This paper describes a set of LED intelligent lighting control system design, which can automatically control the lighting switch and brightness according to whether there is personnel and environment fill light brightness in the working environment. The system has the dual functions of improving power efficiency, saving power and alleviating the power supply pressure of the peak of power consumption.
LEDs are considered to be the source of illumination for the 21st century. The LED light-emitting device is a cold light source with high light efficiency, low operating voltage, and low energy consumption. Under the same brightness, the LED energy consumption is 10% of incandescent lamps and 50% of fluorescent lamps. LED life can reach 100,000 hours, 10 times that of fluorescent lamps and 100 times that of incandescent lamps. Replacing incandescent or fluorescent lamps with LEDs is environmentally friendly and non-polluting. Safe and reliable to use and easy to maintain. China's lighting power accounts for 12% of total power generation. At present, most of the lighting control of public buildings adopts manual switches, and there is often a phenomenon that there is no timely switching, resulting in a large amount of energy waste and inconvenience in use. In addition, unnecessary use will also shorten the life of the luminaire. This paper describes a set of LED intelligent lighting control system design, which can automatically control the lighting switch and brightness according to whether there is personnel and environment fill light brightness in the working environment. The system has the dual functions of improving power efficiency, saving power and alleviating the power supply pressure of the peak of power consumption.
System main control module function
 This energy-saving lighting control system was installed and commissioned in the central control room of the Daqing Petroleum Institute Modern Education Center. According to the national standard civil building lighting design standard (GBJl33-90), we control the indoor brightness around 2001x.
The controller is equipped with 3 sets of sensing systems and strict software control. The working method is:
First, detect whether there is someone through a passive pyroelectric infrared detector and ambient noise, and detect the ambient brightness. If there is no one, all LED lights will not turn on. If anyone, divide into two situations:
• If the illumination of the environment to be illuminated is X>200 lx, the LED lighting fixture is off;
• If the illumination of the environment to be illuminated is x < 200 lx, the LED lighting fixture is turned on, and the ambient illumination is adjusted to the illumination of the LED fixture, and the average illumination of the LED fixture released into the room is E=200-x.
Hardware feeding control system
In view of the above situation, the system uses MCS-51 single-chip microcomputer as the core to form an automatic control system integrating acquisition, processing and control. Its block diagram is shown in Figure 1.
It is mainly composed of three parts: sensor unit, controller unit, LED drive circuit and lighting system.
Sensor unit
Passive pyroelectric infrared detector
Passive infrared detectors have three key components:
The Fresnel filter wafer, which passes through a Fresnel filter wafer with a cutoff wavelength of 8 to 12 μm, acts as a bandpass filter, so that environmental interference is significantly controlled.
Fresnel lens, there are two functions: one is the focusing effect, that is, the infrared signal of the pyrolysis is refracted on the PIR (pyroelectric infrared sensor), and the second function is to detect the change of the infrared energy in the warning zone, and the system is The internal curing software performs arithmetic processing on the collected data, and the control software in the control system determines whether to issue the light-on signal through the control logic.
A pyroelectric infrared sensor (PIR) converts the change in infrared radiation energy through the filter wafer into an electrical signal, ie, thermoelectric conversion.
Therefore, in the warning zone of the passive infrared detector, when there is no human body moving, the pyroelectric infrared sensor senses only the background temperature. When the human body enters the warning zone, it passes the Fresnel lens and the pyroelectric infrared sensor senses. The difference between the human body temperature and the background temperature is obtained. After the signal is collected into the servo system, the software compares the newly collected data with the pre-existing data already existing in the system memory to determine whether someone is actually waiting for infrared rays. When the source enters the warning zone, it is only the environmental fluctuations, or even the internal noise of the component itself, so as to avoid misjudgment. Therefore, the hardware and software of the infrared detection sensing part mainly determines whether someone enters the warning zone that needs illumination by detecting the change of the environment infrared. The function of the matching low noise amplifier is to increase the sensitivity of the amplifier by increasing the sensitivity of the amplifier when the ambient temperature on the detector rises, especially when the body is close to the normal body temperature (37 ° C).
In addition, due to the existence of attenuation factors such as distance, the initial data of the temperature sensor and the internal software does not need to be set at 37 ° C, but to integrate the environmental factors, the component sensitivity of the nearest line performance section to determine the initial value. It is generally lower than the body temperature, which happens to be a component that is more sensitive and the component is closer to the nearest linear segment.
If the system is used in the public area of ​​the building, it is also necessary to consider different initial values ​​as the season changes, and add corresponding control modules to the control software, mainly because the temperature change in the common section of the building is larger than the indoor temperature range. Some, the situation is more complicated.
Environmental noise detection
It is mainly detected by detecting the noise generated by human daily activities in the environment, and the data of the infrared part is performed or calculated inside the system to compensate for the insensitivity of infrared detection when the ambient temperature is very close to the human body, and it is impossible to determine whether someone enters the required illumination. Area.
Visible light detector
By comparing various performances of photodetectors such as phototubes and photoresistors, it is found that the spectral response peak of the photoresistor is closer to the wavelength of the human visual sensitive region. Secondly, when the light intensity is weakened, its response time is relatively increased, and the output state remains relatively stable when the illumination intensity changes. Considering that the photoresistor is sensitive to temperature changes, the resistor in the bias circuit can use a photoresistor similar to the temperature coefficient of the detector element to prevent drift at the operating point. In addition, the internal software design mainly takes the sensitive data interval close to the human eye, so that the probability of misjudgment of the control system is reduced, and the data area of ​​the program is reduced to a minimum, which is reserved for future software upgrades. Space, lay the foundation for the full use of hardware systems, and play an important role in the overall hardware cost control of the system.
control unit
We use single-chip microcomputer as the core of the lighting system. There are many varieties and specifications of the single-chip microcomputer. The principle of selection is to make the system as simple as possible, reliable in performance and low in cost. We use Intel's 8051 microcontroller, which contains 128 bytes of RAM, 32 I/O lines, and two 8-bit timers that can be automatically reloaded with 8-bit timers/counters. After the output pulse of the single chip microcomputer is isolated and power amplified, it can be directly connected to the thyristor control electrode to control the thyristor. In order to reduce interference from the power grid, the trigger pulse generated by the I/O line of the microcontroller must be isolated and sent to the control circuit of the thyristor. The thyristor (SCR) dimmer is mostly used for controllable rectification, inverter, voltage regulation circuit, and it is easy to dim the current. The adjustment of the voltage limit can further extend the life of the lamp.
LED lighting system and drive circuit
We use 1w white LED, the luminous efficiency is 601m/W, and the indoor brightness is expected to be around 2001x.
Formula by average brightness:
In the formula, E is an average illuminance, φ is the luminous flux of a light source, N is a number of lamps, u is a utilization factor of a lamp, K is a maintenance factor, and A is an indoor area.
Taking into account the lower the outdoor brightness, the smaller the compensation for indoor brightness, so we installed 400 LEDs, all lighting up the indoor brightness up to 2081x.
The main issues in designing LED lights are discussed below:
• Selection of drive power
Our AP-28320 LED driver is a dedicated power converter for making integrated semiconductor lamps. It is installed inside the semiconductor lamp and drives 1 series of 10~40 1W high-power LEDs in series. 220V AC mains supply , output 320rrLA stable one-way pulsating constant current. The driver uses a high-frequency pulse width modulation switch conversion circuit to achieve constant current control, high conversion efficiency, up to 85%, and stable operation. The drive is a fully enclosed module package structure, suitable for use in environments with high humidity, high dust, strong vibration, and certain requirements for explosion protection. It is very suitable for indoor use, and can also be used for lighting in public areas of buildings through software upgrades. • LED light connection
At present, the mature application is a single-grain 1W LED. Obviously, it is necessary to use 50 LED tubes for such a semiconductor lamp. There are some problems with all 50 LEDs connected in series or in parallel.
If all are connected in series, if one LED is broken, the whole lamp will not light, and all 50 LEDs are connected in series, and the driving voltage is at least 150V, which reduces the safety. If all are connected in parallel, there is one way to open or short circuit, then 1 current is unbalanced, which affects the service life of the lamp.
From the perspective of the driving technology and the characteristics of the luminous tube, a plurality of luminous tube groups should preferably use the series connection scheme. Thus, as long as the current given by the driver is appropriate, the currents of all the tubes are the same. The use of LEDs in series is often a concern. One is that the entire line of LEDs is not lit. We have used high voltage on the sample lamp and also made a surge test. From the application practice point of view, as long as the drive does not lose control, the current to the light-emitting tube is appropriate, the light-emitting tube rarely sees the open circuit, even if the quality of the light-emitting tube itself is not good, generally it is not bright, but still maintain the path, other The tube is still bright. Moreover, the LED has a strong overcurrent capability, such as a 300 mA 1 watt LED tube with a short time plus 600n1A current will not be bad. Therefore, the use of the light-emitting tube should be based on the series, so that the light-emitting tube has a stable, consistent current, which is beneficial to improve the life of the light. Since the number of tubes is too large, the driving voltages of all the series are too high, and they have to be connected in series, so they are mixed. The dedicated LED driver is generally a current source. Since the LED driver provides a constant current, multiple series and parallel connections must be supplemented by external current sharing measures to evenly distribute the total current supplied by the driver to each string. The simplest The solution is to string a resistor in each string. When multiple series are connected in parallel, the first step is to keep the total tube voltage drop of each string of light tubes as uniform as possible, and then the resistance of the resistors is reversed. The voltage drop on the power pack is too large, and the power consumption is too small. The pressure drop is too small and the current flow effect is not good. Generally, the pressure drop of the series pipe can be taken as about 5%.
• Heat dissipation method
Solving the heat dissipation problem mainly depends on the reasonable lamp body structure design. The solution is to use a thin metal plate as the substrate. The LED can be used to make the hole with the same outer diameter and the outer diameter of the arc tube on the aluminum plate according to the number of the light-emitting tubes used. The distance between the two holes is 0.7 mm, and then the light-emitting tube is tightly fitted. On the metal plate, the LED pins are connected behind the metal plate. The outer casing of the lamp is also made of metal material, and the metal plate of the light-emitting tube is tightly assembled with the metal casing, so that the heat generated by the working of the lamp can be conducted to the metal casing through the metal plate, and the metal casing is exposed to the air, and the heat can pass. Radiation and convection dissipate. In order to reduce the volume of the lamp and ensure a large heat dissipation area, the lamp body casing may adopt a ribbed fin structure.
• LED lighting control module
We divided the 400 LEDs into 10 groups of 40 each. Each group uses an AP-28320 as the current source, and the output of the thyristor is controlled by a single-chip microcomputer to adjust the brightness of the LED. A RC tank can be connected in parallel with the thyristor to absorb the harmonic interference generated by the AP-28320 and the thyristor. The connection method is shown in Figure 2.
software design
This program uses a modular design idea. The function module subroutine is set with the main program as the core, which simplifies the design structure. During the running process, each function module subroutine is called by the main program. Because the real-time requirements of the lamp control are not high, the cycle control can meet the requirements. The working software of the system mainly completes the following functions: the signal input module realizes the corresponding sensor signal input into the single-chip data channel, and in the control system software, the signal of the infrared detector and the signal of the sound sensor are respectively rectified and digitized and processed into a switch of Boolean. Type data, then phase or. The signal generated by the rectified and amplified ambient fill light intensity detection system is divided into two paths, one is a Boolean value, and the output generated by the first two signals is processed and operated, thereby generating a switch signal for determining the switch of the lamp, and the other way The environmental data A/D is converted, and then output as a control signal for adjusting the brightness of the system to the output module of the system to achieve the purpose of controlling the brightness of the LED. Achieve the purpose of intelligent lighting.
Due to the complexity of the actual use environment and the existence of various interference factors, especially the electromagnetic interference caused by a large number of mobile phones. Therefore, the reliability of the system needs to be maintained using anti-interference technology. The anti-jamming technology used here is Watchdog Technology (WDT). The operation of the watchdog enables the program to generate a reset signal in the runaway state, effectively preventing the program from running away.
Conclusion
Since the trial operation of the central control room of the Daqing Petroleum Institute Modern Education Center, the system has saved more than 50% of energy, and the energy-saving effect is very obvious. We also tried out the LED street light, installed on the 6-meter street lamp, emitting soft white light, and the visual effect exceeded the high-pressure sodium lamp. Since the installation, no light decay phenomenon has been found, which is very stable. (small soup)
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