Jensen567's Entry for the 5th Annual Old Lumens Scratch Build Contest - Machine Made Category

You enjoyed building this light and I enjoyed reading about it just as much. I admire your driver modding skills as thats way out of my league. Well done and congrats on the finished working light. :beer:

Awsome job

Thanks guys. Does anyone know if there is another light designed around the 21700 cell out there? I’ve only taken a quick look around Google and didn’t turn up anything. Found a few 20700 and I know you can fit them in some 26650 hosts, but I didn’t find anything made specifically for this cell size.

Nice work and images. I really enjoy seeing how folks work!!! I need more time here. Thanks for Sharing!

TL

So I have identified one mistake I made in my driver modifications. When I changed my LVP value by modifying the resistor, I neglected to think about the fact that this driver can run on 2S cells also, and has LVP for those as well. The result is that with a fully charged single cell the light starts flashing as if the battery is dead, because it thinks it is at the lower voltage for a 2S input.

This goes away once the cell drops below about 4.05V and runs normally down to 2.7V or so. I did all my testing yesterday with a bench supply set to 4V and a cell at 3.7V, so I didn’t catch it.

The solution in this case is to modify the LVP divider again, this time so that I am only using the 2S range, in my case I will swap the stock 33k resistor for a 9.1k resistor, this should give me a cutoff at 2.6-2.7V, and I won’t have any high side problems as there is no 3S LVP value.

All back together and the new resistor mod is working as expected, no more flashing from 4.2V to 4.05V, and cuts off right around 2.7V. I ended up stacking a 13k resistor on top of the stock 33k resistor for 9.326k.

very good build ! i love home build light

Really impressed by how you are able to modify, correct and adapt different situations to your needs to make this final quad 21700 flashlight.
It’s a nice combination of all your current skills and knowledges you’ve accumulated so far.
:+1:

The light may be done, but I’m not! Decided to make some accessories. Some of these are 3D printed items, and I did draw and print them myself, but a 3D printer is not exactly a machine shop tool, so exclude them from judging in the competiton as I don’t think they meet the rules. Still want to share regardless though!

First up I made a lanyard hole in the tailcap. I never use a lanyard with my lights, but I like the hole as it does serve another purpose which will become apparent in a moment.

Next up I 3D printed a diffuser with some Taulman 910 filament, it starts clear but looks translucent white when printed. The surface finish is terrible because the filament I have is fairly old, and has absorbed a lot of water. The water actually boils out when extruded and causes bubbles to form in the plastic. Thankfully for this application, that’s not a problem. The design is similar to the diffuser Convoy sells for the M1 on the end.

Here is the real reason for the lanyard hole. I used a leftover piece of 1/16” stainless rod I had from another project to fashion a small hook, that happens to fit perfectly in the lanyard hole. The idea is that I can just hang the light with the diffuser on it out on a tree branch for a camp lantern, or at home on a ceiling fan if the power goes out.

Works well, already used it to do some work under my desk.

Finally I printed up some battery spacers for 20700 (this one could really just be a piece of paper), 18650, and 16650, so I can throw whatever battery I happen to have ready in the tube. I could have machined these, but it is so much cheaper to just print them, and they aren’t anything groundbreaking, just a size I didn’t have yet.

I’ve also learned some things about this light since I have been carrying it as my EDC. Mainly, that the sandblasted surface finish is fairly delicate and scratches pretty easily, which is not surprising really. There are already battle scars, doesn’t effect the function at all though, so just adds character. Otherwise it has been functioning as expected, I used it Saturday night in ceiling bounce for almost 3 hours on the second mode, no hiccups and the light got warm but not hot.

I built up another H2-C driver to test, oddly using the same sense resistor combination gave me slightly less current, 3.9A instead of 4.0A, but close enough, probably just resistor tolerances. I was really most interested in efficiency.

Also worth mentioning that I would take the measurements in Turbo with a grain of salt, my electronic load showed the voltage bouncing around and around 6.9V, whereas the meter measuring voltage on the driver board was a steady 6.36, all other modes were solid on both with the load showing lower as expected, so not sure what was happening there.

Either way, very happy with these results. Maintains great regulation through the entire discharge (Barring turbo), and efficiency in the modes that matter is basically 90+.

Why is the input current at the turbo mode dropping, when the input voltage decreases? The current should get higher, the lower the input voltage is. Output current is dropping as well. Why is this happening? Is this because the input voltage drops too low and the internal resistance limits the current? But then the internal resistance would have to be like 0.5 Ohm, so way too much.

I’m not sure, but I’m guessing it is related to the issues with my E-Load. I managed to get it stable once, but that was is, I tried a few things with no luck and gave up for now Since it was just turbo anyway, was more interested in the sustained modes. Really just need to use an actual LED and an external current meter, as that would likely solve it.

Ran the light until cutoff over the weekend. Used it in ceiling bounce on mode 2 for several hours. Cell voltage was 2.68V when I pulled it from the tube immediately after cutoff, and it recovered to 2.95 about 2 hours later when I stuck it in the charger. Pretty much exactly what I was going for. Also took a beamshot. Used my phone camera with 5000K WB. The color shows a bit too red in the photo, but not sure how I can fix it with my phone being my only camera. It does look rosy in person, but not pink. Can at least still see the nice beam the khatod optics produce, almost more like a reflector light than what I’m used to with Carclo TIRs.

Is it just me or is that picture missing?

Very nice light by the way. A great way to remember Old Lumens.

It does seem to be missing, I know it was there at one point. I would add the photo back to the post but I don’t want to break the contest rules.

Thats interesting to hear about the water absorption. I’d never have guessed. Its good to see the light still evolving. :+1:

This is a surprisingly practical build. I love the custom driver work and the high-CRI tint mixing with different Vfs in series. The tried-and-true tube design helps too, and if the 21700 battery format develops as expected it should be quite future-proof.

The high-CRI tint mixing is something I still need to do on some of my lights…

Thanks for the kind words guys. I still use this light on a daily basis, works as well as any commercial light I have bought.

I’m more than happy to help out anyone regarding driver modifications where I can.

Here is the photo missing from post #31. I don’t want to break the rules and edit a post during the judging phase, but I want the info out there. If anyone wants to attempt the mods themselves this would help.

Great work, thanks for sharing.

This got my vote as a purist for the People’s Choice Award. And making the diffuser looks fun.