Ok, finished my GXB172 build this weekend and can confirm it works! Overall a decent and fun DIY experience. Pix (complete album):
Fully assembled and operational. Fiat lux!
Halfway done
Fully assembled, top
Close up shot of the driver mounted in the pill. I had to dremel down the inside of the retaining ring, as C1*5* was shorting out on it.
XHP70.2 4000k P2 bin LED for testing
Beam shot, taken during daytime.
Assembled flashlight with the two other GXB172 PCB copies from OSHpark.
Thermal image of light just before it turned off from thermal shutdown (or voltage, hard to tell if it’s 4 or 5 blinks). Outer shell is 64C, which would make the 75C threshold for thermal shutdown likely since it’s going to be hotter inside the brass pill.
Notes for fewllow attempters:
1. Miso en place. I sorted and labeled all my components in to two bins, one for the top and one for the bottom. The resistors are mostly unlabeled, so if something goings flying, you may want some tweezer component testers to make sure you are putting the right value in the right place.
2. Get some magnification, some good tweezers, plenty of toothpicks (for solder paste application), a LOT of light, and plenty of patience.
3. Took me about an hour or so to set all the components on the bottom side. Top side went quicker, though I don’t remember the exact time it took.
4. If you are using a Convoy S2+ as your host, the XAL7070 inductor will fit. However, watch the clearance on the bottom side! C1*5* was shorting itself out on the brass retaining ring for me, so I had to dremel it down until the ring no longer made contact with both sides of that cap. (Contacting some parts is fine, as long as the side is already connected to groud. C16 is sideways, so it winds up shorting out entirely (I did not power it to find out what would happen with it shorted).
5. The ramp-in took some getting used to; sometimes was hard to tell if it switched modes or not. However, I wound up figuring out a way to tell what mode I was in because…
6. There is audible noise for me at the 250mA and 1000mA power levels. I’m using the low/50/250/1000/4200 set of modes, J1 bridged, J2 open. The noise is fairly high frequency but definitely audible (I double checked with my roommate). Strangely, it is NOT present at the low or 50mA levels, nor is it present on the turbo level (due to the ramping turn-on, the noise will start when you switch to turbo mode, then get higher and higher frequency until it is no longer audible).
7. In the S2+, it switches off from thermal limits and does not seem to reduce output to keep within limits. Not sure if this is a bug or something wrong with my build, or working as intended.
Definitely would like to take a look at some source code, to see what can be modified and how to adjust things like power limits (I want a version that tops out at 3A output, so I can do some versions with LH351D’s in 3S and 4S configs).
EDIT: Corrected capacitor name that was causing the shorting problems — C15, not C16 as I originally had (C16 is on the top side of the board).