JP spot-welder, FET-switched, timed adj. pulse

[flangefrog]

Is it possible to show the TVS and Schottky installed? I get it helpdesk, but not sure where it's at here.

Thx!

This shows the Schottky installed by itself (negative battery terminal on left, positive on right):
https://endless-sphere.com/forums/viewtopic.php?f=14&t=81400#p1148953

This one shows both diodes installed. The Schottky diode symbol in this picture is shown the wrong way:
https://endless-sphere.com/forums/viewtopic.php?f=14&t=81400&start=350#p1182616

Do you think I should get a smaller battery too?

I don't think it should be necessary with this mod, but it will be more reliable.

 

[okashira]

One Schottky and One TVS that I recommended is fine.
Tested it on a massive inductor I have here to 600A. worked like a champ. FET's did not even get warm
Going to try 1,200 amps soon. 150 microhenry inductor

Ive also tested leads only to about 3,600 amps and the single Schottky is just fine.

 

[flangefrog]

One Schottky and One TVS that I recommended is fine.
Tested it on a massive inductor I have here to 600A. worked like a champ. FET's did not even get warm
Going to try 1,200 amps soon. 150 microhenry inductor

Ive also tested leads only to about 3,600 amps and the single Schottky is just fine.

I was only recommending to parallel the diodes from reichelt.de as the rated pulse current is much lower than the ones you are using. The Mouser ones I recommended are the same series as yours, just a different voltage rating (and a little higher current rating)

 

[sl33py]

Thank you all. I just finished reading the full 24 pages.

First off - Thoughts are with you Riba - hope you have a speedy recovery and are feeling better soon.

Like others i wish i'd grabbed one of Riba's kits when they were available. Now that are no longer available, i'm looking at the Arduino DIY kit from KaeptnBalu.

After a lot of reading, and listening to you fine folks who know their stuff, i feel much more comfortable building this. I've "upgraded" from the original BOM to the 1324 FETs as well.

On the Arduino spot welder, i'm mostly clear on the TVS and Schottky placements.

I'm going to also try to tape my probe wires together and possibly multiple 14awg (5-7) for the schottky (the easier to understand how to wire). As the layout differs between Riba's and the Arduino i'll re-read some of this and see if i can sort the TVS wiring.

I've learned a ton and really enjoyed the read. Drama aside, and still sorry it's due to illness the Riba spot welders are no longer available, I'm looking forward to this fun project.

 

[Maxid]

Sorry if I am being off-topic - if so please let me know where I can find the right thread for my question.
Basically I just finished my KaeptnBalu Arduino spot welder and made some stupid mistakes while assembling.
Long story short: I need to replace the 4 mosfet drivers.

I was searching the German stores but could only find the MCP14E10 in the reichelt online store.
After reading about the TVS and Schottky Diodes however, I thought it would be a good idea to buy all of it in one go.
Can anyone tell me what parts I should order from reichelt, conrad or somewhere else?
Conrad has the MCP14E4 and a VS-100BGQ100 but I have no idea which TVS will work.
Reichelt has the MCP14E10 but I can't find the diodes there.

Any help is highly appreciated.

Edit:

I was only recommending to parallel the diodes from reichelt.de

You seem to have checked the Reichelt shop already for alternatives for example.

 

[Maxid]

I bought the reichelt parts.
However my arduino freezes when I use it together with the schottky diode.
The status LED does not turn off anymore, the LCD digits stop alternating and no further pulses can be fired. A reboot fixes it until the next pulse.
Without schottky everything works beautifully.

Any idea what can cause this behavior?

TVS Diode is also installed - so it is at least better than without modifications I guess.

 

[Matador]

I LOVE COPPER ! 8)

Here is the update on my build: (as well you will notice that the JP spotwelder is not there yet.. i need to replace all fets! :lol: i blown their gate when shorted them to too much copper :lol: it will be installed on the left of teh first picture you see on the top NEG bus bar from the caps.

The big copper bar you see is one of the two output lead of the system. These will be MASSIVE for maximum current!

-1.25" x 0.25" thick pure copper bus rail for high current connections from teh caps modules to the output tabs of the welder
-high quality industrial ultraflexible TRUE pure copper 4 gauge cable
-3/8" dia pure copper tip holder with fixing dual 8-32 set screw
-1/8" dia x 1" tungsten tip for copper spotweldfing

The measured total resistance of the system including the contact resistance on a 6 mil x 10mm wide copper sheet at distance of 5mm and capacitor ESR is only 2.0 miliohms.

And!...Total measured caps ESR is 0.12 miliohms. Enough for a 100 000Amps short at 12v but that copper would vaposize in fract of a second before reaching that as well!

Total energy stored is 0.5Wh at max 35V ( close to 2kJ)

The highest resistance of the system will be between the two tips! :wink:

Doc

Do you think your setup could permit to solder 0.2mm thick copper tabs to 18650 ?
Also, I was wondering, could car audio capacitors be goood enough for the task ?
I Bought this 10Farads 16VDC (surge 20VDC) car audio capacitor (at 16Volts, should give 1.28 kiloJoules) rated for equivalent series resistor (ESR) of less or equal to 1.5 milliOhms
http://www.bossaudio.com/auto/car-audio-sound-system-auto-stereo-capacitor-farad-boss-audio-cap100cr/

I've seen audio capacitors of up to 50 Farads (at 16VDC, 20 VDC surge) on eBay, for arround 100 USD shipped.
http://www.ebay.ca/itm/Rockville-RFC50F-50-Farad-Capacitor-Blue-Voltage-Display-/301777241854?hash=item46435346fe:g:kqUAAOSw3xJXn8Hh&vxp=mtr

 

[parabellum]

They look like super caps stuffed boxes, with only a fraction of relative low ESR caps inside (those big cylindrical things with little capacitance on outside). Super caps (small in middle row) are useless.

 

[litespeed]

Yeah most of the car stereo caps are junk and a fraction of the listed farrad. 25 years ago there was some great audio caps because they were resourced industrial and computer grade stuff.

True computer caps are really the only good ones these days. I'm sure there are some exceptions but I betcha they are few and far between.

Tom

 

[pguk]

I bought the reichelt parts.
However my arduino freezes when I use it together with the schottky diode.
The status LED does not turn off anymore, the LCD digits stop alternating and no further pulses can be fired. A reboot fixes it until the next pulse.
Without schottky everything works beautifully.

Any idea what can cause this behavior?

TVS Diode is also installed - so it is at least better than without modifications I guess.

Sounds like perhaps your power rail is seeing a dip on weld fire? Does the board have enough decoupling capacitance? I've been reworking my unit today to include a 1uf smd PET film capacitor. This has much better ESR than the electrolytics I've been using so far and is what is spec'd on the mcp1407 (6A FET driver) datasheet. However I have had much success using 3 * 10uf electrolytics and 3 * 100uf ceramics. I have power module separate from control board which helps avoid problems with induced transients.

 

[Maxid]

Sounds like perhaps your power rail is seeing a dip on weld fire? Does the board have enough decoupling capacitance? I've been reworking my unit today to include a 1uf smd PET film capacitor. This has much better ESR than the electrolytics I've been using so far and is what is spec'd on the mcp1407 (6A FET driver) datasheet. However I have had much success using 3 * 10uf electrolytics and 3 * 100uf ceramics. I have power module separate from control board which helps avoid problems with induced transients.

Not sure what you mean by all that. I build the standard version like in the instructable with the parts Kptn Balu listed from Reichelt.
Then I added the TVS and Schottky dioded like discussed in this thread.
I have no idea about what capacitors you are talking about and also don't understand the decoupling of control and power board. The spot welder was a two part design from the start. Control on top and power rail on a second bottom PCB.

 

[pguk]

Sounds like perhaps your power rail is seeing a dip on weld fire? Does the board have enough decoupling capacitance? I've been reworking my unit today to include a 1uf smd PET film capacitor. This has much better ESR than the electrolytics I've been using so far and is what is spec'd on the mcp1407 (6A FET driver) datasheet. However I have had much success using 3 * 10uf electrolytics and 3 * 100uf ceramics. I have power module separate from control board which helps avoid problems with induced transients.

Not sure what you mean by all that. I build the standard version like in the instructable with the parts Kptn Balu listed from Reichelt.
Then I added the TVS and Schottky dioded like discussed in this thread.
I have no idea about what capacitors you are talking about and also don't understand the decoupling of control and power board. The spot welder was a two part design from the start. Control on top and power rail on a second bottom PCB.

Ah yes I just had a look at the schematic for your unit - power board and control are indeed separate modules. Looks like he has one .1u ceramic and one 1uf electrolytic for power rail decoupling? Decoupling capacitors decouple any noise or dip that might appear on the power supply line ie 5v for your chip. There may be another electrolytic on the nano? (The original arduino has a 47u surface mount electrolytic). You say that the chip freezes after a weld - that's probably due to noise on the supply rail - If those are the only caps I would suspect they are barely adequate. Ideally they need to be as close to your MCU as possible. If you know lebowski's controller chip, he had to use a heap of decoupling capacitors around his chip to shield it from noise. The MCU on my welder survived a FET meltdown which even blew the FET driver chip - because I have heaps of decoupling capacitance on the board. Welding is an electrically noisy business As a possible quick fix - maybe try replacing the 1uf electrolytic with a larger value electrolytic, or even better a film cap?

Also, I can't see any FET gate resistors on there? It's best practice to fit these (about 80 ohms, say, one on each FET gate to avoid instability (ringing). This may be a contributing factor.

 

[timmy66]

Okashira / Flangefrog,

Any idea what the residual energy is in the ad-hoc inductive circuit (after turning FETs off) that needs to be disippated by the TVS / Schottky ? With a normal car battery setup.

I think the oscilloscope readings were all measured only across the FET s->d, in the well marked up diagrams by FF.

It would be good to know energy specs are needed for the TVS / Schottky. The two that have been recommended seem like they may be overkill?

Thanks for all your work on this.

 

[Pedrodemio]

Hello guys, i'm about to start building my spot welder

Anyone tried using lipos to weld 0.15mm nickel? i have two Nanotech's 5000mah 35-70C laying around that in theory should be able to reach 900A considering the internal resistance, a car battery is expensive around here and i don't want to risk damaging the family car battery

Thanks

 

[fechter]

Hello guys, i'm about to start building my spot welder

Anyone tried using lipos to weld 0.15mm nickel? i have two Nanotech's 5000mah 35-70C laying around that in theory should be able to reach 900A considering the internal resistance, a car battery is expensive around here and i don't want to risk damaging the family car battery

Thanks

Others have reported good results using Lipo batteries. I think they were using 4 series.

 

[riba2233]

Max 3 series, 4 would blow the irf1324.

 

[Pedrodemio]

Thanks fechter, i will try it and see what happens

 

[ambroseliao]

Has anyone used a Lipo based car jump starter battery as a power source? I know that they rate them as having 550A(!) peak current capability, however, it doesn't look nearly heavy duty enough. It's certainly more appealing than having a huge lead-acid battery sitting around.

Thoughts? I'm thinking of one like this.
http://www.newegg.com/Product/Product.aspx?Item=9SIA0WP4MS9658

 

[ambroseliao]

After reading some of the reviews on Amazon for this unit, it looks like it has quality control issues as some users say it works to jump start cars and others that say it just dies.

 

[amberwolf]

There's a number of people that have used that type of battery in general for various power sources, including to run their bikes. Boyntonstu has a whole bunch of scattered threads with various parts of his testing. I forget who else used them but some of them have their own threads for them. Might give you info on specific models.

Since, like their lead counterparts, they are not really intended to be used for more than a few seconds at a time, they don't generally work well for vehicle traction power, but as long as they can provide the current needed for the welder without sagging too much in voltage, they should work well for spot welders' momentary uses.


Just that, as you note on that model, you have to locate a reliable brand and model.

 

[pguk]

Hi folks,

I found time over Christmas to do a layout on kicad for the power board. Tesseract should be happy - I got the shcottky and the TVS diodes all on the board. TVS's sit above the surface mount FETs.
I finally gave it a proper run at the weekend and it seems to be working as it should with minimal avalanching. I welded .15 nickel on lead acid.

I posted the kicad files on here - they're in the first post of my 6pence thread. 'scope shots on page 4.

Builder has to be able to add copper busbars to the board. I have made the board as small as possible, so that it needs copper busbars soldering on there which solder right up to the drains & sources of the FETs without relying at all on the board foil; build up lengths of 2.5mm sq copper wire. Difficult to achieve this direct contact to the FETs if using copper/aluminium bar bolted to the board. It can be done of course with a large iron + spending a long time heating up large mass of copper = risk of damage to FETs.

I have in mind to build a temp controlled soldering iron station capable of driving the JBC tips. I have my eye on this one:
http://dangerousprototypes.com/forum/viewtopic.php?f=56&t=5264

Does this look okay? Anyone seen others. It needs to be temp controlled, ie delivery of energy when it senses the tip temperature drop.

best, Paul

 

[vel80]

Hello,
Can anyone tell me if it is permissible to replace the IRFB7430 fets working as flyback diodes for the JP welder with IRF2804, because the first are not available in the near store? The datasheet looks promissing, but I would like to ask you for a second opinion.

Thank you in advance!

 

[vex_zg]

Hello,
Can anyone tell me if it is permissible to replace the IRFB7430 fets working as flyback diodes for the JP welder with IRF2804, because the first are not available in the near store? The datasheet looks promissing, but I would like to ask you for a second opinion.

Thank you in advance!

what do you mean by "FETs working as flyback diodes"? flyback diode is sometimes used for MOSFET protection to sink the transients during FET turnoff. I am not aware that FETs are used as Flyback diodes.

if you are after [strike]the latter[/strike] using MOSFETs as switches for the actual welding current, RFB7430 seems better due to higher avalanche energy and pulsed current, which can be quite critical in this application. You can still try using IRF2804 but they might be more prone to dying. Difficult to say without scope snapshot of how big transients are in this case.

 

[parasole]

Hi all,

check out the last post on this thread, below is a copy-paste of my description, for pictures go to the original post:
https://endless-sphere.com/forums/viewtopic.php?f=2&t=2633&start=975

My first attempt was by using microwave transformer, however it turn out there is not enough instant power requred for a quality weld.
Next after somem more research I decided that capacitor discarge welder should be the way to go, however I did not like SCR luck of control from one side and expencive yet unpredictable quality audio caps from other side, so I decided to have the cap bank built from regular inexpencive capacitors, exatly as green666 already did.
My bank is having same characteristics as green666, 1F from 100pcs 10.000uf 16V wired in paralel, that lower the ESR and helps to get high currents. As a control unit I decided not to invent the wheel and just to look around for an inexpencive and easy to reproduce platform, then https://malectrics.eu fit the bill; I bought his PCBs only and started to put it all toghether. Next I found I don't have the required display thus could not use his latest SW out of the box, then as a quick workaround I reused one of his earlier firmware on which pulse characteristics are adjusted by a pot...in fact I left only welding function, and it was enough.
The result was very impressive, especially after failed experience with MOT, the weld quality was outstanding and very stable, alredy build 13s4p battery for my son bike and all the work was done in one evening! As a quick charging option I am using server PSU (plenty of them on ebay) and charge the bank via 12V auto bulbs, cheap and quick solution for high inrush current, with used ones it takes about 5-6 seconds for recharge the bank to max 12.6V, good enough time to reposition for next weld.
Sure enough the cap bank is almost the most expencive part, even considering I used relativelly cheap caps from aliexpress, however it is not more expencive then one good quality and real capacitance audio cap. Another point, I am pretty sure that cap bank is more robust since the total current is distributed among 100 relativelly small caps and I beleive it is less prone to failure.

 

[Mpilley22]

Finished spot-welding 240 cells (20S12P from 5 separate 4S12P packs, LG HG2 cells, 3000mAh/ea, 20A continuous each, total of 2.6kwh). Used 0.2mm x 8mm pure nickel, carefully laid out to achieve approximately 160-170A ampacity.

JP Welder has not been perfect, but I got through it! I blew a trace and a mosfet, but I put that down to the several feet of 1GA welding wire I originally used to extend from the car to the table. Later replaced all the MOSFETS with same type but automotive grade (like another $1-2 total, why not!?). Also implemented the diode mod (VS­100BGQ045) that Okashira recommended. Of course, I also stopped using the long wires (less resistance) and implemented other mods, like the cooling fan and 12GA romex wire from the bus-bar to the MOSFETS. The whole thing runs VERY cool now, used to get almost burning hot! (Only the tips of the electrodes get warm when doing rapid fire welds)

The biggest issue I had (and a scary one) was several dozen times I had blowouts (craters), which are quite scary! My material is pure nickel and I experimented with differing pressure, timings, angle, cleaning the electrodes constantly, etc. I'm thinking the copper electrode material of these is not ideal...there must be something better! Furthermore, the wires themselves are not flexible at all...so I'm glad to see others looking to rectify these issues.

Another issue was sticking, and some of the copper getting left in the weld. This happened for up to half of all the welds. I tried the press and rotate technique others spoke of...which helps some. The sticking seems to contribute to the breakdown of the electrode, and needing to un-screw, put in the drill and spin it smooth and round/pointy again. I also lowered the settings down until pulling hard would "just" not break free of the cell.

I used a single brand-new Rural King battery (same as Exide Edge for a little more than 1/2 the cost, my wife's car battery had just died so the timing was perfect! http://www.ruralking.com/battery-auto-agm-rk-agm24f.html) and it worked VERY well. Before the mods I was up to 2/3 or so on the dial. After the mods, I was down to under 1/3 on the dial. Don't assume that you will need two batteries, for a good battery and 0.2mm nickel, you probably need only one!

SUMMARY: This spot-welding business is not for the faint of heart. Ironically, it's also not for the careless! Biggest improvements (post-mods) would be better electrode material and more flexible welding cables. (Or go with Headways if they dramatically improve the chemistry and you can fit them! )

I like this have a diagram schematic that controller is that from a kit