On 2012-10-28, Karl Townsend wrote:
I've had several queries concerning my spot welder project. The below
pics show a spot welder upgraded to include a weld timer and a power
control.

The timer is just a timer relay set to tenths of a second. It is wired
delay off and closes the power relay seen in pic 1. The switch on the
spot welder itself is wired back to the timer. The power control is a
pair of variacs (free from Pete) on a common shaft. the dial can be
seen in pic 2

Looks nice -- but I have one question. As it is shown, it is
set for 2.7 seconds, which is fine. But how small a time do you expect
as your minimum? The reason I ask is that I wonder what the mechanical
delay time on the relay is. I would be tempted to use a solid state
relay instead for more precise control of time (down to 1/120th of a
second, and then fractions thereof depending on when the relay is turned
on relative to the power line cycles.

If you don't expect to go much below one second, you should be
fine with it as it is.

Can you read the lines on that timer? I've got no idea what
they say. (Nor am I sure what the leading "89" and the 'H' mean in the
switches.

Enjoy,
DoN.

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