>> Homemade Gxb172 led driver (complete!)

I decided to try to make myself the loneoceans gxb172 led driver. This was inspired by success of schizobovine and moderator007 when they try to build the gxb172 driver also, on this forum page https://budgetlightforum.com/t/-/50015?page=5. I am making a new thread because I think there will be challenges to build this driver and want to share my sucess or failure.

First step I use the files on loneoceans website and order my own oshpark PCB.

Next I order the component online. They arrived and I begin assembly. Some components are very small. I decided to solder the top side first where the MP3431 chip is. I use sharp pin to apply thin amount of solder paste to each pad under USB microsope which is essential. This took a lot of time.

Then I carefully place each component on the pad, after dipping each component pad with flux pen. The temperature IC is the most difficult to place and I did not add extra solder since they have solder ball on the bottom of the chip. The big inductor is also difficult to place with out knocking other chips aside. But thin tweezer and paitence help me.

I order wrong component for the 1206-size capacitor, so I will solder it next time.

Finally I use a hot air set on 300C and low strength and manager to reflow all the parts! I use spray flux cleaner to clean the flux after completed.

I use USB microscope to inspect the temperature IC to see if solder ball flow:

This is top side of pcb almost complete.

I recommend useing the website image to place component because some silkscreen is missing due to the text sitting on top of via.

Next step to get capacitor 1206 to solder on, and solder bottom side.

Nice job so far!

Thanks for chronicling your journey here. Those 402 parts are super small. I don’t envy you having to place small parts, but I wish I could get a few of those drivers WITHOUT having to do it myself! :open_mouth:

actually the 0402 parts are easy to place, and quite easy to hand solder using thin tweezer and thin solder wire. The most difficult so far was the boost IC with long pad below, and the small temperature sensor with bga.

size compare: the 0402 is 1mm x 0.5mm size. the temp IC is 0.76mm square. it is easy to breathe it in!

:open_mouth: :open_mouth: :open_mouth:

Hmmm. At least you’d know whether/not you’re running a fever, then.

The only thing that was difficult for me was the temp sensor, the pads are really tiny. The small parts are tedious but reflowed well with the hot air station.
Now if I could just get the 841 programmed I be in business. The USBASP programmer most of us use isn’t wanting to cooperate. I would really like to find away for this to be programmed without having to buy a more expensive programmer to keep the cost down for anyone who ventures after us.
Wishing you luck clientequator, looks good so far. :+1:

Wow! Looks like a chunky box of coiled copper up there.

Given the bill of materials, cost of the board and amount of man hours this totally looks like an inexpensive project. Joking, of course. ;-)

Cheers ^:)

Fri, 01/11/2019 - 07:52

Mr. Barkuti, yes this project is expensive for driver, but it is interesting project and challenge to put together for hobby maker, so I hope the result is working!

You are correct this inductor is one of the most interesting I have used before. It seem quite big and cube shape, but only because 17mm PCB is very small! Even though it is only 7mm square small, on datasheet it is actually 19.6A saturation current, which is amazing!


Soldering this took a while but I recommend just some careful waiting with hot air, and allowing it to cool down before touching it because it remain hot for long period of time and solder will still be wet.

Cool :+1:

Today I solder up the bottom of the pcb.

I have to say it was much easier to do compare with the other side! The most difficult chip to solder is the atmel 841 microchip, but I use the same method of solder paste with pin and hot air and a flux pen and eveyrthing work very well.

The rest of the component are at most 0402 and easy to solder with thin solder wire and USB microscope.

loneoceans suggest the opa333 opamp is temperature sensitive, so I solder that last with soldering iron set on low heat.

The pcb is now complete, minus the 1206 capacitor which is on order, and to program the 841 chip. I was able to email loneoceans and he provided link to make the pogoprog on OSHPARK!


for the component:

Pins - P13-0123 or P50-B1 x 6

Switches - CAS-220TB

Regulator - AP2114H-3.3TRG1

USB - 1050170001

F1 - 0ZCK0100FF2E

C1, C2 - 4.7u 0805

D1 - 0805 LED

R1 - 1k 0805

Header - 2x3 100mil

I will make one and use atmel ICE to program the 841 controller. The pogoprog has external power using USB, so I will use 3.3V on vcc line to program the 841 chip.

Nice, thanks. :+1:

That temperature ic would give me nightmare. Good job!

Nice job clientequator :+1: .
I’m still working on getting the 841 programmed with a usbasp programmer. No luck yet :person_facepalming: .

I got the 1206 capacitors. Now the gxb172 driver is complete. Next step is to solder on spring and wire to the driver, and program the attiny chip with pogoprog programmer.

For the flashlight, I will use convoy s2+ host and plan to use xhp50.2 led.

Today I focus on led.

After reading this forum and thinking, I decide to use brightess possible led, so I decide on XHP50.2 maximum bin led. This is J4 led with 1239 lumen at 1400mA 6V.

For heatsink, I use notigon copper pcb in 16mm size to fit a convoy s2+ flashlight.

To solder, I use datasheet recommended heat with hot air and solder paste (lead). I keep pcb hot at 200C for long time, then turn heat to 240C until solder melt, and place led on solder.

The result looks good to me.

This is my progress so far. XHP50 not as big or bright as schizobovine XHP70 led, but I think will fit Convoy flashlight easier.

I borrow ATMEL ICE from friend and will use Atmel Studio to program 841 and to set correct fuses next.

Mr. moderator007, you say you program this with usbasp in the end - was your pinout drawing of the programming pad correct in the end on the gxb172?

Thank you!

It is correct, all the pads are directly connected to 841 also. No components in series that would cause any interference.
Checked on a unpopulated pcb with a DMM.

Thank you. I have another question. Do you recommend what sort of spring you use for gxb172? I am not sure to use metal button like schizobovine or upside down spring like loneoceans.

Today I make some progress. Silicone wire arrive and I use it to solder to driver.

Like schizobovine say, I test it in Convy S2 brass case and some part almost touching, so I use loneoceans idea and solder copper wire around driver like this.

This is a little tricky and I had to use hot soldering iron and some clip to hold it in place, and add flux.

Finally, my advice to others - I recommend using thinner wire. My wire almost as thick as pcb thick, so it is almost too thick for retaining screw to hold the pcb (just able to fit!!!). I recomennd use thinner wire maybe half thickness. As long as it can clear height of 0402 capacitor, then there is no problem.

I did not solder whole ring in case I decide to remove and use in other flashlight, so I only solder about half ring.

Great work and great pictures. :+1: