# Thread: NBV3 accent LED question

1. ## NBV3 accent LED question

Hey guys,

Sorry but I've got one last newbie question. So I've been going back through some build videos/tutorials for the nano biscotti V3 in which I planned to use the deep sleep pad for my accent LED. While I'm aware the pad puts out a 3.3V, I still assume I need to resistor that LED due to the 20mA max current. However, I've seen a few folks suggest there is no need for a resistor on the accent as it's on a 3.3V output. Is this true? I figured if the battery is able to drive 3 x 1000mA Crees it would way overdrive the accent LED so I assume I need to throttle that down so as to not burn it out. I've calculated out an 18ohm .25W resistor for this particular LED (5mm blue).

I just want to understand where to get my numbers from. How would I know what the current produced by the battery is? I know the 3400mAh is a figure based on longevity, but is there a way to figure out exactly how much current it's actually producing or is that determined by the components in the circuit? I guess I had 2 questions! Still trying to understand the electrical theory behind everything.

Thanks for any input you guys can give me.

2. The battery will have a maximum output, but that's limited by the protection circuit in the battery. Your components will determine the actual draw. Think of it as that the battery doesn't push electricity, your components pull it. They'll pull more than they can handle if you let them, which is why we include resistors.

To calculate a resistor value, you'll need to know the source voltage, LED forward voltage, and the desired current.

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