Eric R Snow wrote:

So, after looking at the SP 125 Plus welder wiring diagram and
corresponding with folks here I have come up with most of the parts
necessary to build my own timing option. Using a kit from Velleman
(PMK 111) will provide the timing. It has two adjustments: Pause and
Pulse. The kit comes with pots that allow for a .5 to 5 second Pulse
and a .5 to 60 second Pause. The Pause time pot is a 10 megohm and the
Pulse is a 50k ohm device. Since the Pause pot has so much more
resistance it is very hard to finely adjust. I will be replacing it
with a 50k pot. In fact, I am going to replace both pots because the
ones in the kit are trimmer pots and I want the adjustment knobs on
the front of the welder. [...]

For pulse, consider a 5K pot in series with a 50K pot, and for the
pause, a 10K pot in series with 100K. There's a vast number of possible
arrangements of pots and fixed resistors in series and parallel to get
different adjustment curves, but two pots in series is probably the best
way to get both fine and coarse linear adjustments.

1) What is the minimum Pulse time.
2) What is the maximum Pulse time.
3) What is the minimum Pause time.
4) What is the minimum Pause time.
5) What exactly is the Spot timer meant to be used for when the timer
is the one provided by Lincoln. [...]

I don't know these answers, and I agree with Don Foreman that
manual control is probably good enough. Imagine sitting
there impatiently waiting for the pause to time out. You might
add a foot pedal if your concern is having your hands full.

-jiw