PWM Based LED Driver
* Updated code for more stability
It has been quite some time since my last post – as often happens, life intervenes and this time just a bit too much hospital time both for myself and one of my kids. Things are good now and normal can resume…
For years I have had this Black&Decker FireStorm FSL18 flashlight, but hardly ever used it due to its anemic light quality. The fixture is powered with an 18v battery pack and uses a KPR18v0.3A bulb putting out 7 candlepower when running at 18 volts. 1 candlepower = 1 lumen. Compared with the brightness of the 12v power LEDs I have been working with lately, the brightness from this incandescent bulb is not much better than a glassed candle. The trigger for upgrading this flashlight came one day when the wife complained an LED lightbulb had failed in her workshop. I replaced the bulb, but rather than throw it away, I took it down to my workshop to disassemble and identify what had broken.
The LEDs themselves were fine, but the power supply had fried. As I was turning the bulb’s heatsink in my hands, I happened to glance at the flashlight sitting on my workbench, and within 5 minutes of realizing the heatsink will probably fit in the case, the flashlight was already being disassembled. Within an hour, I had one of my 900 lumen LEDs mounted on the heatsink and with the help of my Dremel, had the reflector’s neck trimmed down to fit the LED perfectly.
For more detail: PWM Based LED Driver