Led Question

[jabartram]

Recieved my led's from Glowbot, thanks dude! My question is, do you have to have 1 resistor per led? or can 1 resistor handle a few led's and if so how many?

[FormulaNERD]

you can run them in series of 4 with no resistor. (if they're 3v LEDS)

there was a good post on this a while back, i'll see if i can find it.

[bigd6983]

the provided resistors are for one led, like formula said you can put 4 in series if there 3 volt and you wont need a resistor.........you can put two in series and use a different resistor something like 200 ohms or around there.......it just depends on how you wanna hook them up.......

[FormulaNERD]

yea, also depends on how bright you want them, too much resistance and they'll be more dim.

[bigd6983]

the more resistance the less bright yes.......but also the longer they will last......like i said just depends on what you want.....

[gxryan]

Vin = 12Volts or whatever voltage ur car accually runs at
Va(voltage accross LED 1.5V to 3V)

Find Im(max current of LED's) and there Va(Max voltage rating)

Rf(resistor value) = (Vin - Va)/Im

that will give u the minimum value of the resistor any larger willl work just fine.

SO FOR EXAMPLE:

they are 3 volt leds and the max current is like 1ma and ur car runs exactly at 12 volts

Rf(resistor value) = (12 - 3)/1ma
Rf = 9k ohm resistor for each LED


SCORE MY DIPLOMA IN COMPUTER ENGINEERING TECHNOLOGY WAS NOT WASTED

[AnderbrA]

^^^aplaude

[bigd6983]

nah theres something wrong with what equation your using........go hook a 3 volt led up with a 9k resistor and let me know how bright it is.......you can use ohms law........you need a 9 volt drop across that resistor minimum(a 9k ohm resistor is way too much).......degree in electronic engineering too.........so i know a few things as well........

[ImSoBored]

http://www.metku.net/index.html?sect=view&...dcalc/index_eng (http://www.metku.net/index.html?sect=view&n=1&path=mods/ledcalc/index_eng)

[gxryan]

lol

thats the math behind it.
if u wanna find out anther way find for exact maximum just take a 12 volt power supply and a 10k potentiometer and that led and hook them up and adjust the pot until that LED either blows up or is as bright as u could imagin it would go.

Or you could use that website
which i just put in my example values and it worked out exactly the same.
:thumbsup: