Six commonly used sensors of LED intelligent lighting

Sensor, as signal acquisition and conversion of electromechanical devices, its electromechanical technology is quite mature. In recent years, Sensor technology is making great strides in miniaturization, intelligence, multi-function, and low cost. Various types of sensors, such as photosensitive sensors and infrared sensors, can be combined with LED lighting fixtures to form an intelligent control system. The sensors convert various collected physical quantity signals into electrical signals, which can be integrated into an AD (analog-to-digital) converter. The MCU (microcontroller) and DA (digital-to-analog) converters intelligently process the acquired signals to control the opening and closing of the LED lighting fixtures. And can be used to set various control requirements on the MCU, control the switching time, brightness, color, and color of the LED light to achieve the goal of intelligent lighting control.

Six commonly used sensors of LED intelligent lighting

Photosensitive sensor

The photosensitive sensor is an ideal electronic sensor that can control the automatic switching of the circuit due to changes in illumination during dawn and sunrise (sunrise, sunset). Photosensitive sensors automatically control the opening and closing of LED lighting fixtures based on weather, time period and area. In a bright daytime, by reducing its output power to reduce power consumption, a convenience store with an area of ​​200 square meters can reduce power consumption by up to 53% and a lifetime of 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 RGB (red, green and blue) colorful and colorful, making the lights 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 that the infrared ray emitted by the human body is about 10 infrared ray and is reinforced by a Fresnel filter lens and then collected on the pyroelectric element PIR (passive infrared) detector. When the 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 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 area, the pyroelectric lens senses the human body temperature through the Fresnel lens. The difference in background temperature, after the signal, is collected, which is 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 bright and dark areas, so that the moving object/person entering the detection area and varying pyroelectric infrared signal is produced on the PIR to form a temperature change. It is also generally 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 °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 lighting circuit.

Ultrasonic sensor

Ultrasonic sensors similar to infrared sensor applications have found 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 object motion in the area, the reflection of wave frequency will have a slight fluctuation, the Doppler Effect, to determine the movement of the object in the illumination 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 reflection phenomena. It has a low frequency of propagation in air and attenuates rapidly, but decays in solids and liquids, which is smaller and more distant. Ultrasonic sensors take advantage of these characteristics of ultrasound. Ultrasonic sensors have a large sensitivity range, no visual blind spots, and no interference from obstacles. They have 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, 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

The temperature sensor NTC (negative temperature coefficient) is 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 LED lamps used for indoor lighting have very small space, the heat dissipation problem is still one of the biggest technical bottlenecks.

If the LED lamp is not cool, it will lead to 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 the hot air, which affects the life of the power supply. Therefore, when designing the LED lamp, an NTC can be closely attached to the aluminum heat sink near the LED light source to collect the temperature of the lamp in real time, and the circuit can automatically reduce the output current of the constant current source when the temperature of the aluminum heat sink of the lamp cup rises. The lamp is cooled down; when the temperature of the aluminum cup 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 is lowered, the lamp is automatically turned on again.

Voice sensor

A voice sensor consisting of a sound control sensor, an audio amplifier, a channel selection circuit, a delay-on circuit, and a thyristor control circuit. The sound comparison result is used to judge whether to start the control circuit, and the original value setting of the voice sensor is given by the regulator, and the voice sensor continuously compares the external sound intensity with the original value. The sound signal is conveyed to the control center when the original value is exceeded, and a sound sensor is widely used in corridors and public lighting places.

Microwave sensor

The microwave inductive sensor is a moving object detector designed using the Doppler Effect principle. It detects whether the position of the object has moved in a non-contact manner, which in turn generates a corresponding switching operation. When someone enters the sensing area and meets the lighting requirements, the sensor switch automatically turns on, the load device starts to work, and the delay system is activated. As long as the human body does not leave the sensing area, the load device 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. It is really safe, convenient, intelligent and energy efficient.