Help with LED DRL set up - complete with pics

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Originally Posted by oil pan 4

500+ ohms is way too much.
Normally when resistor droping voltage to run LEDs off 12v power you are looking for something well under 100 ohms.
What is your target volt and amp draw to feed the LEDs?
I can figure out the resistors you need.

My target voltage is 12.4 as I tested them for a while at that voltage and no problems. My target current is 131mA. That's what 1 of them draws when connected to a fully charged 12v battery outside of the car, same one I tested on and none of them burnt out.

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Originally Posted by 3dplane

Start parallelling those 560 ohm resistors. Twist the legs together on each end of two and you should end up with a 280 ohm 1/2 watt resistor.

Do four to get a 140 ohm 1 watt etc.

Or just get a pack that has lower value resistors so you don't have to parallel that many.

I'm guessing you will only need a few ohms to protect them from the slight over voltage in your situation!

Trial and error but keep checking current draw for different scenarios (voltage and resistors) and you will get a good picture of what they are doing!

Barna

I only had 8, got it down to 70 ohm and it's an acceptable brightness, this caused it to drop down to 7.8volts measured after the resistors, I can still notice that it's less bright than at 12v so I think I'll try and pick up some 10, 15 and 20 tomorrow.

Thank you everyone for all the help, my university education is actually starting to come back to me.

It might not even need a resistor on this new car since Kia has what they call a smart alternator and it only runs around 14 volts most of the time, 14.2 under load. It may have been the high voltage only from the high end of the revs in the older cars that killed it.

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4.3ohm resistors drop it from 12.16v to 11.27v so I'll try the install with this one. I can't notice any drop in brightness out of the leds.

I left it wired for an hour and it's still cool to the touch.

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Thanks all for the help, here's the finished product









I wired them up on a 10amp relay, pulled power from a 15amp fuse that gets power while in the 1 and 2 key position and stays on while the engine is starting as well so that I won't be flashing my lights when I turn the car on after sitting for a light. I also want to figure out how to wire it up so it also comes on with the headlights so that they flash when I use the keyless entry and they stay on for 30sec after the car is locked.