building Automation Controls Network (BACnet): BACnet is a network protocol specifically used for multiple devices to communicate across building automation systems by system users and building system manufacturers

Modbus: Modbus is a network protocol best used for industrial automation systems specifically for connecting electronic equipment. Although Modbus is best for industrial applications, its simplicity allows it to be a useful tool for building automation as well.

LonWorks: LonWorks is a communication network protocol useful for building automation applications designed on a low bandwidth, for networking devices through power lines, fiber optics, and other media.




BACnet



Modbus



LonWorks



Developed By:



ASHRAE



Modicon Inc.



Echelon Corporation/ Motorola



Use



Communication across devices



Connection between devices



Networking devices through power lines, fiber optics, and other media



Markets



Industrial, Transportation, Energy Management, Building Automation, Regulatory and health and safety



HVAC, Lighting, Life Safety, Access Controls, transportation and maintenance



Home automation, industrial, transportation, and public utility control networks.



Examples



Boiler Control, Tank Level Measurements



Tasks such as request temperature reading, send status alarm, or fan schedule



Security, lighting systems, HVAC, machine control, manufacturing, metering



Proprietary



No



No



Yes



Transmission Modes



Ethernet, IP, MS/TP, Zigbee



ASCII, RTU, TCP/IP



MS/TP, network, SNVT



Standards



ANSI/ASHRAE Standard 185 ;ISO-16484-5; ISO-16484-6



IEC 61158



ANSI/EIA 709.1; ISO/IEC 14908-1, 14908-2, 14908-3, 14908-4



Costs



Low; No charge for usage or licensing fees



Low; No charge for usage or licensing fees



High (proprietary); Limited users (exclusive to actual members; mostly manufacturers)



Network Interfaces



Existing LANs and LANs infrastructure



Traditional serial and Ethernet protocols



U10/U20 USB Network Interface; i.LON SmartServer; i.LON 600



Testing



BACnet Testing Labs



Modbus TCP Conformance Testing Program



Products must conform to LonWorks protocol



Advantages



  • Scalability between cost, performance and system size

  • Endorsement and adoption by nearly every major vendor in North America and many other countries

  • Robust internetworking including multiple LAN types and dial-up

  • Unrestricted growth and the ability to add new innovations and new features anytime



  • Easy connection to Modicon

  • Suitable for small/medium volumes of data (≤255 bytes)

  • Data transfer designed for industrial applications

  • Openly published and royalty-free

  • Easy to deploy and maintain

  • Moves raw bits or words without placing restrictions on vendors



  • Web based tool; saves time and cost

  • Numerous developers of Lonworks products in the market

  • Less Architecture at device level



Disadvantages



  • Limited the number of field devices that can connect to a master station except Ethernet TCP/IP

  • MT/TP-Wire Length

  • Ethernet-Infrastructure

  • New standard has security standard but not implemented in all devices




  • Limited the number of data types; Large binary objects are not supported.

  • No standard method for a node to find the description of a data object, i.e. finding a register value represents a temperature between 30â—¦ and 175â—¦.

  • No security against unauthorized commands or interception of data

  • Transmissions must be contiguous which limits the types of remote communications devices to those that can buffer data to avoid gaps in the transmission.

  • Great amount of configuration and programming required

  • Protocol is not common in the SIMATIC family




  • Outdated

  • Controlled devices & variables are connected to a separate control device. (Not recommended due to network interruptions producing system failures)

  • Extensions are allowed only through the LonMark Consortium.

  • Hardware specific, and requires the Neuron chip for network movement of the protocol.

  • Close to "plug & play" ability, yet still far from achieving interconnectivity using Microsoft Windows.


Check out these 5 Tips for BACnet Best Practices to Learn More.

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BACnet vs Modbus vs LonWorks