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# LED Math Help Answered

I want to create a LED grow light but i am having trouble with the math. I have 5 blue LEDs that are 3w( Vf: 3-3.4 v and If:700ma). Now i want to wire these in a series. So if i were to use two of these for example, would it require more volts and the same current. So: 2@3v = 6v @700ma.

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## 4 Replies

steveastrouk (author)2014-06-27

If you're buying a proper supply, just buy a proper LED driver, then you don't need resistors, and your efficiency will be much higher too.

Choose a 15 W LED driver, with 700mA drive

mpilchfamily (author)2014-06-26

Google LED calc. You still gotta factor in a resistor to limit the current draw. Remember LEDs will continue to draw more and more current till they blow. The 700mA is what they need to run at their brightest for the maximum life span. They can draw more if not limited.

Series = increase voltage usage

Parallel = increased current draw

Lord_Tryndamere (author)2014-06-26

Thanks. I just got started yesterday learning all this stuff so that helps. I knew i still had to add in the resistor but i really need to know that first. So what i want to do is run three different colors in parallel. It will be two blue @ 3v and 700ma, four red @ 2.2v and 700ma, and four red @ 2.3v and 700ma. So i would need a power source with at least 12v and 3amps right? then i could use resistors at the start of every parallel to limit the voltage to what i need and something to limit the current at the very start.

Lord_Tryndamere (author)2014-06-26

I wont be using resistors. I am going to try and use a voltage and current regulator like this (http://www.ebay.com/itm/DC-Buck-Step-Down-Converter-DC-5A-Regulator-Voltage-Current-Adjustable-YG-/111362310695?pt=LH_DefaultDomain_0&hash=item19edb60227).