New LED-Modul for Divers
A newly developed compact LED-module for underwater lights for divers with outstanding features is now available!
The three dimming stages of the LED-based module adapt to the luminous flux of 20W, 50W, 35W halogen bulbs with minimum energy consumption.
The Lighting Technology
The aim of the photometric performance was to produce a luminous flux corresponding to at least a 50W halogen bulb which is around 1000 lumens. No LED should be used with poor color rendering or a high color temperature. At the same time, the LED should not be operated at its maximum power in order to achieve the required amount of light output because of superior performance decrease in both, efficiency and expected lifetime. This bundle of demands could only be met by useing two LEDs. They produce a total luminous flux of around 1250 lumens and are operated at the brightest dimming-level with almost 80% of their maximum current. The color temperature of about 4500K was placed in the neutral white area. At the choosen point of operation both, the color rendering with a CRI of typically 75 and the efficiency, are good. The efficency is only about 10% below that of LEDs with higher color temperatures emitting a considerably bluish light.
Another aim of the development was the ability to use different optics for different applications on one module. Since a louminous flux of 1250lm is sufficiently large enough, it was possible to use lenses with a wider beam instead of narrow beam lenses. This means a considerable gain in comfort. The choice therefore fell on a lens with an opening angle of 17.2° as basic equipment. As a further look, designed for special applications such as cave diving for example, or, if someone simply prefers a wider beam, a 33.5° optic can be installed as well. Third option of the bunch is a lens with an opening angle of 72° which is intended for video use. The optical efficiency is about 87% for the 17.2° optics, about 78% for the 33.5° optics and at about 85% for the 72° optics.
The essential components of the electronics are a constant current source which supplies the current for the LEDs and a microcontroller which controls the lamp function and monitors the battery. It is built on an aluminum printed circuit board (IMS-board) with a very high thermal conductivity. As a result, the heat of the LEDs is dissipated particularly well, resulting in a better efficiency and a longer lifetime of the LEDs due to a lower LED temperature. The disadvantage of the slightly higher price of the IMS-board material with the higher thermal conductivity to material with a lower thermal conductivity is justified.
The abdication of electrolytic capacitors in the circuit design increase lifetime as well. This was made possible by the use of a constant current source with high switching frequency while maintaining a high efficiency. The average output current of the constant current source is adjusted by a PWM signal from the microcontroller in three stages. The three dimming levels correspond to the light output of halogen bulbs with 20, 35 and 50W. The PWM frequency is around 1 kHz and therefore high enough to avoid flickering on video cameras.
To control the ON/Off-funktion and the dimming only a single reed-contact is needed, as in the other available electronic-systems for underwater lights. The proven operating concept was adopted and only adds an additional (20W) dimming stage, which is easily possible with LEDs, in contrast to halogen bulbs, as the halogen-cycle comes to a standstill if too little power is applied to the bulb.
Other tasks assigned to the microcontroller are monitoring the temperature of the circuit board and monitoring the battery condition. In case of overtemperature the current through the LEDs is reduced first. If that's not enough and the temperature continues to rise, the LED current is switched off completely to avoid any damage by overheating. Under normal operating conditions, ie with sufficient cooling, however, this condition is never reached, because the threshold for power reduction is around 75°C and the shutdown-temperature is around 85°C.
If battery-capacity becomes low, the user is warned: the LED current is switched off for 1s and then switched on again automatically. Upon further discharge a second threshold is exceeded. Now, to save power, the light-output significantly reduced to an emergency-light level. The remaining light-output is sufficient for reading instruments etc. However, the battery should be recharged by now. If that does not happen due to an ongoing discharge the voltage of the battery will drop below a third threshold. The LED current is now switched off completely in order to prevent damaging the now fully discharged battery-pack. Only very short flashes indicate that the the lamp is still turned on. The battery needs to be recharged immediately.
- the used LEDs have a color temperature of about 4500K and a CRI of 75 typical
- opening angles 17.2°, 33.5°, or for the video section, 72°
- three dimming levels (similar to 20, 35 or 50W halogen bulb)
- Battery monitoring and lighting control by microcontroller
- an emergency light with (almost) completely empty battery
- deep discharge protection for different battery types
- extremely low power consumption in standby mode (suitable for lithium-batteries)
- overheat protection
- aluminum core printed circuit board with only 50mm in diameter and high thermal conductivity
- low hight (about 15mm max.) for the entire circuit including LEDs and lenses
- only one reed contact is required for control
- long life by eliminating electrolytic-capacitors in the circuit design
- for 3 cells Lithium-Battery (10,8V) with 17,2° optiks (standard)
- for 3 cells Lithium-Battery (10,8V) with 33,5° optics (special for cave diving)
- for 3 cells Lithium-Battery (10,8V) with 72° optics (standard video)
- for 4 cells lithium-Battery (14,4V) with 17,2° optics (standard)
- for 4 cells Lithium-Battery (14,4V) with 33,5° optics (special for cave diving)
- for 4 cells Lithium-Battery (14,4V) mit 72° optics (standard video)
- for 10 cells NiCd-/NiMH-Battery (12,0V) with 17,2° optics (standard)
- for 10 cells NiCd-/NiMH-Battery (12,0V) mit 33,5° optics (special for cave diving)
- for 10 cells NiCd-/NiMH-Battery (12V,0) mit 72° optics (standard video)
- for 12 cells NiCd-/NiMH-Battery (14,4V) mit 17,2° optics (standard)
- for 12 cells NiCd-/NiMH-Battery (14,4V) mit 33,5° optics (special for cave diving)
- for 12 cells NiCd-/NiMH-Battery (14,4V) mit 72° optics (standard video)
They are sold to private buyers who want to build, retrofit or repair their underwater lights, as well as to distributors and OEM-customers.