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Re: [Shop-talk] Wiring a string of LED lights

To: shop-talk <shop-talk@autox.team.net>
Subject: Re: [Shop-talk] Wiring a string of LED lights
From: BJNoSHOV8 <bjshov8@tx.rr.com>
Date: Mon, 04 Oct 2010 20:38:53 -0500
Some of them do have resistors, it all depends on the LED that they are 
using and the battery configuration.  The Luxeon and Cree LED's have 
forward voltages of around 4-4.5V and up.  The cheapest of these that 
you can buy in stores run off of 3 AAA batteries, but as the batteries 
wear they can drop below the voltage required by the LED.  You can't get 
a good LED flashlight with just 2 AA, C or D batteries because the 
voltage isn't high enough, unless there is a boost circuit, and that 
makes the light quite a bit more expensive.  The new Maglite LED 
flashlights have a boost circuit, but they don't have a good means of 
dissipating heat so they are not as good as they could be.  The small 
police-type flashlights that use a pair of 3V Lithium batteries 
sometimes have resistors, or sometimes they just drive the crap out of 
the LED to get a little more brightness, but again the good ones like 
Surefire have circuitry to maintain the voltage right where the LED 
wants it.

> Led flashlights get away without an external current limiting resistor
> because they've got a big honking current limiting one in the battery.
> They also tend to use higher power drawing diodes.   But better flashlights
> have driving circuits that provide both current and voltage regulation.
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