DIY LED clock light (w/ pics)

how long did it last with the 350? ive been driving around tonight and mine is still good haha...it might also have something to do with gauge dimming. my gauges are almost all the way dark. im curious how much the voltage varies when you turn the potentiometer under the tach...hmm...

when its mounted 90 degrees it has the huge hot spot. idk maybe shaving the led would help a bit...but i dont want the clock to be super bright. my head unit takes that job well ill snap a pic of it tomorrow night.

edit: theres a light bulb inside the hazard switch? lol i didnt know until tonight. that will be getting a red led once i figure out which resistor to use

http://led.linear1.org/1led.wiz

or

http://www.luxeonstar.com/resistor-calculator.php

rant 1:

the max voltage on most 5mm leds is 3.8v and the current is typically 20ma
car batteries are rated at 12v but actually put out closer to 12.6v, which means 8.8v (12.6v - 3.8v) needs to be absorbed by your load resistor

voltage = current * resistance
so, voltage/current = resistance
8.8v / .02a = 440 ohms

so, for simplicity sake, just use 470 ohms.

also, if you're using a 350ohm resistor your putting 5.6v on your led and you are at risk of letting the magic smoke out. if you keep lowering the resistance and your voltmeter doesn't show an increase in voltage across the led, it's a good sign to stop.

rant 2:

running your led at (and above) it's max power will make it visibly brighter, but it will cost you a lot of lifespan, and imho it's better to run it at a slightly lower voltage and have it last forever. my whole reason for swapping to leds is so that i only have to change it once. if you want it brighter buy a brighter led. (and go crazy waiting for them to ship)

fun fact:

if you run a green led straight off of 12v it will glow red a few seconds before it burns out. i use this trick to impress the ladies and, consequently, have no girlfriend.

now it's off to continue my allnighter studying for cal II...

ryan s said:

overall, for less than $6 im pretty pleased with the outcome. my clock works now

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lol my clock hasnt worked since i bought the car, when people were like clock light this clock light that, i was like WE HAVE A CLOCK LIGHT?!!?

you should do the led polarizing it looks so much better and easier to read

Sinful said:

you should do the led polarizing it looks so much better and easier to read

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elaborate, please.

thejameshimself said:

elaborate, please.

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Excerpt from my "Member's Ride" post:


Un-lit clock:


lit clock:


Lit odometer (Yes, there's a major hot spot, and at this moment in time I couldn't care less):


And when I used the flash the first time, it made my odometer look like it had no led in it whatsoever... weird... Anyway, this is what it looks like minus the blue and with polarizing film:

if it burns up...oooooo...ive owned my car for like a year and a half and this is the first time the clock has ever lit up. the hazard switch has never lit up (i never even knew there was a bulb in there til last night lol). im just experimenting...why rant? when i get around to other things like the dome light, then i will take my time. but the clock only took a few minutes

haha my clock light doesnt work either since i bought the car in 2001 How sad. I dont know how to fix and im to lazy to do mines.

Jeffro said:

Excerpt from my "Member's Ride" post:


Un-lit clock:

And when I used the flash the first time, it made my odometer look like it had no led in it whatsoever... weird... Anyway, this is what it looks like minus the blue and with polarizing film:

Click to expand...

cool, where can you pick this stuff up at?