LED train headlight design achieves increased efficiency
In order to optimize the LEDs’ light output, the researchers came up with a novel design, packing several LEDs within the horizontal divider separating two half-circular parabolic aluminized reflectors. This way, the LED’s light is collected on both sides, resulting in two strong beams that combine to generate maximum light intensity.
“Some LED headlight products sold on the market are designed with many LEDs that have outputs that overlap in large sections. These designs waste a lot of energy,” explains Wei-Lun Liang of the Micro Optics Device Laboratory, who was instrumental in designing the new train headlight. “Our research showed that electricity use can be reduced by focusing on the best way to distribute the LED energy equally.”
In a paper published in Applied Optics under the title “Design of a high-efficiency train headlamp with low power consumption using dual half-parabolic aluminized reflectors”, the researchers unveils the new train headlight design based on ten precisely positioned high efficiency LEDs.
The design draws only 20.18 Watts to accomplish the same light intensity as an incandescent or halogen lamp that uses several hundred watts. The new headlight can also be dimmed by turning off some of the LEDs to avoid blinding waiting passengers when the train passes a platform, for example.
The researchers’ goal was a headlight that would provide light 1.25 times the brightness required by U.S. federal regulations. These regulations require train headlights to have a peak intensity of at least 200,000 candelas and illuminate a person at least 800 feet in front of the headlight.
To determine where to place the LEDs in the reflectors, the researchers first estimated the best location of each LED and then used a series of tests and simulations to fine-tune the final position for each LED based on its corresponding illumination pattern.
Image Credit: Wei-Lun Liang, National Taiwan University.
National Taiwan University – www.ntu.edu.tw/english
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