Simple DIY Arc Wire Welder

[Pipes]

Hey guys. A while back I got myself a new RBA and it is the type that you need to attach pieces of non resistive wire to the ends of the kanthal wire. I have been doing the twisting together method which works but seems to loosen up over a short time. Read up on how ecig guys made the weld. Seems there are some battery tab welders which will do the job. Seemed a lot of work to make a spark.
My theory was that the only thing I intend to use it for is attaching kanthal to wire rap type wire so a million options was not needed.
Found that 35 volts and 2200 microfarad seemed close for the procedure.
Got together what I could find around the shop and came up with the following.

-DC/DC converter capable of 4-55 volts out 5 amp peak and 3 amp running. More importantly over current protection and self resetting.
-Push non-latch button switch
-2200 cap 63 volt max
-A 5.5X2.1mm DC plug for supplying power
-A box to hold it. I found a LED variable power box left over from a different project.
-Connectors for the output. Found some banana type plugs and one with a BNC adapter.

So this is the parts before wired:

A very tight fit. Like it that way.....

And with the connectors installed.

Wired and ready to close er up.

Looking good. The hole is to adjust voltage if need be. 36 volts works fine for my needs.

It took a few times to get it down but works quite well. Just put the kanthal (which is a twisted pair of 32 AWG in this case) in the ground side and alligator clipped the non-resistive, aligned, pushed button for a couple seconds and bring the tips together.

The circuit is quite simple. The output of the converter goes to the push switch and when pressed it charges the cap which is on the output leads. The leads are safe until you press the button. The only safety feature here is common sense, always short out the output when not using.

Have gotten good results.

Nice small footprint. Specially once the output is detached.

And I found if more power is needed, the voltage can go up or increase the capacitance externally. This way you can join larger things.

Anyway, thought I'd share. Now don't blame me when you zap yourself...

Pipes

 

[Hippie Dickie]

wait ... what? ... is this a spot welder? could i make k-type thermocouples with this rig? the ones i buy are $6 each, but the wire used is about $0.15 (+ a weld).

i'm using 0.010" wire = 30 awg.

What is RBA?

 

[Pipes]

I'm not sure about making thermocouples as I was looking for a way to attached the kanthal element wire to non-resistive wire. RBA = ReBuildable Atomizer. There are some out there that require the wires to be attached in this way. Or twisting together.
It should be considered a battery tab welder without all the bells and whistles. I guess you could add power LEDs, voltage display yadda yadda but in reality, if only using for one thing, are they needed.?
The voltage in this can be varied but need to use meter and tweaking tool. Capacitance can also be added as shown. The internal cap is good for thin wire.
It is also missing a trigger button, meaning you cause the arc by pushing the contacts to be welded together. A triggered device means you can have the two pieces of metal to be welded pinched together before the voltage is pulsed on.
Missing this feature is what makes this so simple. Key is a variable supply that has good output protection against over current and self resets.
The input supply voltage can go as low as 3.5 volts and works with an 18650 battery even. I have been using a 12 volt supply.

wait ... what? ... is this a spot welder? could i make k-type thermocouples with this rig? the ones i buy are $6 each, but the wire used is about $0.15 (+ a weld).

i'm using 0.010" wire = 30 awg.

What is RBA?

EDIT:
Was thinking about your thermo couple application. If you can find out the magic numbers as in voltage and capacitance needed, why not? If the wire is so cheap, can play around to get the same weld as a bought ones. Are they not just joined at the tip and then twisted for support? Not sure but that is what I recall they look like.
Voltage, Capacitance, surface area and pressure are the only variables.
Pressure would be the pushing together thing which does take a bit of practice and hit and miss.

Fun toy.

 

[Hippie Dickie]

Was thinking about your thermo couple application. ... Are they not just joined at the tip and then twisted for support? ... Voltage, Capacitance, surface area and pressure are the only variables.

Yes, just joined at the tip. Not twisted, i use bare thermocouple wire and add a polyimide sheathing. This would be ideal -- the ones i buy are 6" long and i only need 2" length.

 

[Pipes]

Yes, just joined at the tip. Not twisted, i use bare thermocouple wire and add a polyimide sheathing. This would be ideal -- the ones i buy are 6" long and i only need 2" length.

Cool, that would at give a 2 for one if not three. Even more if you can find the wire on spools.

Just remember the voltage provides the heat and the capacitance determines the length of time it is heating. So what you look for is how much discolouration there is around the weld caused by the heat.

Too much voltage and material will disintegrate, not enough and weld will break easily.
Too much capacitance and the discolouration will be large and/or material will melt too much weakening it. Too little capacitance and again bad weld.

At least that's what I found in searching the right balance for my project.

Another note worth mentioning is the grade of capacitor. In my case I am not too worried as have caps coming out of my yingyan. My understanding is I should be using a high grade cap which are like normal marine batteries verses car batteries. Looking for ones with large pins or screw type connections are a clue to this apparently. I am no expert on capacitor grades but maybe someone could chime in on this and how to identify the better caps?

Good luck.

 

[Hippie Dickie]

@Pipes - thank-you, i very much appreciate this info. i can see spooling the two wires out and every 2" do a weld and cut. sweet. now i need to research the voltage and capacitance for k-type wire.

i want to build a vape with three heaters in a line, each with its own temp control. work with any bong. should be awesome.

 

[Pipes]

Sweet, a cascaded heating system.
Sounds awesome in deed.
Having (making) the right jigs to make stuff is half the fun.
Your quite welcome and will keep an eye out for your results.