Fusion Message Board

In this space, visitors are invited to post any comments, questions, or skeptical observations about Philo T. Farnsworth's contributions to the field of Nuclear Fusion research.

Subject: Re: Home Made Spot Welder
Date: Jun 24, 1:54 pm
Poster: Scott Stephens

On Jun 24, 1:54 pm, Scott Stephens wrote:

>All sounds fine, but two points might work against you here.
>1. The soldering gun may not be insulated well enough on the input side to handle high pulse voltages.
>2. A really superior SCR would be needed to handle the discharge firing along with some snubbers and other anti kickback protection circuitry. Looking at ratings for the SCR seems simple. In practice, the 1000 volt plus pulse at 100 or more peak amps into a totally inductive load is a duanting task for the survival of the small silicon pellet switch.

I checked peak currents a while back, and IIRC found a cheap 20 amp SCR can hanldle 100 amps for breif surges. There are lots of app notes that describe diodes and snubber protection, and using ballast resistors and inductors to parallel them.

>Naturally, let us know how it works out.

I would suspect the brief pulse would simply heat the crude tape core of the soldering iron.

Hopefully we'll be hearing back from Don! A safer approach I've seen on a book describing how to build your own model turbojet (another safe hobby!) is to remove the lethal microwave tranny's secondary and wrap a few turns of copper strap. IIRC a second or two of heat spot welds. He modified a pair of pliers, drilling holes in them and inserting welding electrodes.