4 minute read
THE EASY ROUTE INTO THE INTERNET OF THINGS
IoT applications offer attractive options for increasing efficiency and comfort in building and room automation. An ideal communication protocol for this is MQTT (Message Queuing Telemetry Transport) –as long as its strengths are utilised and weaknesses are compensated. SAUTER's intelligent IoT-capable solutions show exactly how this is done.
Open communication protocols are the backbone of modern building and room automation. As new technological possibilities come to the fore, the requirements for the protocols and their diversity also evolve. MQTT, one of the newer-generation protocols, is now viewed as the most important open protocol for IoT applications. The strengths of MQTT are played out especially in efficient communication, data-intensive applications, remote monitoring and control as well as cloud integration. It is also a powerful addition to established building automation protocols such as BACnet, KNX, DALI and Modbus.
Lightweight but packing a punch
MQTT was specifically developed for use in networks with limited bandwidth and high latency – a key constraint in many IoT networks and when integrating cloud systems. It is because of its simple structure that MQTT is so lightweight. It calls on far fewer resources than other protocols to manage and transmit messages. This low overhead also enables numerous devices and systems to be run efficiently. It is particularly beneficial for equipment with limited resources, such as sensors and microcontrollers. This results in broad scalability, making MQTT ideally suited to decentralised structures. Other advantages include excellent reliability due to different service quality levels for different data types, encrypted data transfer via TLS and options for integration in existing systems.
Communication by subscription
This lightweight, efficient and dependable principle stems from the publish-subscribe architecture. There is no direct communication between clients (subscribers). A broker is used as an intermediary instead. MQTT clients can act as both publishers (data providers) and subscribers (data recipients). When the value of a client changes, it sends the new data to the broker. At the same time, it can subscribe to the broker for data from other clients on specific topics. It is also sent the information if a relevant value changes. The eventdriven principle streamlines network resource use.
Topics can be freely designed by the application designer or automatically generated by the publishing client. The subscribing MQTT clients must thus adapt flexibly to the specific topics or applications.
BACnet and MQTT – a powerful team for building and room automation
The flexibility of MQTT is a mixed blessing. The topics and data information (payloads) are not standardised on the application level. This leads to challenges regarding interoperability and data interpretation.
SAUTER therefore employs a combination of the tried-and-tested and the new. SAUTER uses BACnet as a uniform data source. It automatically generates MQTT topics with clearly defined MQTT payloads in the JSON data format (JavaScript Object Notation). SAUTER thus combines the advantages of both protocols. Standardised BACnet objects are converted into structured MQTT topics. This ensures a consistent data structure allowing seamless integration of IoT and cloud-based solutions.
Example applications
Centralised management of buildings
An example of this could be multiple premises managed centrally by SAUTER's cloud-based building management system, Vision Services. Here, SAUTER modulo 6 automation stations provide the necessary MQTT interfaces in the buildings. Each station offers both client functionality for supplying the measurement data and broker functionality (B) for transferring the data. The stations using BACnet communication as standard automatically restructure BACnet objects into the JSON data format (payload) and transmit them with MQTT.
Room operation via smartphone
The SAUTER ecos-IoT room automation stations also speak MQTT. ecos-IoT is a programmable BACnet server with integrated BACnet/MQTT gateway. It enables, for instance, building users to perform room operations – such as adjusting setpoints or switching and dimming lights – with a smartphone app. An ecos-IoT room controller in the building acts as the MQTT client, exchanging information via MQTT with the broker in the cloud (B). The room user's smartphone receives the automatically generated MQTT data from the broker (B).
ecos-IoT as client and broker
If using the cloud is not the preferred form of communication, brokers can be optionally integrated on room controllers. ecos-IoT room controllers are now both the client and broker – on an office floor, for example, where tablets are used as room operating units. The broker function allows the stations to transmit the measurement data directly to the tablets via MQTT. They can also send the user commands in the other direction, i.e. from the tablets to the room controllers.
