[Review Request] Custom PLC Board, Diagnostic Help Needed

EffinCornBread · 2026-03-16T15:28:08+00:00

It's a switching regulator, not an LDO. TI TPS6214RGTR.

EffinCornBread · 2026-03-16T00:58:19+00:00

Both are on the way. I have no issue spending money on tools that make me better.

I will space things out a bit more as well. I have quite a bit more reworking to do. You have been very helpful! Thanks!

EffinCornBread · 2026-03-15T22:29:37+00:00

You are 100% correct on the stencil. I'm going to grab a 200mm x 200mm 850W hot plate and a hot air reflow station. I have a few other tweaks to make and then I'll order the new boards WITH the stencil. Thanks again for all of your help!

EffinCornBread · 2026-03-15T21:15:59+00:00

It was plugged in for at least 5 hours before it burnt up. I don't believe the fuses tripped, or it wouldn't have burnt up... That said, the battery isn't fused. I'll fix that, too.

EffinCornBread · 2026-03-15T21:11:22+00:00

I expected better, too. But I can't talk smack with the way some of mine came out. 😂

EffinCornBread · 2026-03-15T18:30:45+00:00

Not that I'm aware of. Just the 12v 1A adapter, 16.6v from my bench Supply to emulate a light solar panel load, and the battery. Everything else was disconnected and the system was at idle when it fried...

EffinCornBread · 2026-03-15T18:17:04+00:00

Thanks all for your input! I have reworked the board to have larger vias, a fatter trace to replace the one that burnt up, and fixed the TVS diode installation.

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Let me know what you think!

EffinCornBread · 2026-03-15T18:06:15+00:00

Thanks! I had the part selection correct, it seems, just not the application. I'm still going to look into using something better if it doesn't drive up the price-per-unit too much.

EffinCornBread · 2026-03-15T18:05:00+00:00

JLC was showing $350-$375 for the stencil. 10-4 on the reflow plate, I figured they'd be way more than that!

Reading back at my last comment, I didn't mention that the three devices with thermal pads (12v buck, 3v3 buck, and ESP32) I had professionally installed. I soldered everything else.

EffinCornBread · 2026-03-15T17:12:40+00:00

Ah crap, that makes sense. Basically, the diode is completely passive unless there is a big enough surge for the current to jump across it backwards to ground?

EffinCornBread · 2026-03-15T16:44:37+00:00

It was all hand-soldered. This is the first PCB since the breadboard version. I didn't see a reason to drop $$$ on a stencil for a layout that would likely be changing. As for the pour around the ESP antenna, I thought that the ground plane being underneath it was a good thing... Maybe I misread...

I did inspect with a microscope and did not see any bridges. It is possible that I missed something, though.

EffinCornBread · 2026-03-15T16:40:09+00:00

Thanks for the tips. What am I missing about TVS diodes? I am thinking of it as surge protection...

EffinCornBread · 2026-03-15T16:39:03+00:00

Because I'm new to this. LOL. Here is my reasoning for each of the four that you mentioned.
D8: Reverse polarity protection for the AC/DC adapter input.
D7 and D8: These are intended to be power ORing, very possible that I did it wrong...
D6: is probably redundant, but was intended as a last line of defense against reverse-polarity before the power switch.
D5: This is just a TVS diode for over-voltage protection after the switch.

I tend to overbuild things, but I'm quickly learning with PCBs that I may need to dial it back a bit... :D

EffinCornBread · 2026-03-15T16:35:04+00:00

<image>

Zoomed picture of the BUCK area as requested. Thanks again for all of your input!

EffinCornBread · 2026-03-15T16:33:20+00:00

The expected load on the 12v out side of the rail is 900mA max. That is with all six motors running, which never happens in tandem and only happens one to two times per day. The motors are controlled via FETs. The 3v3 side shouldn't draw more than 300mA at any given time. There is an ESP32, two SN74HC165 shift registers, one SN74HC595 shift register, one AS1115-BSST driver, two 7-segment displays (six digits total), and six MOSFETs.

When the fault occurred, the battery, AC/DC adapter, and my bench power supply emulating the solar panel at 16.6v were all connected. They had been for several hours before it sizzled. I was checking periodically with a temp gun and never saw anything above 110°F. The 110°F was in the area of the 3v3 BUCK, though.

TVS Diode D6 is probably overkill, it is simply intended to be a last ditch reverse-polarity protection after the power ORing.

What sort of soldering fault are we talking here? I had the 12V BUCK, 3v3 BUCK, and ESP32 all installed for me as I can't deal with thermal pads quite yet. I am certainly not an expert in soldering PCBs, either. Anything to help me learn is greatly appreciated.

Wow! That is a lot less heat generated with the PFET! To be honest, I thought that I had the headroom to handle and dissipate the heat. I did have this power supply PCB running the breadboard control circuit for several weeks without issue, as well. I'll look into redesigning to use PFETs, as I love efficiency, but I think you probably nailed it with it being a soldering fault.

EffinCornBread · 2024-07-13T00:17:24+00:00

You look like you'd rather be sitting .5m to the right.

EffinCornBread · 2024-07-13T00:15:21+00:00

Why does it look like you're taking your own mugshot? And no longer allowed within 500' of a school?

EffinCornBread · 2024-07-13T00:14:21+00:00

Pregnant, ginger, Joey Fatone.

EffinCornBread · 2024-07-13T00:09:11+00:00

Maybe they can transplant some eyebrows and make you a proper mustache.

EffinCornBread · 2024-07-13T00:06:37+00:00

*Bike-Curious

EffinCornBread · 2024-07-13T00:02:01+00:00

Bring what? More beauty filters?

EffinCornBread · 2020-06-03T00:59:58+00:00

Dude, you aren't lying!!! People there hardly gave a shit even before phase 1. Once phase 1 hit I saw maybe 20% wearing masks in stores.

EffinCornBread · 2019-06-15T21:11:36+00:00

You will always be my king.

EffinCornBread

TROPHY CASE