On Mon, 11 Jan 2010 21:06:32 -0500, Charlie Smith wrote:



Been reading the thread. A combination of switching to a 7809 regulator and using
two LEDs in series may save some power/reduce heat. (Ed and Speff IIRC)

You also need to protect the input of the regulator just like automobile applications,
able to withstand up to 100 v spikes in either direction for 5 ms duration. Also for
30 to 40 V for 200 ms.

If you go with PWM you may wish to consider a lower resistor on the base of the 3055,
typical Beta is about 50 at 500 mA IC.

I also suggest some isolation between the regulator and the LED block, say a lossy
inductor with about 1 ohm resistance. Inductor size should be premised on discontinuous
conduction at low brightness and continuous conduction at max brightness. A couple more
diodes may be appropriate.