Sethaa created this wonderfull work of a star constellation of a red panda. It will be at the MMC artshow and as a special feature she asked me to equip it with a lightsource which enlights the stars of the constellation, 13 in sum.

Sadly, the camera wasn't in the condition to copy all LEDs, cause of the angle. The Stars will light up depending on the viewing angle.

I choosed bright white (not blue as in the picture - the mobilephone camera does recognize them wrong) SMD 1206 LEDs with 20mA each and designed 7 constant-current power supplies around them.
In front of the power supplies I set up a intermediate circuit which is powered by a DC/DC boost-converter, to compensate the decreasing batterie voltage while they're discharging. So the LEDs shine bright the same way until the batteries are empty.
A little trick of a schmid-trigger indicates when the batteries are empty (which will be after 17-20h of runtime).

Uin = 3...7.4V (3 or 4 pieces of 1.5V or 1.2V cells, or 2 pieces of LithiumIon)
Iin = 0.05...0.3A (depents on connected LEDs)
Uout = 0...Uin>6.6V (internal intermediate circuit/ maximum forward voltage of the LEDs)
Iout = 7* 20mA (ges. 0.925W)
low_batt_indication: below 4.1V (adaptable, depents on the cellcount)
efficiency: about 84% or above

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