dimming 3 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=103656
Printed Date: April 28, 2024 at 1:09 AM
Topic: dimming 3 leds
Posted By: midwestoffroad
Subject: dimming 3 leds
Date Posted: April 02, 2008 at 7:29 PM
I have a pillar gauge in my truck. and each gauge has a white LED. i currently have them all running the the factory dimmer knob but when i get them to the desired brightrness the factory gauges are dark. my question is can i dim all 3 in 1 shot or do i need a resistor on each lead.. or would a POT be better. i tried a 0-25 ohm dial resistor one and it didn't do anything that was at the suggestion of the radio shack guy.. otherwise he has 1000k POT,s
Replies:
Posted By: midwestoffroad
Date Posted: April 02, 2008 at 7:54 PM
if it isnt obvious i have no idea what i am doing ot talking about.. each gauge came setup with a led.. i just want to dim them.. any idea on a starting point with a resistor. . one chart i found shows the resistor on the - side . i tried the reostat on the + ..
Posted By: KPierson
Date Posted: April 02, 2008 at 8:14 PM
It doesn't matter which side you put the resistor on, as it will limit current either way. 25 ohms is really, really low. I would look for a pot in the 0-25K range. ------------- Kevin Pierson
Posted By: midwestoffroad
Date Posted: April 02, 2008 at 9:34 PM
thank you. i did find in our maintanace department a 91 and 100 ohm resistor i may try to see way happens.
Posted By: KPierson
Date Posted: April 02, 2008 at 9:51 PM
That 100 ohm resistor will limit current to 120mA, roughly 80 times more current the the LED can handle anyway - that 100 ohm resistor isn't going to help at all, it is too small. ------------- Kevin Pierson
Posted By: dudehitt
Date Posted: April 02, 2008 at 9:52 PM
I had a similar situation with some switches I swapped LED's in to match my dash (which were also swapped from factory). I finally got noticeable results with a 5k resistor and left if at that. They're still a little brighter than the others, but not by much. I think the 25k pot. is a great idea.
Posted By: midwestoffroad
Date Posted: April 02, 2008 at 9:57 PM
OK i will try Radio shack again i think all he had was a 1k pot maybe i am wrong
Posted By: midwestoffroad
Date Posted: April 03, 2008 at 10:55 AM
After I came home last night I tried some of the resistors from work , no idea on there size it is a blue resistor with 5 bands
Violet-Black Red Brown and sliver it ohmed to 409.5 and worked perfectly.. so i have no idea if it will work or for how long.
The color bands confuse me even after looking at the Resistor page
Posted By: i am an idiot
Date Posted: April 03, 2008 at 6:51 PM
It will work pretty much forever.
Posted By: midwestoffroad
Date Posted: April 03, 2008 at 9:02 PM
That would be nice.
Can anyone decipher this resistor
orange,purple,yellow,black,brown
Posted By: i am an idiot
Date Posted: April 03, 2008 at 9:08 PM
Sounds like a pretty one with all of those colors.
374 Ohms with a 1% tolerance
Posted By: midwestoffroad
Date Posted: April 03, 2008 at 11:50 PM
Thank you thats what i thought. I have a multimeter but not real fluent with it.
My maintaince guy handed me a handful of resistors that he had laying around and of course there all 5 band so i wasn't sure if i had my meter on the right range. But the one i put in was 400 ohm so now and it is pretty good so i can either try a few other resistors in 50 or so increments to adjsut brightness or find a pot that will work.. So now i can School the radio shack guy
Thanks again
Posted By: i am an idiot
Date Posted: April 04, 2008 at 2:30 AM
You said SCHOOL the radioshack guy. That is funny. I have frequented a many a radio shack stores, had to go to 2 of them just yesterday. In probably 1000 visits I found only one radioshack guy that even kind of had a clue. Her name was Michelle.
Posted By: midwestoffroad
Date Posted: April 04, 2008 at 12:23 PM
Well i picked up a few resistors today they didn't have a POT that would work and only had 5 packs of resistors so i picked up a 5pk of 100 and 150 to try in series.. This guy (different Radio shack) knew STUFF and what I was talking about so i let him know about this site..
thanks again for the help..
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