>> Homemade Gxb172 led driver (complete!)

KnHawke that’s great idea starting it up.
Well any of you guys with skills to make them i’d be happy and i’m sure a dozens people who expressed their interest so far.

OK, heres an update, im currently in contact with the manufacturer in China and getting quotes.
I want to ask the community a few questions, so I have started a new thread on this.

wow this is a great news! Thank you to Nzoomed, for helping to make this group order! It is right that when making this driver, small parts are challenge to solder, so it is good to have professionally soldered driver if people do not have small soldering iron and tools!

It not only is the challenge to solder, reflow or assemble the parts in a driver (or whatever), it also is the man-hours cost. It can be fun the DIY thing for a while but once a piece or two is done and the experience is assimilated, all it remains is the inherent, high effort involved.

This driver is a unique piece in itself, and even if relatively expensive its sales will never dry, always dripping at least.

Yes I agree, I hope I can get it made for the most reasonable price for everyone.
Will keep everyone updated.

I’ve finally designed and successfully built my own boost driver based on the GXB172 schematics but with a few changes to suite my own purposes. As my design is based on the GXB172 I also get this flash. I have found my own solution to it, but I’m trying to find a post from loneoceans (I think it was from him) that included some suggestions on addressing this. I think one of the suggestions was lower values on the feedback divider resistors. I’ve spent quite some time using search words and I’ve read through the GXB172 threads but I can’t find this post… I know I read it, I just don’t remember where… Does anyone know where the post I’m looking for is and can point me to it?

Edit: No worries, I found it… It wasn’t a post, it was in an email conversation. No wonder I didn’t find it here :person_facepalming:

Mike C, that is good! Do you figure out the best method for removing turn on flash for dim mode?

Well, I can’t say it’s the best method, for me it’s the only method. Probably considered as an ugly hack by the electronic gurus, and it won’t work as a permanent solution on the current GXB172 design.

I’ve been trying a few different things for a few days now, then I remembered something loneoceans wrote: He wrote that the capacitor connected between -IN and OUT on the op-amp (C8) can be reduced to lessen the flash, but he recommended 1nF for stability. That’s when the penny dropped. The flash is caused by the inrush current to that C8 capacitor. The voltage from the feedback divider is “sucked” up by it, making the boost IC get lower feedback voltage, so it in turn raises it’s output to get feedback voltage up to 1V. Once the C8 capacitor is “full” the feedback voltage stabilizes and the boost IC reduces output to keep the feedback voltage at 1V.

My solution is to pre-charge that C8 capacitor before enabling the boost IC. I’ve only tested the concept by soldering a wire to battery+ and another wire to the OUT side of C8, and connected them with a switch so I can see the difference. It works, the flash is totally gone. The concept itself can be tested on the GXB172 but a new design is needed to utilize this. I just made a new design with output pin from MCU through a small voltage divider as my C8 “pre-charger”. I’ll turn it on, wait a small moment (will need to test how long) and then enable the boost IC as I turn off the “pre-charge” pin.

A xhp50.2 in a s2+ sounds interesting

Have you completed the project

Beam shots !!!

Are you asking me about the project? Here in post 34 i write about complete project: >> Homemade Gxb172 led driver (complete!)
Since I complete project, no problem with S2+! Still working flashlight and very bright, I use for hiking and daily, but usually keeping light lower brightness because I do not need turbo most time, but it is very good for making friends go wow! I feel motivated to upgrade to XHP70, but I think it need some modifying on the reflector to fit bigger led.

Update- I read that now there is 3V XHP50 led, so it is probably possible to use regular fet driver to acheive similar result. When gxb172 first appear, there was no such led and was a very new inventive driver.

thank you Mike C for explaining. I wonder if loneoceans has fix for it, and if it appear in new lume flashlight driver!

I have a bunch of these 3V XHP50 LEDs but I’m not very fond of them myself. I built my boost driver for the MT-G2. I’m also going to have a go at a single 18650 zoomie with XHP35 HI.

What are the bin, tint and CRI options for 3V/1S XHP50s? This matters, a lot. I don't have a need to brag about how much pieceofshite lumens my flashlight outputs. 3V/1S XHP50s are only “B” generation, made only in DT and 51 chromaticity region kits (above 5000K, “cool” white only) and only @#$% CRI. No thanks.

With GXB172 you have full regulation an can utilize most of the battery capacity at the specced output power levels, while also enjoying your favorite CRI and tint emitter.

Has anyone loaded the firmware into Arduino? It’s available on Github. GitHub - loneoceans/gxb172-attiny841: Firmware for GXB172 Flashlight Driver; Atmel ATtiny841

I’d like to tweak the power levels but I can’t get the original program to verify. I have the correct versions of the included libraries.

The error is at line 395.

“GXB172ATtiny841_V1p0_WIP:395:24: error: ‘void PID::Initialize()’ is private within this context


i think i remember this. loneoceans has modified the PID library from the original. To make this work, you don't need to install pid library in arduino, but instead, use the pid files included on his source code. Just copy the pid cpp and h file to same folder as the arduinio ino file, and it should work from my memory.

Funny mess there, did you wanted to say Arduino Uno? :-D

Thanks. I still had the same problem but you got me thinking.

Turns out it was using the same two pid files in the default libraries because it could not find them in the sketch library. The ino file is in a subfolder, copied the two files there and it works.

My English is not the best, but it is ino. The file extension that Arduino toolkit use is .ino.