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3v leds x 20, leds paralel, 3v in, led calc says use 1 ohm each resistor, can I skip that since 3v led and 3v input v? Answered

I am building a led array light bulb.

3v leds x 20, leds parallel, 3v in, led calc says use 1 ohm each resistor, can I skip that since 3v led and 3v input v?
Led calc also says 0 ohm / use the next standard resistor 1ohm..

does 1 ohm x 20 really needed for a 3.0- 3.2v white led with  a  3v 2000ma source>
thanks in advance..

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steveastroukBest Answer (author)2010-07-28

You need SOMEthing to current limit. As you say, you're so close to "3Volts" it doesn't seem necessary, but as the temperature of the dies change, so does the current curve for the LED and it WILL start to draw more current tthan it can handle. You really would be better running them as multiple parallel chains with either sensible resistors, dropping ~three volts, or use a decent constant current driver.

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Willard2.0 (author)2010-07-28

I would use the 1ohm resistors. Without them, any slight surge in the power supply goes directly to the LEDs, likely killing them. A resistor will suppress some small surges and keep the current to the LEDs limited to a safe level.

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celalboz (author)Willard2.02010-07-31

Thanks for answering my question, I will use resistors.

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Re-design (author)Willard2.02010-07-28

I don't think a 1 ohm resistor is going to suppress enough current to help.

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lemonie (author)2010-07-28


If you're using a 3V supply, I'll guess you're on AAs?
Bump it up to 9V at least, run some in series.
It's easy to double-up 9V batteries to 18V - so you might run 5 in series with a resistor, 4 times.

L

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