Follow up Mini Spot Welder revised/different edition (BK11-1K)

If you like and appreciate my content, feel free to offer me a beer @ my paypal: [e-mail] - cheers!
There is (another) flaw in this (and some later) versions - please check your main cap input diode! More info here:
• Another Flaw in the Bk...
And here: • All "Mini Spot Welder"...
Additional comparisons with Bl18-2k version:
• New Mini Spot Welder B...
Follow up Mini Spot Welder revised edition (BK11-1K) with more details on problems and fixes (trigger driver resistor replacement).
Here is the model in question:
www.aliexpress.com/item/10050...
Here is the circuit layout by Kai_xxxxx:
hieroben.de/wp-content/uploads...
Here is further description on the problems regarding this version specifically the DRIVER circuit and the 1K resistor swap with a 470Ohm:
/ gknc9oy
P.S. in my version I tested the gate voltage and I did not see 4V on the gates but around 8.4, though I did test this after changing the resistor even if of same value (10K). I suggest changing that resistor in any case, it increases the drive and secures a better saturated ON signal.
Arduino port in the works:
• A little progress on t...
Weld tests with Arduino port:
• Mini Spot Welder (BK/B...
Components used:
FETS (should be replaced all together from same batch):
www.aliexpress.com/item/10050...
OLED 0.96" 80x160 FP-096H09A ST7735 SPI Color Display:
www.aliexpress.com/item/32955...
it.aliexpress.com/item/193633...
NUVOTON N76E003AT20 (STM8S003 clone, same pinout but different IDE) - can use an
STM8S003 or 103 (identical pinout only internal eeprom memory difference):
www.aliexpress.com/item/10050...
www.aliexpress.com/item/33000...
ST Documentation;
www.st.com/en/microcontroller...
Nuvoton documentation:
www.nuvoton.com/products/micr...
More info on STM8S003 vs N76E003:
www.programmersought.com/arti...
More info on how to use it here (can be used with Arduino):
www.electronics-lab.com/proje...

[@josephdewuhan]

Hi Luca, you do not know how much I appreciate your videos of the mini spot welder. I watched 3 of them carefully. As a result, I was able to modify my BL18-1k version and made it work. Before this one, I bought another BK11-1k version which blew the mosfet on the 3rd weld I did. That made me buy the second and started searching info about them. At the time I blew the 1st one, I did not know about your video. Now, with this video I understood the resister problem and made the BK11-1k work too. Now, I got two working spot welders thanks to you although they were both flawed when I received them.

[@Luca_Techy]

For instructions and code on my Arduino port visit: www.instructables.com/Arduino-Mini-Spot-Welder-Port-BK111820-Series/

[@chamikaraj]

I too have the experience of burning few FET s and kept replacing thinking that the my supply battery was the problem. now only got to know that its a issue from the item it self. Finally gave up on this and tried making a spot welder using a Microwave transformer and the timer unit which can be purchased from eBay very cheap. This system works flawlessly and suggest that's one option that can be worked.

[@gregkretchmer3588]

I have commented on other discussions. Excellent video. I have the -2 version, there is a problem with the 1k resistor on the top board which when replaced with a 470 ohm resistor makes the thing live longer. Someone posted a schematic on maker favrio's discussion. The resistor array version (I think) converts the 3 volt system to 12 volts and back, with the processor supplied through the regulator on the upper board. I noticed the resistor/transistor setup makes an inverter driver, which makes the whole circuit sensitive to exact components and versions as the mosfets are powered as soon as the battery is connected and the voltage on the gate has to be 0 or the mosfets start conducting partway on. The processor output needs to be high to drive the gates low, shutting the mosfets off. The processor takes a while to start up and set the outputs high. The processor will be generally at ground as a unit at startup, so the welding probes may be conducting at startup for a short time, and if shorted, will pop the mosfets. Also, the little power on switch does not control power to the mosfets, only the screen and processor. The switch is very low quality and can cause the unit to beep once, but not light the screen and leaving the processor turned off. I jumpered the switch out of the circuit so it is always on when the battery hooks up. The whole thing is very static sensitive with no actual earth ground. As the processor has the markings scrubbed off, we can't read the spec's to see if the processor outputs go to high Z or to ground waiting programming. I also used #8 wire from the battery to the unit and reinforced the lower board traces with solid wire. Welds good at 10. On the plus side, the unit was quite cheap and is a real nice red color.

[@Luca_Techy]

I explain the operation in my latter videos (check out my last one on the Bl18-2k version and comparison) and the various mods to be done to ensure a more reliable operation. The MCU triggers the first transistor with a negative pulse (inverted) from pin 19 but the 1K resistor drops the voltage too much and the push-pull does not drive the gates with enough ON voltage. The gate circuit operates in inverted mode so when the input is high the gates are OFF. The switch is also unreliable and should be bridged as shown in my latest video, have a look for all the other tips.

[@sd906238]

The red color makes it weld better just like a chrome air cleaner and valve covers on a car's engine adds 10-20 horsepower.

[@audiokurt]

Great video, thanks for the info and for sharing your experience! I am about to order one of these little units and I would have preferred the older version (because it is easy just to add a cap to make it working more reliable), but unfortunately the two versions look identical on the photos, so you never know what you get.

[@Luca_Techy]

If you source them from AliExpress, you can still find the previous version (at least on the photo description, which may not be reliable) if you look for the text "WISE MAPLE" on the face plate. The display is on the right side also. Check it out here: it.aliexpress.com/item/1005001928429272.html Errata Corrige: that model is an even different one (I ordered one) so I don't know where you can source the former/different versions unfortunately

[@letsfixit1594]

Great info thx.

[@lynnenux5763]

Thanks for doing the schematic and excellent videos. I ordered one of these things for fun but I'm not even going to try welding anything with it as the fundamental design is so poor. It's better for me to remove the IPLU300N04S4-R8 fets and build them into something respectable.

[@Luca_Techy]

Check out my followup video linked at the end - I am working on an Arduino driver version using the same board. Will post updates when I start running some tests.

[@th3drizzl378]

it seems there is an even newer revision where they fixed these issues also. some people are getting what some call mk2.1 problem is no real way to know what you will get and with the ali sellers they all will usually say they ship the newest or "best" one

[@seaford258]

Hi. Thank you for the Video on the new version. The MCU could be a STM8S003F3 or similar. It's the MCU of choice in china products for the past one or two years. Keep up the good videos thank you.

[@Luca_Techy]

Yes it may very well be by having a quick look at the pinout of the STM8S003F3 it matches the pins or it could also be the STM8S103F3P6 (both 8K flash but one has more eeprom memory). In the mean time I have made an Arduino (328p) port of it (more info on my last video) but come to think of it it could be possible to also port it to this MCU in order to add functions to the ones already out there (the header pins to program it is apparently already present on the MCU board)

[@ScrewBot]

Can i use a 12v 60amp SMPS. As the retailer suggested that i can use this spot weldet with 12v 40 amp SMPS. Should i use an smps?

[@betterthannotgoodmtb]

Thank you sir for sharing this valuable information. After days and days of researching these little spot welders, I began to question why folk aren't using car batteries due to their ability to emit high amperage quickly? Seems like a no-brainer to me. I ended up ordering one of these and I hope it's the earlier rendition that simply requires the capacitor mod.

[@Luca_Techy]

You will probably receive the "new rev 0" - check out my latest video about it in the playlist!

[@ttttenney]

Thanks for this video. I just wish I would have seen it 4 days ago, before frying my second mini spot welder. Both happened within the last two weeks (newer version, one w/ black buttons & other w/ white). Bought them on ebay. First one blew a FET on my 3rd attempt using a 3s 5000 mAh LiPo, so I de-soldered the bad FET and it immediately burned another one. I used a 35Ah AGM batt for the 2nd mini spot welder and it burned up & welded the probes just as explained in the video. I had it set to 30E, because I was getting absolutely nothing, not even a spark at the lower pwr settings. It's so frustrating knowing they are putting out subpar products like this with such a high failure rate.

[@Luca_Techy]

Unfortunately the quality control and dodgey post build mods are very low quality which increases the failure rates. This version didn't look too bad but the last minute "fix" they implemented created all the problems plus the insufficient current to drive the first pilot transistor makes it very prone to fail. I'm waiting for another version (not sure if it will be this or another version - itìs always a surprise!) and will probably post a follow up with all the needed mods (cap, resistor etc). I think that an arduino "adapter" wouldn't be too bad as I see many people have blown and unuseable boards so it wouldn't be bad to at least re-use the board with FETs driven by open source code using a cheap Arduino mini or nano.

[@ttttenney]

@@Luca_Techy your knowledge and feedback is very informative and I'm looking forward to a follow up video. Do you have a recommendation for a different style mini welder, that doesn't have so many quality issues? Thanks again!

[@Luca_Techy]

@@ttttenney I can't vouch for any at the moment as I haven't had a chance to try others but I see there is another model without "shell" which seems more stable but less adjustable and no display (example it.aliexpress.com/item/1005001664819305.html). The thing that makes these versions attractive is the adjustable fine timing and oled display.

[@lynnenux5763]

@@ttttenney kweld from keenlab.de would be my suggestion. They measure the energy supplied to each weld, rather than applying an unknown current for a set time. If I remember correctly they also use proper fet drivers. They are comparatively expensive but way more professional.

[@mdaslamknl]

Excellent I burst my spot welder doing the things which you are saying not to do Thanks

[@potterteksmith7548]

Had some adventures with one of these myself (CA04-2K). Had a mosfet fail short cct when first testing it, replaced the mosfet with a new one and had it working nicely until it failed again on the 2nd day after the initial repair. Seems the 3.3V regulator failed and cooked the MCU (& probably the LCD display) but the mosfets etc are fine so currently looking into an Arduino + OLED solution just for the challenge of it all :)

[@Luca_Techy]

Hi, you can check out my instructables link and my video of my Arduino port of my broken bk version (the MCU died). It's in this playlist. Only the MCU died so I reused the onboard OLED display. However it's pretty trivial to modify the code (linked in the instructables) and just use your own standard Oled and library.

[@potterteksmith7548]

@@Luca_Techy I've been using your code (thanks for sharing that :) and just working out some kinks in changing it to SSD1306 OLED library which has some quirks in refreshing/updating the display cleanly. I'll be using that with a home-brew setup for evaluation. Managed to source a new SE8533 voltage regulator and colour LCD so should be able to get the original welder going as well.

[@rcscalebuilders8268]

Thank You very much for the wonderful video. I did some looking through the comments and it looks like for my version CA04-2k all I need to do is change R4 to a (471). Is there anything else on this revision or is that it? Thank You very much for your time. Now I just have to figure out how to change this thing with my shaky hands!! Do I need to remove my blown mosfet if it is blown open?

[@Luca_Techy]

Hi, if the FET is blown open and the Gate is not shorted then you don't need to remove it though it is always better to remkve a faulty component as you can't know if it may interfere on the long run (especially the Gate). You also need to add an inrush current limiting resistor in the cap input diode. Please check out my other later videos where I explain this additional problem/fault and how to fix it.

[@rcscalebuilders8268]

@@Luca_Techy thank you very much. I'll check then out

[@radekzmazur3389]

I have destoryed mosfets from k99 spot welder. Accu was 12 62Ah internal resistance of accu was 8mohm ale seetting of welder was 20.

[@jordan123089]

I have this same spot welder, only mod I mad was to solder on some nickel strips on the traces for better conductivity. The problem I have with mine is that I have to wait about 12 minutes for it to charge up before it will make any spot weld. Any idea why that is? I am using a lead acid car battery with 625 CCA, fully charged.

[@Luca_Techy]

Define "charge it up" - if you have a good battery and cables are connected properly it has to work immediately. Maybe you have a dodgy connection like I had on pin 4 under the main board. The only way to know if your FETs are driven properly is to use a scope on any FET Gate (u can solder a wire) and check that the voltage is at least 8Volts when triggering. If you check out my latest video you will see what I mean. It's either a trigger/driver problem or connection problem - try to check the gate trigger voltage!

[@jzflmr6089]

Just received one- i was about to do the cap but i got the same version- still i have no smd resistor on the bottom, but there are 4 by the diode you have two there/ dont know shoud i still put the 10k on the bottom or not- will power on n check if there is any volt on the end label CA04-2K

[@Luca_Techy]

Yes do the resistor mod, u see 2 because that's the old version you see yours isnthe newer same as BL18. Do the R4 resistor mod and add the 20Ohm inrush current resistor.

[@jose83771]

Hi i just received my spot welder and I got the original one that is been shown on other videos, and my do have the chip number is a nuvoTon MS51FB9AE 033HBHA maybe this will help.

[@garyhollands7044]

B101 -2k The sub board 470 6.3V capacitor fell off. Free to a good home ( Australia )

[@oleksii.zagorskyi]

I bought my mini spot welder on June 2020 and I see not scratched MCU name - NUVOTON N76E003AT20 It's with MOSFED driver, but without any model versioning printed.

[@Luca_Techy]

Yes thanks - this is actually a chinese clone of the STM8 series 003S, same pinout same memory same core.

[@regishenrion]

Thanks. Mine is the B101-2K with white buttons. The problem is the same. I have change the 10K resistance. But my integrated circuit is certainly dead too. Screen stay black.

[@Luca_Techy]

The same happened to mine, I suspect it's some transients due to the high current welds which destroys the MCU. It probably needs an additional resistance/capacitor filter one the input sense pin.

[@paolodilorenzo9894]

@@Luca_Techy il mio è uguale, B101-2K e funziona una meraviglia senza fare nessuna modifica, ho gia saldato con punti perfetti parecchi pacchi batteria, ad una potenza di 20.

[@Luca_Techy]

@@paolodilorenzo9894 sei uno dei pochi fortunati allora - purtroppo il controllo qualità è molto scarso e spesso le saldature dei componenti non sono ottimali e si rischia di bruciare un FET o nulla di fatto. Cmq se fossi in te darei una ripassata alle saldature almeno dei transistor e resistenze della scheda FET. Se puoi per curiosità verifica anche che tensione ha l'impulso su un qualsiasi gate.

[@paolodilorenzo9894]

@@Luca_Techy gia rifatto quasi tutte le saldature, ed ho implementato delle strisce di rame saldate a stagno sulle piste dei MOS e piste positivi- negativi. funziona bene, ed è quella che ha gia la modifica della resistenza smd.

[@3rdpig]

I bought one and got a BL01-2k. Turns on, beeps, looks and sounds like it wants to weld but does nothing at any power setting. Trying it from a new, fully charged 3s 2200mah 60c LIPO. Would a 5000mah battery make a difference? Seems to me like it should work just as good with the 2200mah battery just get fewer welds before needing charging.

[@Luca_Techy]

I haven't physically seen the BL01-2k: please first check to see if it has any smd components under the large capacitor or it has components on the underside of the FET board (near the FETs). If the former then it is similar to BK11/bl18 versions else it's another version of the former one which needs the additional cap mod - but I'd need to see the MCU board and the Mainboard. Before running any further tests I suggest you check this because without the cap mod you may destroy FETs. Regarding the 3S 2200 Lipo pack, if it's really 60C it should be able to weld something at least at the 25-35ms setting but that really depends on the condition of the pack as it's rather small (you'd need a 4000mAh 50C at least). Don't try setting it over 50 as if there is some contact issue or as I said cap mod to be done then you risk blowing FETs. First check what kind of board you have and then if needed add a 450-1000uF 25V cap on the MCU board between diode output (+) and gnd. If instead you have the versions I show, that mod is not needed but you need to be sure your battery is good enough (maybe try with a car battery always starting from 5ms upwards the first welds to calibrate your setup).

[@3rdpig]

@@Luca_Techy I'll put a link below to photos of it. The MCU board is very different than the ones I've seen get the capacitor fix. If you can't see it in the photos, the MCU board is labeled BL01-2k and the FET board is labeled BL18-2k. I haven't tried a different battery yet. I've got a 3S 5200 mah 80c battery, would the 80c be enough to damage it? I'm just trying to avoid purchasing yet another LiPo battery, but I will if I have to. photos.app.goo.gl/YZPPvi5Jy6CB44x1A

[@Luca_Techy]

Thanks for the details - the main FET board is identical to my BL18-2k and in fact it is labeled the same. The MCU board is labeled BL01-2k BUT it is identical in layout and components so I am wondering why they have changed the label. As I said it would be interesting to see the gate pulses in order to compare them. Your 3S 5200 80C battery is more than enough to weld up to .12 mm strips - about damaging it well that depends on how much you set as the weld time. If you are satisfied with 7ms then don't overdo it as you may damage the FETs if you set an extreme value (over 30 at this point). Consider that professional welders with large AWG 6 cables don't exceed 15-20ms for .20 mm strips. Anything over 35ms is overkill - but this is spot welders with thick welder contact cables and 300+ Amp impulses.

[@3rdpig]

@@Luca_Techy I didn't realize the weld time is adjustable. All I really want to do is make replacement 18650 packs for my power tools and equipment. Thanks for the info, I appreciate it!

[@Luca_Techy]

@@3rdpig You're welcome - keep in mind that a 2200 is a bit small for this kind of application, it may suffer in the long run. I suggest using a 4000mAh or more with 60C - you'll get stronger welds with less time and less dissipated heat. Also, the leads included in this kit are made of tinned aluminum strands which is not reall great for conductivity so if you use thicker or better quality leads/wires alwasy at least 10AWG you'll get even better performance but take care not to exaggerate on the time (ms) - always start from 5 and work your way up (usually this welder works well around 25-45 based on your battery and nickel strip thickness).

[@GeertDroid]

Great video ! Why not starting a topic on this at EEVblog forum, just a thought.

[@Luca_Techy]

Could be, I honestly don't have a lot of spare time left and I know forums can eat up a lot of your time, but will consider it!

[@petvdv9671]

Great video can help me, Mini Spot Welder BL01-2k I hear a beep but does not working

[@Luca_Techy]

Change resistor on trigger output to 470Ohms on the MCU board, reflux solderings on transistors and resistors on main board. Check Gate signal with scope and verify you read at least 8V peak trigger.

[@tabangfarm1989]

hello ,, I have with version CB23-4K . i try to run with li-ion pack 3s10P..but it can't work properly. I tried with settings 20E-50E the result is the same, not so strong enough.. can you give me advice??

[@Luca_Techy]

Have you applied the R4 (470 Ohms) mod and the current limiting resistor mod as described? You can also refer to my test video using a 12V light bulb to check if the trigget works correctly.

[@tabangfarm1989]

@@Luca_Techy i trying to use lipo 3s 2200 double with paralel . So the capacity 4400 .. and its work well in 10E .. after 1 minutes test, the mosfet broke ... Im not yet to applied the R4 mod and reverse the resistor.. Any advice ?

[@Luca_Techy]

@@tabangfarm1989 you should have immediately applied the mods - now you will need to locate the shorted FET(s) and remove it. If only one is shorted you can still use the welder with 4 FETs.

[@pietroxxx5232]

Ciao Luca, grazie molte per il video del secondo modello (ed anche del primo). Ti scrivo in italiano perché non sono abbastanza forte con l'inglese, e mi scuso. Io ho ricevuto questo secondo modello ma non ho le resistenze nella parte inferiore. Posso (devo) metterle io? Purtroppo non ho la preparazione da tecnico elettronico o programmatore, sono un autodidatta. Grazie.

[@Luca_Techy]

Ciao Pietro, non ho ben capito se il tuo modello coincide con uno dei 2 che ho mostrato (BK11 o BL18) oppure è diverso ancora e se si avrei bisogno di sapere che modello è. Se intendi che sotto la basetta dei FET (quella più grande) non vedi nessuna resistenza sui pin indicati vuol dire che hai la versione già modificata e non devi fare nulla almeno qui (quindi la tua dovrebbe essere una BL18-2k o CA02). Dovresti però sostituire la resistenza siglata sulla maschera silkscreen R4 sulla basetta più piccola (situata in basso a sinistra guardandola dritta con lo schermo in alto) con una da 470 Ohm per sicurezza dato che quella originale è da 1K (sigla 102) e abbiamo notato che non sempre garantisce un buon segnale ai Gate dei FET. Potrebbe benissimo andare anche così (se sei fortunato), ma non guasta sotituirla. Purtroppo se non hai dimestichezza col saldatore risulta un po' difficile cambiarla dato che è un componente SMD piccolo e ci vuole un po' di mano - puoi anche sostituirla con una resistenza normale da 1/4 di Watt sempre 470 Ohm (o 560) piegando i terminali in modo che ci stia - vedi tu.

[@pietroxxx5232]

Luca, grazie per la risposta. Il mio è il Bl 18- 2k. Ho abbastanza dimestichezza con il saldatore ma non sono un perito elettronico. Mi approccio all'elettronica, venendo anch'io dal modellismo dinamico, non avendo, alcune volte, conoscenze tecniche se non "rubate" ad amici più preparati di me o ricercate su internet. Detto ciò, nel ringraziarti, aggiungo che, avendo prima visto solo il tuo primo video, ho rinforzato le piste. Spero che non venga compromesso il funzionamento (penso di no). Grazie ancora. PS: ritengo tu ti riferisca alla resistenza (delle 6) situate posteriormente allo schermo. Se così fosse, quella in basso a sx (siglata 102) da me è identificata con R7.

[@Luca_Techy]

Sono le 6 resistenze (di cui una manca) dietro lo schermo, quella subito sotto a quella che NON è saldata è appunto 1K (102) e andrebbe sostituita con una da 470 / 560 Ohm. E' siglata *R4* (almeno sul mio). Guardando il pcb da dietro (con quindi con il piezo a destra) è tutta in basso a sinistra verso l'interruttore.

[@pietroxxx5232]

@@Luca_Techy Ok. Ma nel mio, sotto allo spazio vuoto, ce n'è una con sigla OlB. Grazie mille. Sei gentilissimo. Vorrei farti vedere una foto ma non saprei come fare. Saluti.

[@Luca_Techy]

@@pietroxxx5232 puoi fare delle foto e uploadarle su imgur.com e linkarle qui

[@azoxer]

I have aded a 60A Fuse to the battery connector to prevent explosion from battery.

[@Luca_Techy]

That *might* help but it's a tricky business: the transients are fast so for ex. you could even use a 20Amp *slow* fuse which can handle the transients. If there is a short circuit there might be a resistance "lag" due to some wire or strip getting hot which won't trigger the 60 Amp fuse so you will still have a fire hazard. The safer way to go would be to have a smaller battery but with a large capacitor bank in front of it. The cap bank will take care of the high current transients and will recharge between pulses (though you would need to wait some time between them based on the energy you use). In this case you could use an even smaller fuse or even an NTC type fuse rated for say 5 Amps which in case of a short will limit the current and save your battery and nothing will catch fire.

[@meanxmeanx1763]

Mine is BL101-2k, i did the 1k=> 470 Ohm R1 change, but it's unreliable. It seems to have issue turning off the mosfets so they keep being powered on for too long / even long after the pulse should be done. I noticed several things: 1- The mosfets are all different ! So it's possible that the strain is focused on the weaker one. 2- There are solder balls *everywhere* 3- The NPN transistor soldering is not good at all. So far, blown one mosfet, and it's unreliable. The first few welds are sending way too much current/for way too long.

[@Luca_Techy]

Yes the solder work is definitely bad - which is why I suggested to check all the solderings especially on the smd resistors regarding the base BIAS and while you're at it you can reflux them all. If you have a scope, check the gate output before the resistor array (from the trannsistor) and see if you're getting enough voltage (>8V) and that you see a good square wave. Also the fact that you have *different* types FETS is very strange, I haven't heard of this yet - can you take a picture of your boards and post it?

[@meanxmeanx1763]

@@Luca_Techy My bad, i looked at the date code . They are all 4NOxx. I've reflowed most of the components and will check the gate with a scope. It's nice unit, but too bad it's manufactured so poorly. Just for fun i started reverse engineering the control board (im more of stm32 guy than an arduino guy :) )

[@Luca_Techy]

@@meanxmeanx1763 if you're all set for STM dev for fun you can rewrite the code, the headers to program it are all there and the SPI 7735 libs are available.

[@meanxmeanx1763]

@@Luca_Techy I wonder if it would not be simpler to replace altogether the control board. You can put the screen/button you like and the connection to the power board is just dupon pins. I first need to fix my blown mosfets (despite the 480 ohm patch i had 2 blown mostfet and one of the 30 ohm resistore blown also)

[@Luca_Techy]

@@meanxmeanx1763 That's what I did basically with my Arduino port: I just kept the display and buzzer of the MCU board and use the buttons - the rest is all driven by the pro mini. Still you have to be certain that the main FET board components are soldered and working properly to avoid other failures!

[@SebVsR]

I just bought a B118-2K version, and nothing happens when I want to weld. I have the 3 beeps, but nothing, its like no current goes to the welding pen. Tried with different batteries, lipo, 70ah car battery, always do the same :(.

[@Luca_Techy]

I don't know that version - maybe you can make a short video showing the control board and main PCB or post some photos of them? If you're not getting any activity either the FETs aren't turning on or they are not being driven correctly. It may be it needs that 470Ohm resistor mod or/and check the 10K divider (if it is based on the same circuit as mine)

[@SebVsR]

@@Luca_Techy yes it beeps when I contact the welding points, but nothing happens. Like the mosfets are not opened to deliver the current.

[@SebVsR]

I am uploading a video, I will share it here, I know nothing in electronic .

[@SebVsR]

@@Luca_Techy here is the link of my video. The spot welder is on 60E or 70E i don't remember. kzbin.info/www/bejne/aomWnHmBi5Whgq8

[@Luca_Techy]

@@SebVsR yes your FETS are not driven - did you change the resistor labeled R4 on the MCU board? It's a 1K smd resistor (102) - change it with a 470 Ohm one (use any size resistor just solder it on the same pads). Reflux the solderings of the main FET board of all the resistors and 3 transistors to be sure they make good contact. If you can check the gate pulse with a scope - must be at least 8V peak.

[@abesmith8642]

On the bottom does that 1k resistor do anything Do I just need that 10k

[@Luca_Techy]

If you have the bk11-1k board the underside of the board has a post manufacturing fix with 2 resistors, 1k and 10K, that's normal. Just check that both are soldered on well and if in doubt just replace them with normal resistors as I specifiy. If you have a different board then you probably don't need any modifications apart from changing the 1K resistor on the MCU board with a 470 Ohm as specified. Please check the follow up videos.

[@abesmith8642]

@@Luca_Techy drive.google.com/file/d/1-1m_f3VfulTBLycPTtBm2Vl8FpzwfWDn/view?usp=sharing here is some picture of mine

[@Luca_Techy]

@@abesmith8642 You don't need any modification on the main FET board as yours is the revised version but you need to swap the 1K (102) resistor labeled R4 on the MCU board with a 470 Ohm resistor to properly drive the FETS. If you have a scope please check the gate voltage when triggering to verify you're getting a proper pulse with at least 8V peak.

[@abesmith8642]

@@Luca_Techy ok thanks I will try to change it to a 470 ohm resistor

[@abesmith8642]

@@Luca_Techy I have a 560 ohm resistor would that be adequate

[@osvaldonobuo3663]

Hi Luca, YOU ARE A GURU in ADVANCED ELECTRONICS"!!!! I have the new version with the 2 resistor in the MOSFET BOARD solded near the 2 PUSH PULL transistors. But the sport welder is not working. The display shows up and works as designed: you can configure the energy amount, change from AUTO to MANUAL, But when I tried to welder, the controller board startS the 3 bips and NOTHING HAPPENS! I put my oscilloscope in the pin of trigger signall that goes to the POWER BOARD and there is a DC level of 1V and when the controller send the trigger signal it goes down about to 0,5V for the time set in ENERGY setup. When you set to 20E the trigger signal goes down for 20ms. The trigger signal should goes to more than 8V and this is not hapenning... Do you any ideia of what could be happening??

[@Luca_Techy]

Hi Osvaldo, the trigger signal on the trigger PIN 4 (counting from the square pin down) will give around 1V - the problem is that it should drop a little more to drive the trigger transistor well. You should measure the signal on *any gate pin* of *any FET* or the Emitter of the push-pull setup - that should be at least 8V (positive pulse in this case). Please replace the 1K trigger resistor on the MCU board with a 470 Ohm one (it is placed after pin 19 of the MCU) - this is the first thing you should do, and refresh the solderings on all the resistors and transistors on the main FET board.

[@osvaldonobuo3663]

@@Luca_Techy Hi Luca... I much apreciatte your quick response!!! I saw your AWESOME article at instructables.com about your ARDUINO mod project and I read your recommendation to change that resistor. I will do that and keep you posted of the results!! Thans a lot!!

[@nickkitson]

Many thanks for sharing your info. I have just received a unit ordered from a seller on e-bay in UK and it is yet another version - CA04-2K I've taken photos of both sides of the boards photos.app.goo.gl/xxxBK6B7A1yEUSkf7 They look clean and don't appear to have any post manufacture modifications. I powered it up (see photo of display) and get three beeps, the switches change the 'Energy' and let me change from 'Auto' to 'Manual' but I have not tried to weld with it yet as I'm getting 12.0V on the output (with 12.3V input) whether the unit is on or off, Manual or Auto. Is this a sensing voltage for the auto function or does it indicate a fault? (With no power connected, the FETS are open circuit if measured with a meter)

[@Luca_Techy]

The logic board is identical (so this is the 4rth variation of the BK11-1K) and the main board has already the resistor divider fix. However I note that resistor labeled R4 on the logic board is a 1K (102) where it is suggested to change that to a 460 Ohm (461) or similar value before using it to avoid under driving the FETs. The voltage you see on the output (12V) is the sense auto trigger voltage: the negative is going "back through" the resistor divider used to give the OK to trigger. If you have doubts that the FETs are driven just use a 10 Ohm or so resistor across the leads to see if the auto triggers the pulse or simply power it using a bench power supply with limited current (1Amp for ex.) and test it (it will simply trigger and just enter current limit for the set ms time). However before testing with a live battery, please modify R4 or even better check with a scope if you have one the GATE voltage when triggering (you can still use a bench PSU, the trigger voltage should always be >8V whatever the input voltage for that amunt of time).