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

Grat work ! I want one !
Welcome to BLF :beer:

Nice!! Can’t stand the wait to see these kind of drivers for sale. Would you consider selling some drivers here?

Omg… I want one! Put a price on it, please. Btw, welcome!

Very nice!!! Welcome to BLF……… :slight_smile: …. :+1:
I also would love to get a couple of these………. :wink:

I would take one in parts, can do solder job on my own

That has got to be the most amazing “first post” I have ever seen.

Sounds marvelous, I can’t wait to hear about the real-world experience!

I agree with everyone else, I want :stuck_out_tongue:

Very nice…finally good runtime by using a 18650 instead of two 18350s!!

Is it compatible with low current button? Or can be easy modified for it?

Welcome to BLF. Subbed!

Absolutely brilliant! :+1:

I’d bet you have some other great projects we’d love to see too.

Welcome and Wow! I very much look forward to seeing how this works out, You have our attention. :+1:

Loneoceans, welcome aboard. For me your timing couldn’t have been any better. I’m working to get a bit more life back into the P60 style flashlights. A machinist is currently building a prototype host for the newer 20700/21700 lithium-ion cells. This would allow dropins another host with more potential. Your 17mm driver combined with the new Cree XHP50.2 would push this project to a pretty decent level. I can only hope your driver comes to life in 17mm’s soon.

I think you wont be able to put out more than 1.8A with this inductor.

Thanks everyone for your kind words and comments! Hopefully when I get this driver done people will find it useful!

This really wasn't my intention and I plan to release all this open source if people find it useful!

However if enough people are interested I can find a way to see if I could get a batch of them fabricated, so do let me know! Assembling by hand takes a little too long since soldering does take a while, so I'll have to see what sort of assembly options there are before I can give a price estimate. :) Unfortunately I wasn't able to put up an OSHpark order since the PCB spec is a little smaller than OSHpark... (trace / spacing limitation).

Also, just thought I'd ask - are there any companies whom I might be able to do some sort of collaboration with to offer these for sale who can help with assembly and distribution? I'm just doing this for a hobby and I'd be happy to have people solder up their own drivers but this driver does have a few pretty challenging components to solder due to the small pitch QFN packages.

I specifically designed this (as a quick weekend project!) as a mod for my cheap flashlight from Amazon which only has a single tail-end switch. However this necessarily requires the switch to handle the full current. Fortunately it can be easily modified using the internal boost converter fet as the main switch for true low-current button operation. The Attiny84A is also much more capable than the usual ATtiny85s often used so there's a lot of overhead available. Regardless, I'm very new to the budget/flashlight community so I'd like to understand these kinds of topologies better - do such flashlights have 2 switches? Or just 1 switch having the main power from the battery permanently connected to the driver?

Thanks for the background! Once I make sure the 20mm driver is working fine, I'll definitely look into doing a 17mm version. So any features / suggestions / thoughts are most welcomed :)

That was a concern I had as well - how to find an inductor small enough to fit!? Fortunately this mighty inductor has a 12A rating with 13 DC saturation current rating! Based on my simulations with 3.9V input and 6V 3A output at my operating parameters, the inductor only sees between ~5.7 to 6.2A and well within spec.

But the proof of the pudding is in the eating! So I managed to do more work and run it at full power - it works great with some ~6+A at the input side!

I was able to spend a bit more time to work on the firmware, with the idea of keeping it as simple as possible and avoid making it far too complicated with too many modes. It's still far from complete, but I was able to test basic functionality of different brightness values and under-voltage sensing and protection.

I was also able to run it for a while at its full 18W (6V 3A) output driving the XHP50 LED! The LED (on the 20mm heatsink) gets - extremely hot - really quickly, so the limiting factor of running a XHP50 at its highest power certainly seems to be more of a heatsinking issue than being a challenge for the driver! :) The LED is of course, very beautiful and bright!

Next step is to tidy up the firmware into something presentable (I'm sure lots of people here can do a much better job than I can!) and then I'll put it into the host and see how it performs!

Respect go to you loneoceans :smiley:

when are they available to purchase ? :slight_smile:

Amazing work! Thanks for sharing it.

I am a fan of boost drivers and buck/boost drivers. I like the predictable output levels they provide. In some ways, I am a throwback. For flashlights that use low-voltage emitters, such as the Cree XP-L, I would rather have a well-behaved boost driver—and the flat runtimes it produces—than a FET driver that runs "direct drive" in its highest modes. I don't need a flame thrower that pushes an emitter to its limit.

Yes, I know. That makes me the oddball around here!

In one fell swoop, you’ve managed to address several longstanding limitations of running lights off single cells:

  1. Lack of a widely available open source boost driver (allowing high voltage LEDs)
  2. Lack of a programmable current controlled driver
  3. Perhaps a shift away from dependence on 7135s
  4. A programmable board with a smaller QFN package (Most drivers here use the larger SOIC-8)

Welcome to BLF! This may be the beginning of a new wave of drivers.

To answer your question, most flashlights have a reverse-click switch on the tailcap that handles the full current. The other common type is an e-switch, where a single low-current electronic switch (often side mounted near the driver end) controls the modes with the battery permanently connected, variations on the theme include having 2 buttons or a magnetic ring as a switch.
There are some rarer lights with the e-switch mounted on the end, but these require a carrier for the battery with a separate signal wire going to the tailcap.

Welcome to BLF! This is truly a wonderful first post. Thanks for sharing this with us! I hope you enjoy your stay!

A few thoughts I have:

  1. Learn about Direct Thermal Path MCPCB boards for LEDs. This will help you tremendously with heat issues.
  2. Have you thought about using solder paste and re-flowing the components on the driver board? If done right, it’s a lot easier than individually soldering tiny components with a soldering iron.
  3. 17mm really is the most common driver size we see in most flashlights. So getting your design into a 17mm footprint will certainly make it more universal.
  4. Other sizes are nice, too. If you’re interested, the easiest way to make multiple sizes is to lay out for the smallest possible size, then keep the same layout and only extend the board diameter for the “larger” driver sizes.
  5. Have you thought about making a single-cell 12V boost driver? We could certainly use one for the XHP-35!

^ about 12V, i think he(we) can modify the Feedback Resistor, so the voltage can change
if only this driver is 17mm