An example of a smart industrial application is the use of occupancy detecting sensors to improve lighting efficiency and reduce power consumption. Its usage is particularly applicable in commercial, industrial and warehouse settings. In the past, PIR and camera sensors have generally been the technologies of choice. However, PIR have the tendency to cause annoying false positive triggering and camera sensors typically draw too much power. Having a fool-proof, robust, energy-efficient and economical occupancy sensing solution that works when required is particularly appealing in an increasingly cost- and energy-conscious world. In this article, we will explore the different types of occupancy sensors for lighting applications.
Challenges for building light automation and deployment
The common obstacles for lighting efficiency include identifying the most suitable solution, upfront costs, and implementation challenges, as well as human adaptability/behavioral differences and changes.
A suitable solution should take into consideration the following:
Sensors should be located so that they have the least possibility of nuisance switching and activate the lights as soon as a person enters the space. Another aspect of location is orientation. For example, the receiving side of sensors should be positioned toward the area of greatest traffic in a space.
One of the most common problems for properly matching the right sensors to applications is to avoid issues such as false triggering, in which the sensor alters the lighting condition when it shouldn’t.
Different types of occupancy sensors for lighting applications
Passive infrared (PIR), ultrasonic, camera, and electromagnetic field (RADAR) sensing technologies are common types of occupancy sensors for building light management. Depending on the sensor, they can be used for detecting presence, distance to target and events of entry/exit.
Camera sensors is a type of motion sensor that triggers lights on/off when a person enters/exists a space. It uses a sensor which the camera lens directs light to and generates individual pixels records of light it's getting from pattern of light to dark areas to form a complete image. Camera sensors are usually mounted on a region above the doorway and peform continuous monitoring which require constant power supply. The monitored images are then captured sequence and if enough of the pixels have changed between the frames, the camera MCU software detects movement and switches the light on. Conversely, light is switched off when it detects lack of movement over a prolonged period of time.
Passive Infrared (PIR) sensors
Passive infrared (PIR) motion sensors detect changes in thermal energy (IR) between moving people and their background by triggering the light to go on and off when an occupant enters the room.
Ultrasonic sensors work by emitting sound pulses at specific frequency and measuring the distance to the target by measuring the time it takes for the echoes to return. Ultrasonic sensors are best positioned strategically so that the lights turn ON as soon as a person enters the space. They are more sensitive than PIR sensors, ideal for applications with minor body movements such as typing in an office or test taking in a classroom.
DT (Dual-Technology) sensor
DT sensor combines both PIR and ultrasonic sensing devices. It is a sensor fusion type of solution that helps to mitigate and compensate for inadequacies of a single sensing technology. This setup eliminates the possibility of false-on problems but requiring either one of the technologies to sense motion in order to keep the lights on. However, neither solutions, even if combined, will solve the problem of environmental influences, air flow and temperature fluctuations. Passive infrared (PIR) sensors will only detect ‘major motion’, such as a person walking for more than a meter. Ultrasonic sensors, with a slightly higher level of sensitivity, will detect what is defined as ‘minor motion’ but succumb to air fluctuations and vibrations.
Radar sensing, although not a new technology, has been gaining favor in the market. This market gain is influenced by the following factors:
- Radar supplies additional data types that the other sensors do not.
- Advanced CMOS semiconductor processing has shrunk these sensors down to a small and manageable size.
- The reduction in size has the associated value of reducing both component and system implementation costs.
There are different technologies applied in various radar sensors. These type of radar sensors make use of Frequency Modulated Continuous Wave (FMCW) technology to reliably detect moving targets.
Benefits of radar motion sensor for lighting applications:
- Radar sensors can penetrate through non-metallic physical barriers, which is ideal for fully enclosed product designs
- Zero-sensing-delay as movement can be detected even before human enter the coverage space
- Radar sensing can cover and automate lighting in a larger area with longer range compares to other existing sensing technologies
- Applicable for high ambient heat environments
- Configurable for increased detection accuracy
Socionext 24GHz FMCW radar sensor for lighting automation
Socionext’s FMCW radar is a versatile, all-in-one 24GHz CMOS sensor that enables entry motion, presence detection, and distance detection without the need for an external MCU.
The radar sensor features:
- Not affected by direct sunlight or other strong illumination on the sensor face
- Reduction of BOM with an "all-in-one" radar sensor package
- Can be placed behind non-metallic surfaces, walls or plastic housings as in switch faceplates
- Wide industrial temperature range tolerance
- Built-in autonomous entry motion and distance detection functions
- Wide detection range & area from centimeters to greater than 8m/26ft forward beam, 120 degrees FOV (Field of View)
- 2RX antennas capable of 2D angle detection.
- Consumes only 0.6mW average at 0.1% operating duty cycle ideal for human detection applications
- Suitable for battery operation with energy-saving sleep mode
As businesses become more cost- and energy-conscious, radar sensors are an ideal solution in building automation systems implementation. What make them so appealing is that they can reliably detect occupants and intelligently control light sources without the limitations from other types of sensing technologies.