Thanks, DIWdiver -
You are correct, the schematic in the instructable is downlevel for sure. I have waited to change it only because I had to work through the issue of how to handle the ground bounce caused by the long wire length between the controller (mounted in the cockpit) and the wingtip mounted strobes. Along the way, in addition to adding the protection diodes, I changed to a XM-L2 LED (because the CXA LED has a 9.6V turn on voltage), and also moved to a IRL-2505 mosfet... which I surely should have used right from the start. I had a bin full of the old IRF-1501s to use up... that's my only excuse.
Boy do I wish there was a step-function improvement in the LM338 regulator the way there was for the mosfet!
Your point regarding moving to a series/parallel setup is exactly what I was hoping to learn about by starting this post. THANK YOU! But here's my question...
Here's the relevant chart from the Cree datasheet:
The specific LED I'm using is Cree's PN XMLBWT-02-0000-0000T5051, which according to the datasheet has an output of 260 lm @ 700ma and 85C. So, with 5A total current, assuming even current distribution, the landing light should be putting out about 260*7 or 1820 lm total.
Using the chart above, if I run 2.5 amps by using 6 LEDs in two strings of three, the math works out to approx. 2.8*260*6 = 4368 lm... well over 2x!
Outside of the potential electrical issues (such as the increase in forward voltage), the issue is going to be LED heat... There is very little I can do to dissapate the heat in the wingtip strobes. The only knob I've got to twist would be the duty cycle of the strobe.
So, here's the question... as I've cranked down the pulse width of the flash, I've not visually been able to see much difference. Right now, I've got it set to a six flash sequence with 16 ms flashes. How short of a flash can I use? What's the relationship between flash length and visibility?
THANKS AGAIN! That's a GREAT idea!!!
Dave