How to make a spot welder.

[eccerr0r]

Re: How to make a spot welder.

Well, just saying, I spent 50¢ per 9V battery and it lasted at least 4 years so far, I don't think it's a bad deal, and nothing sticking out of the meter... This is specific to the Fluke.

That is not to say the same 9V battery (out of the same 2-pack) lasts less than 2 years, possibly only a few months on my other 7106-based meters...

[Sparkey55]

Re: How to make a spot welder.

The easies video I ever found. I will try it with 120vAC. the capacitor in the video is a 440 volt 20uf AC capacitor. we can make a one with two DC capacitors.

How to make a spot welder.
https://youtu.be/sYR4RuqEIjs

I once blew a hole into a 1/4 inch screwdriver when shorting a 25,000UF 75VDC capacitor.

[stj]

Re: How to make a spot welder.

http://ultrakeet.com.au/write-ups/cdWelder

[eccerr0r]

Re: How to make a spot welder.

I guess the trick is for capacitor discharge welders is finding good capacitors...
Ever since I destroyed a capacitor by repeatedly charging and shorting it (for entertainment purposes) it's something to consider...

Currently I've been using a 51mF capacitor charged at ~18V to blast through shorts in NiCd cells... Doesn't always work but at least this capacitor is capable of dealing with shorting, at least its performance hasn't dropped compared to that other capacitor I was playing with when I was younger...

[stj]

Re: How to make a spot welder.

shorting large caps can melt the wire inside the bung where it's flattened to go into the foil.
the cap can store more current than the wire can hold.

it's also not a good idea to short a crt anode by shoving a pair of screwdrivers under the cap - you can damage the diode with the emf spike!
i'v seen old gits damage them a few times like that - modern-ish transformers arent as robust as the 70's
besides, does a chain of resistors really cost that much? /sarc

[capwizard]

Re: How to make a spot welder.

If you want to make best spot welder then you need to use the best and biggest capacitor in the world and that is battery.

So I'm going to switch my attention to 12 v battery spot welder is that sound right?

[stj]

Re: How to make a spot welder.

no, batteries explode!!
what's wrong with using a microwave oven transformer and changing the windings?
others have done it.

[capwizard]

Re: How to make a spot welder.

Yes that will be a workhorse. then we pretty much go back to old solder gun like this guy eccrr0r said...

I was wondering is whether just using a old solder gun to weld with... Get rid of the resistive tip and use two probes there instead, and depend on that low voltage high current to weld with. It's on the order of a hundred amperes, which is a bit low, but might be enough...

I have tried that before I think old solder gun has no enough current.

[eccerr0r]

Re: How to make a spot welder.

Using a car battery, you must have some sort of control like an IGBT or MOSFET bank. People have welded with a car battery but that tends to blow small battery tabs up. A capacitor is good because the amount of energy stored in a capacitor is limited.

Might need to look for a bigger solder gun that has a bigger transformer in it...

[sam_sam_sam]

Re: How to make a spot welder.

All you need is transformer controller and these are easily found today on eBay ( when I get home I will post where you can find some)

The hardest part is getting a 1000 watt microwave transformer (or two of them depending how hot you want the weld to be) and converting it with out distorting the primary winding but if you take your time it can be done

Now the battery spot welder that I have if I change the breaker from 15 amp and went to a 30 amp breaker I could get some very hot welds and I might have to do this I would have to change wiring to go to a 30 amp breaker and just have not been motivated to do it so far but if I keep getting cold welds that the battery tabs do not stay on I will have to do it

Because I can only turn the current controller to no more than 70% with out tripping the 15 amp breaker

Another reason that I have not change the breaker is that when the current controller start taking a shit when you hit the trigger button it bounce and rapidly fires the transformer and trips the breaker

Or

This happens when you first turn power on it rapidly fire the transformer and this might happen a few times before it stops doing it so you can use it

In either case when it works right it does not do this

[eccerr0r]

Re: How to make a spot welder.

So, that's another benefit of the capacitor discharge welder versus transformer based
Alas the recycle time of the transformer based should be quite a bit faster...