A couple of Micro ATL projects put on hold

I mentioned early on, in the G5 build post, that I had some side projects in mind to help fund development. Well, when you work on flashlight designs, there are hits and there are misses.

I was all set to let these projects go quietly into that good night but with all the time, effort and more than a small bit of $$ involved, I thought I would post them for a thought exercise or maybe just entertainment if nothing else. So read on if you're so inclined.

Project 1:
This was going to be a simple one. The idea was to offer a couple of small updates to an already awesome little light, the Nitecore Tube.


If you haven't heard of the Nitecore Tube, this is a slick little rechargeable light with a great interface. It has a 100mah lipo battery and a 45 lumen coolish neutral HKLeled LED (more on the HKJeleds in project 2). There are two brightness settings that cycle from low to high or instantly to high if the button is held instead of pressed and released.

My idea was to offer individual or combinations of three upgrades; magnets, beacons and or a warm version of the HKJeled.





Sorry for the blurry pics, they looked great in the viewfinder but you get the idea. Note the green beacon. The HKJeled doesn't exhibit the strange, green blocking phenomena that Nichias seem to exhibit. Went with a green beacon as the charge indicator for the battery was blue and a blue beacon made it hard to tell when the battery was charged.

These upgrades turned out really great; the warm version of the HKJeled looked warm, the beacons worked every bit as well, if not better than on the Micro ATL G series lights (because of the clear or mostly clear plastic housing) and the magnets did what magnets do.

The problem with this project turned out not to be technical but rather financial. Ie, what could I possibly charge for these upgrades to make a $10 light worth it to a customer to upgrade and worth it to me to invest the time and expense to do the upgrade?


Project 2:
This was actually two separate projects rolled into one.

Hoping to capitalize on my experience with the HKJeleds from the Nitecore Tube project, I came up with an idea for a HP versions of the Micro ATL G4 and a more HP version of the Micro ATL G2 ULE HP. Both lights would have been available in aluminum, copper and brass and outfitted with HKJeled LEDs.

If you're not familiar with HKJeleds, these are 5mm LEDs that have 5 dies within them and run at 100ma. The primary downside to using these LEDs in a flashlight, is that they are 60 degree rather than the traditional 15 degree LED typically found in flashlights. So, the HKJeleds produce a crazy bright and still very useful but floody beam. Was all set to post a pic of a HKJeled but realized I didn't take one. Look on the interweb and you can see what they look like. These look very similar to a typical 5mm LED but with a bit of heatsink at the tail end.

The Micro ATL G2 (version 3 or V3 was the working project name).

Note, these are just beautiful LEDs! I mean the package just looks fantastic, water clear epoxy, attractively colored dies, just a really well done 5mm package.



The chassis looked identical to the Micro ATL G2 ULE HP, until you hit the go button that is. There is just no denying 120 lumens. Beam shot from a prototype Micro ATL G2 V3 running three HKJeleds at 300ma and producing around 120 lumens of light in neutral cool and warm.




And the beacon.


Had high hopes for these! And it looked really good on the bench but the problems started showing up when testing the completed lights. The lights definitely got warm, 300ma or a bit over 1 watt in such a small package will make a decent hand warmer for sure. I had thought that metal in the chassis would help dissipate the heat but I think it did just the opposite; caused the heat to stay around the LEDs rather than drawing it away. Eventually, the LEDs would start to fail (the strobe of an expensive dying LED is a sad sight to behold). The neutral cool version seemed to be the most susceptible but the warms had failures as well.

I think this project could still be viable, sometime down the road but it would require some type of a metal heatsink attached to the LEDs heatsink at the tail. So the HP G2 and G4s are on hold for the foreseeable future.

So, it's back to the G5 full time. Look for several G5 build updates over the next couple of days and as always, thanks for looking!

Thank you for sharing that with us. Kinda behind the scenes in your lab is awesome.

Thank you sir!

your lab

Click to expand...

Lab - I like the sound of that

Building a flashlight can be extremely educational and eye opening. The deceptively simple, everyday nature of it make it a perfect place to start to "build something yourself". In my own case, I found similar things - it costs more money to do something that expected, and it isn't unusual to find out that you missed a technical detail, even when you thought everything was covered.

Home building lights is really a great general life learning hobby, and now that you have a few test builds, the old saying kicks in. If at first you don't succeed, try, try again.

Perhaps start by looking to see if the LEDs have a data sheet, and reading it very carefully. Certainly by the time an LED is running 1 watt, it will need a good, continuous thermal path from the LED heat sink to the body of the light, and into your hand. In case you are curious, the heat is carried by your blood stream (like a liquid cooling system) and spread out over your skin. This is why a cold drink and testing hobby flashlights with your friends is so fun.

Perhaps try to modify the case of the small flat light body (project 2) so that it has a real thermal path from the LED to the body. Maybe there is a "prototype" way to take an Al screw and run it from the larger side of the case to the area near the LED heat sink. A file can flatten our the side of the screw so that the LED heat sink fits flush to the screw, which could provide an imperfect, but perhaps sufficient heat path.

By the way, LEDs from companies like Lumileds, Osram, and Cree will have some, but much less light output droop than other brands. They spent a lot of money on the technology to solve this problem. All would still need a continuous thermal path from the LED heat sink to the flashlight body and into your hand. There is no free lunch.

HarryN - thanks for the tips! And I absolutely agree with you that a cold drink while testing a flashlight couldn't hurt!

I started thinking about what a heatsink would look like for the HKJeleds after writing this post up last week. Over the weekend I headed out to the band saw and came up with this simple prototype for a copper heatsink.


Hard to get an idea of scale without a size reference but it is made from 1/16", 110 alloy copper. The LEDs would have the cathode soldered to the heatsink.


I put this combo together (had to get the 60 watt iron out, woof woof), replaced the non heatsinked and failing LEDs and began testing on Saturday. So far this setup looks very promising. The area around the LEDs is noticeably cooler and the heatsink appears to be transferring heat to the aluminum case very well.

So, if a small heatsink works, why not stuff the biggest heatsink possible into the light? Came up with this second prototype that I am assembling now. Looks rough but if this light goes into production, the watejet version would be much more refined.

Well, sometimes you need a really good setback to allow you to move forward. And I had a couple of potential show stoppers with the Micro ATL G2 V3 project.

As I mentioned earlier, the LEDs seemed to be very sensitive to overheating and I came up with the idea of adding a heat sink. That idea worked so well that I decided to build a bigger heatsink. That's when things really went off the rails. LEDs on the larger (and in theory at least) more efficient heatsink began failing, while the LEDs on the smaller heatsink happily continued to produce bucket loads of light. Then I noticed something.

The setup with the smaller heatsink was put together quickly to see if I was on the right track or not and did not include a beacon. The setup with the larger heatsink did include the beacon and it was always the two LEDs in front of the beacon that failed while the third beacon that was not in front of the LED never failed. The beacon was right up against the primary LEDs and what I think was happening is that the beacon kept heat from escaping out the back of the LED and caused them to overheat and fail.

So what to do. I really didn't like the idea of abandoning the beacon, I find myself completely dependent on that to find the lights. And then it hit me, one of those ah ha moments that make me wonder why I didn't think of it before... I decided to use the primary LEDs as the beacon.

This is what I came up with, driving the primary white LEDs at around 20 micro amps (have to do some more calculations to verify that but this prototype should be in the ballpark).


Compared to a G4 with the blue beacon.


Sorry for the fuzzy quality of the photo, just couldn't get the camera to focus but you can see that the primary LED beacon is at least as bright as the blue beacon.

A big bonus is that this is phenomenally easier to wire up than the standalone beacon.

Going to do some more testing and this might be optimistic but the Micro ATL G2 V3 might be back on track.

Where does one source HKJeleds?

Good question. That is one of the challenges using HKJeleds in the G2 V3; sourcing the LEDs.

You can find the warms in small quantities and at a decent price on Ebay. There are two versions of the warm, I'll have to look up the specs but there is the warm that I plan on using and a much warmer version that I wouldn't recommend as it is really too warm and not nearly as bright. The neutrals can also be found on Ebay but only in large quantities and at a bit higher per unit price. I got lucky with my initial neutral purchase and found a source on Ebay that sold the neutrals in smaller quantities but that source doesn't appear to be around anymore.

Good work there. What circuit do you use to drive those and where do you get them? I imagine it would be a boost driver that can still drive the LEDs when the battery voltage drops below fV. I wanted to drive some of those too but don't know where to buy the driver circuits.