The There Are No Stupid Questions Thread

No, because “3” already has an intrinsic and local value equal to 1+1+1.

+1 this

This is why I have two DMM’s dedicated to Amp measurements only :person_facepalming:

BTW, those Aneng DMM’s are pretty precice. Considering the price.
I have an Aneng 8004 that’s only used for milli/microAmp/parasitic drain measurement. Compared to a calibrated Fluke DMM, the yA are “only” off by 1-2yA :student:

Anyone having facebook problems atm

> if the government tells you ….

Not Indiana: Indiana Pi Bill - Wikipedia

I’ve got a couple potentially stupid questions.

1) I’ve got a utorch lantern/bug zapper that takes a 18650. It has a sleeve inside that when removed it looks like it can fit a 21700. Will this break the light? isn’t the voltage the same?

2) Simon already said no, but if I had a convoy m3 that takes one 26500 battery and found a long enough tube to fit two 26500’s would it break the light? why?

Thanks!

1/ 21700 batteries are fairly new, and predominantly used in high-end flashlights. That’s why I think this sleeve is meant to fill the space needed for a 3*AAA battery carrier. Those have a diameter of a bit over 22.6mm.
Edit: a 21700 has the same voltage as an 18650, that does not hurt a bit. But I may be too long to fit.

2/ 2 batteries “in a row” have a voltage of 2*4.2V = 8.4V. You fry the driver when that is built for 1*4.2V.

I bet a 26650 battery may fit

And yes two batteries stacked together results in 8 volts instead of 4 volts

I found the perfect holster for the emisar d4s, I just received it today. It is a pistol magazine/flashlight holster I found at my local academy

Any way I can upload a pic on here to share? I may find the link on academy’s website and copy and paste it but I’d rather show you guys how perfect of a fit it is!!!

thanks everyone! there will be more.

You can’t directly upload photos to BLF. You’ll need to upload them to a photo-sharing site and post a link.

It’s not complicated. Here’s a how-to guide put together by BLF member ‘raccoon city.’

I recommend using imgur.com as the host site. It’s easy and you don’t need to create an account.

Thanks figured it out from another blf member

Guys, I can’t find the answer although I’m pretty sure there is one within BLF “borders”. Hence my post here - I feel stupid asking you for a shortcut instead of making full research.

The question is: how to calculate the size of hotspot at a particular distance?

Let’s say I want a hotspot of diameter =3 meters at a distance of 150 meters. (numbers are taken out from nowhere, so might be odd). Which LED should I choose (de-doming/slicing is within scope of my poor abilities)?
Or the other way round. Let’s say I have Samsung LH351D, how can I know what would be the hotspot size at distance of 150 meters?

Your hints will make my research way easier.

I am by no means an expert but I’d say it’s all up to the reflector or optics. Too many variables to be able to use a simple formula.

I found something relevant here
But my geuess is that’s not the only one. Anyway, thank you Enderman

I’m sure you’re right but since I’m interested only in hotspot I think the reflector has not that much impact?

But it’s the reflector that focuses the light into that hotspot. Just see what happens when you don’t have any reflector at all, it turns into a mule light with no beam at all. With any given LED you can have widely different beams just by switching reflectors.

I didn’t know about Enderman’s calculations. At least with that you can enter some reflector data.

Yes, you’re right Mike, w/o ref it goes insanly wide. So if won’t have any other option I’ll use Enderman’s method.
However, the LED area are must have a meaning, since by just replacing the led you get more/less focus as well.