I have a 240v to 12v transformer even bigger than a microwave transformer and i want to control how long it is switched on for in the range of 50-300 milliseconds to spot weld things.
I was thinking of a big momentary push button switch same as thet have on factory walls to control robots, that i can hit a bit like swatting a mosquito at different speeds in order to get different contact durations.
Perhaps i could make a switch to control the transformer input, out of wood, copper and some silicone rubber springs? to finely adjust the physics of the spring to change it's rebound depending on how it is wedged?
Is it a feasable DIY experiment? would a switch on the AC side be too imprecise, seeing as the AC phase is 20ms and i need to let through 5-10 periods of AC into the transformer, is it not logical?
Best Answer
Using a switch to directly control a large current like this is extremely hazardous if the switch is not specifically designed for this application — if the current is large enough, it will strike an arc when the switch opens. This will rapidly destroy the switch, and may end up fusing it closed.
A homemade switch like the one you're describing ("wood, copper, and some silicone rubber springs") is likely to be particularly prone to this issue, as it is not specifically designed to extinguish an arc, and its contact surfaces are not designed to carry high currents. Do not attempt to build your own switches for high-voltage, high-current devices.