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Five common sensors for LED intelligent lighting

  • GLD
  • 2022-04-03 00:07:02
  • 105

In the era of Internet of things, small bulbs are also undergoing great changes. With the blessing of various sensors, intelligent lighting has provided a more convenient and colorful way of life. The innovation of various sensors is also constantly stimulating new consumer demand and experience.

As a device for signal acquisition and electromechanical conversion, the electromechanical technology of sensor has been quite mature. In recent years, the sensor technology has made great strides towards miniaturization, intelligence, multifunction and low cost.

Photosensitive sensors, infrared sensors and other types of sensors can form an intelligent control system with LED lighting fixtures. The sensor converts various physical quantity signals collected into electrical signals, and can intelligently process the collected signals through integrated circuit ad (analog-to-digital) converter, MCU (micro controller) and DA (digital to analog) converter, so as to control the opening and closing of LED lighting fixtures. It can be used to set various control requirements on 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.

1. Photosensitive sensor

The photosensitive sensor is an ideal electronic sensor that can control the automatic switching of the circuit due to the change of illumination at dawn and dusk (sunrise and sunset).

The photosensitive sensor can automatically control the opening and closing of LED lighting fixtures according to weather, time period and region. In bright days, reduce the power consumption by reducing its output power. Compared with the use of fluorescent lamps, the convenience store with an area of 200 square meters can reduce the power consumption by 53% at most, and its service life is about 50000 ~ 100000 hours. Generally, the service life of LED lighting fixtures is about 40000 hours; The color of light can also be changed in RGB, making the lights more colorful and the atmosphere more active.

2. Infrared sensor

The infrared sensor works by detecting the infrared ray emitted by the human body. The main principle is: 10 μ The infrared ray of about M is gathered on the pyroelectric element PIR (passive infrared) detector after being enhanced by the Fresnel filter lens. When people are active, the emission position of the infrared radiation will change, and the element will lose the charge balance. The pyroelectric effect will release the charge outward. The infrared sensor will convert 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 body moving 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 difference between the human body temperature and the background temperature. After the signal is collected, it is compared with the existing detection data in the system to determine whether there is really someone and other infrared sources entering the detection area.

Passive infrared sensor has three key components: Fresnel filter lens, pyroelectric infrared sensor and 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 and dark areas, so that the moving object / person entering the detection area can produce a changing pyroelectric infrared signal on the PIR in the form of temperature change. Generally, it will be matched with a low-noise amplifier. When the ambient temperature on the detector rises, especially when it is close to the normal body temperature (37 ℃), the sensitivity of the sensor will decrease. Through it, the gain will be compensated 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.

3. Ultrasonic sensor

Ultrasonic sensors, which are similar to infrared sensors, have been widely used in automatic detection of moving objects in recent years. 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, 25 ~ 40KHz wave is selected, and then the control module detects the frequency of the reflected wave. If there is movement of objects in the area, the frequency of the reflected wave will fluctuate slightly, that is, the Doppler effect, so as to judge the movement of objects 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 refraction and reflection phenomena. It has low propagation frequency and fast attenuation in air, while it has small attenuation and far propagation in solid and liquid. Ultrasonic sensors make use of these characteristics of ultrasonic. Ultrasonic sensor has the characteristics of large sensitive range, no visual blind area and no interference from obstacles. It has been proved to be the most effective method to detect the movement of small objects. Therefore, the system composed of LED lamps can sensitively control the switch. Due to the high sensitivity of the ultrasonic sensor, air vibration, the movement of the ventilation, heating and cooling system and the surrounding adjacent space will cause false triggering of the ultrasonic sensor, so the ultrasonic sensor needs to be calibrated in time.

4. Temperature sensor

The temperature sensor NTC (negative temperature coefficient) is widely used as the over temperature protection of LED lamps. If high-power LED light source is used for LED lamps, multi wing aluminum radiator must be used. As the space of LED lamps for indoor lighting is very small, the heat dissipation problem is still one of the biggest technical bottlenecks at present.

5. Voice sensor

The sound control sensor is composed of a sound control sensor, an audio amplifier, a channel selection circuit, a delay start circuit and a thyristor control circuit.

Judge whether to start the control circuit based on the sound comparison results. The regulator is used to set the original value of the sound control sensor. The sound control sensor constantly compares the external sound intensity with the original value. When the original value is exceeded, it transmits a "sound" signal to the control center. The sound control sensor is widely used in corridors and public lighting places.