Resistor size needed

Thread Starter

star71981

Joined Sep 30, 2016
1
I'm trying to add a resistor to the positive parking light wire on a led 1157. 12volt car. I want to dim the parking light bulb so when I use the brake or turn signal I can notice the difference. Right now the brightness is about the same between the parking light and brake light on. I don't know what size resistor. I was going to cut the wire and add the resistor. I've tried a 50w 6 ohm resistor used for hyper flash and it changed it very little. Thank you. I was thinking a 400ohm. But what wattage 1?
 

mcgyvr

Joined Oct 15, 2009
5,394
Watts = V^2/R
Where V = voltage and R = resistance
and triple the calculated value or more for a safety factor/to keep the resistor from running too hot..
 

panic mode

Joined Oct 10, 2011
1,845
that is LED bulb drawing some 0.18A

no wonder 6 ohm didn't do much. 400 Ohm will turn it off completely.

you may want to try to cut that down by maybe 50%.

12V / 0.18A = 67 Ohm (this is bulb alone)

so something in order of 30-60 Ohm may do depending how much of a dimming you want to see. 5W resistor is ok
 
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