T12 STM32 V2.1S Soldering Station Controller - schematic etc.

[Mindstorm88]

Here the schematic of my model.

- the driver for the mosfet is a NPN , no resistor to the STM
- R1B a pullup of 910k, never seen on other model, maybe to help with temp measurement.

[floobydust]

Does the 78L08 run hot?
PCB trace J1 is for the JBC option.
Q2 should be a mosfet (and is on some other 2.1S boards), I agree there's no base-drive limiting resistor which might be hard on the MCU pin.
R1B 910k is a pullup for open-thermocouple detection, it works without it but picks up noise and the controller looks like it's spazzin if there is no tip in the handle.

[Mindstorm88]

for Q2 according to marking J3Y it is a S8050 NPN and after vérification with a meter it is confirmed a NPN

the 78l08 in heating mode, i put a TC on its gnd tab, it reached 66 C. May have to do a mod on the long run !!

[floobydust]

Other boards, Q2 is []url=http://aosmd.com/res/data_sheets/AO3422.pdf]AO3422[/url] (same pinout as BJT) and likely what they ran out of. Hard to know if the firmware is using PBO open-drain/40k RPu or just under the MCU max. rating of 25mA.
If the 78L08 could run a bit cooler, the OLED wouldn't need the resistor R2 on 3.3V feeding it and could be brighter?

Old boards with no copper pour at all roasted their LDO, it would shut down or burn up. But this board looks OK at least the parts are better quality and aren't black-topped. It's hard to compete, would you lower quality and price or not? russian forums complain KSGER quality is lower but it seems their best doesn't always go there.

[Mindstorm88]

for now display brightness is good enough for me . For Q2 i'm sure i have some mosfet pin compatible in stock. If the 78l08 dies, i wil put a small buck step down module to replace it, but as this is not my main soldering station , i'm pretty sure it will live long !!!

[floobydust]

Last question - is the soldering tip grounded to mains earth-ground, or floating?

[Mindstorm88]

The tip is grounded to mains earth-ground , psu is a Rev 2.04.

Wire has been added to case and encoder.

[floobydust]

Good, the V2.05 PSU ungrounded things which is a mistake.

[Ricks_Radio]

Many thanks to all who have put this gold mine of information together. I have recently purchased a KSGER soldering station and I have used the info posted here to upgrade the V2.05 power supply.

My KSGER T12 is the current V3.1S and has a different controller board.  It is Ver-20. Yes that's 20 not 2.0? I am attaching a photo for comparison purposes. As you can see R10  (4.7k) is there in all it's glory. Unfortunately I've never seen a photo  of the Ver 2.0 board so I have no idea if this is the same beast?

Any insight would be appreciated. Thanks.

Rick

[floobydust]

As I've mentioned- the soldering station model number, controller H/W version number, software version all seem to get blended. The chinese copy each other along with mistakes.
I would say your board is yet another copy of the Ver2.0 controllers out there, with some changes. Not from the "KSGER" store. edit: yes it's from the KSGER Store as "OLED V2.01" board says "T12-V20".
The linear voltage regulator overheated in many Ver2.0 designs, yours at least has a little copper heatsinking I think it's an LM317EMP but I would say it will run hot. The AO4409 mosfet seemed to fail for some people, it has no thermal pad underneath. Don't hot swap tips with power on. It's difficult because sometimes the semi's are low quality. Yours look decent marking though.
Definitely check what you've got for grounding and add the PE ground wire. You can do a finger test for how hot the Vreg and mosfet get.

[Ricks_Radio]

Thanks for getting back Floobydust. It's disappointing that they coupled this old controller board with the latest software and power supply. I'll mention that in my review of the product. I agree it is likely an LM317EMP. It might be possible to add a small piece of copper at right angles to the board near the regualtor to help with the heat dissapation. (If I give it a try I'll post a photo.)

Has anyone posted a schematic of the Ver 2.0 controller board? The PE is now grounded and the regulator is running cool to the touch.

I've encountered another "problem" this one seems to be a firmware glitch. The TIPs menu seems to think I have a J02 tip. I don't and there's no way that I have found to un-check that tip from the menu. I've tried everything I can think of including a complete reset. This is not a big deal .... more a slight inconvenience.

Thanks again.

Rick

[floobydust]

Let us know if the Vreg runs too hot. And it's got the battery drain resistor? I also see the cold junction thermistor NTC R21 on board, which is rare.
I have a few V2.0 controller schematics. There's no big difference with the latest OLED V3.0 or V3.1 controllers aside from the 3.3V power supply being done with a buck-converter, the JW5026 is out of stock for a while now and more likely why KSGER rolled back- component shortages.
As far as the tip list, I thought it needs to have at least one in the list, so first try add another to the list and then select it.

[yelkvi]

I also see the cold junction thermistor NTC R21 on board, which is rare.

What is the point of NTC on the board if the "cold" end of the thermocouple itself is in the soldering iron handle?
Why measure the temperature inside the soldering station case? It will also be different from the one in the handle. And, accordingly, thermal compensation will not work correctly. This is a mistake of Chinese manufacturers, for whom the main thing is to sell goods,
without understanding how it works.

[omega9380]

OK, so after reading thru this thread and wanting a "definitive T12 board", I took a look at both floobydust and Mindstorm88s schematics, and kinda zoned out for a few days 

Here's the results.  I have created a KiCAD schematic and board, complete with JLCPCB part numbers.

I want to stress a point that I am not an electronics engineer.  In fact, my day job is an IT administrator.  I play with KiCAD as a hobby.  I'm not formerly trained in electronics or PCB design, so be gentle with the pitchforks when you see my trace routing 

I would like to get this board manufactured but I wanted to send it to the experts here on EEVBlog Forums first.  Please tell me if this will burn down my house, blow up my computer, or steal my wife and car.

The full design files are up on GitHub:

https://github.com/omega9380/KSGER-Coverplates

I'm attaching the board renders and the schematic PDF for all to see.

Happy soldering!

[floobydust]

Welcome to the forums. I think it best to start a new thread for your design review, to not derail this thread about the OEM parts. I could not find the schematic pdf.
Right off the bat, power traces are too thin for the heater and mosfet, thermal reliefs as well, for the many amps of current. It's best to keep the high current section close together. How can you put a GX connector on the front panel and not have it hit the board? If you're planning on using the original aluminum enclosure I could also see the four corner mounting holes not working out, hitting the extrusion housing. The original boards have a cutout/space for the GX and four corners.

[DavidAlfa]

Those mosfet 0.1mm tracks
Check this example, keep power traces as short and thicker as possible.
Move the transistor closer to the connector.
Also increase the width of VDD tracks, just a little, about 12-15th.
Add more decoupling capacitors to the stm32, in every VDD/VDDA pin. This also happens in the original crappy design.
Place the decoupling capacitors closer! C3 placement is terrible, rotate it 90° so the positive is much closer.
Add more vias to join the ground planes, specially close to the stm32, regulator, amplifier... Avoid those barely connected islands like in U3, adjust the traces so the plane isn't broken everywhere.

[omega9380]

Thanks for the feedback folks!

@flobbydust, I did go ahead and create a new thread so not to take over this one:

https://www.eevblog.com/forum/projects/t12-soldering-iron-controller-board-based-on-ksger-board-v2-1s/

To answer some of your questions, I wasn't designing the board to be exactly like the original KSGER one, nor for it's case.  I have an aluminum project box that I was designing the board for, planning on getting custom endcaps made for it based on the board I'm designing.  I mostly wanted the schematics up on GitHub for anyone to fork who wants a custom made T12 controller.

@DavidAlfa, thanks, this is the exact feedback I was looking for!  My board design experiance is mostly relegated to YouTube vids, like the ones Dave posted on board design.  Again, I'm not an engineer, just someone who likes to play around with this stuff.  As stated above, I created a seperate post for this project.  Also, are you the same as "deividAlfa" that forked PTDreamer's custom firmware?  I plan on using yours for the new board, and I want to put it on my current KSGER v2.1s...as soon as I remember how I flashed that one in the first place......

[DavidAlfa]

Neither am I am enginner!
Ah yes, davidalfa was already taken, not willing to make davidalfa1234, I took the phonetic pronunciation of "David" in english, but written in spanish. That's a common way to friendly call Davids here. Like Jimmy for James.

Check the readme in Github, you have programming, etc...  I think everything is pretty clear there?

[Enric]

A year ago I bought my welder on aliexpress, it has an OLED screen and on the board you can read Oled-V3.0, it has worked for me for a long time without any problem until suddenly it has not turned on anymore, neither the screen nor the buzzer. Yes, before it took about 5-10 seconds to start but now there is no way, if I connect it I don't read voltage on the screen pins, but on the input capacitor.
The power supply I use is 24V and 160W.
Thank you very much!

Enric

[yelkvi]

Show a photo of your board (on a large scale). I will show in the picture at which points to measure the voltage.
Then we will analyze what is broken.

are there any similar ones? -

P.S. Board photo taken from https://github.com/deividAlfa/stm32_soldering_iron_controller/tree/master/BOARDS/KSGER/%5Bv3%5D/Schematic
I hope DavidAlfa doesn't get offended

[mastershake]

typically the oled v3.0 board is the same as the 3.1 and 3.0 versions except some had the battery either in a different place, on leads, socketed, or not installed at all. i have a few styles here of that board.

[Enric]

There is none similar, this is the photo of the back, I have measured the electrolyte capacitor and the display, and the display does not give voltage.
Thank you very much for your quick response!

[mastershake]

yours is the same as the bottom v3.1 the differences are in the battery in the corner. yours has the spot for it to be attached to the pcb where the v3.1 has a socket for a lead otherwise they should be the same thing

[Enric]

Yes, I see that it is very similar but I wanted to confirm just in case I am not receiving wrong advice and wasting your time.
So where can I find the voltage measurement points?

[yelkvi]

Connect 24 volts to the board. Measure the voltage at point "1" and at point "2" (relative to "-").
What is written on the chip "3"?
Take a higher quality photo of the board.