I’m pretty sure there are different drivers for different currents.
I’m aware of at least two versions of the K1 driver, with different sense resistors for different currents. IIRC it’s about 5A for W1, or 8A for W2. A similar trick is used on the KR4/KR1 driver’s 5A linear circuit.
There’s no firmware difference, and the driver is identical aside from the resistor value. It just has one component to tweak to adjust the maximum flow.
Yep, I see your cfg and hwdef files for the SBT90.2 (wide open) and the XHP35 HI (12V) versions. The 12V and SBT90.2 versions could be different designs, but maybe same core design - we don't know. I'm sure Hank had someone design them. Gotta check my stock of sense resistors. I know some of them are pricey, like $1+ each.
OK, Hank responded - said changing R3 will increase current. I assume that a lower value would - R3 is 180K ohms.
Sorry if this has been answered already, but is there a way to change the brightness of the aux LEDs while the light is on? They’re way too bright for me.
Not without changing the source code. At the moment, it’s hardcoded to display battery voltage while on, using the brighter of the two button LED levels.
But if you have the reflashing kit, the code is open-source and there are people willing to help with understanding how to modify it.
Makes sense. Some kind of biasing with a voltage divider.
Updated circuit diagram. Some guessing involved.
OK, so swapped the 180K R3 for a 100K - now getting 7.6-7.7 amps at the tail - little overshoot, but decided to test it anyways.
Throw went up from 652 kcd to 712 kcd, lumens from 885 at start to 960 at start (calibrated #'s).
So what else could be keeping the throw # down? Still well centered, good looking hot spot. The centering piece - it's a bit high, and the style of have a curved cup around the LED, and it's colored white. So decided to sand it down a little:
- base from 0.96 mm to 0.85 mm
- sanded top down - took off 0.03 mm (little)
- overall height from 1.83 mm to 1.69 mm
New numbers:
- 725 kcd (1703 meters), taken at 5 m
- 996 lumens at start, 954 lumens at 30 secs (temp calibrated, raised max)
As you can see, it doesn't drop much over 30 secs, and the droppage slowed down to a crawl at 30 secs (expected for this kind of regulated driver). Lumens is quite lower than what djozz measured, but could be from several things:
- maybe I got a lower bin LED
- my cheaper light meter may be under measuring green
- my PVC lightbox may have issues with throwers
- etc...
Now it's performing to Hank's spec. I would experiment with the centering piece more, but I got no backup, so afraid I'll make it worse then have no way to go back.
A resistor value of 120K for R3 may be ideal for this green LED. These are 0603 sizes.
4.8 -> 7.6 for change of 180K to 100K. If it's somewhat linear, 120K should be about 7.0 amps which is the peak on djozz's chart. Hhmm - might have to go with that. I bought a huge collection of 0603 resistors so I got a ton of sizes and about qty 50 of each size.
Ok, the 120K R3 resistor is installed - 7.21 amps now on a 40T, better. #'s got a little bump as well, so guess the 7.6 amps was over the hump.
New numbers w/120K R3:
- 730 kcd (1709 meters), taken at 5 m
- 1002 lumens at start, 960 lumens at 30 secs (temp calibrated, raised max)
My stock K1 SBT90.2 on a fresh 30T at 4.20V:
- 19.1 amps at the tail
- 510 kcd (1428 meters), taken at 5 m
- 4800 lumens at start
After adding 20 AWG bypasses to all 3 springs on the SBT90.2 K1:
- 22.3 amps at the tail
- 520 kcd (1442 meters), taken at 5 m
- 5358 lumens at start
Not sure why I didn't see a bigger bump on throw - could be my 510 kcd on stock was high (the 30T helps btw). Forgot to de-lens the LED - should add about 5% in kcd and lumens, so should be ~545 kcd, right where vinh claimed for his mod.
Bypass mods on the SBT90.2 version. What the USB-C charge circuitry looks like:
Bypass on the charge board:
Bypass on the driver:
Bypass on the tailcap:
Hi, I got a K1 today and there was a smudge or scratch on the reflector so I took it apart and can’t get it back together again. 
There’s a rubber gasket on the glass that I’m not sure if it goes between the glass and the reflector or the glass and the bezel. And there was a split rubber o-ring that I’m not sure exactly where it goes. I could’ve sworn it came off between the bezel and the bottom of the threads, exposed to the outside. But then the reflector rattles so I think it goes somewhere between the edge of the reflector and the glass. Can anyone help?
Update: I saw that there’s a recessed groove on the inside of the bezel so the rubber gasket side of the lens must go there. And I think I had the bezel cross threaded a little bit. Now it tightens down all the way and sandwiches the bezel just fine. And I think the split o-ring does on between the bottom of the bezel and the head, exposed to the outside, and works as a lock washer of sorts. But I can’t seem to get the bezel on tight enough with it.
Update 2: It took a lot of grip strength to tighten down the bezel with the split o-ring but it seems to be necessary to have a nice even focus on the hotspot. Too tight without the rubber ring and the led goes too deep into the reflector. Anyways, fixed. Phew!
! Didn't take apart the front end on either K1 yet. Hope you didn't fiddle with the smudge or scratch - usually it's only made worse - I know...
Yeah, it looks like the remnants of glue or something. I couldn’t clean it off. And I know what you mean! Luckily I tinker with watches and have everything I need to clean smudges such as a Rocket Air Blaster and Rodico putty.
Forgive the lazy post (I’ve scanned back a couple of pages, but would rather not do the other 19) but as per my thread here I’m considering the K1 for spotting wildlife (and generally showing off, pointing it at distant objects.) Insofar as it’ll be used practically, it’ll be for spotting wildlife at night.
I’m looking at the Osram LED’s, which should I go for (or what are the pro’s and con’s of each)?
And there’s a few comments about scratched reflectors on here, is that just lengthy discussion of a small number of people having issues or is it quite common?
I think they are fairly isolated problems, not common. Folks are more likely to post about a problem than about ‘no problem.’ I got one with sbt90.2 and it is fine, no issues. For your purposes (I read your other thread), I’d recommend the W2.1 Osram for most throw and least spill (should give you good runtime also). That is, unless you fancy a green-colored emitter (W1).
The light comes with a belt holster, which is good since it does get a bit tiresome to carry in the hand for much more than a half hour… not that it’s heavy, but it’s front-heavy (not balanced) with its large head.
I got 2 K1's - one W1 and one SBT90.2. There is a small, minor mark in one reflector but has no effect. Both are great lights, great quality, great design. Absolutely the best driver design I know of for the W1 LED's - perfect max amp level (4.9 amps), solid regulation, and re-programmable.
I'd buy a 3rd, maybe 4th with different LED's if I could reason why I need them
Hi guys, thinking of buying it and wondered what is the inner tube diameter of this light? Have some rewrapped vapcell batteries and I am not sure if they’ll fit…
I use Vapcell Red 4500mah 20A n G50 for K1. No prpblem.
Thanks for the info!
On mine, it measures 21.8 mm inner diameter. I tried a thick-wrapped cell with 21.8 mm outer diameter, and there’s just enough space for the cell to work without getting stuck. It slides out easily with just gravity.