LED/resistor question

[Crazy Jayhawk]

I recently bought some white LEDs from www.eled.com . I'm not sure what resistor to use. The link below is for the specific LED that I bought. Note that it lists 20mA maximum current but not maximum voltage.

I'm going to be running these off of a 12V source. What resistor should I use?

http://www.eled.com/product.asp?catalog_name=LEDs&category_name=&product_id=E7114QWC-D

 

[warrior_king]

up to ~600ohm resistor, the more ohms the resistor, the dimmer the light emitted

 

[NookieN]

Ihttp://www.eled.com/product.asp?catalog_name=LEDs&category_name=&product_id=E7114QWC-D

The pdf linked on that page says 3.5V typical, and 4V maximum. So to run it at 20mA, you'll need about a 420Ohm resistor.

 

[Crazy Jayhawk]

I know that part.

I'm trying to figure out what resistor value will get me the brightest light without burning out the LED. Maybe the packaging will tell me what voltage it's supposed to use.

I want the LEDs to be bright because I'm going to use them for the reverse lights in the taillights of my car.

 

[Crazy Jayhawk]

Re: Re: LED/resistor question

The pdf linked on that page says 3.5V typical, and 4V maximum. So to run it at 20mA, you'll need about a 420Ohm resistor.

Ah, thanks. I just reformatted and haven't reinstalled Acrobat yet.

 

[Fushyuguru]

The higher the Voltage the brighter the light. Now you can go up to the maximum rating (maybe a lttle over without damaging the silica element). If you over blow it the duty cycle decreases exponentially.

Take a multimeter to that 12V line. Find out the max amps. Then use that in your little Ohm's law'age V=iR to find your resistor value based off all that junk.

What you needed to look for is the highest MCD rated LED's you can get. A rating of 1k-3000 is a normal LED. The bright ones go up to 6-7k which is obnoctiously bright. Hopefully you bought those, then youll be good to go.

 

[Wolfe]

That E-Led site has a 10K Mcd Red LED!!

 

[Fushyuguru]

Beautiful! You should have no problem having it bright as hell. Just run that puppy close to 4volts.