Introduction: Make a Simple LED-Lamp

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instructable about how to make a very easy LED-Lamp in about 30 seconds using a laptop buffer-battery.

Comments

mad_b (author)2011-09-27

A LED will overcurrent, in general, only if it will have aplied more voltage than it can handle. A 3.3V led can have attached directly a 3V battery directly, the current over the led will be its nominal, it will run with this current until the battery is depleted.

Now, if you overvolt a led (i.e. put 3.5V over a 3.3V LED, it will burn out after some time, because the number of charges passing through it will increase exponentially ant the increasing heat will little by little (or even fast) burn out the LED until it dimm out, maybe flash, then die for good.

That´s why people gets confused about if putting a battery directly over a led will it burn? will it work? What will happen. So if you will have more volts than your led can handle, you MUST use a resistor properly calculated to limit the current. Or else, (no resistor and less volts) even the led won´t lit, or it will at its nominal current.

So with most of 3.3 volts leds nowadays, applying a 3.0~3.2 V battery directly to the led won´t burn it, and it will light up at its nominal bright. That´s the voltage of a computer bios (usually CR2032) battery. So, no resistor if you please. Now if you want to limit the current more, you must add a resistor and make proper calculations.

berky93 (author)2009-03-12

with a button cell battery like the one in this project, theres not enough current to short out the LED. even AA/AAA (they have the same charge, just the AA lasts longer) batteries don't present much of a problem. but I tried connecting a LED to a 9-volt battery once, all I got was an incredibly bright flash (for this particular LED) and then nothing...

berky93 (author)2009-01-16

it would make it better if you put a thin plastic washer (make sure the hole is big enough) in between one of the led's leads and the battery, making a push-button momentary switch.

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