LED question

[lostforawhile]

Ok I got a bunch of those clear LED white lamps for christmas lamps for pennies a pack, 4 per pack, I'm trying to calculate the current requirements for a resistor, I divided the voltage first at 120 volts divided by 25 lamps, got 4.8 volts I believe these LED's are 1 watt each, that would give me a current of .0083 if i divide one watt by 120 volts . i'm getting at least a 1/8 watt 1000k ohm resistor required, can someone double check my math? these look to be excellent for installing in the switches etc, to replace those tiny factory bulbs, just with a resistor wired in the wire going to each switch.

[Bass Man]

120volt?? Factory bulbs??? Where are these going?

[lostforawhile]

120volt?? Factory bulbs??? Where are these going?

the light strings are 120 volts, there are 25 LED's in series, with a rectifier in the wall plug to change the voltage to dc, they are regular high brightness LED's but I don't know the current requirements of them. they are about the same size as the little bulbs in the switches, HVAC lights,etc. you just solder them in place instead of the little twist in sockets, and solder a resistor in line with the illumination wire feeding the factory bulb, with the correct current they will never burn out again.

[Civic Accord Honda]

use a multimeter on the bulbs socket with the string of lights plugged in?

[lostforawhile]

use a multimeter on the bulbs socket with the string of lights plugged in?

I don't have an entire string, i just know these are for a 25 light string, they were 15 cents for a pack of four, i got a bunch, they are white LEDS these things are usually pretty expensive

[labeledsk8r]

i have a set of the same lights in purple (picked them up from hallowen on clearence for mad cheep) they way they look there still your standard 3 volt led so if your takeing out the rectifier you should be fine to do the normal math of every so many lights

[60408CC]

every intrested in the math on the light volts and everything keep it posted cuz i have a idea that i would need to know to make them for our cars

[accordion89]

Look up circuitmaker student edition, its free
I used it to double check my voltage drops when I was taking electronics courses

[LX-incredible]

You're not factoring in the resistor at the beginning of the strand. More than likely it's a 2.2K for 25 whites. 4.8v will kill most LEDs in a matter of seconds...

Check this site out:

http://www.ciphersbyritter.com/RADELECT/LITES/LEDLITES.HTM



Measured Voltages

LED forward voltages exhibit substantial variation, even for the exact same color in the exact same string. Here are few actual values for 3 bulbs of each color from these strings, measured at 20.1mA DC:

RED: 1.95V, 1.96V, 2.10V,an average of 2.00V
ORANGE: 1.95V, 2.13V, 1.96V, an average of 2.01V
YELLOW: 2.06V, 2.18V, 2.09V, an average of 2.11V
GREEN: 3.11V, 3.14V, 3.15V, an average of 3.13V
BLUE: 3.28V, 3.16V, 3.24V, an average of 3.23V
WHITE: 3.26V, 3.32V, 3.40V, an average of 3.33V

Led array calculator:

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

Should be good with a 470 ohm resistor for a single bulb, 330 for 2 in series, 150 for 3.

[firefighterwhite89]

Check This Site Out--->oznium .com

That's A General Link. You Can Get 12 Volt Pre-Wired LEDs For $1.19 Each, Already With A Correct Resistor Built In To Handle 12V, And You Can Get Just LED's W/O Resistors 2-4V Compatible, In 9 Colors, Including UV For Florescent Gauge Glow Effects, For Just $.29 Ea.

I Got 18 Pre-Wired 12V Pink Lights And Installed Them As Gauge Lighting, Replacing The Stock Bulbs, And Created New Lighting For My Ashtray, Radiohead, Front Flooring Pass./Driver Side, And Trunk Lighting When It's Opened. Worked Beautifully. Sister Has My Camera, But, I'll Take Pics And Post Them Soon. $25 For 18 12V Pre-Wired LED Lights Is Cheap. Especially Since It Arrives Next Day Via USPS In The Mail.