Combination of photosensitive sensor and LED lamp
Wind power LED street light is a highly intelligent and unattended road lighting fixture. It uses wind and sunlight to generate electricity and uses battery storage to store energy. Therefore, the automatic management of energy is very important. The light-sensitive sensor is an ideal electronic sensor that can control the automatic switching of the circuit due to the change in illuminance during daylight and darkness (sunrise, sunset). Figure 2 shows the appearance of a photosensitive sensor. Figure 3 is the photoresistor board of the photosensor, which is very sensitive to the brightness of light. Figure 4 is a basic schematic diagram of photoelectric conversion.
Photosensitive sensor, which can automatically control the opening and closing of shopping mall LED lighting according to the weather, time period and area. In bright daytime, the power consumption is reduced by reducing its output power. Compared with the use of fluorescent lamps, the convenience store with a store area of ​​200m2 can reduce the power consumption by up to 53%. The life span is also about 50,000-100,000 hours. Under normal circumstances, the life of LED lighting fixtures is about 40,000 hours; the color of the light can also be changed with RGB colorful, making the mall lights more colorful and the atmosphere more active; and the original blue LED matching the use of $ phosphor Compared with the purple LEDs with red, green and blue phosphors, the color rendering is higher.
Combination of infrared sensor and LED lamp
Infrared sensors work by detecting the infrared rays emitted by the human body. The main principle is: about 10um infrared light emitted by the human body is enhanced by the Fresnel filter lens * to the pyroelectric element PIR. When the person moves, the emission position of the infrared radiation will change, and the element will lose its charge balance When a pyroelectric effect occurs, the charge is released outward, and the infrared sensor (PIR) converts the change in 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 senses only the background temperature. When the human body enters the detection area, through the Fresnel lens, the pyroelectric infrared sensor senses the human body temperature and The difference in background temperature, the signal is collected and compared with the existing detection data in the system to determine whether someone or other infrared source has entered the detection area.
The passive infrared sensor has three key components: Fresnel filter lens, pyroelectric infrared sensor (PIR) and matched low noise amplifier. The Fresnel lens has two functions: one is the focusing effect, that is, the pyroelectric infrared signal is refracted on the PIR; the second is to divide the detection area into several bright and dark areas, so that the moving object (person) entering the detection area It can produce varying pyroelectric infrared signals on PIR in the form of temperature changes. It is generally matched with a low-noise amplifier. When the ambient temperature on the detector rises, especially when it is close to the normal human body temperature (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. Figure 5 is the appearance of the infrared sensor, and Figure 6 is the internal structure and internal circuit diagram of the infrared sensor. Figure 7 is an LED lighting fixture with an infrared sensor. This is an E27 standard screw cap luminaire. Its power supply is applicable to AC180V-250V (50 / 60Hz). The infrared sensor detection range is about 3M-15M Standard products IFS-Bulb 3W lamps reach 80 lm, 5W lamps reach 140 lm. An infrared sensor is embedded in the central part of the LED light source module. Once the infrared sensor detects human body temperature, the LED bulb will automatically turn on and off within 50 seconds. Suitable for any kind of indoor applications, such as corridors, storage rooms, stairs and hall entrances.
Ultrasonic sensors, which are similar to infrared sensor applications, have found more applications in automatic detection of moving objects in recent years. Ultrasonic sensors mainly use the Doppler principle to emit high-frequency ultrasonic waves beyond the human body's perception through the crystal oscillator. Generally, 25 to 40 kHz waves are typically selected, and then the control module detects the frequency of the reflected waves. If there is object movement in the area, the reflection There will be slight fluctuations in the wave frequency, that is, the Doppler effect, to judge the movement of objects in the lighting area, so as to achieve the purpose of controlling the switch. Fig. 8 is the application scheme of the combination of ultrasonic sensor and microprocessor.
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, propagating in air has a lower frequency and a faster attenuation, and attenuates in solids and liquids Smaller, spread farther. Ultrasonic sensors make use of these characteristics of ultrasound. Ultrasonic sensors have the characteristics of large sensitivity range, no blind spots, and no interference from obstacles. This technology has been used in commercial and security fields for more than 25 years, and has been proven to be the most effective method for detecting the movement of small objects. Therefore, the system composed with LED lamps can sensitively control the switch.
Due to the high sensitivity of the ultrasonic sensor, the air vibration, ventilation, heating and cooling system and the surrounding space will cause the ultrasonic sensor to trigger falsely, so the ultrasonic sensor needs to be calibrated in time.
Temperature sensor NTC is widely used as an over-temperature protection for LED lamps earlier. If LED lamps use high-power LED light sources, they must use multi-wing aluminum radiators. Since the LED lamps used for indoor lighting have very little space, the heat dissipation problem is still one of the biggest technical bottlenecks. Unsatisfactory heat dissipation of LED lamps will lead to early light decay of LED light sources due to overheating. After the LED lamp is turned on, the heat will also be concentrated to the lamp cap due to the automatic rise of hot air, which affects the life of the power supply (Figure 9). Therefore, when designing LED lamps, an NTC can be placed close to the aluminum radiator near the LED light source to collect the temperature of the lamp in real time. When the temperature of the aluminum radiator of the lamp cup rises, this circuit can be used to automatically reduce the output current of the constant current source, so that The temperature of the lamp is reduced; when the temperature of the aluminum radiator of the lamp cup rises to the limit setting value, the LED power is automatically turned off to realize the over-temperature protection of the lamp. When the temperature is lowered, the lamp is automatically turned on again (Figure 10).
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