So, I have a project, where I am testing the strength of a thin >30AWG wire, under different conditions. Anyways, it involves basically shorting the wire, and watching it melt. I am looking for a safe way to short the wire, with no risk to my power supply. I was thinking something along the lines of a current limiting circuit. I have a 20A power supply for my 3D printer, so I was hoping to use that, with some form of current limiting, to melt a wire. Anyone have any ideas about what I should do? I would prefer not to use a current limiting resistor, but i am still open to that option.

 

I'd use a constant current control circuit. You watch the voltage on top a low ohms shunt resistor, maybe 0.1Ω, with an op-amp. You put a reference voltage on the other pin so that, when the voltages are equal, the current through the shunt resistor is in the range you want. For instance 100mV across the 0.1Ω shunt gives you 1A. One volt would be 10A. The output of the op-amp controls the power supply voltage.