Though it is out of sight, a computer network exists within the walls and ceilings of a modern building. Those computers help manage the systems of the building. These computers are called embedded systems. To utilise embedded systems in buildings, construction professionals should have an understanding of how they work in order to integrate them effectively into a structure.
What Is an Embedded System?
An embedded system is a computer system designed to perform a specific function. Unlike other computers, they can’t run general applications. Instead, they run a single application or programme. These systems consist of a microcontroller and are designed to perform a single function. They can be found in a variety of systems and equipment such as thermostats, HVAC systems, and lighting systems.
Building Systems
The systems and equipment within a building typically consist of sensors, controllers, and actuators. A sensor can be anything from a thermostat, carbon dioxide sensor, occupancy sensor, or a humidity sensor. The controller is the brain of the system and allows the system to compare the reading of the sensor to a target and change the state of the system. Once a controller has determined a change is needed, an actuator alters the state of the system.
This loop occurs many times each second or minute. Simple logic functions like keeping a room at a set temperature are efficiently handled by small controllers. More complex functions are handled by multiple controllers working together.
Where They Appear in a Building
They are common in HVAC systems. Controllers are used to manage boilers, heat pumps, fans, dampers and zone valves to keep spaces comfortable while optimising energy usage. Lighting systems contain controllers to dim fittings, respond to daylight and occupancy sensing. Similar controllers are used in access control, security, fire and lifts.
Embedded controllers are also used in solar shading and are now also included in smaller building systems such as EV charging points and metering equipment. These devices connect to the building management system to share data.
The controllers are connected in a network, either by a wired connection or wireless. Some networks allow interoperability with equipment from other suppliers and are known as open networks. Others are proprietary. The type of network chosen early on affects how easy it is to integrate and expand the systems.
A supervisory layer, the building management system, is a top-down approach used to control and monitor multiple controllers. If the top-down supervisory layer fails, controllers continue to run to ensure the local control system continues to operate the building.
Reliability and Safety are paramount in Building Automation Systems (BAS)
Because buildings are occupied and often critical, embedded controllers must behave sensibly when things go wrong. Good design defines safe states so a failed sensor or lost network connection can’t drive unsafe behaviour. Life safety features, such as fire and smoke detection, and controls are typically provided as part of a separate dedicated, certifiable, safety and fire system of engineering.
Security Considerations
Given the ubiquitous nature of connectivity and inter-connectivity of devices, there is always the risk of a security breach. Default passwords should be replaced, networks segregated, and firmware kept up to date. Building systems should be treated like any other networked devices and equipment and responsibility should be assigned for their maintenance.
Coordination During Construction
This is true for controls contracting as well. Electrical, Mechanical and Controls contractors need to agree who supplies and installs sensors, how cabling is routed, and who commissions each component. Clear descriptions of all I/O prevent misunderstandings. Access for maintenance should be included in design, rather than determined on site.
Commissioning and Handover
There is more to installing devices than just the installation. Each part of a control system needs to be commissioned to ensure that the sensors are reading correctly, the actuators are responding, and the control logic is operating as designed. Thorough testing and clear handover of the system to the building operations staff can be the difference between a trusted and functional building control system and one that is constantly overridden.
Operation and Maintenance
Sensors and settings can drift, and spaces can change use over the life of a building. Regular checks of control systems can ensure they are aligned with the intended use of a space. If control systems are altered, documentation should be updated to show what is currently used and control systems.
Looking Ahead
As the capabilities of embedded systems and processors increase, systems can be designed to be more responsive to their environment and more effectively identify and reduce wastes within the system. The same basic principle will remain. Small, dependable controllers doing specific jobs, will be used to run large and complex building control systems.