“Some time ago I wrote an instructable where I explained how to control a spot welder in a sophisticated manner using Arduino and commonly available parts. Many people built the control circuit and I received quite some encouraging feedback.
This is a circuit operating at mains voltage and high currents, so the quality of the build is important to guarantee safe operations. While it is ok to prototype the sport welder using a non permanent setup, if you plan to build and really use this a good PCB will help a lot to achieve both a professional and a safe result.
Please read the first instructable, called Part I for short in the following, if you have not done so already. There is a lot of information there that will not be repeated here.”