LED tail strobe

You can find examples on how to power the LEDs on the manufacturer web
site.

Having said that...

What is typically done is the LEDs are just put in series with a
current limiting resistor. This forms a circuit akin to a kind of
voltage regulator called a "zener regulator". LEDs have a fixed
forward voltage for the recommended drive current, say for example its
2.8 volts for a green LED. Divide the power supply (e.g. 12V) by the
forward voltage of the LEDs and drop any fraction (12/2.8=4.3 make
that 4 even) Put those in series with a current limiting resistor that
will drop the fraction (.3V). So lets say the recommended current for
the LED is 20mA. Ohms law is R=E/I, so that gives you a resistor
value of .3V/.02A=15 ohms. Check power to make sure it won't over
heat (P=IV) so thats .3V*.02A=.006W so a typicial 1/4 watt resistor is
fine. You must of course have some kind of resistor in series to limit
the current. If you math works out that you need no resistor, put one
less LED in series and then recalculate the limiting resistor. Put
the LEDs and resistor in series (in any sequence) observing the proper
polarity of the LEDS. If you hook up your entire string backwards, no
harm will be done, but if you happen to solder one LED backwards, it
will likely be toasted on power up.

Need more than 4 LEDS? Replicate this circuit in parallel as many
times as you need to get the luminous flux you need.

Of course the numbers (Vf, If) used here are for the older style
single chip LEDS. The parts that are getting everybody excited these
days are the multi-chip variety whose forward voltage and current will
vary alot from my example.

"Dean Head" wrote in message .. .
Jeff,
Would you consider sharing your design for the driver electonics?
Dean
Cozy MK4
BKV FL

"Jeff Peterson" wrote in message
om...
I am building an LED tail light for my Lancair 360. It uses 6 ea 5
watt luxeon LEDs. I can strobe 1 amp through each of these which
should give enough light to satisfy the FAA regs. Runs surprisingly
cool. I have posted photos he

http://w1.lancair.net/pix/album01\

Its not quite finished, but I thought you might like to see my
progress.

cheers,

Jeff
N273CK stilll building.

ps thanks to Eric Jones for his posts on the Lancair Mail List, his
web pages on the subject and many emails and phone calls.