The original coilgun circuit used a relay which quickly suffered from contact problems due to the large current flow so I have replaced it with a thyristor.

I’m using a FS2514MH thyristor with an non-repetitive on-state current rating of 330A.

Datasheet: https://www.fagorelectronica.com/images/download/semiconductor/fs25st.pdf

I took the oportunity during testing to record the current waveform using a LEM PR1235 current probe.

As you can see, the peak current is 216A.

Test bed is now wired up and with connector blocks so I can swap out parts.

Here is a quick demo shot against a energy drink can.

And the damage done.

I made this simple wooden test bed to hold all the parts of the coilgun securely. When firing there is some recoil so it’s good to keep everything in place.

The small PCB on the bottom left is a mystery chinese DC-DC boost converter. The control chip had it’s part numbers ground off but I manged to read them under a bright light and it’s a flyback based design. Takes 5V in and gives a nice 300-400V which is perfect for capacitor charging.

I made this tool so I could discharge the large capacitors I’m using in a controlled maner as just shorting them with a screwdriver leads to big sparks and contact errosion.

It’s simply a 10 Ohm 50 Watt power resistor attached to a nice thick cable and some crocodile clips all with plenty of heatshrink. I settled on 10 Ohms after doing a few rough calculations given the level of voltage I’d be using it at.