Beginner's Guide to explain simple LED flashlight.


Jan 8, 2017
Always easy to appreciate a simple diagram and clear explanation. Many thanks! Any chance you happen to have a diagram for LED driver design basics as well? :grin2:
The only thing I have found so far is this thread -
What the schematic does not show is the input voltage is regulated to this driver somehow. Unless it is a Li-ion type battery, then maybe you could run it direct, but you likely would not use the entire voltage range capability of that battery. For Alkaline or nimh some sort of boost circuit is required to drive the driver shown.


Newly Enlightened
May 25, 2017
I am using FENIX PD35 1000 LUMEN CREE XP-L LED COMPACT FLASHLIGHT . Measuring at under 5.51 inches, it can easily fit in the smallest pockets. In the practical deployment, you get up to 656 feet of beam output. If you use it in its Outdoor mode, you have a choice between six modes and its effectiveness is attested to by its use by professional law enforcement officials. The smart charger it comes with can charge two batteries at once, but it's best used with 18650 batteries; you'd be wasting its power if you tried to use it with CR123 batteries.


Newly Enlightened
Dec 12, 2023
Thank you! That is helpful info. The noted safety aspects of lithium are definitely making me think some things over...
Is there something somewhere that helps people understand lumens better? Nitecore is advertising a 4,000 lumen compact EDC light. People talk about how bright the Malkoff and Streamlight lights are; but the lumen output seems only a fraction. I've been around enough to know that lumens aren't everything; but... On the surface, it seems like a 4,000 lumen light should be ten times brighter than a 400 lumen light.

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