Pulse oscillogram

A project log for Not-so-smart capacitive discharge spot welder

Portable spot welder that doesn't need microcontrollers, uses recycled industrial thyristor and mostly off-the-shelf components

wojciech-adalbert-jWojciech "adalbert" J 07/16/2023 at 13:420 Comments

I managed to capture oscilloscope image of the pulse with an old analog Philips PM3226 oscilloscope. It was a bit tricky, as analog scope don't have digital storage capabilities, so I put a camera in long exposure mode and tried to capture the trace. I measured the voltage drop in DC mode. It worked, and the observations are as follows:

The probe was connected to the capacitor bank as that was the simplest thing to do. The test was done while spot welding two nickel strips. I guess I could also measure the voltage drop across the welding lead.

If I get the math right (I entered discharge time of 0.001s from 30V to 15V into this calculator and got 0.01012418ohms) the pulse should be close to 3kA.