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# What kind of LED is this? And how to use this using DC or AC? Answered

Good day everyone. I'm new to Instructables and I'm searching for LED projects. I have destroyed our old CD player which have so many LEDs in it, and found out they are not the conventional circle LEDs. They are rectangle-shaped. I remembered that these LEDs light different colors, but I'm not sure. I want to use it in my first project using LEDs but I don't know how to use them, or are they RGB LEDs. I also cannot  test it because I haven't bought a soldering iron to melt the solder and remove the LED. Please help me. Thanks in advance. I have pictures to show the LEDs I'm referring to.

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## Discussions

The shape of the LED case isn't very important. What is inside is pretty much the same.

You need to control (limit) the current through the LED - Generally this is done with a resistor.

To calculate the resistor value you need to know a few things:

The forward current of the LED

The forward voltage of the LED

The supply voltage

The easy way for a beginner is to use an LED calculator like this:

http://led.linear1.org/1led.wiz

You won't know the voltage and current for these LEDs but they will have a resistor attached alread - Possibly on the back of the board. As they came from a CD player it is most likely they use 5 volts as a power supply - You can take it from there.

Will I be able to know the LEDs' voltage and current if I use a multimeter? I'm planning to buy one...

And by the way, on the topmost picture, the LEDs are attached on a long circuit board, 10 LEDs in total and only one resistor. I calculated the resistor's value and its 56 Ohms. I don't know why, but I guess you know why it's only 56 ohms. I'm so sorry by the way about my questions, I know they are very basic but I'm new to this kind of thing. Thanks by the way :)

We all learned some time :-) The resistor is probably feeding all of the LEDS, Not a recommended practice but reduces costs.

Your meter won't tell you the basic spec of the LED you either have to buy something your sure about or can look up the spec or take a risk on reclaimed items that cost you little anyway.

Most domestic electronics will run off 5 volts though so that's a good place to start and if you reckon 10 Ma for the forward current then you should be in a safe area.

If your getting into electronics a batch of resistors of different values would be useful.

330. Ohms, 1 K ohms and 10K ohms are useful values.