bongo Posted March 7, 2012 Share Posted March 7, 2012 sorry if this is stupidly obvious but....... swapped my grren leds in my heated screen switch (3mm 12v prewired blue led) now as ive seen 99 percent of the time they are too bright for my liking,how do i reduce the brightness? is it as easy as fitting 5v leds? thanks. Link to comment Share on other sites More sharing options...
Stu Posted March 7, 2012 Share Posted March 7, 2012 Add a suitable resistor inline to give you the brightness you want.. you may want to play around with a potentiometer to get an idea of the resistance you need. Putting say a 10k ohm pot inline (middle pin and one of the outers) inline WITH THE LED ONLY would be a start. Link to comment Share on other sites More sharing options...
bongo Posted March 7, 2012 Author Share Posted March 7, 2012 the resistor controls the current yeah? so as you can buy prewired 3v,5v leds,these are fitted with higher resistance resistor? so would a 5v prewired led be roughly half the brightness of a12v prewired led? and would a 5v prewired led be ok to use incar? thanks. Link to comment Share on other sites More sharing options...
Stu Posted March 7, 2012 Share Posted March 7, 2012 No, a 5v LED would most likely pop if you put it on a 12-14v power source. A '5v' LED would have a lower value resistor than a 12v one. You need to increase the resistance to reduce the brightness. Yes, the resistor limits the current that flows through the diode (LED). Link to comment Share on other sites More sharing options...
bongo Posted March 7, 2012 Author Share Posted March 7, 2012 ok thanks stu,i'll order seperate resistors and led. Link to comment Share on other sites More sharing options...
Stu Posted March 7, 2012 Share Posted March 7, 2012 ok thanks stu,i'll order seperate resistors and led. What value resistors will you buy? Link to comment Share on other sites More sharing options...
bongo Posted March 7, 2012 Author Share Posted March 7, 2012 going to order some 1000mcd and see how bright they are.the resistor thats wired in is 7000mcd. Link to comment Share on other sites More sharing options...
bongo Posted March 7, 2012 Author Share Posted March 7, 2012 ive misunderstood and above is nonesense. this is the spec of what ive got. High Power 3mm LEDs - 7000mcd 12V DC Presoldered Resistor 20 mA 20 cm Wire Length High Intensity - Low Power 0.36W Simple to Use Long Life and Energy Saving how would i reduce the brightness by half? Link to comment Share on other sites More sharing options...
Stu Posted March 7, 2012 Share Posted March 7, 2012 By following my original guidance and wire up a potentiometer inline and measure the resistance when you get it to a brightness level you're happy with. Link to comment Share on other sites More sharing options...
bongo Posted March 7, 2012 Author Share Posted March 7, 2012 im sure ive got a spare tps down the garage,although i would have liked a straight answer,its good to learn Link to comment Share on other sites More sharing options...
Stu Posted March 8, 2012 Share Posted March 8, 2012 (edited) There is no straight answer. There is no magical value or formula which will give you 'half the brightness'. Twice the resistance won't give you half the brightness, every LED is different, you have to do the test. Edited March 8, 2012 by Stu Link to comment Share on other sites More sharing options...
bongo Posted March 8, 2012 Author Share Posted March 8, 2012 the beam angle has a lot to do with the brightness,so im going to get some 120 d flat heads and go from there. Link to comment Share on other sites More sharing options...
bongo Posted March 8, 2012 Author Share Posted March 8, 2012 also did a bit of experimenting with what i had.... sanded the top of led with file to diffuse the beam a little and give it a coat of black ink which has seemed to have reduced the brightness by roughly 50 percent. but i would like to do it tidy. Link to comment Share on other sites More sharing options...
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