Is that something you would sell or is it for personal use only?
Realy like the output of my ee x7 xhp50.2
But the driver is….not great.
Would love to put one in a m2 or similar host.
Thanks for your kind words! I’m currently working on a write-up on this project and releasing all open-source as well as offering the boards on oshpark so everyone can build one for themselves. I do have extra boards and I can offer firmware-flashed boards with MCU at a later time, but I really will not have time to offer built drivers. I do understand it’s a bit tricky to put together and I highly recommend either a micro-soldering station with magnification for hand-assembly, or even better if you have solder paste (can apply using a needle) and reflow with an oven or hot-air. Updates will be on this thread.
I’m not quite sure if it makes sense from an electrical point of view, since there’s really not much use case for it except in flashlights (which makes up a very small % of their sales), and that it’s not electrically efficient since resistive losses go up by the square of the current.
I’m 100% sure I can fit it all onto a 17mm driver with no less functionality and with a single PCB. Just need to find some time to do it!
It takes a while to assemble this together by hand only because it’s fairly small. So I don’t really have any plans to offer these for sale as whole drivers, unless I have some help in getting this mass-produced! Otherwise I’ll be releasing more open-source so anyone can buy the PCBs themselves on OSHpark or similar and assemble it 
I'm seconding Dale's post, wow!
Very much interested in building a couple of these. Also very interested in the "New 0.4mm pitch micro programming header for ATtiny84A" you mentioned, and how to utilize it. I would like to be able to make "tweaks". I'm sure real estate is tight, but if you haven't yet, if you can add 1 to 3 pads for spare I/O pins, much appreciated. Indicator LED's is one thing I'm thinking of or possible dual e-switch support.
I'd also love to see those pics of the board blown up a bit.
What Dale and Tom said. Wow. Thanks for sharing the project with us and who knows, maybe I’ll build one that works. 
Totalt understand that.
To me it would probably be morr of a pain to find all the correct components than the accual soldering.
I think if the 17mm works it would be a huge demand as there is nothing like it and lots of people want to get away from a 2×18350 setup.
I managed to get all the components on a 17mm board, I used a different digital potentiometer, so I had to change the connections to the ATTiny.
One more thing: In this design you need one wire across the board on the top side, so it’s usable, but not great…
Much more work needed for this design…
Would anyone buy these over the H1-A which is also 20mm?
If you could get a better firmware for your driver (with off time memory, etc…) then that would surely give it an advantage.
Squeezing it down to 17mm would be another big advantage for those that already use hosts with that size.
Otherwise, new builds can be done with hosts that take 20mm drivers.
Could you eliminate the air wire by using four-layer boards and running traces in the middle layers?
Sure that’s possible with blind vias and buried vias, but I’m stuck with 2-Layer designs on my software.
I think it’s even possible with 2-Layer and without an air wire, but that takes a lot of time, just positioning all the components.
Does Oshpark even do 4-layer? I think you’d need a larger minimum order from Seeed studio or someone else to get them. This is where I was thinking some of the miller’s donation/developement money should go if we want a boost design to get from open source to production.
Yeah, OSHPark does 4-layer. Richard made one of his MTN-MAX buck drivers in 4-layer. I don’t know if he still sells that one. But, he was getting them from OSHPark. The price is a bit higher and the lead time is longer compared to the regular 2-layer boards.
OSH Park does four layer boards. They don’t support buried or blind vias though. The lead time is shorter than the two layer boards with extra copper thickness, and not noticeably longer than regular two layer boards.
Oh yeah, I forgot that they don’t do blind vias. But, even if you have to do a via all the way through the board, that still takes up less space on the top and bottom than a complete trace. The vias can be made small and placed under components or in some other out-of-the-way place. Still, if the layout can be made to fit onto a regular two-layer board with a 17mm diameter and no air-wires, that would be better.
Cool, great way to add copper
Very nice indeed. I just saw this thread after finished reading your PM. I’ve been looking for a compact 20mm buck boost driver for some of my projects too (non flashlight). Sweet, now we have a good programmable driver for those 144AM.
- Clemence
Mike C asked me to share the libraries I used in EAGLE to design my first attempt of the 17mm board,
so here are the devices I created myself: My Library
If you need the ATTiny84a footprint as well, I suggest downloading the Sparkfun library here: Sparkfun Library
If you want me to design the MAX5424 as well, just ask for it
Thanks for sharing Schoki!
loneoceans: When you have made these boards, have you used stencils or applied solder paste by hand? I have had a few shorts on MCU pins when using default MCU footprint for my 841 when applying by hand. The default mask pad size is bigger than the actual pin and overlapped with the other pins. I made it better by customizing the footprint so the mask pad size is exactly the same is pin pad size. However, I’m now using stencils I made with an even smaller cream pad size for the pins.
I think he soldered it by hand, pre tinning the pads and then reheating them holding the parts with tweezers
Looking good! The 20mm version would be perfect to put into a Convoy L2 with short battery tube.
Laying out the board on 4 layers would certainly not only allow better performance but also allow better routing. However specifically avoided a 4 layer stack to keep the PCB costs as low as possible. Adding blind or buried vias significantly increases cost so I usually try to avoid them as much as possible. I'll explore a little with the 17mm version when I have time though it looks to me that there should be no problems making a 2-layer 17mm version.
I didn't bother fabricating a stencil for this since I was expecting to only make a very small number of boards, so I soldered them all by hand with a combination of reflow and solder paste applied by hand using a toothpick (typically I don't get any bridges if the right amount of paste is used, or I fix it using solderwick), and solder the rest by hand under magnification with a tiny tip soldering iron. Like you mentioned soldermask expansion needs to be adjusted. I think I used 1 or 2mil expansion, depending on the fab I go with.