I'm thinking of converting a basic Buzz Box 200 amp welder into a Spot
welder.  I've got a physical arrangement for the output end in mind using a
couple of copper rods.  The electronics I'm envisioning like this:

One the 240 volt side of the welder (which is just a big honkin' variable
transformer) use a heavy duty triac control powered by a PIC.  There would
be an LED interface that would tell you how many milliseconds your spot
welding pulse will be, and a two button up/down control to change it.  When
you press the footpedal, the PIC responds by energizing the TRIACS and
turing on the welder for the required number of milliseconds.

Probably going to be a REAL noisy environment, plenty of spikes and EMI and
etc.  Anybody ever designed something like this?