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6 Common Sensors That Intelligent Lighting Practitioners Must Know

Introduction

In the era of the Internet of Things, small bulbs are also undergoing major changes. Through the blessing of various sensors, intelligence has made life more convenient and colourful. And the innovation of various sensors is constantly stimulating new consumer demands and new experiences.

As a device for signal acquisition and electromechanical conversion, the electromechanical technology of the sensor is quite mature. In recent years, sensor technology has made great strides toward miniaturization, intelligence, multi-function, and low cost.

Various types of sensors, such as photosensitive sensors and infrared sensors, can form an intelligent control system with LED lamps. The sensor converts the collected various physical quantity signals into electrical signals. The collected signals can be intelligently processed via an integrated AD (analogue-to-digital) converter, an MCU (microcontroller), and a DA (digital-to-analogue) converter to control the intelligent lighting to be turned on and off. And you can set various control requirements on the MCU. Control the switching time, brightness, colour, and colour of the intelligent lighting to achieve the goal of intelligent control.

#1. Photosensitive sensor

The photosensitive sensor is an ideal electronic sensor. It can automatically switch the control circuit due to the change of time in daylight and sky (sunrise, sunset).

The light sensor automatically controls the intelligent lighting switch according to the weather, time period, and area. In the daytime when the brightness is sufficient, the power consumption reduced by reducing the output power. Compared with the case of using the fluorescent lamp, the convenience store with an area of 200 square meters can reduce the power consumption by up to 53%, and the life span is as long as about 50,000 to 100,000 hours. Under normal circumstances, the life of LED lamps is about 40,000 hours; the color of the light can also be RGB colorful and varied. So that the lights are more colorful and the atmosphere is more active.

Photosensitive sensor

#2. Infrared sensor

Infrared sensors work by detecting infrared rays emitted by the human body. The main principle is that the infrared light emitted by the human body is about 10 μm and is reinforced by a Fresnel filter lens and then collected on a pyroelectric element PIR (Passive Infrared) detector. When a person moves, the emission position of the infrared radiation changes, the component loses its charge balance, and the pyroelectric effect releases the charge outward. The infrared sensor converts the change in the infrared radiation energy of the Fresnel filter lens into an electrical signal, that is, thermoelectric conversion.

When there is no human body moving in the detection area of the passive infrared detector, the infrared sensor senses only the background temperature. When the human body enters the detection zone, the pyroelectric infrared sensor senses the difference between the human body temperature and the background temperature through the Fresnel lens. After the signal is collected, compared with the existing detection data in the system to determine whether an artificial infrared source or the like enters the detection area.

Passive infrared sensors have three key components: Fresnel filter lenses, pyroelectric infrared sensors, and matched low noise amplifiers. The Fresnel lens has two functions: one is the focusing effect, which is to refract the pyroelectric infrared signal on the PIR; the other is to divide the detection area into several zones and dark areas so that the moving object/person entering the detection zone can The form of temperature change produces a varying pyroelectric infrared signal on the PIR. And it is also generally matched with a low-noise amplifier.

When the ambient temperature on the detector rises, especially near-normal human body temperature (37 °C), the sensitivity of the sensor decreases, and the gain is compensated by it to increase its sensitivity. The output signal can be used to drive an electronic switch to achieve switching control of the LED circuit.

Infrared sensor

#3. Ultrasonic sensor

Ultrasonic sensors similar to infrared sensor applications have gained more applications in the automatic detection of moving objects in recent years. The ultrasonic sensor mainly uses the Doppler principle to emit a high-frequency ultrasonic wave that is more than the human body can perceive through the crystal oscillator. Generally, a 25 to 40 kHz wave is selected, and then the control module detects the frequency of the reflected back wave.

If there is an object moving in the area, the reflected wave frequency will have a slight fluctuation, that is, the Doppler effect, in order to judge the movement of the object in the area, thereby achieving the purpose of controlling the switch.

The longitudinal oscillation characteristics of ultrasonic waves can propagate in gases, liquids, and solids, and their propagation speeds are different. It also has the phenomenon of refraction and reflection, which has a low frequency of propagation in air and a relatively fast decay. While in solids and liquids, the attenuation is small and the propagation is far.

Ultrasonic sensors take advantage of these characteristics of ultrasound. Ultrasonic sensors have the characteristics of a large sensitive range, no visual blind zone, and no interference from obstacles.

It has been proved to be the most effective method for detecting small object motion. Therefore, the system with the LED luminaire can be sensitive to the control switch. Due to the high sensitivity of the ultrasonic sensor, the vibration of the air vibration, the ventilation, and the heating system. And the surrounding space will cause the ultrasonic sensor to trigger falsely, so the ultrasonic sensor needs to be calibrated in time.

Ultrasonic sensor

#4. Temperature Sensor

The temperature sensor NTC (negative temperature coefficient) widely used for over-temperature protection of LED lamps. If LED lamps use high-power LED light sources, they must use multi-wing aluminum radiators. Since the indoor LED lamps themselves have small space, the heat dissipation problem is still one of the biggest technical bottlenecks.

Temperature Sensor

#5. Voice sensor

A voice sensor consisting of a voice sensor, an audio amplifier, a channel selection circuit, a delay on the circuit and a thyristor control circuit.

The sound comparison result used to judge whether to start the control circuit.  And the original value setting of the voice sensor is given by the regulator. The voice sensor continuously compares the external sound intensity with the original value. When the original value is exceeded, the “voice” signal transmitte to the control center. The voice sensor widely used in corridors and public places.

Voice sensor

#6. Microwave sensor

Microwave induction switches mainly use the Doppler effect principle. Independently research and develop the planar antenna transmitting and receiving circuit to intelligently detect the surrounding electromagnetic environment. Automatic adjustment of working status, built-in integrated filter circuit. It can effectively suppress the interference of high harmonics and other clutter, has high sensitivity, high reliability, safety and convenience, and intelligent energy saving.

It is a new and practical energy-saving product. The microwave inductive switch can penetrate some non-metallic objects and is especially suitable for hidden installation inside the lamp; therefore, it is widely used, plus micro power consumption, sensitive sensing, and wide application range. Can be used with a variety of ordinary lamps to make it a microwave induction lamp.

When someone enters the sensing area and reaches the intelligent lighting, the sensor switch automatically turns on. So the load appliance starts working and starts the delay system. As long as the human body does not leave the induction zone, the load appliance will continue to work.

When the human body leaves the sensing area, the sensor starts to calculate the delay. The delay ends, the sensor switch automatically turns off, and the load device stops working. Really safe, convenient, intelligent, and energy-efficient.

Microwave sensor

Conclusion

According to different lighting application scenarios, using the above sensors to realize intelligent control of LED lamps will be the future development direction of the lighting industry. As a practitioner in the lighting industry, this is also the technical point we must understand. Let us work together to make lighting more energy-efficient and smarter in life.

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