[Techtalk] matching LEDs to resistors

[Tracey Hytry]

> OK electronics gurus-- how do I know which resistors go with LEDs? Other than 
> asking the vendor. Like this one 
> http://search.digikey.com/us/en/products/WP7113SRD%2FE/754-1276-ND/1747675

You need to know the voltage drop of the LED, subtract that from the driving voltage(5V?);  and decide how much current you can put through the LED.  Then use ohm's law to find the dropping resistor value.