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Discussion Starter #1
As a newbie, I'm trying my hand at some LEDs that a friend gave me. He won a lot off Ebay and they came with resistors. They are not individual LEDs but attached in a string as shown in the picture.




I'm planning on wiring 5 at a time since they are different colors. How can I tell which lead is the positive and which side is the negative? I plan on using a 9V battery.

Any suggestions on how to do this? Is there a better way than using a 9V battery?

Thanks!
 

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All LED's have a flat part on one side of the actual light part. What ever side that flat part is on, that lead is the negative side.

 

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Your LEDs are individuals, they're just taped together. Assuming each LED needs 3 - 3.5 volts at 20mA, wiring 5 of them in series won't work, the 9 volt battery doesn't have enough voltage to light all of them. Wiring in parallel is the way to go if you want to use that many LEDs. Here's a calculator that will help you choose the resistors and shows the wiring layout. Just plug in your values and click.

LED series parallel array wizard
 

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Discussion Starter #4
Thanks NTX JX and Otaku! So if I wire 5 in parallel with a 9v battery, could I use the 470 ohm resistor that comes with them? Here are the specs. Thanks!

Emitted Color White Red Blue Green Orange ---
Lens Color Water Clear ---
Size 5.0 mm
Peak Wave Length --- nm
Forward Voltage 2.0~3.4 V
View Angle About 25° °
Luminous Intensity 4000~15000 mcd
Max Continues Current 25 mA
Max Peak Current 75 mA
Operating Temperature -40~+85 °C
 
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