Building automation systems (BAS) are paving the way in smart buildings and how businesses operate internally. Controlling your critical systems like heating, cooling, and lighting can expose the many benefits that building automation systems bring to the table. The benefits can be anything between energy savings and facility visibility. Whatever your driver to investigate the smart building, we will dive into the infrastructure of a building automation system to help introduce you to the ins and outs of its components.




These are the devices that collect the data from each component that is connected to it. They can range from a desktop machine, a rack-mounted server or a digital server not even located in the building. These servers run the BAS software and connect to the network using network interface cards (NIC).






Supervisory Devices

These devices can either be hardware or software based, they are a system component that originates transmission of a change-of-state condition, like a smoke detector, manual fire alarm box, or supervisory switch. Software supervisory devices, also known as soft-supervisors, use communication cards to communicate with field buses. Their counterpart the physical supervisory devices have an Ethernet NIC and a port to connect to field buses. They are the most common devices of the two.


Field Buses

Field buses make it possible for building automation field controllers to communicate back to supervisory devices. Two types of field buses, BACnet MS/TP and LON FT-10, connect field controllers back to the supervisory devices via a daisy chain. Once the supervisory device is connected to the field controller they work hand in hand to send messages across the field bus to other field controllers in the network.




These are stand-alone devices that control a defined set of systems. The system settings are defined by using a programming software where specific parameters are set for each system. There are two types of field controllers:

  • Free programmable

    • These controllers are able to be programmed freely, you can configure the controller with any set of parameters from anywhere.

  • Application specific

    • These controllers are specific to an application, which means you can only adjust the pre-programmed settings. There is not a lot of room for customization here.


Inputs and Outputs


These values are small but are vital the BAS functioning properly. The input value is a signal from a sensor, for example, a temperature sensor gets to 59 degrees, your input is the 59 degrees. The output is what you want the controller to do based on that input value. A sort of IF THIS THEN THAT structure.





The infrastructure of any BAS is what makes it capable of running small buildings to the largest of skyscrapers. Understanding how they work hand in hand helps the individual better program the system to optimize the efficiency of the building.