How to Test the Quality of LED Street Lights?

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How to Test the Quality of LED Street Lights

LED street lights are a significant lighting facility for cities, so their quality is a high priority in major projects. However, sometimes the quality of LED street lights on the market doesn’t match the price. It is common for low-quality street lights to go dark after being used for a short period of time. And it can be troublesome to replace these street lights. The lights will malfunction due to damage to various components as well as the light source (chip). The LED street lights need to be returned to the manufacturer for testing since it is hard to determine the cause of the damage on the spot. Poor product quality makes maintenance costs high.

Therefore, after purchasing LED street lights, it is essential to assess their quality. The test can identify the quality of LED street lamps from multiple angles, such as the materials used for the whole lamp, product defects, sulfur emission detection of lamps, photoelectric performance, heat dissipation performance, assembly, and safety.

Common tricks of unscrupulous LED street light manufacturers

False product specifications:

The popularity of LED street lamps leads to a decrease in profits. The fierce competition has made many manufacturers start to cut corners and falsely mark product parameters.

Applying counterfeit chips

The chip, which is crucial to LED lamps, controls the lamps’ performance directly. However, some dishonest producers employ cheap chips for the sake of profit, preying on consumers’ lack of knowledge of technological matters. This reduces the quality of LED street lights and makes customers buy low-quality products at high prices.

Using copper wires rather than gold wires

Several LED producers attempt to replace pricey gold wire with copper alloy, silver alloy, and silver alloy covered in gold. While these substitutes are superior to gold wire in several aspects, their chemical stability is significantly lower. For instance, sulfur, chlorine, and bromine will easily erode silver wire and silver alloy wire covered in gold, while copper wire can be easily oxidized and sulfided. These substitute cables’ increased susceptibility to chemical corrosion may lessen the light source’s reliability. They increase the chance that LED lamp beads will malfunction after extended use.

Unreasonable design of the light distribution

The lighting will not be optimal if the light distribution pattern is unreasonable. Problems such as only illuminating their nearby areas, being too dark under the lamp, emitting uneven light, producing light that looks like zebra stripes, etc. will appear in the test.

Poor heat dissipation design

The lifespan of the LED chip will decrease exponentially with increasing PN junction temperatures. Since LED street lamps have high brightness requirements and often work in harsh environments, if the heat dissipation is not properly addressed, the LED lights will quickly age.

Power supply failure

If the quality of the power supply is low, during the test, the street lights may go out and some of the components will be damaged. Several LED lamp beads will break down, and it is also possible for the lights to emit weak light and flicker.

Safety is not guaranteed

Some safety issues that are often ignored by some manufacturers include:

  • The power supply of the street lamps has no leakage protection.
  • The quality of the street lamp ballast is inferior.
  • The rated tripping current of the circuit breaker is excessively high, and its sensitivity has not been tested.
  • The use of the metal sheath of the cable as the PE main trunk is complex and has low reliability.
  • The waterproof and dustproof level is insufficient.

Substances that are harmful to the light source

LED light source blackening is a common issue that many manufacturers may encounter. The lamp’s materials need to be inspected for compounds that could shorten the light source’s lifespan.

What does the LED street light test include?

  1. Whether the products have relevant certifications
  2. Comprehensive photoelectric performance test of lamps
  3. Quality evaluation of the core light source in lamps
  4. Evaluation of the heat dissipation performance of lamps
  5. If the light sources have any harmful chemicals in them
  6. Power supply quality test
  7. Chip quality test
  8. Inspection of the appearance and structure of lamps
  9. Waterproof testing

How to test the LED street lights?

Identification of LED street light quality

LED street lamps are mainly composed of light sources, power supplies, and radiators. The quality of materials and the process directly affect the price of street lamps. We need to test the following aspects to have an overall evaluation:

1. Comprehensive photoelectric performance test of LED lamps

PA photoelectric performance test is important for evaluating the quality of LED lamps and determining whether they have false labels.

The test includes:

  • total luminous flux;
  • luminous efficiency;
  • light distribution;
  • correlated color temperature (CCT);
  • color rendering index (CRI);
  • chromaticity coordinates or chromaticity coordinates;
  • input AC or (DC) voltage;
  • input current;
  • input power; (10) input voltage frequency;
  • power factor.

2. Quality evaluation of the core light source of LED lamps

The tests of the LED light source include:

  • Lens evaluation, packaging glue type, presence of pollutants, bubbles, and airtightness evaluation.
  • Phosphor layer coating process evaluation, phosphor particle size, particle distribution, composition, presence of agglomeration, and sedimentation
  • Chip manufacturing process evaluation, chip pattern microstructure measurement, defect detection, chip pollutant identification, and the and the presence of leakage and damage.
  • Evaluation of the wire bonding process, observation of first and second welding morphologies, arc height measurement, diameter measurement, and identification of wire composition.
  • Evaluation of the encapsulation process: check whether the protective layer has voids, whether it is layered, protective layer composition, and thickness.
  • Evaluation of bracket coating process, bracket composition, coating composition, coating thickness, and bracket airtightness.

3. Evaluation of the heat dissipation performance of LED lamps

As energy-saving lamps, LEDs only convert 30-40% of the energy into light, and the rest is converted into heat. Moreover, the life and quality of LED lamps are closely related to the temperature of the lamp beads and the shell. The evaluation of the heat dissipation capability of LED lamps includes:

  • Evaluation of LED lamp heat dissipation design
  • After the lamp reaches thermal equilibrium, determine whether the temperature of each component is too high.
  • Whether the heat dissipation materials have high specific heat and high thermal conductivity

4. Harmful substances test

More than 50% of LED light failures are caused by the sulfur-bromine chlorination of the silver-plated layer of the lamp beads. Following the sulfur-bromine chlorination reaction, the color temperature will change dramatically and the light will turn black. During use, leakage is very likely to occur. What’s more, if the silver layer is completely corroded, the copper layer is exposed, resulting in dead lights. LED lamps are made of more than 50 different types of materials, some of which may include sulfur, chlorine, and bromine components. These components have the potential to evaporate into gas in a closed, hot environment, which could damage the LED light source. The detection of sulfur elements is the key to ensuring the quality of LED lamps.

5. LED power supply quality test

When selecting and designing LED drivers, factors that need to be considered include reliability, efficiency, power factor, driving mode, surge protection, temperature negative feedback protection, etc. LED drivers for outdoor lamps should be waterproof and moisture-proof, and their shells should be sun-resistant and not prone to aging. In this way, the lifespan of the drivers can be suitable for LED lights. The tests of LED drivers include:

  • Output voltage and current
  • Whether the driver can ensure constant current output
  • Whether there is protection against overcurrent, short circuit, and open circuit
  • When the power is on, the shell should not have current.
  • Ripple voltage detection: no ripple voltage is the best, but if there is ripple voltage, the smaller the peak value, the better.
  • Flicker evaluation: There should be no flicker after the LED street light lights up.
  • Power-on output voltage and current: When being turned on, the power supply should not output a large voltage and current.
  • Whether the power surge meets the relevant standards.

Chip source identification

 Through retrieval and matching in the chip database, we can identify the chip model and manufacturer, which helps the light fixture manufacturers improve their quality control and production efficiency.

Inspection of the appearance and structure of lamps

The bidding documents usually stipulate the materials used for the exterior lighting of lamps, so the lamps should be inspected according to these regulations.

  1. Appearance inspection: the painting should have a uniform color, have no pores, cracks, or impurities, and the coating must be tightly adhered to the material. The housing of each component should be smooth and flat and should not have scratches, cracks, deformations, or other defects.
  2. Dimension inspection: the external dimensions ought to line up with the specifications stated in the drawings.
  3. Material inspection: Every component’s materials and structural design should adhere to the required specifications.
  4. Assembly inspection: Make sure the lamp’s surface fastening screws are tight. The connections should be solid, and the surface should be free of burrs or sharp edges.

Waterproof test

LED street lamps are outdoor lighting fixtures and are often more than ten meters high. It is difficult to replace and repair street lamps, so they should have good waterproof and dustproof performance.

Conclusions

Knowing the tricks of street light manufacturers and how to carry out tests can ensure that the products are worth the money. It can be really annoying and costly to find out your street lights are not up to standard and have to replace them. While testing, pay attention to the photoelectric performance of the light sources, quality of the chips, heat dissipation capability, materials, drivers, structure of the lamps, waterproof performance, and so on. If you want to buy high-quality products that have gone through multiple tests and can meet your requirements, you can contact us for more information.

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Victor Guo

Victor Guo

Lead electrical engineer with 17+ years of experience designing electrical street lighting systems, monitoring electrical-related work at site, and discussing proposal and lighting implementation options. Bachelor’s degree in electrical engineering. Knowledgeable in LED lighting design, project management, safety and compliance.
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