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LED lighting systems for signaling (road, railroad, aeronautical lighting systems)

  Transport services, in present, are challenged by many new situations such as increasing traffic, high speed and of course the cost rising. A great part of costs deal with infrastructure.
Signaling systems must accomplish new requirements also being flexible and highly reliable.
  One of the most important issue regarding safety of passengers but also the costs of infrastructure is high rate of
failure of light systems and necessity of repair / change.
  Solid state lighting (LED light systems for signals) is an innovative solution:
- Life time of LED light system is 25 time longer then the present incandescent or fluorescent lamp;
- Do not require periodical change such the other classical light systems;
- Decrease the maintenance costs;
- Efficient during operating procedures;
- The process of changing classical lighting lamps with the new LED lighting systems it is quite fast, both types of lighting systems having the compatible electronic connectors.
  One specific and custom designed LED light lamp for signaling, realized and tested in Microelectronica it is a 37 LED light units. The system was designed to allow two ways of functioning: 37 units lamp or 19 units lamp.
  LED dies are integrated in a customized electronic system that fits the requirements and also maximizing LED light efficiency.
  The electronic system comprise a source system and a LED matrix system integrated in a single lighting lamp.
  The Lens that are selected are Diakon PMMA (Lucite International). This type of lens material has very good optical characteristics (refraction index of 1,49; 92% light transmittance). The lenses are very careful mounted for the LED die to be in the focal center for optimal increasing light emitted.
  The housing of LED lamp is an aluminum material, designed and realized for the specific properties of material. One important is the high heat dissipation, enabling cooling of LED dies and electronic system too. Aluminum has low specific density, high hardness and good corrosion resistance.
  The tests over the LED lamp show good to very good mechanical and thermal properties, centrifugal 10 min. at 3000rpm, variation of temperature between -40° C and +120° C, humidity variation 40-90% for 8 hours; the LED system keep functioning.
  Optical properties
The signal lamp has 37 LED light units with PMMA lens, red color 625 and 626 nm wavelength. Wavelength and chromaticity coordinates accomplish the CIE1931 standard. All tests were performed in daylight.
Medium values of luminance, vertical plane, 19 LED units with lens were 1286 -1145 cd/m², at 10° angle against the LED emission surface.
Medium values of luminance, horizontal plane, were 1733 - 5039 cd/m² for 0°, 6°, 12°, 24° angles.
Medium values of illuminance were between 1845 lux at 1m and 310 lux at 5m.
  Luminous intensity
The parameter in candela (cd), was calculated using luminance and angle correction. At 20 m the corrected Luminous Intensity was approx. 997 cd.
The medium value of wavelength is 626 nm (from 15 measurements).
Diagram of chromaticity using the 626nm wavelength was realised measuring thrichromatic parameters x and y (see CIE diagram).

Front and back view of LED electronic circuit

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