For the airsoft flag device project I have been working with normal or semi-high-powered LEDs. And they just weren't bright enough so I had to step it up to proper 1W or 3W LEDs.
However, that required me to change the circuits since it's not a good idea to drive a 1W LED with a series resistor since way too much power will get wasted in the resistor. The correct way of driving high-power LEDs is with a dedicated constant current circuit.
So I decided to make a small board with just the driver circuit and external leads for power, GND and LED control as well as leads for the LED itself.
Of all the many ways of making a constant current regulator, I decided to go with the ZXLD1350 IC for reasons I can't remember.
EAGLE files: Eagle files