wiring high power leds

Printed From: the12volt.com
Forum Name: Lights, Neon, LEDs, HIDs
Forum Discription: Under Car Lighting, Strobe Lights, Fog Lights, Headlights, HIDs, DRL, Tail Lights, Brake Lights, Dashboard Lights, WigWag, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=133562
Printed Date: May 21, 2024 at 2:27 AM

Topic: wiring high power leds

Posted By: raverx3m
Subject: wiring high power leds
Date Posted: February 10, 2013 at 12:43 AM

i bought some LEDs to test and trying to figure out the best way to wire them up.

20watt led white 13-15volts 1200ma

10 watt led white11-12volt 100ma

10 watt led yellow5-6volts cant remember amps

and i mistakenly bought 6 step up voltage converters on ebay thinking they can also lower voltage.( the auction was chinese crap poorly translated to engrish...)

they are going in thecar and i want to make sure they stay within their required voltage.

what do i need to use to make them work?

my electrical skills are bit rusty.

since the car is 12-14.6 volts its slightly out of range for both 10 and 20 watt leds

and the yellow led has 1 volt range so i dont even know how to wire it up..

those voltage regulators on ebay my friend bought a set and wired up a pair of 5 watt leds and it seems to work but im not sure if hes just getting lucky or they actually automatically control output even with variable 12-14 volt input.

i just dont want them to dim when the engine is off.

Replies:

Posted By: oldspark
Date Posted: February 10, 2013 at 5:24 AM

Excluding dimming issues:
12V strings can just be paralleled across 12V.
Two 6V strings in series across 12V.
No (single) LED is 1V. They range from ~1.7V to ~4V.

To have no dimming they need a constant voltage source or current limiting to the lowest current - eg, a 12V or 24V converter etc for the 12V strings; a current limiter for single 6V strings (eg, 20mA).

Posted By: raverx3m
Date Posted: February 13, 2013 at 10:34 PM

actually heres updated specs from their webpage

10W Yellow: 300-400LM 7.0-7.5V 1400mA

10W Warm White: 500-600LM 10-12V 1A

but for 20 watt it says 13-15 volts on the package

and 16-20 volt on the webpage

Posted By: oldspark
Date Posted: February 14, 2013 at 1:35 AM

Actually LEDs are current devices and high-power LEDs are usually supplied by constant current drivers.

Maybe the 20W packages have their own drivers but I suspect the 10W units need their own 1.4A & 1A drivers respectively.
I suggest you look up the datasheets for each LED to see what is recommended.
And note that it is one driver per string, not 2.8A for 2 strings etc - unless their datasheets say otherwise. (It's the same for low-power LEDs - it should be one resistor per string.)

I'm unsure of the effects of variable undercurrents - maybe high-power LEDs have thermal (change) considerations and hence you cannot series the 7-7.5V 1.4A LEDs (unless the constant current driver is an SMPS that can step up the required (voltage &) current, or you use a dc-dc converter to fed several LEDs in a (or several) string(s) each string with its own current driver or limiter. Current limiters are easy to build - 2 transistors & 2 resistors or an LM317 regulator.) But they are dimmable so an "average" under-current seems ok.