4 types of sensors used in intelligent LED lighting
There is a big difference between LED lighting fixtures and traditional lighting fixtures. LED lighting fixtures are a complete electronic product, while traditional lighting fixtures are only an electrical product. Therefore, LED lamps can be easily associated with various types of sensors, so as to realize light control, infrared...
There is a big difference between LED lighting fixtures and traditional lighting fixtures. LED lighting fixtures are a complete electronic product, while traditional lighting fixtures are only an electrical product. Therefore, LED lamps can be easily associated with various types of sensors, so as to realize various automatic control functions such as light control and infrared control. For example, the automatic switching of LED street lamps can be easily realized with a photosensitive sensor; for the lighting of walkways and courtyards in the community at night, infrared sensors can be used to collect human activity information and automatically turn on and off lighting fixtures.
LED lighting switch automatic control
As a device for signal acquisition and electromechanical conversion, the sensor's electromechanical technology is quite mature. In recent years, the rise of MEMS (micro-electromechanical system) technology has made great strides in sensor technology 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 lighting fixtures. , MCU (microcontroller), DA (digital-to-analog) converter to intelligently process the collected signals, so as to control the opening and closing of LED lighting fixtures. Humans can use this to set various control requirements on the MCU to control the switching time, brightness, color rendering, and colorful changes of LED lights, so as to achieve the goal of power saving and energy saving. System block diagram of sensors and LED lamps. The current integrated circuit manufacturing technology can integrate AD, DA and MCU in a package of 5mm×5mm or smaller, which does not occupy an area and is very convenient to install in the lamp.
Photosensitive sensor and LED lighting combination
Wind-photovoltaic LED street light is a highly intelligent and unattended road lighting fixture. It uses wind and sunlight to generate electricity and uses storage batteries to store energy. Therefore, the automatic management of energy is very important. The photosensitive sensor is an ideal electronic sensor that can control the automatic switch of the circuit due to the change of illumination when it is bright and dark (sunrise, sunset).
Photosensitive sensors can automatically control the opening and closing of LED lighting fixtures in shopping malls according to the weather, time period and region. Convenience stores with a store area of 200m2 can reduce power consumption by 53% compared to when fluorescent lamps are used by reducing their output power during bright daytime. The lifespan is also about 50,000 to 100,000 hours. Under normal circumstances, the life of LED lighting fixtures is about 40,000 hours; the color of the light can also be changed by RGB (red, green and blue), so that the shopping mall lights are more colorful and the atmosphere is more active; Compared with the original blue LED, the color rendering of the purple LED with red, green and blue phosphors is higher.
Combination of infrared sensors and LED lamps
Infrared sensors work by detecting infrared rays emitted by the human body. The main principle is: the infrared rays of about 10 μm emitted by the human body are enhanced by the Fresnel filter lens and then concentrated on the pyroelectric element PIR (passive infrared) detector. When people move, the emission position of infrared radiation will change. The element will lose the charge balance, and the pyroelectric effect will occur to release the charge outward. The infrared sensor converts the change of the infrared radiation energy through the Fresnel filter lens into an electrical signal, that is, thermoelectric conversion. When there is no human movement in the detection area of the passive infrared detector, the infrared sensor only senses the background temperature. When the human body enters the detection area, through the Fresnel lens, the pyroelectric infrared sensor senses the temperature of the human body and the The difference of the background temperature, the signal is collected and compared with the existing detection data in the system to determine whether there is really someone waiting for the infrared source to enter the detection area.
A passive infrared sensor has three key components: a Fresnel filter lens, a pyroelectric infrared sensor and a matched low-noise amplifier. The Fresnel lens has two functions: one is focusing, that is, the pyroelectric infrared signal is refracted on the PIR; the other is to divide the detection area into several bright areas and dark areas, so that moving objects/people entering the detection area can A changing pyroinfrared signal is produced on the PIR in the form of a temperature change. Generally, a low-noise amplifier is also matched. When the ambient temperature on the detector rises, especially when it is close to the normal body temperature of the human body (37°C), the sensitivity of the sensor decreases, and the gain is compensated through it to increase its sensitivity. The output signal can be used to drive the electronic switch to realize the switch control of the LED lighting circuit.
In recent years, ultrasonic sensors, which are similar to infrared sensors, have been used in automatic detection of moving objects. The ultrasonic sensor mainly uses the Doppler principle to emit high-frequency ultrasonic waves that exceed the human body's perception through the crystal oscillator. Generally, the 25~40kHz wave is typically selected, and then the control module detects the frequency of the reflected wave. If there is object movement in the area, the reflection The wave frequency will fluctuate slightly, that is, the Doppler effect, so as to judge the movement of the object in the lighting area, so as to achieve 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 refraction and reflection phenomena. Smaller and spread farther. Ultrasonic sensors take advantage of these properties of ultrasonic waves. Ultrasonic sensors have the characteristics of a large sensitive range, no blind spots of vision, and no interference from obstacles. This technology has been used in the commercial and security fields for more than 25 years and has been proven to be an effective method for detecting the movement of small objects. Therefore, the system formed with LED lamps can control the switch sensitively.
Due to the high sensitivity of the ultrasonic sensor, air vibration, the movement of the ventilation, heating and cooling system and the surrounding adjacent spaces will cause the ultrasonic sensor to falsely trigger, so the ultrasonic sensor needs to be calibrated in time.
Temperature sensor for over-temperature protection of LED lamps
The temperature sensor NTC (negative temperature coefficient) has been widely used as the over-temperature protection of LED lamps. If LED lamps use high-power LED light sources, multi-wing aluminum radiators must be used. Because the space of LED lamps for indoor lighting is small, the problem of heat dissipation is still one of the biggest technical bottlenecks. If the heat dissipation of LED lamps is not good, it will cause the early light failure of the LED light source due to overheating. After the LED lamp is turned on, the heat will be enriched to the lamp head due to the automatic rise of hot air, which will affect the life of the power supply. Therefore, when designing LED lamps, an NTC can be attached to the aluminum radiator near the LED light source to collect the temperature of the lamp in real time. When the temperature of the lamp cup aluminum radiator rises, this circuit can be used to automatically reduce the output current of the constant current source. Cool down the lamp; when the temperature of the aluminum radiator of the lamp cup rises to the limit set value, the LED power supply is automatically turned off to realize the over-temperature protection of the lamp, and when the temperature drops, the lamp is automatically turned on again.
Conclusion:
Because LED lighting is a complete electronic product, with the diversification of LED lighting structure and the expansion of applications, with more creativity and innovation in LED lighting design, more sensors will be combined in LED lighting and LED lighting. Go to the system of lighting engineering. A new era of intelligent LED lighting is coming, and human lighting life will become more and more bright and comfortable.
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