Eltronics help needed

[Andy A]

To put lower voltage LED's into the 12 volt power of me car, what resistor will I need, thanks

 

[Daz]

I guess it depends on what voltage the LED's are?

Best way, get 12v LED's

 

[sn00p]

Here's the famous pyramid....

V
I R

V = IR
I = V/R
R = V/I

You need to use the bottom equation. Your LED will have a current rating, most are around 20ma, but will depend on brightness & colour.

R = 12/0.02 = 600 Ohms

And the other thing to make note of:

P = VI (Power in watts)

P = 12*0.02 = 0.24W

So you need your resistor to be at least 1/4 of a watt rated.

Just replace 0.02 (20ma) with the rating of your led in the above equations and you should be good to go.

 

[Andy A]

OK, probably a silly question, but can I find the current rating with a multimeter?

 

[sn00p]

OK, probably a silly question, but can I find the current rating with a multimeter?

No. It'll have been specified either in the catalogue or on the packaging (if you bought from tandy or such like).

 

[Andy A]

Rite, I used this earlier http://led.linear1.org/1led.wiz

And I've brought all of the LED's from Rapid, should be getting them tomorrow, then let the conversion begin :evil:

 

[Dink]

i've used this before to find out what resistors to use

yeah it's all about current when it comes to led's

 

[Andy A]

too complicated, lol

I like the simplicity of the other one, just gotta hope its right and all my LED's don't blow

 

[Dink]

what led's did you buy from rapid?