[[ GXB20 Driver – Homemade Constant Current Programmable XHP50 Single-Cell Boost Driver! ]]

What Dale and Tom said. Wow. Thanks for sharing the project with us and who knows, maybe I’ll build one that works. :slight_smile:

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.

“Improved lowest level of CC brightness (just around 1mA - true ‘firefly’ mode)
Modes for my own firmware: 1 = firefly <1mA, 2 = low ~180mA, 3 = mid ~600mA, 4 = ~1.8A (~1000 lumens), 5 = 3A (turbo)
Measured efficiency of 92% at 3A (~6.5V) output”

Can this driver correctly work with triple LEDs, 8-9V ?

17mm 9V/1A for 219C triple will be very interesting driver.
(and <=5mm height, for E2L host)

Yes it will work just fine with some small adjustments (e.g. to make sure it doesn't try to drive 9V at 3A, adjust components to make it more efficient st the desired drive currents etc).