Skilhunt E3A (AAA twisty) - First Look

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Forsythe P. Jones
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Wow, that is interesting about switching the resistors in and out with FETs. I was aware of programmable resistors like the DS1841 but that didn’t seem so suited to the application. For a very low moon mode maybe it’s possible to have an MCU pin switch a series resistor in and out in front of the led, so when switched in. Any idea what the max voltage is that can come out of that boost converter, or could it possibly fry itself if it sees too high an output impedance? The E3A must have a fairly large inductor that I imagine could cause a big voltage spike. Maybe there could be a parallel resistor also switched out. That might need another FET, but having 2 levels instead of 3 would eliminate one. I guess modding an E3A this way is not really feasible.

I suspect that MCU is something like a Padauk PMS150C that is much cheaper than any PIC or AVR that I know of:

https://jaycarlson.net/2019/09/06/whats-up-with-these-3-cent-microcontro...

Forsythe P. Jones
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Ordered one E3A from Skilhunt.com, $9.80 base price, high CRI led and slate blue ano added $1 each so $11.80. Then $6 shipping since order was below $49, so $17.80 total. I guess it might have been slightly less through Aliexpress but I’m just as happy to buy directly from Skilhunt. Aliexpress reminds me too much of Amazon sometimes ;).

SammysHP
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It’s $7 from Aliexpress. Wink At least I’ve ordered one for that price few weeks ago.

Lightbringer
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Ummm…

https://www.amazon.com/dp/B08B8D9Q26/

Beats waiting 6mos and still paying out the wazoo or any other orifice for shipping.

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Forsythe P. Jones
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Ehh same $12.90, maybe a couple bucks less for shipping and less waiting, but with less of the smelly feeling I get whenever Bezos is involved with anything. I’m not in a hurry as I have tons of lights to use before the E3A gets here.

Does anyone know a board like that suitable for bringing less power to the led? Like maybe 3mA, for a button cell light.

Lightbringer
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Goggle “vampire” on the site. People were doing exactly that.

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Forsythe P. Jones
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Thanks Lightbringer. I looked at a bunch of vampire threads and I did some studies like that myself on CPF some years back. But that idea is to get every last bit of energy from a depleted battery, running the led at super low levels (like below 0.1 lm) that are still surprisingly usable. What I’m hoping for is a bit different, running the led at fairly low level (1 lm) even on a full battery, to decrease the drain on small batteries (coin and button cells). 3mA to a led with 3V forward drop is 9 mW which should be about 1 lm with efficient modern leds.

I picked 1lm since that was the intended brightness of the original CMG Infinity, one of the early flashaholic lights, that gave way to the Arc AAA which overdrove its led to produce around 3 lumens, seemingly amazingly bright at the time. The best known 1AAA light before that was the Mag Solitaire at about 2 lumens, so this is a perfectly usable “fully functioning” rather than “vampire” light level.

My actual idea is to make a super light and compact headlamp, along the lines of a Photon keychain light with a headstrap, and that motivates the question. I was looking at the Black Diamond Flare which is unregulated, so it is quite bright at first but depletes its batteries fast. I’m thinking to use 1xCR2032 or 1xCR2450 and a regulated boost converter, to maximize the “functional” (above 1lm) runtime. Vampirism would also be a nice feature for this sort of light, but it’s separate. If the light has a microprocessor it seems reasonable to also monitor the cell voltage and adjust power output downward once the battery gets near dead. It would still be above 2 volts for that.

My original idea had been to use a 1.5v hearing aid battery but I decided that is just too crazy. 1AAA is still possible. I don’t know why there have been so few 1AAA headlamps.

SammysHP
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Btw the E3A from Aliexpress arrived in less than a week with free shipping.

https://www.aliexpress.com/item/4001144192612.html

Forsythe P. Jones
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Mine just arrived from Skilhunt. There were a bunch of weird Christmas cards in the envelope with it. I don’t know how they got there but it may have happened at my end. It’s a lot brighter with the included alkaline cell than with a random but fully charged nimh cell that I tried. I might try with an eneloop but if the difference is still visible I’ll probably run it mostly on L92 Energizer lithiums.

I feel a little regret from having spent so much on shipping instead of ordering from Aliexpress but it’s not a big deal in the scheme of things. It’s a nice light. The 2cm or so length difference from the Sofirn C0S is very noticeable.

The threads really are pretty stiff and the shorter body means there is less to grip while trying to operate one handed. It is doable but awkward, while with the Sofirn it is quite easy. I also like Sofirn’s style of flat-ended tailcap better than the E01’s lanyard staple which adds about the same amount of length. Sofirn’s adds a fraction of a gram in weight, though.

Anyway I guess I will carry it for a while. Since it will mainly be a pocket light, I’m tempted to sand off the lanyard lug completely, saving a few mm of length and removing a possible source of snags.

Forsythe P. Jones
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I’ve been using it a while now. I love the small size. I forgot about the stiff twisty so it’s not a problem, though I doubt I can operate the light one handed as I can with some twisties.

I’m sure that nowhere near 100 lumens was coming out of the light with the generic (Titanium Innovations) “1000 mah” AAA nimh cell I had in it. I could believe maybe 20 lumens. I just swapped out that cell for an L92 lithium and it is a lot brighter now (I could believe 40?) but still nowhere near 100. That is fine, I didn’t really want a 100 lumen 1 level AAA light anyway. But it’s odd that the light’s flat regulation in the runtime graphs I’ve seen didn’t equalize the brightness between the nimh and the lithium cell.

I do have some old (age-wise, but unused) eneloops around here so I guess I’ll put one in tomorrow and see if it’s any different.

TermsakC
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Got my Pink Skilhunt E3A on Monday, together with my Brass Astrolux FT03.

The E3A was bought on Ali Express for S$10.98, or about US$8.10. Free shipping from China to Singapore. No sale tax.

All beautiful colours, but I like this Pink one the most.

Forsythe P. Jones
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Yeah I derped up badly by paying so much for shipping instead of noticing the free shipping offers on AE. Oh well. I like the light enough that I might buy some more at some point, and now I know where to get them.

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