Not new information here, and you do not even connect a source so you could actually do a spot weld; the pictures provided when purchased (AND THE ONE YOU SHOW IN THE VIDEO) provide more information than this video. I was hoping for an explanation of the LEDs and seeing it operate with a source connected to the TRIAC. To those curious, the large component (BT100-1200B on mine) at the back with nearby connections labeled 1 & 2 is an 1200V TRIAC rated for 100 Amp. For those who may have wondered if your source for the spot weld could be a DC source such as a car battery? NO YOU CANNOT USE A DC SCOURCE. Despite the timing being done by using the frequency of the AC power (via the 9-12 VAC transformer) The power for the spot welder comes from a larger transformer (typically a MOT with the secondary winding replaced to provide 3-12 Volts but thick enough to handle 100 Amps... I defer to others who cover this tropic already) One thing I find disconcerting is one my board, it is clearly letting a small amount of current flow through the primary windings of the spot SRC primary winding despite not being triggered. This may be normal and the result of residual charger on the gate... since the specs for the TRIAC show a notably low gate current. I suspect the circuit board lacks the expected safety components to ground transient currents and the diagram does not show how to handle them either. Silly me for expecting to get a circuit that doesn't try to do the minimum to avoid injuring you. And it bears repeating, be cautious around these voltages and currents. Know your limits; if you don't put safety first, ATLEAST PUT STUPID LAST.