Recent content by PeterH

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    Maglite Mini Mods Questions

    One slightly dodgy mod is to replace the hot wire bulb with a red or yellow 3mm LED, direct drive. The LED needs to be plugged in the right way around to work.
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    Don’t do this in a restaurant. (When they reopen)

    Roughly 30 years ago my father got a 4D cell maglight. GREAT flashlight by the standards of the day. Today I have budget pocket size LED lights that put out as much light. Such is the march of technology.
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    LED collimating and beam diameter/divergence

    One parameter I'm not seeing is the effective size of the emitter. For tightest focus the lens would be projecting an image of the emitter to the desired size at distance. (object_size/distance_1) = (image_size/distance_2) There's also a relation between those distances and the lens focal...
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    Claim: New chemistry could overcome key drawbacks of lithium-air batteries

    http://news.mit.edu/2016/new-lithium-oxygen-battery-greatly-improves-energy-efficiency-longevity-0725 Interesting proposal. But I question the stability of Li2O2 and LiO2.
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    Improved, long life flow battery electrolyte, non toxic, non corrosive.

    I thought lithium electrodes would have a problem reacting with water, releasing hydrogen.
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    Hearacy? LiIon cells not damaged by discharge to zero?

    Research suggesting that a LiIon cell isn't observably damaged by discharge to zero, but by a modest degree of reverse charge. But series packs discharged to zero are still a problem, as some cells in the pack will be reverse charged. https://www.nature.com/articles/srep30248 , or a more human...
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    What would the ideal reflector look like to you?

    I have to agree that reflector shape should follow from desired beam shape. That leaves the question of what is the ideal beam shape? I my opinion an ideal beam shape would be characterized mostly by width angle, how wide being a function of intended use. Light distributed smoothly across the...
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    DIY LED reflector, how to design one?

    What kind of throw pattern are you looking for? For good throw you're looking for a parabola. For a wider pattern the shape can be less critical. For most high power LEDs I've seen the intensity follows cos(A), where A is the angle away from straight out. For validating a pattern I've had...
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    Confused about my LED flashlight battery recommendations

    There are a lot of cheap 3*AAA flashlights that depend on the battery internal impedance to limit current.
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    Help me understand what I'm looking for: extremely low amp charge circuit.

    My understanding is that charging LiIon cells without a full charge cutoff is asking to overcharge, with very bad results.
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    Why does anyone make incans anymore? Just bought a 2xAAA MiniMag and it's incan

    Incandescent is still the gold standard for color rendering. And cheap to produce in some variants. As far as "converting" a 2xAAA mini mag, I believe a 3mm red or yellow LED should fit in place of the bulb and operate on the supplied voltage. Most white LEDs won't find enough voltage to...
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    Steel pie pan

    What do you want the thin steel for? Closest I've seen is nickel plated serving trays in dollar stores, similar to https://www.dollartree.com/Party-Supplies-Party-Favors-1-Each-Buy-Bulk-at-DollarTree-com/tableware/Serving-Trays/Nickel-Plated-Metal-Serving-Trays/574c511c530p340777/index.pro
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    3D printed 18650 light, playing with the idea

    How much power are you planning to feed the LED with that tiny heat sink?
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    Are Leds too hot for plastic lenses?

    The plastics used for optics can easily take any temperature that is healthy for an LED. I wouldn't worry about too much heat for a plastic lens from an LED emitter.
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    Driving a low current LED of a 18650 cell for a candlelight

    https://en.wikipedia.org/wiki/File:Current_Limiter_NPN.PNG R2 can be bypassed.
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