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With the maturity and development of LEDs, in addition to replacing traditional lighting systems, LEDs can also be used in different applications with different technologies. In today's market, it is not difficult to find some wireless lighting control systems such as Wi-Fi systems for wireless switching, dimming and color mixing. The Hong Kong Applied Science and Technology Research Institute (HKTRIA) has developed two technologies based on this, namely the wireless motion sensing module for LED lighting systems and the hybrid real-time positioning system for LEDs.
Wireless motion sensing module
The current mobile sensor products on the market are based on passive infrared (PIR) and microwave Doppler principles. The passive infrared sensor itself does not emit an infrared beam, but is triggered by the movement of the heat source that senses the object. Passive infrared is usually used in indoor enclosed environments because external factors such as outdoor temperature and climate change may cause passive infrared false alarms.
The Doppler principle is to detect the frequency of the reflected wave by transmitting a high frequency microwave and then transmitting it through the receiving module. If there is an object moving in the area, the frequency of the reflected wave will change slightly, and the change will be used to judge whether the object is moving. The Doppler principle is not affected by sunlight and temperature changes, so it is suitable for outdoor and indoor use.
In 2011, the Hong Kong Academy of Sciences (Materials and Construction Technology Group) developed a wireless motion sensor that uses the Doppler principle on a structure that specifically transmits and receives ZigBee modules.
1. Light control mode: After the sensor analyzes the signal, it controls the switch, dimming, etc. through the wireless mesh network.
2. Mobile sensing mode: The sensor emits microwaves from the most suitable working channel and processes the received reflected waves. As the body moves toward the motion sensor, the amplitude of the signal increases as the body approaches the sensor.
3. Detection and avoidance of interference mode: The sensor selects the most suitable working channel by scanning the signal strength of different working channels in the frequency band, which greatly reduces the possibility of interference.
The entire light control system is fully software controlled and requires no additional hardware costs. The intelligent calibration function helps to increase the sensitivity of the sensor and reduce false alarms. Ultra low power consumption features extend battery life.