BACnet over the Internet

In general, BACnet is a broadcast network protocol. For this reason it is not well suited to use over a wide area network, or the Internet. To facilitate the transport of BACnet information over a WAN the BBMD (BACnet Broadcast Management Device) was introduced.

I like to compare the operation of BBMDs with the operation of a CB radio. On the local network all controllers can "hear" each other talking as would everyone in the cab of a truck when one person talks into their CB. The communications are then sent to other BBMDs over the wide area network that are aware of each other (each BBMD must be aware of every other BBMD, like being on the same CB channel). On the receiving end, all controllers "hear" the remote device's broadcast on their local network as would everyone sitting in the cab of a truck receiving a CB transmission.

That said, the use of BBMDs makes BACnet over a wide area network possible. At each site a BBMD is needed. Each BBMD must be programmed to know about every other BBMD that will be part of the system. The front end must have either a local BBMD or act as a foreign device to at least one of the remote BBMDs.

Lonworks Over Fiber

Recently I had a situation where I had to run lonworks over fiber (the lonworks wiring was too close to power wiring). At one time in the past, I had tried fiber by lon routers and although it worked, my experience was not very good.

For this job I am going to try:

(2) Black Box Corp. LBH100A-H-ST
(2) Echelon i.LON600 (24 VAC)
(2) Cabinets as appropriate for conditions on either side of the fiber run.
(2) 50 VA Transformer for i.LON600

Copper from the near iLON600 or a switch where i.LON600s are connected will go to the first media converter. Then fiber will traverse the distance in question. On the far side, the fiber will enter the 2nd media converter and exit as a 2nd copper segment. This second copper segment will enter the iLON600.

Building Automation Graphics

For those of us engineering types, that don't have an eye for color and art, developing graphics for a control system can be one of the most frustrating parts of the process.

Make no mistake, even though the graphics don't have a significant impact on how the system functions, they are what the end user sees every day. Often a control system is judged by the graphics alone. Even if the air handler is grossly innefficient, it will still impress an end user if it looks good.

Here are some resources that I have come across in my search for tools to make graphics easier:

Free BAS Graphics from Computrol.
http://www.computrols.com/3d

The best part of this offering from computrol is the file containing Visio stencils. You can put together a good looking graphic and export it from Visio into a file format that your package can use.


If you're just not up to the task, you can also have someone else build them for you:

BAS Graphics
http://www.basgraphics.com/

Control PIX
http://www.controlpix.com/