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door trigger leds stay on but dim

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=96299
Printed Date: May 12, 2024 at 1:49 AM


Topic: door trigger leds stay on but dim

Posted By: maxtomori
Subject: door trigger leds stay on but dim
Date Posted: August 10, 2007 at 4:43 PM

Hi all, this place looks really promising so I registered.

01 nissan maxima.
I bought super-white LEDs for the door courtesy lamp:

TYP voltage = 3.4Vf
MAX voltage = 4Vf
Current = 30mAf
Reverse current (VR=5V)

I used a 270§Ù plus 22§Ù in series for the LED. I tested it, works fine.

Door wire harness:
RED / green stripe (constant 12V)
RED / white stripe
I put my voltmeter to the RED / green and I get ~12V when the door is closed and open. RED / white is 0 both ways, of course.

Here's the enigma : I close the door and the LED doesn't shut all the way off. It's dim but power is still running through this thing. Incandescant had no probs, I don't want to drain my battery. ANY insight appreciated.
--------------

my homemade setup: cut PC board to fit in light fixture. Soldered 22 gauge wires to +/- terminals. pos.wire goes to series of resistors > pos. lead of LED. neg.wire goes to neg. lead of LED.



Replies:

Posted By: hotmilk400
Date Posted: August 12, 2007 at 12:12 AM
if there was a Incandescant bulb there before.. then dont worrie, the same voltage was running though that bulb too.  ALOT of power is needed to run a  Incandescant bulb...  a led can basicly run itself.. dont worrie.. and injoy the cool glow effect 24 / 7

normally for a LED u would use a 470 ohm resister.  your resister is to low, and may burn out your LED.  now what is your problem.  they are on ALL the time right?  if they are the same brightness all the time, nomatter if your car is on or off, then your led went bad, and is on a constant power line. its dull becuase you blow it.   if its bight and normal when it should be, and dull when it should be out, then its just picking up stary voltage somewhere. it might just be voltage that is running though your line all the time, or just voltage that is stored up in something like your radio or amp.    you can basicly run a white led like this by holding it in your hands and dragging your feet on the carpet.   also, it wont drain your battery that quickly.  led's use almost no power.  i have a Blue 5mm LED on in my car that glowes 24/7 .. i left my car sit for 2 months, with this blue led glowing full power, and it didnt even effect my battery when i tried to start it.  and led like that uses .019 amps .. you say its dull.. so it running at about .01 amps or less. it can run a very long time..  dont worrie about it.. like i said before, that Incandescant bulb was getting that same power, but couldnt convert it to light becuase it wasnt enough power to see it




Posted By: maxtomori
Date Posted: August 12, 2007 at 10:46 PM
hotmilk400,

Oh, thanks so much for the reply. I did calculations for my LED resistor based on 12V, 3.4forwardvoltage, .03amps. My voltmeter actually registers 12.5-12.6v so I may be cutting it close, but why 470ohms? That means I should be running 17-18V power.

Still, thanks for the reassurance and the interesting lesson on static electricity. Also for the example of your blue LED.




Posted By: hotmilk400
Date Posted: August 13, 2007 at 5:46 PM

12.6 volts
-3.3 volts
=9.3 volts

9.3 volts
.02 amps

465  ohms

---
Most people consider LED's to run at .02 amps (2mA) .. u figured it at 3mA .
i know all the LED's i bought aways say 2mA but yours may be differnt. 

this is the normal standard used by everyone for a 12 volt system
Use 390 Ohm resistors for a special project or LED configuration.
Use 470 Ohm resistors with Blue, Green, White, U.V., Aqua & Pink LEDs.
Use 560 Ohm resistors with Red, Yellow & Orange LEDs.

it also doesnt hurt to have a resistor that is alittle higher then what it shoudl be.  if there is a surge or the voltage changes alittle, it wont wreck your LED light any faster. 





Posted By: maxtomori
Date Posted: August 13, 2007 at 8:05 PM
Hi hotmilk400,

I think you mean .02A (20mA), but I get your picture. Yeah, keeping in mind a buffer for voltage spikes is a good idea. I wonder what the luminoscity difference is per 100 ohms... or even noticeable at 50ohms difference?? Somehow I doubt any difference.





Posted By: hotmilk400
Date Posted: August 14, 2007 at 12:25 AM
i doubt there is much of a differnts, and also LED's can handle alittel higher voltage (like 3.3 - 3.6 volts) so i guess thats your buffer voltage.  normally i dont think this much, just add a 470 ohm resistor to each LED.   im gald to give u some advice.  i hope it all works out for you





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