Specifications

110
5.15 LED flashlight
Both to the well-being of seafarers and the buoy, Datawell buoys are equipped with a flash light
as a standard. The colour and flash pattern, group of 5 yellow flashes every 20 seconds, comply
with regulations for Ocean Data Acquisition Systems (ODAS) in the International Association
of Lighthouse Authorities (IALA) buoyage system A. The visibility range amounts to 4 nautical
miles (Nm) under standard atmospheric conditions. All light is emitted 360º round in the plane
perpendicular to the HF whip antenna and up to 45º above and below this plane. The flashlight
operates below a daylight level of 60 lux. Table 5.15.1 summarizes all LED flasher
specifications.
Use is made of long-life, high illuminance LEDs. The LED flasher assembly is integrated
at the top of the HF whip antenna. In case of significant wave height the high elevation over the
sea surface is advantageous. The design with countersinking LEDs is highly robust and will
withstand smashing against the ship sides during deployment or recovery operations.
The DWR-G 0.4 m LED is of a slightly different design with a transparent cone-shaped
reinforcement. Due to lesser transparency and a lower elevation, the visibility range will be less
than specified in the table. Furthermore, below 80% battery capacity the LED flash intensity
will already begin to diminish until it flashes no more at all. Buoy retrieval in the dark will not
be possible anymore. However, buoy GPS position will be HF transmitted down to 10% battery
capacity.
The HF whip antenna with LED flasher should be mounted on the option port labelled
HF. To avoid shortage and leakage make sure both connector sides are clean and dry. Don’t
forget to place the rubber sealing ring into the groove. Fasten the six hexagon socket screw-
bolts. Upon powering-up the buoy, the LEDs will produce at least 3 normal flash cycles (a
pattern of 5 flashes every 20 seconds). This applies to the situation when the buoy is placed
outside under normal daylight conditions. Otherwise the LEDs will continue their flash pattern
until the flash-off daylight threshold criteria have been met for at least 5 min. The LEDs and the
driver electronics may be tested by covering the top of the HF antenna with your hand for at
least 20 seconds. Then after removing your hand the LEDs will flash for at least 15 cycles (5
min.). The light detection algorithm controlling the LEDs detects the ‘dark’ situation
immediately and requires at least 5min. of the continuous ‘light’ situation. This makes the
‘light’/’dark’ decision algorithm very sensitive as well as very robust, making sure the LEDs
always flash when required, even during the roughest weather conditions.
To rule out defects in the HF/LED antenna, the LEDs may be tested directly at the base
of the antenna. Arrange for a current limit of 100 mA otherwise the LEDs may burn out. For
testing purposes a voltage of 7.5 V is sufficient and the current should remain far below the
100 mA limit. The positive end should be connected to the centre pin of the connector and the
negative end to the jacket or the antenna base itself. Only leave the LEDs on for a fraction of a
second each time you test them, particularly near the 100 mA limit the LEDs may overheat and
burn out.
Some further remarks on visibility. Standard atmospheric conditions imply a clear sky.
During rain, snow, fog, spray, etc. the visibility will be impaired. Also background lights will
reduce the sensitivity of the human eye for weak lights in the distance. Finally, if the visibility
range during the night significantly exceeds that during the day than daylight visibility must be
improved first, e.g. by painting the buoy.
Table 5.15.1. LED flasher specifications.
Parameter Value
Visibility range 4 Nm*
Flash pattern 5 flashes in 10 s
20 s repetition
Light angles 360º around
±45º out of plane
Operation threshold 60 lux
*DWR-G 0.4 m range is less