Mini death-dalek camping light.

I noticed that one takes AAA size cells. That makes it inferior to this little one that takes the AA cells with three times the energy capacity.

Big Clive

They've been advertising this one on TV i've noticed (think it was MSNBC), and at first I thought it was one of the death lights. Then I thought it was this. But now it appears its neither, a COB is visible on the lantern bit. <a href="https://www.amazon.com/Bell-Howell-1454-Taclight-Portable/dp/B01N7FRQSG" rel="nofollow noopener" target="_blank">https://www.amazon.com/Bell-Howell-1454-Taclight-Portable/dp/B01N7FRQSG</a>

I'd say this would make for a rather nice and cheap lantern for emergency situations. Pair it with Lithium (primary) AA batteries for long self life, decent runtime (~3Ah at 0.1-1A CC), good performance in the cold and so on. Obviously with these the current draw would be higher but these do hold quite a bit more energy as well, so maybe the runtimes would be similar but you just get more light out of it.

The discharge curve is also an issue - cells with a straight line discharge go dim quickly due to the switching point of LEDs, unless the resistor value is high which is also wasteful. Perhaps it's time for a lesson in Joule thievery - and I can think of no-one more qualified than yourself Clive!

Gordo

..or a mini warp core like the one on Star Trek Voyager ;-)

Gordo

A couple/few in the diffused section would be awesome. Maybe switched between white and multi-phasic chromatic anarchy? I may look into that as I have ordered one. Thanks man!

Michael Thompson

The chemistry of NiMh cells sets their voltage. Many applications would benefit if they did actually put out 1.5V . LED light strings being a good example. They'd run brighter for longer on two cells.

Big Clive

I'm thinking UV luxeon replacement = disco lights

Gordo

The voltage of any type of cell depends on the chemistry - ie. what materials are used for cathode, anode and electrolyte (the goo) - Alkaline are 1.5V whether AAA, AA C or D cells, NiMh are 1.2V, Li-Ion are 3.6V, LiPo are 3.7V, Lead-Acid 2V etc. A "battery" is several cells connected in series - so a PP3 has 6 alkaline cells in series, a car battery has 6 Lead-Acid in series and so on..

Gordo

As a newly graduated EE, seeing a low-value resistor and the term 'current source' anywhere NEAR each other makes my skin crawl! Lol. For no good reason, obviously, it really doesn't matter here (except for the brightness varying between 1.5-1.2V). It just 'feels' wrong, I suppose. :)

That's a really good habit, actually. Especially when troubleshooting...

It makes much more sense for the application circuit to include conversion circuitry than to force the primary energy storage to do so. Just look at the discharge curves for alkaline and NiMH: Alkaline is all over the place (and higher than 1.2V only for a small bit of its capacity), while NiMH acts much more like a voltage source. So why force capacity and efficiency down to make NiMH be a constant 1.5V when Alkaline battery applications can't even rely on &gt;1.2V being present for most of the operational time of the circuit? (Sorry, I'm on mobile so Patreon won't allow me to insert line breaks to make nice paragraphs) Secondly, it would make more sense to design your DC-DC converter for what your application values, be it power handling capability, efficiency or cheapness, since a jack-of-all-trades solution, built into the batteries by the manufacturers, would cost more than the cheapest solution while also being unnecessarily crappy in all other departments, for higher performance applications.

So I've always wondered, why are NiMH cells 1.2V and not 1.5V anyway? I can't see it being a size issue as the capacity is ever increasing. I had never considered it to make much of a difference but there certainly seemed to be quite a significant difference in the LED intensity here. Personally I'd take a capacity cut to have a little board built in to the cell to increase the voltage to 1.5V if that's even required.

Matt Tester

Make one that is somehow still live at mains voltage with no mains... just to confuse people lol

It could be made more dangerous if desired.

Big Clive

The wires resistance will be low. The resistor is a safer way to get a predictable current.

Big Clive

difference between wire resistance and resistor?

Alexbleks

It's just habit. I like to get all the data at the same time.

Big Clive

It'll be relying on the battery and wire resistance, The resistor is probably a better idea.

Big Clive

MINI death Dalek? Oh I'm so in...

Michael Thompson

“Won’t kill you”. What a boring USP.

evilution

I'm sure you know this already, but I have noticed you doing this a couple of times now, so I would just like to ask, in regards to calculating the power dissipation of a resistor: Obviously, measuring the voltage of a resistor is completely unnecessary if you already know the value of the resistor, as well as the amouny of current going through it. My question then is, why do you prefer to measure another value anyway? Wouldn't it make for a clearer explanation to just use P=(I^2)*R?

Glad you liked my suggestion! Interestingly... mine didn't have a resistor...

iamdarkyoshi