The complete guide to using LEDs

6 Steps
LEDs con be confusing sometimes so I decided to make a guide on using them. If you have any Questions about LEDs that werent answered in this instructable, Please feel free to comment or question.
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Step 1: Power intake

LEDs are wiered about there power intake. Most LEDs require about 3 volts any more, and they burn out and smell bad. any less, and they dont light up good. I know what you are thinking you can use a 1.5v battery such as a AA or AAA if you have a Joule Theif, but that is another instructable. As of amperage, LEDs very greatly across a wide spectrum of highs and lows, but 20mA is standard.

saurabh_1603 says: Dec 3, 2011. 6:30 AM
can u tell how to light led using AC.
Do i have to use diode.
i used 100k resistance for a 230v AC supply, red led worked properly but white led stopped working after 5 seconds and was damaged.Can u tell me why.PLZ
jpgomez says: Mar 24, 2011. 9:46 PM
your explanations are really easy to follow thanks. i have no electrical background, voltage im guessing is the power of something what is amperage?
techturtle2 (author) in reply to jpgomezMar 27, 2011. 5:37 PM
Amprage is how fast the electrons are moving, Voltage mesures how far from ground the positive is:
karlpinturr says: Dec 24, 2010. 12:04 PM
Right..., so, taking your "R=V/A" to the circular chart, the resistance can be found by dividing I (volts) by E (amps), dividing P (watts) by the square of I (amps), OR dividing the square of E (volts) by P (watts)..?

And the same principal (ie, the central value can be found by ANY of the 3 methods shown) applies to the other segments?

So, if I know the voltage (E) of my power supply and the amps (I) of my LED/LED's, I divide the first by the second to find the necessary resistance..? And I assume that if there's no exact match available, I'd be best using the nearest HIGHER resistance?

But, just a minute. LED's are measured in MILLIamps - does that mean I have to divide/multiply the result of my calculations by 1,000? And how would I know which?
techturtle2 (author) in reply to karlpinturrDec 28, 2010. 1:27 PM
yes.
if you had a 9v power supply and a 30mA LED, you would divide as follows:
9/0.003=R=3000=3kOHMs
rickharris says: Jul 17, 2010. 2:34 PM
As an aside your using the wrong symbol for an LED.
techturtle2 (author) in reply to rickharrisJul 17, 2010. 9:24 PM
I most certainly am not.
techturtle2 (author) in reply to techturtle2Jul 17, 2010. 9:25 PM
Oops i frogot the arrow thingies.
rickharris says: Jul 17, 2010. 2:32 PM
Not at all resistors cost pennies - You should still nclude a resistor no matter what the power source to allow for changing battery voltages.
techturtle2 (author) in reply to rickharrisJul 17, 2010. 9:20 PM
I use Metal oxide film instead od carbon film. they are more accurate and thus more expincive.
rickharris says: Jul 17, 2010. 1:09 AM
There isn't any reason not to use the 9 volt battery as long as a suitable resistor is put in series with the LED to limit the current drawn.
techturtle2 (author) in reply to rickharrisJul 17, 2010. 1:06 PM
That is true but you need a strong resister which will probably cost alot of money.
Rorymi6 in reply to techturtle2Jul 17, 2010. 2:22 PM
You are also at a disadvantage with the mAh of the button cell which can be rather small compared to a PP3 or a AA cell. A single LED on a 9v supply would generally require around a 300 ohm resistor which costs me around half a penny per resistor for a 270 Carbon film 1/4W resistor. This page really needs to explain about resistors and their usage aswell. Rory
rimar2000 says: Jul 16, 2010. 6:53 PM
Well, because this is the introduction to the prologue of the first chapter of the first delivery, not bad! We'll see how it continues...
lemonie says: Jul 16, 2010. 1:41 PM

This needs work doing on it (e.g. spelling), and some more information that gets you towards "complete".

L