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Introduction to BACnet
Presented by Jianqing Zhang
2
Overview
• BACnet: Building Automation and Control Networks
• Supported by SPC of ASHRAE since 1987– Standard Project Committee (SPC) 135P – American Society of Heating, Refrigerating an
d Air-Conditioning Engineers
• Position:– American national standard– European pre-standard– ISO global standard
3
Benefits of BACnet
• Single point of control• Competitive system expansion• Eliminate fear of being “locked in”• Possibility of integrating all BAC functions• Low cost• Interoperability
– Data sharing– Alarm and event management– Trending– Scheduling– Remote device and network management
4
BACnet Application
• Scope– Scalable from small to large installations– Mainly for large installation– Different buildings using equipments from different
manufactures• Equipments
– HVAC control (Heating, Ventilation and Air-Conditioning, i.e. Climate Control)
– Fire detection and alarm– Lighting control– Security– “Smart” elevators– Utility company interface
5
BACnet Protocol
• Set of Hardware + Software of Rules• Apply to
– Electrical Signaling– Addressing– Network Access (Master/Slave, Peer-to-Peer)– Error Checking– Flow Control– Message Sequencing, Segmentation, Check pointing– Presentation Format (Compression, Encryption)– Message Format
6
Objects
• Definition – Collection of information related to a particular
function that can be uniquely identified and accessed over a network in a standardized way.
• Objects represent– Physical inputs– Physical outputs– Software processes
7
Objects example
• Each object is characterized by a set of “properties” that describe its behavior or govern its operation
Object_Name SPACE TEMP
Object_Type ANALOG INPUT
Present_Value 72.3
Status_Flags Out-of-Service
High_Limit 78.0
Low_Limit 68.0
8
Objects Summary
• 23 standard object types– Binary Input/Output/Value– Analog Input/Output/Value– Multi-state Input/Output/Value– Loop– File/Program/– Device…
9
BACnet Device
• A collection of objects that represents the functions actually present in a given real device– Device– Loop– Schedule– Group– BI/BO– AI/AO/AV
10
Communication
• Client-Server model
• Application Services– Alarm and Event Services– File Access Services– Object Access Services
• Read/Write the properties of an object• Manage objects
– Remote Device Management Services– Virtual Terminal Services
11
LAN Options
Network Tech. Introduction Speed
Ethernet 10-100M bps
ARCNET Attached Resource Computer NETwork 2.5 Mbps
LonTalk Part of LonWorks 2.5 Mbps
Master-Slave
/Token-Passing1 Mbps or less
Point-to-Point 115.2 kbps
BACnet/IP • Transporting BACnet messages between IP devices
• A framework embracing other new networking technologies
12
Native BACnet
BACnet Workstation
BACnet LAN: Ethernet, ARCNET, LonTalk, MS/TP, LonTalk or BACnet/IP
BACnet Field Panels
Sensors and Actuators
Native BACnet devices provide BACnet communications directly, device to device
13
Interconnect Multiple LANs
BACnet Workstation
BACnet LAN: Ethernet
BACnet Field Panels
Sensors andActuators
BACnet LAN: ARCNET
Sensors and Actuators
BACnet LAN: MS/PT
Sensors and Actuators
Ethernet to ARCNETRouter
Ethernet to MS/PTRouter
BACnet Field Panels
BACnet Field Panels
“Re-package” BACnet messages and re-transmit them unchanged
14
Gateways
BACnet Workstation
BACnet LAN: Ethernet, ARCNET, LonTalk, MS/TP, LonTalk
BACnet Field Panels
Sensors and Actuators
Sensors and Actuators
BACnet to Vendor B Gateway
Non-BACnet Field Panels
Vendor B Proprietary LAN
15
Working over IP internet
• IP Message Tunneling– BACnet devices don't know, or need to know,
anything at all about IP
• BACnet/IP– BACnet device is actually a full-fledged IP nod
e, complete with its own IP address and IP protocol stack
16
IP Message Tunneling
Annex HRouter
BACnetDevice
BACnetDevice
BACnetDevice
A
Annex HRouter
BACnetDevice
BACnetDevice
BACnetDevice
B
Internet
Net 1
Net 2
1
2
3
4
5
17
BACnet/IP
• BACnet + Intrinsic IP– BACnet devices access the IP infrastructure as if it we
re just a different kind of LAN or “virtual data link”– A devices IP address serves the same purpose as a d
evice’s MAC or physical LAN
• BACnet Virtual Link Layer (BVLL)– Deals with specific idiosyncrasies of IP networks, suc
h as broadcast– Encompass virtually any kind of new network technolo
gy or other “micro protocol”• ATM, SONE, ISDN, etc.• Data encryption, data compression• Enhanced security and efficiency measures
18
BACnet/IP-Unicast
BBMDBACnetDevice
BACnetDevice
BACnetDevice
BBMDBACnetDevice
BACnetDevice
BACnetDevice
Internet
Net 1
Net 2
BACnet Broadcast Mngt. Device
A
B
19
BACnet/IP-Broadcast
BBMDBACnetDevice
BACnetDevice
BACnetDevice
BBMDBACnetDevice
BACnetDevice
BACnetDevice
Internet
Net 1
Net 2
BACnet Broadcast Mngt. Device
1
2
3
4
A
20
BACnet/IP-Foreign Device
BBMDBACnetDevice
BACnetDevice
BACnetDevice
BBMDBACnetDevice
BACnetDevice
BACnetDevice
Internet
Net 1
Net 2
BACnet Broadcast Mngt. Device
Foreign Devices
Foreign devices can register with certain BBMDs to receive forward broadcast message
21
Application Example:
BACnet-Compliant Lighting
• A Lighting Applications Group, Jan. 2001
• Different vendors provides different products– Gateway, Controller, Software
• Example: Synergy Lighting Control System
22
Competitor: LonTalk
• Open protocol offered by Echelon– Part of LonWorks
• A LAN specification
• Different control communication
• Different aligned manufactures
• Rapid increase in BACnet installations– a promising indicator of market penetration?
23
Summary
• BACnet– BAC Model and Message + Network Layer + LANs– Objects: Representing information– Services: Making requests and interoperating– LANs: Transport system
• Features– No fixed architecture– Object model is easily extended– Doesn’t depend on current technology– Broad participation in its development– Many vendors are committed to it– Global interest
24
Supporting Vendor
• Totally nearly 70 by 2/4/06– Controller: BACnet-capa
ble sensors and actuators
– Gateway– Router– Workstation
• Web server
– Tools: Protocol analyzer