LED resistor help

[mr_alberta]

Hi,

I'm trying to remember how to calculate the size of resistor I need to run my LED but I can't for the life of me remembe how to do it.

I have a power supply that is 12VDC @ 300mA, but my LED is 12VDC @ 10mA. Now, what it simply R = V/I to find the resistance I need to step down the current?

Thanks for your help!

[cc_bruno]

Check out the following site:

http://<a href="http://metku.net/ind.../index_eng</a>

Hope that helps.

Robert

[beaker020]

the led will only draw as much current as it needs. As long as the supply is capable of supplying it. In your case then, no limiting resistor is required. However I would double check the voltage of the LED 'cause most LEDs are only 2 to 5 volts.

What you do, if you dont have a nifty website calculator handy, is take your total supply voltage and subtract the voltage "used up" or dropped across the LED and then divide by the current (in amps) to yield the value of the resistor needed. when looking for a suitable resistor always round up.

ie. 12v supply, 2v 10ma led

12-2=10 10/.010 =1000
so a 1k ohm resistor would be the minimum (brown-black-red)
a 1.2 k ohm would be safer (brown red red)