Lighting control sensors and their benefits

When lighting your building could be accounting for 40% of your electricity bills, using lights with more care and attention becomes an important money-saving measure.

Lighting control systems such as CMD’s Audacy are a proven method of cutting energy costs. They use special sensors to detect certain conditions within your building and adjust the lighting accordingly.

Below, we look at how these different sensors work and some of the benefits they can bring to your business.

The principles of lighting control

Generally, lighting control systems use three types of detection:

  • Occupancy—when someone has entered the room
  • Vacancy—when the room is empty
  • Ambient light—measuring the amount of natural daylight coming into the room

The sensors gauge the conditions and change the lighting as necessary, whether that’s dimming, brightening or switching them on or off.

The best systems also allow you to set timers and schedules for the lighting, and override any automatic functions.

How sensors work

Motion sensors for occupancy and vacancy

Detecting when someone has entered or left the room means using motion sensors.

Motion sensors employ what’s called passive infrared (PIR) technology. By measuring the infrared light reflected by the objects in an empty room (e.g. floor, walls and furniture), they can sense the change in temperature that occurs when a human body moves into the space.

That said, they are reacting to movement and not temperature. The sensors won’t be activated by temperature changes in the room caused by sunlight or heating systems, for instance. They will dim the lights if there’s no movement in their field of vision for a certain period of time.

The sensors do require a direct line of sight between themselves and the person entering the room. For this reason, they are useful for enclosed areas such as private offices, hallways, lobbies and conference rooms.

PIR sensors are thought of as ‘passive’ because they work based on signals they receive (i.e. infrared light), not those they gather themselves by transmitting pulses of energy (as with microwave and ultrasonic sensors).

Light sensors for ambient light

Many workspaces rely on a combination of ambient light (daylight coming through the windows) and electric light provided by overhead lighting.

Light sensors installed as part of a lighting control system measure the amount of ambient light present and adjust the electric lights accordingly. This is known as daylight harvesting, and helps with energy efficiency by ensuring no electric light is wasted.

There are two kinds of system for detecting and measuring light: open-loop and closed-loop.

  • An open-loop system measures just the ambient light, and will adjust the electric light as necessary based on the amount of daylight it reads. The electric lights have no bearing on the light sensor’s readings.
  • A closed-loop system measures both the ambient light and the electric light (sometimes called the ‘available light’). The sensor detects the electric light it’s controlling itself, using the feedback to make adjustments.


  • Allow significant savings on energy bills
  • Cheap and simple to install, particularly wireless systems
  • User-friendly
  • Convenient—lights switched on automatically when needed
  • Long battery life due to their low power consumption
  • Help with health and safety requirements (e.g. lighting in corridors)

Related content

A guide to Audacy, CMD’s wireless lighting control system

Benefits of lighting control systems