Induction coil for AAA flashlight question

Still got the coil, or no?

Generally, those circuits use the coil to determine LED current. The lower the inductance, the higher the LED current.

I’ve seen circuits mainly using 22µH coils, but try 47µH or even 100µH first and see how much current goes to the LED.

Can you read the markings on the boost IC between the LED’s legs ?

There is no coil here at all and it has not been preserved (it rolled off somewhere and got lost), I see only the remains of its base.

Thank you very much! I’ll take a better photo now.


6 к

black between legs

black on the side
828 or B2B or B28 or 82B

Hmm, can’t find which part that is, that said it seems that the majority of those low current, low Vin boost controllers have a low switching frequency (~100kHz) and require a fairly high inductance of 100uH, so I’d go with that. For the current rating and saturation current go with something > 200mA

I would contact Don directly. He’s helpful and friendly.

If you can’t get any help, you could swap the electronic from a Sofirn C01. You would get an high CRI led and a very efficient driver, better than the old Arc one.

Thank you! In my nearest store, the choice is small, only 1 are suitable in size and characteristics, the rest are either larger than the board itself, or less current and less inductance: 100 uH / 260 mA SDR0302-101KL smd D3x2,5 mm

there is a second one, but it is only 68 uH / 600 mA LQH66SN680M03L 6,3x6,3x4,7 mm

I’ll try with the first one now and let you know what happens

Thanks for the advice!
I never thought about Sofirn. I searched a bit, you mean this one?

The DCR of SDR0302-101KL is maybe a bit high, I’d say less than 1Ω would be preferable.
The 68uH one will still probably be okay, if it fits.

Yes, exactly. It should be an almost direct fit since both light are similar sized AAA and 5mm led based.

Unfortunately it’s getting late, I went and got SDR0302-101KL. It was rather inconvenient to solder all this, it turned out like at a freak fair, where dwarfs walk on stilts. I had to add blue electrical tape so that the legs from the coil did not close the diode.

He it is alive))

I have nothing to measure the current through the diode, the current through the AAA battery is 140 mA. Outwardly, it looks like 6-8 lumens, when compared next to two HDS on 15 and 16 levels.

The diode is very blue, I’ll see how it behaves. I have some 5mm 96CRI diodes 3300K, maybe put them in here later.

I am very grateful to all of you for your help :slight_smile:

Does the DADKZ chip have 3 pins?

It might be a transistor used in a single inductor “joule thief” type of circuit, or something like the HH004F ic but in a SOT23 package.

It’s hard to say, a lot of solder, but it looks like there are 4 legs

Like derfyled said, my first thought would be to shoehorn a driver from a C01 into it. They’re made in a similar fashion with the 5mm LED being soldered in like that. And they’re cheap enough that you could buy a C01 just to grab the driver out of it.

On the driver, I mentioned the wide area at 11.87mm and the narrow part at 10.45mm. Note: that’s not the stock inductor, I had to replace a broken one and grabbed this chip-style inductor.

Yes thanks derfyled and you. Don also replied to my letter. It doesn’t matter where to get a new driver, in any case, its path to me will stretch for 2-3 months. So while I run it in a row on several AAA, it will work almost continuously for several days or weeks, I’ll see how it behaves.

It looks like the coil hit the target, I was looking through old reviews on Arc and found here:

ARC AAA Ti means the same driver and the same 140 mA :partying_face:

There is a photo here, on the original coil there is an inscription 223, what could this mean?

22 micro henrys (uH)

Yeh, like I said… :stuck_out_tongue:


Yep, you guessed it :+1:

I wonder why then, no matter 100 or 22 microhenries here, the current 140 mA is the same?

The IC is most likely a fixed voltage boost controller, so the current through the LED is whatever it is at the output voltage. Unless the circuit resistance (inductor DCR, switch FET resistance, cell… etc) is high enough to limit the current.

I just thought, if 100 uH works the same way as 22 uH, then maybe if replace them with 0 uH, that is, instead of a coil, just a wire, then this will not affect the operation of the diode in any way?

The inductor is a key component of a boost converter, you can’t just remove it :open_mouth: .