i'm making a capacitive welder

[mkawa]

i'm just posting this thread in case i die in the next couple of weeks. OK THAT'S ALL DUDES

[SpAmRaY]

i'm just posting this thread in case i die in the next couple of weeks. OK THAT'S ALL DUDES

Would it be a side effect of the welder?

[bueller]

i'm just posting this thread in case i die in the next couple of weeks. OK THAT'S ALL DUDES

BE SAFE DUDE, RUBBERISE EVERYTHING!!!

i'm just posting this thread in case i die in the next couple of weeks. OK THAT'S ALL DUDES

Would it be a side effect of the welder?

More like the massive string of capacitors all storing a charge, can be quite dangerous if not careful.

[mkawa]

there will be a lot of silicone involved.

[mkawa]

actually that sounds dirty

oh well

[rowdy]

First excessive lube, now excessive silicone, what's going on here??

[mkawa]

...

[JPG]

... kk, deleted post, but there was a strong correlation!

[mkawa]

we do not endorse these kinds of chauvinistic things on geekhack sir

[mkawa]

THIS is an elna dynacap DZ-2R5D475T



it's rated at 2.5v 4.7F. ESR is 200mOhm

i have 22 of them.

[mkawa]

so i've worked out the final supercap specs. it's going to be a 14.1F capacitor with ESR of 100mU at 20v. i will be charging it to 18v and using it with at least a 200A thyristor for DC welding. peak current output will be 180A at 18v. it will be foot pedal operated but otherwise direct current. i toyed around with bringing current down then buck driving with a large number of beefy sinked darlingtons, but for efficiency and simplicity will just be putting the capacitor network together so that i can sink them directly into the welding point. (as it's a CD welder it can only weld points. it may have enough reservoir capacity to cut as well, but i don't expect to be able to bead long joints. frankly, it's mostly for making thermocouples and stitching the sides of sheet metal for the ssk plates).

[oTurtlez]

so i've worked out the final supercap specs. it's going to be a 14.1F capacitor with ESR of 100mU at 20v. i will be charging it to 18v and using it with at least a 200A thyristor for DC welding. peak current output will be 180A at 18v. it will be foot pedal operated but otherwise direct current. i toyed around with bringing current down then buck driving with a large number of beefy sinked darlingtons, but for efficiency and simplicity will just be putting the capacitor network together so that i can sink them directly into the welding point. (as it's a CD welder it can only weld points. it may have enough reservoir capacity to cut as well, but i don't expect to be able to bead long joints. frankly, it's mostly for making thermocouples and stitching the sides of sheet metal for the ssk plates).

3240 Watts of POWAH! Good schtuff kawa.

[mkawa]

the thyristors have significant power loss (they need to be sinked big time as well as the cap network) so it won't quite hit optimal power or current. that said, it should be plenty for small stitches. high current battery connector welding is another application

(lifepo4 cells are fascinating me right now. incredibly power density WITHOUT the volatility of li ion or li polymer (which was the initial attempt to keep the lithium in check.. the tradeoff is that they don't deep cycle, period. deep cycles actually temporarily kill the cells (!!!). MCUs to the rescue! etc).

[TheSoulhunter]

Found this clip on a old cellphone...
Thin aluminum sheet -VS- 380A A/C Arc, fun times! )

[mkawa]

SWEET

[mkawa]

i present this without comment:

[Tarzan]

i present this without comment:

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Good grief!

[RabRhee]

i present this without comment:

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Are these the capacitives that you want to weld together? :P

[Binge]

My jimmies are scared for Kawa... be safe fine prince

[AKIMbO]

Kawa's crazy.

[TheSoulhunter]

Nice battery!

[MOZ]

i present this without comment:

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Ca, ca, ca, capacitors!

[tjcaustin]

Did you find your keys before you die?

[Thimplum]

i present this without comment:

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That's awesome! Will you be providing source files for us?

[damorgue]

i present this without comment:

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Safe handling guide: After unplugging, let it be for a few years to discharge. Then take long insulated grounded metal rods and poke around with them. Then use a large pair of plastic grippers and throw the entire thing in the river. It should now be discharged and ready to be left there forever.


Farad count on that?

[Game Theory]

Safe handling guide: After unplugging, let it be for a few years to discharge. Then take long insulated grounded metal rods and poke around with them. Then use a large pair of plastic grippers and throw the entire thing in the river. It should now be discharged and ready to be left there forever.


Farad count on that?

)

[MOZ]

i present this without comment:

Show Image

Safe handling guide: After unplugging, let it be for a few years to discharge. Then take long insulated grounded metal rods and poke around with them. Then use a large pair of plastic grippers and throw the entire thing in the river. It should now be discharged and ready to be left there forever.


Farad count on that?

LOL. He is making a battery.

[mkawa]

4.7F * 5 = 23.5F (approximately, too many unknowns to actually measure exactly at the moment)

i'm not getting enough current out of it right now. one of the banks has an issue. so sadly it isn't all that dangerous yet. peak current at the moment is about 10A, so i suspect one bank has a couple cold joints or a bad cap in it. my calculated peak current was over 400A @ 18v. it's also possible that i simply don't have a measurement device that can capture the peak current interval, as you only get peak current for like a ns before it discharges below say 12v and then sits at 5-10A the rest of the way down.

also, i have a 300W 8ohm resistor that i discharge it into.

here's the current experimental setup. it's DC coupled right now but i have darlingtons to buck drive if i have to and a whole bunch of fast power mosfets if i need to go the other direction.

dicharging it through those 18ga clamp wires is fun. HOT STUFF COMIN THROUGH



the big brown thing that looks like a turd is a single resistor. it's a bunch of nichrome wires baked into a 1.5" diameter piece of ceramic. i collect huge passives. it's a hobby.

[mkawa]

oh, the little brown things are 50W 1.2ohm resistors. those are fun too. they can take a lot more than 50W

[mkawa]

crap, i found some wtf wires in the middle of the board, surrounded by capacitors that i can't get to at all.

[MOZ]

Mad scientist at work

[mkawa]

i was trying to figure out why the ESR seemed so high and i realized it was actually all the wires in the network, not the caps themselves.

RESULT:

it pops now when shorted  my clamp meter isn't fast enough to see the transient current, but it is quite high.

[StrikeEagleCC]

mkawa, that pic of your bench made me drool.

[mkawa]

[StrikeEagleCC]

Is that first aid tape?

[mkawa]

the tape is fiberglass weave in tape-form with an ultra-high temp silicone adhesive (260c+). it's a much more effective and tougher insulating electrical tape than the classic rubber crap. i believe there's some kind of resin impregnated in it as well, since i've already heated some to 200C and all that happens is that the resin takes on a glossy appearance, no other ill-effects and it maintains both its strength and dieletric properties. i purchase it from mcmaster, but i'm sure there are cheaper sources. it's made (like everything else) by saint-gobain

http://www.mcmaster.com/#fiberglass-tape/=o9y0ux

[mkawa]

also, i thought about it quite a bit and i decided the other fairchild darlingtons just weren't beefy enough, so bought two of these: http://www.onsemi.com/pub_link/Collateral/MJ11028-D.PDF

max collector amperage continuous is 50A and it has an h_{fe} of 1000x @ 5v V_{be}

MUAHAHAHHAA

[Melvang]

Just want to give you some notes for personal info on actual welder voltages and amp for actual welding

Stick welding with 1/8" 7018 weld rod ~71.2 volts and I run at about 115 to 120 amps unloaded

Wire welding I am a little fuzzier on but I believe amps was set to around 23.5 but not sure where voltage is set to but that was for DC welding.

AC welding for the most part is only used on aluminum due to the way the aluminum reacts to the weld arc and the tungsten.  Also aluminum has a fairly low melting temp (1244F).  It can be melted on top of a charcoal chimney for grills with some forced induction via shop vac with hose plugged into the exhaust port.

[mkawa]

the rectifier in the last picture (which i've tossed and decided to require point to point) will make this a point discharge DC welder. i'm not sure what my transient amperage at full charge is @ the full 18v, and won't until i get the rectifier set up. once i do i'll report and see if i even need to buck convert. basically, if i throw those buck converters on there, i'm going to be getting an initial 1kA transient then a few hundred amps sustained @ 5v. if i just rectify, i'll get the initial pop transient of maybe 500A and then it will actually settle around 20A @ 18vDC

[mkawa]

which reminds me, i'm going to have to pick up more safety gear. i'll probably pick it up next time i'm at IMS grabbing remainder stock

[Melvang]

If you are going to be picking up welding gear you might want to get a cheap welding hood or borrow one.  Extended exposure of your eyes to the massive amounts of UV light that is given off in a weld arc will cause what is called arc flash.  Basically what it amounts to is a very painfull temporary blindness.

[mkawa]

oh yah, just discharging the caps with bare copper wire left an afterglow. the actual welding light at 1000A peak is going to be INSANE. especially switched at high speed to maximize power. i plan on getting a full auto-shading hood from IMS or MCM

[mkawa]

they had a sweet one at IMS with flames on the side (really!). yea or nay?

ims = industrial metal supply, a local awesome metal supplier that serves all of the southwest.

[Melvang]

Personally I don't trust cheap auto tint hoods.  To me that is something that if it is cheap it is crap.  My suggestion is just get a Jackson hood with the large lens and buy a gold tint lens at shade 11 minimum

[mkawa]

ok, i'll run my cart by you before i buy. thanks melvang! going blind would suck. so would burning my hands off

[JPG]

What do you want to meld with it? Your car? Or just for fun?

[mkawa]

thermocouples and SSK plates primarily. anything else i get to fry is just for fun

[mkawa]

melvang: does this fit with what you were saying?

http://www.mcmaster.com/#56405t63/=o9zzcc
http://www.mcmaster.com/#9716t26/=o9zzpg

presumably you can replace the polycarb lens that comes on the hood with the gold-coated one? or is that something you add onto the lens that comes with the hood

[TheSoulhunter]

Personally I don't trust cheap auto tint hoods.  To me that is something that if it is cheap it is crap.

Indeed...
3M Speedglass or bust!

[mkawa]

aaa! i don't want to die. someone tell me what to get