Some time ago, i took part in the creation of an artistic project along with two artists from Germany, Diane Müller and Werner Magar [puplik.org]. The project name was "SOUNDBOMBs". The SOUNDBOMB is a multimedia sphere made of semi-transparent material. Inside there are six 3-watt Nichia LEDs for the light effect and a large sound speaker underneath for the audio. Their purpose is to draw the attention of the visitors, speak to them, and provide various audible information.
My part in this project was to make a high wattage LED breathing circuit. A typical analog LED breathing circuit was not a choice because 20 watts of power would require a huge heatink with fans to cool the power transistor. Therefore, i used an A6210 driver along with a PIC microcontroller. The difficult part was to simulate analog breathing with digital circuitry. I achieved this by changing the PWM duty cycle with the parabolic function X = Y2 + a.
SOUNDBOMBS @ CyCon 2012
More info and photos from the SOUNDBOMBs at the CyCon 2012 can be found in this link
SOUNDBOMBS @ KUMU Art Museum
More info and photos from the SOUNDBOMBs at the KUMU Art Museum can be found in this link
Here is the top and bottom side of the PCB with the parts soldered. The board was powered directly from a 2x18 transformer to provide the 23V 0.75A at around 800 KHz switching frequency to the 6 LEDs connected in series. Each board had a rectifier and smoothing capacitors, as well as 4 precision potentiometers to adjust min and max brightness levels and breathing speeds. Additionally, 4 jumpers were used to select the different modes: Adjustment mode, linear/parabolic mode, Symmetrical breathing mode and slow/fast breathing mode.
Thank you Werner and Diane for trusting my skills for your project!