Vermes
Advanced Member level 4
It is an useful device for everyone who need to have a small and not heavy LED light, which is to be an emergency light for a camera, such as Panasonic. This lamp weighs only 48g and its dimensions are 60x30x30mm + 35mm high stand.
The assumption was to create a device that can be powered from the common accumulator which also supplies GH2 (home made coupler made of processed accumulator-substitute). Current consumption was to be up to 200mA, what in this system (converter approximately 18,5V) and six warm diodes corresponds to about 4W and it is enough, because only the foreground is to be lit up additionally. The efficiency of step-up converter was 81%. It can be powered from 4,5V to 10V.
PCBs were made in thermal transfer method. The converter was designed in Attiny13 in a standards configuration step-up (keying frequency about 19kHz). Program was written in BASCOM and compiled it takes about 55% of memory.
Power is adjusted by one button. When switched on, there is smaller power of about 1W set by default (current consumption about 50mA) – using the button you can switch it to 4W (about 200mA) or back to 1W. This prevents a surge if the accumulator is weaker and you have to light up something. Switching between modes is smooth (smooth increasing the current in order to reduce surges), and switching on the light has also a soft start. The device provides total filling the frame 16/9 and in practice it works excellent.
Diodes used in the design are fourfold diodes, that consist of four very bright components of warm hue. Their aggregate current is 80mA. Choke 2A was used, but it could be as well 0,5A. The choke determines size of the PCB, which could be twice smaller (its dimensions: 25x30mm). All components of the converter including the coil and transistor stay cool, so that there is no need to use any heat sinks. The housing was made of a rectangular cap of a deodorant which was cut a little.
This is an example of picture taken from 3m and 1m at ISO3200 F3,5 S1/50.
Attachment to the original thread includes schematic in Eagle and load.
Link to original thread (useful attachment) - Lampka LED do kamery na Attiny13 (przetwornica step-up)
