Mini battery operated spot welder

Glad you brought up the technique Phil, I was surprised to see the technique used on the batteries, would have thought one probe on the battery top and the other on top of the strip would guarantee the current went through the intended joint. I still don't see how that technique worked in the video except if the strip was stainless, it might have more resistance, so through the metal strip to the battery top and over to the other probe on the strip would be less resistance than straight across the strip?

Greg
 
phils2um said:
Micheal - can we persuade you to try again with a piece of flattened brass wire? But, unlike the technique used to attach wires/bus strips to batteries shown in the video I think one electrode needs to be solidly connected to the rail near the weld location. The other pushes the wire against the rail at the intended point of attachment. This is essentially how we spotweld Pt leads used to monitor crack progression in miniature fracture toughness test specimens. A heavy Cu ground cable is clamped on the specimen. A jig holds the Pt wires in position. The welder's other Cu electrode pushes the Pt wire against the specimen and triggers a current pulse that welds the wire to the steel test specimen.
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I really think the one I use is only suitable for it's intended purpose, and that is for lithium or equivalent batteries.

It is in fact just 5 FET's in parallel, a control ciruit with display and buttons (for adjusting the on time) and a large capacitor to help with the current. It relies on the 'on' resistance for the FETs being matched so that they share the current. Read the reviews and the FETs do have a habit of failing especially when misused.

Operation can either be via a switch (not supplied) or automatically. I used the automatic method. When it detects that you have connected both probes there are 3 beeps. It fires on the last beep.

I hold one probe on the wire pressing it hard down onto the metal cap and then put the other probe hard down onto the cap a couple of mm away.

If you look carefully at the battery photo I shared, you can see two small marks for the two welds I gave each wire.

I tried again with 1mm brass wire (the smallest diameter I have), cleaning the rail first. No joy at all. I did get the 0.37mm wire to weld once but the wire easily came away. I tried again with a battery and it was fine, it takes a lot to pull it off.

I only have experience of Peco 250 code track but with the correct temperature controlled soldering iron (a must for anyone dabbling in electronics) it is very easy to solder wire to the rail. I can't see therefore why you would want to use a different technique.

Michael
 
Greg Elmassian said:
It's usually hard to change the laws of physics
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True, but try telling that to the fast food outlets. Their containers seem to be far heavier empty than when they are full. So much so some of the poor customers can't possible carry the he empties to the nearest bin, and just have drop them on the floor where they stand
 
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