LED light source has the advantages of low power consumption, long life, intelligent control, green environmental protection, color adjustment and easy maintenance. It is considered to be the most competitive new green light source in the 21st century. The promotion and application of LED lighting has become one of the effective ways to solve energy saving and emission reduction. Since 2009, the development of the LED industry has been promoted through application demonstrations throughout the country, especially the application and promotion of
LED street lamps has progressed rapidly.
For an emerging product,
high-power LEDs are key components of semiconductor lighting, and high-power LEDs have deficiencies in reliability. Poor heat dissipation can cause irreversible damage to the LED semiconductor device, resulting in red shift of spectrum, shortened service life and light decay.
Due to the technical characteristics of LED street lights and the complexity of their working environment, it is difficult for a single laboratory test to meet the stringent test requirements of LED street lights. The life test of LED street lamps is particularly important, but the on-site light attenuation detection technology and detection equipment are still in a blank state.
At present, the light decay test of LED street lamps generally adopts the method of removing the lamps and taking them back to the laboratory for measurement, but the test procedure is cumbersome and the practical operation is difficult to realize.
LED street light field light decay test lacks clear technical standards, testing instruments, and effective monitoring methods. This leads to the uneven quality of LED street light products on the market. The LED road lighting degradation problem seriously affects the application demonstration effect of some energy-saving renovation projects. .
Therefore, this paper conducts an in-depth study on the on-site detection method of LED road light decay.
Based on the principle of relative light decay, a field light attenuation test method is obtained, which is in line with LED street lamps and other LED lighting fixtures, and corresponding test devices are developed to solve the problem that the current photoluminescence life detection of laboratory lamps is widely different from the actual application environment. The problems of long test time, complicated process, high cost and difficulty in monitoring the time point of failure caused by light decay are of great significance for improving the quality of LED lighting products and promoting the healthy development of LED industry.
Laboratory light decay detection method
At present, the detection of the light decay life of LED street lamps is mainly carried out in an ideal laboratory environment.
According to LB/T001—2009 “Measurement Method of Integrated LED Street Light”, CJ/T420—2013 “LED Street Light”, GB/T24907—2010 “Performance Requirements for LED Lighting for Road Lighting”, GB/T24824—2009 “General Lighting LED module test method and other standards, under the standard conditions, the old LED street lamp, until the old refining time t at least 6000 hours, at least every 1000 hours to measure the total luminous flux Φi of the LED street lamp, according to formula (1), The initial luminous flux Φ0 is compared to obtain its luminous flux maintenance ratio ΔΦ, that is, light decay.
At the same time, some standards are recommended for testing. A test method for relative luminous flux maintenance rate (relative light decay) is recommended, that is, the illuminance E at the point of the lamp at a specified distance is substituted for the luminous flux Φ, and the luminous flux maintenance is calculated according to formula (2). The rate and test schematic are shown in Figure 1.
Figure 1 Schematic diagram of relative luminous flux maintenance rate (light decay) test
Fig. 1 separated lumen maintenance (light attenuation)
In formulas (1) and (2), Φ initial and Φi represent the luminous flux at the initial time of the initial refining t and at a certain time point ti, respectively. E initial and Ei represent the initial tempering time t and the relative ti of the time point ti, respectively. .
On-site light attenuation detection method
This paper refers to the simple test method of relative luminous flux maintenance rate (light decay) recommended by the laboratory, and studies the LED street light by using the principle that the LED street lamp has a linear relationship between the illuminance of a fixed point and the whole luminous flux in the illumination range. On-site detection method for relative light decay.
As shown in FIG. 2, the relative light flux Φ is represented by testing the illuminance E of a test point of the light pole in the illumination range, thereby calculating the relative light decay trend of the LED street light.
Fig. 2 Schematic diagram of relative light decay test of LED street lamp
Fig. 2 LED street lamp o nsite relative light attenuation testing
The development of the required illuminance test device is the most critical research content of the LED street lamp on-site relative light decay test method. By fully considering the complexity of the LED street lamp field lighting field application environment and the harsh climatic conditions, the interstitial illuminance test device is developed. As shown in FIG. 3, the technical problem of automatically detecting the illumination of a certain test point on the spot to calculate the relative light decay of the LED street lamp is solved.
Figure 3 Mechanical structure of the intermittent illuminance test device
Fig. 3 The mechanical structure drawing of testing
Equipment of intermittent illumination
Before the test, the illuminance probe is automatically popped up by the two-way corner motor. The probe starts to test after 30 seconds of stabilization. The illuminance test is completed in 30 seconds and the illuminance probe is recovered by the two-way corner motor. The illuminance probe is not only protected by the pop-up and retract mechanism. It also effectively prevents the illumination probe from prolonging exposure to light and prolonging the life of the probe.
In order to solve the problem of drift of the photoelectric probe during the long time of use, the test device specifically adds a standard light source and two light-shielding bars to realize the self-calibration function of the illumination probe; at the same time, the device is built in the protective shell to protect the core component from being avoided. Rain or other climatic factors that may damage the unit increase the reliability of the test unit as a whole.
The illuminance detecting device further comprises a control circuit developed based on the C51 single chip, the control circuit is correspondingly connected with the illuminance probe, the bidirectional corner motor and the standard light source, and the control circuit can control the bidirectional corner motor, the standard light source on and off, and the illuminance probe to collect the illuminance value and temporarily store Then, the measured illuminance value is remotely transmitted to the upper computer through GPRS or ZigBee wireless communication method for data storage and tracking analysis.
Analysis of on-site light decay test results
Using the unit's own road, a 120-meter-long field test circuit with 12-inch LED street lights can be installed, and an electrical parameter test module and an intermittent illuminance test device are installed in the LED street lamp test road, and the LED street light is monitored in real time for half a year. Changes in parameters such as operating voltage, active power, and relative light decay.
For example, the monitoring results of an LED street lamp in the past three months are shown in Figures 3 to 5, respectively.
Figure 3 operating voltage curve
Fig. 3 The curve of working voltage change
Figure 4 Active power curve
Fig. 4 The curve of active power change
Figure 5 phase contrast (light decay) curve
Fig. 5 The curve of relative illumination change
Figure 5 reflects that the LED street lamp has a certain degree of light decay during the past three months of operation, and the maximum light decay is about 6%. The trend change curve calculated by linear regression reflects the lumen maintenance rate of the LED street lamp. Has been in the decline channel.
The curve of the electrical parameters and the light decay curve obtained by normalization is shown in Fig. 6. The trend change straight line calculated by linear regression of the active power and the phase contrast respectively reflects that both are in the descending channel, but the LED road light is caused. The factors of fading are multifaceted, and a large number of relative light decay field tests are required.
In order to obtain the relevant factors causing the light decay or to find out the correlation of these parameters, it is also necessary to combine the monitoring data of other factors for data mining analysis to determine the main factors causing the LED road lighting failure.
Figure 6 normalized curve
Fig. 6 The change curve after the normalization
From the test results, it is concluded that the intermittent illuminance test device can achieve continuous and effective monitoring of the on-site light fading of the LED street lamp. The LED street lamp relative light fading test method based on the illuminance test device is feasible.
in conclusion
The relative light decay test method of LED street lamp based on the gap illuminance test device proposed in this paper not only makes up for the blank of the field light decay test technology of LED street lamp, but also overcomes the characteristics of long life and slow light decay of LED lamp by automation. The traditional laboratory light attenuation method generally has problems such as large difference from the actual application environment, long test time, complicated process, high cost and difficulty in monitoring the critical time point of failure caused by light decay.
At the same time, this test method can also be extended to the on-site light decay test of other LED lamps, providing effective monitoring means for the construction of semiconductor lighting demonstration projects that are being promoted by governments at all levels to ensure the quality of lighting products and quality control of the project. Research and promotion value.
However, for the subsequent research work on the relative light decay test and test device development of LED lamps, the focus is on verifying the test results through laboratory light decay and on-site relative light decay, further improving the accuracy of test results. The installation convenience, high reproducibility, etc. carry out subsequent in-depth research and effective application and promotion through various channels.
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