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My goal is to flash a few white LED in serial using 9V battery.

Here are the specifications of this LED.

As I saw the Forward Voltage is 3.4V, but what does it really mean?

Can't I plug this LED into more than 3.4V battery without using resistor?

Also I know that max current of this 10mm LED is 300mA.

As I know during serial connection voltage is trying to split to each LED equally. But in parallel connection voltage is the same to each LED and current is growing up!

So tell me can I flash a few 10mm white LED without using a resistor?
If I can.. then tell me how many LEDs should I use?
So what is a solution?

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marked as duplicate by tcrosley, Ricardo, PeterJ, Daniel Grillo, pjc50 Mar 16 '16 at 13:34

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

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Forward voltage is a voltage necessary for LED to conduct electricity. If the voltage across your LED is 3.4V, it will draw as much current as it can, and burn out eventually. So you need to limit this current to 300 mA. If you have power source of 9V, it means you can fit 2 LED comfortably in series as they will need 6.8 V together. Remaining 9-6.8 = 2.2V will be over your current limiting resistor. Since your current is 300 mA, resistor value should be 2.2V/300mA = 7.3 Ohm!

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