newb looking to build automotive led driver

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Thread Starter


Joined Jan 22, 2014
Hello everyone!
Been reading for a few weeks now, lots of great info here! Love the worksheets and videos!!
A little background, im 31 yrs old and have no circuitry experience at all, but 8 yrs in HVAC experience. in that time ive learned how to read (hvac equipment)schematics - pressure switch, and rollout switches etc.. not the usual circuit symbols. But that has slightly changed..

I decided to try and 'build' a 12 xml led light bar for the cost of one. I was told on candlepowerforums(many times) i should use a driver, but insisted that using the $4 in resistors it was worth a shot..
Scenario: lightbar is attached to a quad for plowing snow, with a winch to raise/ lower plow. Running voltage is 14.4V idle or revved, drops to 12.8V under winch load. I 'think' it has a 15A alternator..
I have 3 parallel strings 4 xml's in series, with a .5ohm 10w resistor in each series. Ill add one very patient member from CPF insisted i install a TVS to save leds from winch load dump.
Worked fine while bar was in warm temps, but outside in 0' weather, the leds barley pull 1.8A when i where i want 2.7ish..

So, the learning curve of playing with Fv of leds, resistance and amperage piqued my interest. i have since researched, studied and built a single fm transmitter for my work van(cd player broke) and works great!
you can see the complexity is pretty low, but i still made a trial run 'supergluing' single sided clad board to the respective places to connect componets.
Ive since found the laser toner transfer method, etched with muaritic acid/ hydrogen peroxide mixture and have had great results with thru-hole components. Many friends are happy lol. Since then ive aquired an old toaster oven,(id like to modify) and would like to try my luck at surface mount components.

So, on the the point.. i wanna ditch the resistors, and build a 3A boost driver for 12 xmls in series. ill even build 2 drivers if 120 watts is to much for a single driver.(even at 95% itll be 6-7W to dissipate)

Heres my problem. I dont know how to "construct" such driver. I can follow a schematic 'sorta' like a road map, but no idea how i can manipulate one..

Ive googled 3A led driver and found many images, but some displays wont drive 3A, cant find parts, or dont display component specs.
No component specs listed(honestly i like this as its 10A output, and voltage is in range.)
Ex 2:
PERFECT except input voltage

Ive also found things like the LT3477, but all schematics only show 1A draw per string..

I was hoping someone here could point me to a simple 14v auto 3A driver schematic, with parts that are easily obtainable from digikey or mouser etc..

Thanks for your time!!


Joined Mar 24, 2008
The owners of All About Circuits has elected not to host discussions of automotive electrical system modifications/enhancements due to safety concerns, the potential of legal ramifications and the possible circumvention of vehicle regulations at the state and federal level.

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