LED help.

[klampykixx]

Hi guys, i had a bit of a look around but there is surprisingly little info about LED setup. most involving an LED controller and single led lights.

my question is this. I plan on using about 9/10 LEDs per headlight. yes, you read right. each side. so, how do i wire them?

i was thinking that since theyre 3v LEDs, if i run them in three groups of three, it will give me approx 9v power handling. but i was reading that its not the volts that hurts them its the amps?

so if i was to run the 9v setup on a 7.4v lipo would they burn out from the amps? or be ok coz the voltage is within range?

i dont want to go too deep with the details coz i wanna keep it somewhat secret until theyre produced as its not the sorta thing everyone does. but the other option i was considering was to run them all in parallel and use a single resistor to drop the battery down to 3v .

in saying this, i have a couple of SMD LED panels with 18segments on each one (and 5panels) would be perfect for a micro LED light bar type thing, but they run on 12v (car BA12d was what they were originally)

so that gives me a 3rd option. run 2x 2s lipos in parallel to get me 14.8 v which is perfect if not a little high for the SMD LEDs, and then resist it right down for the rest,

or

run all 18+ rear reds(maybe 6?) all in series without a resistor which would be 24v total handling running on 14.8-15v (dependant on charge state)



so whats the common opinion here? best way to illuminate my truck??

[Trubble]

Originally Posted by klampykixx

.....i have a couple of SMD LED panels.......... but they run on 12v.......... so that gives me a 3rd option. run 2x 2s lipos in parallel to get me 14.8 v

Nope. Running them in parallel will still only be 7.4v. Running them in series will get you up to 14.8v nominal, or around 16.8ish fully charged. Might be better off buying a purpose dedicated 3S (separate from the main pack), 11.1v nominal, 12.6ish fully charged. A LVC/LVA for that circuit would be a good idea, too.

Or, if you already have (2) 2S's and are bent on using them, hook them up in series and run a CC BEC Pro (20 amp) to drop it down to 12 volts. (I recommended the 20 amp version 'cause that's a LOT of lights!) If your main pack is 3S or higher, you wouldn't have to carry a separate battery for the lights, you could run it off the main pack. Just remember that when your truck stops (hopefully you've got your ESC's LVC set), those LEDs can still drain the battery down to dangerous levels.

Need to know more about the truck you plan on putting this stuff in, to know better how you'd be best in hooking it up.

[Olle P]

Originally Posted by klampykixx

... i was reading that its not the volts that hurts them its the amps?

Correct! That's why they have a current rating.

Originally Posted by klampykixx

... so if i was to run the 9v setup on a 7.4v lipo would they burn out from the amps? or be ok coz the voltage is within range?

They won't burn out. They'll barely even glow since they're not fed the ~2.9V (each) minimum requirement to make them let any current through.

Originally Posted by klampykixx

... the other option i was considering was to run them all in parallel and use a single resistor to drop the battery down to 3v.

That's probably also a bad idea, since the resistor will overheat and just reduce the efficiency.

What you should do is to arrange the LEDs (assuming they're all the same type) in serial pairs (give you a 6.0V drop). Then you can combine a few of those pairs in parallel with one proper resistor.
Assuming the LEDs have a nominal 30mA current rating and they're fed directly from the 2S LiPo (typical 8.0V in use) the resistor should be 2.0V/0.030A = 67ohm (and 60mW) for one serial pair. Divide the resistance value by the number of pairs mounted in parallel.

Originally Posted by klampykixx

... so that gives me a 3rd option. run 2x 2s lipos in parallel to get me 14.8 v which is perfect if not a little high for the SMD LEDs, and then resist it right down for the rest, ...

With 4S feed you can just have the LEDs mounted in arrays of 4 in series, with a 133ohm current limiter for 30mA.