TIG Welder and Power Control

This project started from seeing pages describing arcstarters that could be constructed for practically no cost from stuff just laying around in the typical tinker`s shop. It has been a fun project, but I have a basement crammed full of stuff and I still had to spend over $600 to build the thing. My arcstarter section runs at 300kHz, uses Miller a
TIG Welder and Power Control - schematic

rc points, a homemade ferrite core coil/transformer, homemade multi-capacitor modules for the filter and tank capacitors, and generates a tremendous amount of radio-frequency interference. I guess you would say it is a typical homemade arcstarter. On the other hand, the power control section is not typical of homemade circuits. Power control is linearly contolled from zero to full power at no, partial, and full current. The circuit uses zero-crossing detection and multi-pulsed gate triggering to ensure symetrical firing of a reverse-parallel SCR module. Making a decent looking case has always been the slowest part of a project for me. I use to have access to a metal working shop, but now I can only do it at home. So my case started as a computer case that I cut down to a size close to the size of my arc welder. The arcstarter section is on the left. I wanted to put the arc points at the rear so I could adjust them by removing a panel. Due to the available space, I had to move the arc points to the side. This location also provides a way to incorporate the ceramic tile insulator into a plenum to cool the points and keep the UV light from the point arcs away from eyes. A fan at the front cools the tank coil secondary and the MCM. The cooling air then is divided, with part flowing past the arc points, and part flowing over the heat sink for the power control SCR module. Control of the arcstarter and the welder is on the right....

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