LED lighting is developing in the direction of intelligence. The purpose of intelligent LED lighting is to save energy and realize intelligent control. The intelligentization of LED lighting technology needs to integrate sensing technology, signal intelligent processing technology and electronic control execution technology into one. In the system, the lighting of the LED light source module also needs to be driven by a DC constant current power supply. This article will focus on intelligent LED lighting and several sensing technologies, as well as photosensitive sensors, pyroelectric infrared sensors, Fresnel lenses, signal amplification processing and control circuits, infrared self-control LED energy-saving lighting system design.
Intelligent lighting control system
Intelligent lighting control systems can generally be divided into three categories: one is indoor intelligent lighting system - suitable for commercial lighting, home lighting; the second is outdoor intelligent lighting system - suitable for landscape lighting, public buildings and road system lighting; the third is professional intelligent lighting System—Applicable to art lighting in a specific location.
At present, the intelligent lighting control systems with more application opportunities are landscape lighting, public buildings and road system lighting, most of which are multi-lamp intelligent network control lighting systems; home lighting is indoor intelligent lighting control system, most of which are intelligent single lamp automatic control.
Simple intelligent LED lighting system
A simple intelligent LED lighting system is shown in Figure 1. It consists of sensor + MCU + control execution + LED (including LED light source, drive power). Especially suitable for indoor intelligent lighting single lamp.
The main function of the sensor is to collect various useful signals, convert the non-electricity signal into a power signal, and amplify the weak signal. At present, sensors suitable for LED intelligent lighting include infrared sensors, ultrasonic sensors, photosensitive sensors, illuminance sensors, acoustic sensors, and Hall sensors. They can automatically collect information on the activity of the human body, information on the light and dark changes of light, information on changes in sound and sound, and information on the displacement of objects. These non-electrical signals are converted into electric quantity signals, and after intelligent processing, the lighting fixtures can be automatically controlled to turn on or off the LED lighting fixtures. Most of the sensors used for LED lighting are designed and manufactured by microelectronics technology, such as MEMS. Because of their small size, they are easily arranged in a lamp unit with the LED light source and the driving power source. MEMS can be mass-produced like an integrated circuit at a low cost.
The electrical signal output by the sensor is very weak, and the small signal needs to be preprocessed. Therefore, the signal conditioning processor is needed. The intelligent signal processing includes analog-to-digital conversion (ADC), multiplexer (MUX), programmable gain amplifier (PGA), and voltage. References (REFERENCE), excitation power supplies (EXCITATIONS), and even embedded microprocessors (MCU, ASIC), memory (RAM, E2PROM) and other units, they are manufactured using integrated circuit technology. This signal pre-processor can be used as an input signal conditioning front end integrated with the MCU. The MEMS process technology is completely different from the integrated circuit and therefore cannot be fabricated on the same wafer as the integrated circuit. However, MEMS and MCUs can be packaged in a single module using system-on-a-chip (SOC) technology.
The MCU or ASIC automatically intelligently processes the acquired signals, and can write some intelligent programs in software during production. So that the product automatically implements these established functions when it is in use.
The electronic control execution part is an automatic operating system realized by the intelligent processing result. In the intelligent lighting application, it generally directly controls the electronic switch of the power source to control the lighting or extinguishing of the LED light source. If you need remote control or group control, you can also add wireless communication chips such as Zigbee, WLAN, TCP/IP, WiFi, etc., and transmit and control the control signals over long distances.
Figure 1 Simple intelligent LED lighting system
The technology of MEMS sensors and intelligent MCUs packaged in one SOC unit is quite mature. The MEMS sensor with physical quantity, chemical quantity, and biomass and the MCU with sensor signal conditioning are packaged in one SOC to facilitate the design of intelligent lighting fixtures (Figure 2). The ASIC has powerful features that make it easy to perform small model processing and conversions from sensors, driving control execution.
Figure 2 SOC of MEMS and intelligent MCU
Seven or eight years ago, the automotive electronic products----the automatic tire pressure alarm system (TPMS) used in the tires of the sensor module, is the MEMS pressure, acceleration, temperature sensor and ASIC chip packaged in a SOC At the bottom right of Figure 3 is the internal view of the module after removing the packaged plastic. It can be seen that the pressure sensor, acceleration sensor and MCU (ASIC) are packaged in a SOC unit.
Figure 3 SOC module of TPMS
Single lamp intelligent lighting control system
The single-lamp intelligent lighting control system must be made very compact to fit inside a space-limited fixture. A single lamp for intelligent lighting requires a sensor that collects external information, an MCU with signal processing, an electronic switch, an AC/DC constant current power supply, and an LED light source panel (Figure 4). To design a single-lamp intelligent lighting control system, the fixture must first determine the application target in order to determine which sensor to use.
Figure 4 Single lamp intelligent lighting control system
LED lighting fixture with infrared sensor is shown in Figure 5. This LED lighting fixture with infrared sensor uses E27 standard screw head lamp. Its power supply range is AC180V-250V (50/60Hz), infrared sensor detection. The range is about 3M-15M, its standard product IFS-Bulb 3W lamps up to 80 lm, 5W lamps up to 140 lm. As the luminous flux of LEDs increases, current products can reach 300-450 lm. It can be seen from Fig. 5 that an infrared sensor is embedded in the central portion of the LED light source module. Once the infrared sensor detects the person's temperature, the LED light source will automatically turn on within 50 seconds and then turn off for a certain period of time. Suitable for any indoor application such as corridors, storage rooms, stairs and entrance to the lobby.
Figure 5 LED lighting with infrared sensor
Design idea of ​​infrared self-control LED energy-saving lamp system
The specific IR self-control LED energy-saving lighting product design ideas should be based on the signal acquisition and processing path, design each functional part, and meet the product design goals as a whole. The signal output from the infrared sensor is very small and must be amplified to be used. Therefore, the design of the infrared self-control LED energy-saving lamp system is as shown in Figure 6. The weak signal of the infrared sensor is amplified and compared by a four-op-amp (LP2902M) instrumentation amplifier. The timer circuit composed of the CD4538 multivibrator is turned on and off by a large power triode driving relay, and the LED driving power source is used to illuminate the LED light source or the LED light source array in the lamp. The electrical schematic is shown in Figure 7.
Figure 6 Infrared self-control LED energy-saving lamps product design ideas
Figure 7 Infrared self-control LED energy-saving lamps system solution electric schematic
Infrared sensor and Fresnel lens
The infrared sensor is a pyroelectric infrared sensor, which is a heat detector made of a material having thermoelectric properties, and may be one of the infrared sensors used in the industry.
The principle of signal generation of infrared pyroelectric sensor is shown in Figure 8. When the temperature of the surface of the sensor is unchanged, the sensitive element charge balances T [K]. When receiving infrared radiation, the surface temperature changes, and the sensitive element changes. T+∆T [K]. That is, when the temperature of the surface of the sensor sensitive element changes due to infrared radiation from the outside, the infrared sensor releases the charge (current); when the temperature changes tend to be stable, the internal charge tends to balance, and the sensitive element has no charge (current). There is no current output to the stationary heat source. Using the infrared sensor, it is possible to detect moving infrared heat sources in time, such as human walking. The infrared sensor is a passive temperature sensitive device that is not demanding on the application environment temperature, has high sensitivity, and has a wide spectral response. It can be widely used in various infrared intrusion detectors and automatic sensor switches for lighting fixtures.
The shape of the infrared pyroelectric sensor is shown in Figure 9-1. Figure 9-2 is the electrical schematic of the sensor, and Figure 9-3 is a typical application diagram of the sensor. Shanghai Nisella Sensor Co., Ltd. manufactures infrared sensors in large quantities in Shanghai and Kunshan, providing high quality and stable supply for domestic and foreign markets.
Figure 8 shows the principle of signal generation of infrared pyroelectric sensor
The successful application of the infrared pyroelectric sensor requires the Fresnel lens. The Fresnel lens has the function of focusing and viewing angle modulation in front of the infrared pyroelectric sensor. The Fresnel lens can expand the infrared pyroelectric sensor to receive the infrared signal source. The viewing angle and detection area allow monitoring of the moving infrared source or moving heat source (Figure 10). The general types of Fresnel lenses are: horizontal multi-segment (or horizontal curtain, special application), vertical multi-segment (or vertical curtain, special application), horizontal and vertical division (common), conical Area division type (top view type, common type) and other types should be selected according to the product function requirements of different lamps. Fresnel lenses are made by professional manufacturers, with special optical design and special plastic parts pressed by special molds.
Figure 10 Fresnel lens and infrared pyroelectric sensor
The principle of photosensitive sensor and photoresistor
A photosensor is a photodiode that is a semiconductor device that converts an optical signal into an electrical signal. Its core part is also a PN junction. Compared with ordinary diodes, the structure is different. In order to facilitate the acceptance of incident illumination, the PN junction area is made as large as possible, the electrode area is as small as possible, and the junction depth of the PN junction is very large. Shallow, generally less than 1 micron. A window that is in contact with ambient light is required for the application. When the light changes in light and dark, the PN turns on or off automatically (Figure 11).
Figure 11 Photoelectric sensor electrical principle
Figure 12 Photosensitive sensor and photoresistor
Similar to the working principle of the photosensitive sensor, there are also photoresistors, the working principle is the same, can be used to collect the light and light changes of the signal, as a light sensor, the physical Figure 12.
Outdoor intelligent lighting system solution
Outdoor intelligent lighting systems generally refer to landscape intelligent lighting, public buildings and intelligent lighting of road systems. Intelligent lighting control technology is developed with the development of architecture and lighting technology. It uses advanced electronic technology and computer network technology to monitor and adjust the lighting in real time to save energy; manipulate multiple circuits to create specific visual effects. Lighting is not only to meet people's visually bright requirements, but also to meet artistic requirements, to adjust the lighting to change the feeling of a space. The role of lighting control: energy saving, extended light source life, improved lighting quality, a variety of lighting effects. Lighting control principles: safe, reliable, flexible and economical.
Figure 13 Schematic diagram of the National Stadium - Bird's Nest LED lighting control system
Figure 14 A building LED intelligent lighting network solution
Intelligent LED lighting systems can be used separately for small-scale applications, such as shopping malls, offices and other places. It can also be controlled on a large scale, such as hotels, buildings, landscapes, etc. The networking form is simple and flexible, and the newly added lamps can be connected to the existing network at any time without changing the original structure, facilitating the application of LEDs in various fields. Through the remote control, control panel and LCD touch screen, all LED lamps in a certain range can be conveniently managed to realize wireless control and scene control; the traditional set of switches can be used to control a group of lights, and the digital management and network management of LED lights can be improved. . The schematic diagram of the Beijing National Stadium Bird's Nest LED lighting control system architecture is an example of intelligent lighting multi-network networking control (Figure 13). A building LED intelligent lighting network scheme is shown in Figure 14. The intelligent control system can intelligently control the LED lighting switch and dimming of each room in the building through Ethernet and Zigbee wireless communication. Because the outdoor intelligent lighting system technology involves a lot of content and a wide range, it needs to be detailed in different categories. This article will not be specifically introduced here.
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