Author Options:

How can I tell what sort of battery and resistor I need for my LED's? Answered

I recently purchased a set of LED's (cgi.ebay.com/ws/eBayISAPI.dll), and they came with a set of "Green Brown Brown Gold" resistors, and a set of "Green Brown Black Black Brown" resistors aaaand... I have no idea how to sort any of this out. Halp!


The forums are retiring in 2021 and are now closed for new topics and comments.

11 years ago

In case you didn't know the resistor color code:

Black      0
Brown     1
Red         2
Orange   3
Yellow     4
Green      5
Blue         6
Purple     7  (also known as violet)
Grey         8
White      9

The first two bands give two digits of accuracy. The third is a power of ten -- thus brown black black is a 10-ohm resistor, whereas yellow violet orange is a 47 kohm resistor.

The fourth band indicates "tolerance" -- how close the resistor can be expected to match its labelled value. No band (or brown, sometimes) indicates the resistance is within  10% of nominal. Silver indicates within  5%. Gold indicates 1%. (Important point: A 10% tolerance resistor will almost _never_ be within 5%, and a 5% will almost _never_ be within 1% -- because what the manufacturers do is produce a bunch of resistors, sort them by accuracy, and label them appropriately.) For most purposes 10% tolerance is close enough, and the cost is lower if you're willing to tolerate more variation.

Websearch for "resistor color code mnemonic" will find several ways of remembering which color is which number. I still use the one I first learned (bad boys rob our young girls....), but it isn't the best.


11 years ago

You can find the answer to the right

LEDs for Beginners, it goes through resistors towards the end.