I have been working on a high-powered LED light bar. The design powers them almost directly from the mains, but limits current using a 555 and beefier NPN. Below is a simplified schematic.
Obviously the LED resistance changes with several factors, and I have blown out a few, but that was due to soldering issues on my part. Essentially I know the circuit works. The only hold-up is that I have tried two different NPN transistors (salvaged from old CRTs) and both end up with Vce voltages around 35V causing them to heat up rather quickly since the current is around 1 amp. I will link the datasheets for the two in below. I have measured the output of the timer at 2V RMS and set the resistor values for each transistor according to their Ib vs Vce graphs (around 0.2A) since neither include a Beta value. My question is: how do I bring the Vce down to around 5V or lower?
Fuji C3866 | Toshiba 2SC5386 https://drive.google.com/folderview?id=0B4n242xWd2TBOUVBZF9uQ1BDc2M&usp=sharing
EDIT: Removed terrible CAD, added hand drawn circuit These are 10W, 12V LEDs