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Anthroplast 6th June 2002 22:42

Weerstand voor leds

Heb al veel mensen gehoord die niet weten welke weerstand bij welke led hoort.

de formule is echter simpel :


dus: Weerstand = ( inputvoltage - doorlaatvoltage van de led) / stroomsterkte

inputvoltage; waarschijnlijk 12v of 5v
doorlaatvoltage van de led; hangt af van het soort ledje. Rode leds hebben laten minder door, blauwe laten meer door... neem 2,5 als universeel getal als je het niet weet.
Stroomsterkte; meeste leds verdragen 0,02 Ampère max.
sommige high bright leds tot 0,05 Ampère..
ook hier kun je 0,02 ampère als universeel getal nemen.

U kan dan berekenen bijvoorbeeld:

Een standard ledje op 12 volt aansluiten :


U = 12 v
Ud=2,5 v
I=0,02 A
R = (12-2,5)/0,02
R = 475 Ohm

De dichtstbij gelegen waarde is 470 Ohm

hope this clears things up :wtf:

Greetz Anthro

jmke 6th June 2002 22:48

any chance in a translated version for our non-dutch speaking folk?

great post :super:
quality over quantity!

Anthroplast 6th June 2002 22:59

oke morgen komt er een vertalingske, nu slapen... Morgen exaam Frans :puke:

TerAngreal 6th June 2002 23:05

seen there are still so many people not knowing which resistance should be used for which LED ...

the formula is rather simple actually:




Resistance = (Mains Voltage - LED Voltage) / LED ampère
  • Mains Voltage = most likely +5V or +12V
  • LED Voltage = depends on the led itself. Red LED's pass on less, blue LED's pass on more voltage ... if you're not quite sure, take 2,5 as a universal value
  • LED Ampère = most LED's can only take 0,02A max !
    (exception: some high bright LED's can take up to 0,05A)
    here 0,02A might be used as universal value

so - example given:


U = +12V
Ud = +2,5V
I = 0,02A

==> R = (12-2,5)/0,02 = 475 Ohm

the closest value is 470 Ohm in this case ...

Hope this clears things up :wtf:


all credits go to Anthroplast :ws:

(fair enough ? had nothing to do for about 3 minutes ...)

Anthroplast 7th June 2002 10:33

nice work :king:

TeuS 8th June 2002 15:11

can you give wich values resistors have?
between 50 and 1000 ohm or something...

DUR0N 8th June 2002 16:47


Originally posted by TeuS
can you give wich values resistors have?
between 50 and 1000 ohm or something...

hèhè, those colored strips on the resistor indicate it's resistance...

google tells me this:

and: handy calculator:

[Bonbon] 9th June 2002 22:31

MEEEP error

Ter·Angreal posted in the translation:


and this should be

as in Anthroplast's dutch post
at least someone is awake @ 23h40

TerAngreal 10th June 2002 12:02

point taken & formula corrected

tnx [Bonbon] :)

you try and translate that text after spending a couple of hours learning physics and chemistry ... eat me :p

TeuS 10th June 2002 15:58

I know, duron

my blue leds need 435 ohm resistors
nearest value: 470


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