Powering 20 CREE XP-E's

[jungleb0y]

Wondering if anyone has any experience powering an array of 20 LED's at 700ma 3.4v in an automotive application?

The circuit will have to be small enough to fit on a board about 1"x3"

Not sure if I want to go the resistor route as I have read there not as reliable? But then again mom told me to not always trust what I read.

Any thoughts? 

[justDIY]

Check out the series-parallel wizard:

http://led.linear1.org/led.wiz?VS=14&VF=3.4&ID=700&N=20

The suggested design should easily fit in your space requirement, but such a small space is unlikely to deal well with the heat involved with these power levels.

[jungleb0y]

Think I'm going to be using the LM3429 to drive the 14 strobe LED's and use a 7X2 array.

Each side is going to have 2 circuit's in them one for NAV (green or red facing fwd) and one for POS (white facing aft) the center and center of fwd and aft will also have 2 strobe led's sitting in the array to get the 180 deg viewable angles for strobe. Going to be using the same cirucuit to power the white POS as is powering the red and green NAV.. Found some matching LED's that are only off .04fv at 700mA dont think it should be noticable.

I havent decided on the sequence of the flashes but they will be flashed max twice a second and pause for maybe 2 seconds which I'll controll and sync via my pic.

RR-------------WW <--R&W are within the same circuit
SSSSSSSSSSSSSS <-- seperate circuit
RR-------------WW
|
sync
|
GG-------------WW <--G&W are within the same circuit
SSSSSSSSSSSSSS <-- seperate circuit
GG-------------WW

[jungleb0y]

One more thing.. On the DPAK diodes never used one but looks nice and want to use it in my circuit..  Do you bridge both anodes?

[cadstarsucks]

Check out the series-parallel wizard:

http://led.linear1.org/led.wiz?VS=14&VF=3.4&ID=700&N=20

The suggested design should easily fit in your space requirement, but such a small space is unlikely to deal well with the heat involved with these power levels.

No, no, NO!!!  http://forums.linear1.org/index.php/topic,1617.0.html

The car power rail is a noisy and dangerous place for expensive LEDs in that circuit ... and VERY inconsistent, ranging from 6V cold cranking and 10V at low battery to 14V normal charging and 50V surges with 90V spikes when the starter stops.
 
Dan