Comments on: LED Resistor Calculator

By: admin

admin — Sat, 17 Apr 2010 13:55:13 +0000

Dan, That LED is fine. You can use the 2v rating in the calculator but the 20ma rating is the maximum that the device can sustain in standard operation… you do not have to use that much current, and if you use lower current, the battery in your effect will last longer. Start with 3ma and see if that is bright enough for you.

By: Dan

Dan — Tue, 13 Apr 2010 02:49:03 +0000

Thanks for this calculator. Does this mean I can order any LED and then look up the specifications to figure out the resistor needed? What specific LED do you suggest? I was looking at the Mouser stock list today and had no idea which LEDs to buy, so I picked this one (kind of randomly!):

http://mouser.com/Search/ProductDetail.aspx?R=WP7113HDvirtualkey60400000virtualkey604-WP7113HD

The operating voltage is 2V, and the operating current is 20mA. So, according to the calculator I need a 350 ohm resistor… Right?

Thanks,
Dan

By: admin

admin — Wed, 06 Jan 2010 00:07:14 +0000

The formula is:

Resistor in ohms = (V-Vf)/Current

V= the voltage supply, and Vf is the LED voltage drop. Current is in Amps.

So, for a 9v powered pedal that we want to use a red LED (1.95 voltage drop) at 10 milliamps, we would have:

Resistor = (9-1.95)/0.01 for a value of 705 ohms

By: Rick

Rick — Tue, 05 Jan 2010 14:57:21 +0000

Hi, what is the formula that you used?
I am also interested in the other formules of the ‘calculate XX’ pages of your great site!

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