Light is done! Really happy with it, a nice 4000k color temperature, guessing around 2000 lumens, beautiful beam from the khatod 10 degree quad optic and RMMs quad board, and lots of runtime from that almost 5Ah 21700 cell. The host doesn’t look half bad either. Lots more details with the pics.
Finished up the machining on the tailcap first. Some grooves to match the head and give it a little style. Sand blasted finish of course.
Tailcap assembled. Brass ring was a very tight fit, but not interference fit like the insert in the head, so I used a center punch to peen it into the tailcap around the edges. Won’t be going anywhere. After that it is a standard tailcap assembly, boot, washer, switch. Then soldered in place. Measured it at about 5 milli-ohms at 10A with the big Omten.
Now to take care of the driver. I used a heavily modified H2-C from kaidomain. First I removed the reverse input protection FETs on the bottom and bridged them with lots of copper braid and solder. Should help with heat from the IC too. I have covered this more in my thread on buck and boost converters here.
After that I changed the spring for a convoy spring and bypassed it with solder braid. I also replaced the short wire off the inductor from 24ga to 20ga, and replaced the output wires with nice short 20ga as well. That was the easy stuff. Next, using the schematic I posted (also in the driver thread above), and the MP3428 datasheet I did some resistor mods to change a bunch of parameters.
Once the inductor is off we can see the circuit. The purple circle is the current sense resistor, stock is 2XR100 in parallel, giving about 1.5A on high. I replaced these with an R025, R075, and R500 in parallel to give me about an R018, which I measured at 4A on high. In the green circle we have the high side FB resistor (R1 in my schematic) for setting the output voltage. Stock the driver is setup to run an XHP35, but to help efficiency I wanted to run 2P2S emitters so I needed a 6 volt type output. I swapped the 200k resistor for an 82k, giving me about 7.5V OCV, which is decent for 2S emitters. Finally, in the blue circle is the high side resistor for the battery voltage divider (R11 in my schematic), this is used for driver LVP. Stock is setup to reduce current and eventually cut out at 3.0V, I wanted to get a lower cutoff, so I stacked a 130k resistor on top of the stock 33k resistor to give me a 26.3k resistor for a roughly 2.7V cutoff. Put it all back together and it worked great. 4A on turbo to the emitters, after 60 seconds it starts dropping to about 2.8A over another 60 seconds. Low mode is about 20mA to the emitters, nice and low.
Next up was emitters, since it was a quad I would need 4, and Nichia is my go-to, after using the 90 CRI Nichias, nothing else seems good enough. I used one of RMMs MTN Quad boards which I slightly modified. It is setup for Carclo quad optics, the khatod has the same emitter spacing, but the standoffs are further out, so I turned the optic leg holes into slots, the khatod optics hit the edge of the board to press it to the head once the bezel is tight. Since i am a fan of tint mixing and Vf mixing with boost drivers, I decided to go with 4 separate emitters, and get as much red as I could at 4000k. I went with a 219B SW45k R9080 in parallel with a 219B SW40 R9080, then those were in series with a 219C SM4070e and a 219C SM353 in parallel. The net tint is about 4000k, with a nice rosy hue. The reason I decided to stick the two pairs of emitters in parallel is so that I should be able to keep running if any 2 emitters fail.
Finally time to assemble the head. First I dropped the driver in, perfect fit, and soldered it around the entire ring. Next up was the emitters, some AS5 thermal paste for the MCPCB, solder the driver wires, then just stack on the khatod optics, Kaidomain AR lens, and screw down the bezel. Now there is just one thing left, screw the parts together, pop in a battery, and turn it on. And….
It works perfectly first press of the button!