Outdoor landscape lighting fixtures need to withstand the test of ice, snow, scorching sun, wind, rain and thunder for a long time, and the cost is relatively high. Because it is difficult to dismantle and repair when used on the exterior wall, it must meet the requirements of long-term stable operation. LED is a delicate semiconductor component. If it is damp, the chip will absorb moisture and damage the LED, PCB and other components. Therefore, LED is suitable for working in dry and low temperature. To ensure that LED can work stably and long-term under harsh outdoor conditions, the waterproof structure design of the lamp is extremely critical.
At present, the waterproof technology of landscape lighting fixtures is mainly divided into two directions: structural waterproof and material waterproof. The so-called structural waterproof means that after the various structural components of the product are combined, it has a waterproof function. Material waterproof means that when designing the product, a position for encapsulating glue to seal the electrical components is reserved, and glue materials are used to achieve waterproofing during assembly. The two waterproof designs are suitable for different product routes, each with its own advantages.
structural waterproofing
Landscape lighting fixtures are based on structural waterproofing design. They need to be tightly matched with silicone sealing rings for waterproofing. The shell structure is relatively precise and complex. They are usually suitable for larger lamps, such as strip floodlights, square and round spotlights and other medium and high power lamps. Structural waterproof lamps are only assembled with pure mechanical structure. The tools are simple to use, the assembly process and process are few, the assembly cycle is short, and the rework on the production line is convenient and fast. The lamps can be packaged and shipped after passing the electrical performance and waterproofing tests. They are suitable for engineering projects with short supply cycles.
Only with suitable materials and structures can its waterproof performance be guaranteed. The following are the design points.
(1) Designing silicone waterproof rings, selecting materials with appropriate hardness, designing appropriate pressure, and its cross-sectional shape are also very critical. The cable lead-in line is a channel for water seepage. Waterproof wires need to be selected, and a strong cable waterproof fixing head (PG head) can prevent water vapor from penetrating through the gaps in the cable core. However, the premise is that the insulation layer of the wire does not age or crack under the long-term strong squeezing of the PG head.
(2) At room temperature, the linear expansion coefficient of glass is about 7.2×10-m/(m·K), and that of aluminum alloy is about 23.2×10-m/(m·K), which is a big difference. Careful consideration should be given when the outer dimensions of the lamp are large. Assuming that the length of the lamp is 1,000 mm, the shell temperature is 60°C during the day, and the temperature drops to 10°C when it rains or at night, the temperature drops by 50°C. The glass and aluminum profiles will shrink by 0.36 mm and 1.16 mm respectively, and the relative displacement is 0.8 mm. The sealing components are repeatedly pulled during the repetitive displacement process, affecting the air tightness.
(3) Many medium and high-power outdoor LED lamps can be installed with waterproof breathable valves (respirators). The waterproof and breathable function of the molecular sieve in the respirator is used to balance the air pressure inside and outside the lamp, eliminate negative pressure, prevent the absorption of water vapor, and ensure that the inside of the lamp is dry. This economical and effective waterproof device can improve the waterproof ability of the original structural design. However, the respirator is not suitable for lamps that are often immersed in water, such as underground lamps and underwater lamps.
The long-term stability of the waterproof structure of lamps is closely related to their design, the performance of the selected lamp materials, processing accuracy, assembly technology, etc. If the weak links are deformed and water seeps, it will cause irreversible damage to the LED and electronic devices, and this situation is difficult to predict during the factory inspection process and is sudden. Therefore, to improve the reliability of structural waterproof lamps, it is necessary to continue to improve the waterproof technology.
Material waterproofing
The lamps with material waterproof design use filling potting glue for insulation and waterproofing, and use sealant to bond and seal the joints between the structural parts to make the electrical components completely airtight, so as to achieve the waterproof effect of outdoor lamps.
