I've got an old railway lantern that I am converting it to LED. I have an Adafruit Neopixel ring to take the place of the coloured filters but am fitting a CREE XP-L LED in the middle of the ring to be a torch.
I'm using an Adafruit Pro Trinket 5v to run everything inside the lantern, and with power from a bank of 18650s.
The LED pulls a max of 3A at 3.25v Vf. What driving circuit can I use so that I have full control of brightness from the Trinket?
Ross, you need a constant current driver with a current output to match your led and a pwm control input. Constant current drivers are easy enough to find, but they don't often have a pwm control input. You can't apply pwm switching to the input or output of an ordinary constant current driver using a MOSFET, it would prevent the CC driver from working. Keeping the led cool is also very important. If you can find a way to thermally bond the led to the metal case of the lamp, that would be good.
Thanks, Paul! I'll start researching into one of these.
I plan on running heat pipes from the LED to the case, in an effort to keep it cool. I want to move heat from the back of the LED as this is where the switching mechanism is, and I'm trying to replicate the original switch arrangement.