As a device for signal acquisition and electromechanical conversion, the electromechanical technology of the sensor is quite mature. In recent years, the sensor technology has made great strides towards 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, thereby controlling the LED lighting to turn on and off. and can take advantage of this in M

As a device for signal acquisition and electromechanical conversion, the electromechanical technology of the sensor is quite mature. In recent years, the sensor technology has made great strides towards 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, thereby controlling the LED lighting to turn on and off. In this way, various control requirements can be set on the MCU to control the switching time, brightness, color rendering, and colorful changes of LED lights, so as to achieve the goal of intelligent lighting control.

List of sensors that may be used in LED lighting control systems

light sensor

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 according to the weather, time period and region. In bright daytime, the power consumption is reduced by reducing its output power. Compared with the use of fluorescent lamps, a convenience store with an area of ​​200 square meters can reduce the power consumption by up to 53%, and the lifespan is also about 50,000 to 100,000 hours. Under normal circumstances, the life of LED lighting is about 40,000 hours; the color of the light can also be changed by RGB (red, green and blue), which makes the light more colorful and the atmosphere more active.

Infrared sensor

Infrared sensors work by detecting infrared rays emitted by the human body. The main principle is: the infrared radiation of about 10μm emitted by the human body is enhanced by the Fresnel filter lens and then concentrated on the pyroelectric element PIR (passive infrared) detector. When the person moves, the emission position of the 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 in the background temperature, the signal is collected and compared with the existing detection data in the system to determine whether someone is really waiting for the infrared source to enter the detection area.

A passive infrared sensor has three key elements: 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.

Ultrasonic sensor

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 25-40 kHz wave is typically selected, and then the control module detects the frequency of the reflected wave. If there is movement in the area, the reflected wave will be reflected. 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 wave can propagate in gas, liquid and solid, and its propagation speed is different; it also has the phenomenon of refraction and reflection, the propagation frequency in air is lower and the attenuation is faster, while in solid and liquid Smaller and spread farther. Ultrasonic sensors take advantage of these properties of ultrasonic waves. Ultrasonic sensors have the characteristics of large sensitive range, no visual blind spot, and no interference from obstacles. It has been proved to be the most 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

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 very 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 decay 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 the lamp; when the temperature of the aluminum radiator of the lamp cup rises to the limit set value, the LED power supply will be automatically turned off to realize the over-temperature protection of the lamp. When the temperature drops, the lamp will be automatically turned on again.

voice sensor

It is a voice-activated sensor (microphone array) composed of a voice control sensor, an audio amplifier, a channel selection circuit, a delay opening circuit and a thyristor control circuit. Use the sound comparison result to judge whether to start the control circuit, use the regulator to set the original value of the voice-activated sensor, and the voice-activated sensor constantly compares the external sound intensity with the original value, and when it exceeds the original value, it conveys to the control center “Yes. “Sound” signal, voice-activated sensors are widely used in corridors and public lighting places.

Microwave Inductive Sensor

Microwave induction sensor is a moving object detector designed using the principle of Doppler effect. It detects whether the position of the object moves in a non-contact way, and then generates the corresponding switch operation. When someone walks into the induction area and the lighting demand is met, the induction switch is automatically turned on, the load electrical appliance starts to work, and the delay system is activated. As long as the human body does not leave the induction area, the load electrical appliance will continue to work. When the human body leaves the induction area, the sensor starts to calculate the delay, and when the delay ends, the sensor switch is automatically turned off, and the load electrical appliance stops working. Really safe, convenient, intelligent and energy-saving.

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