This is the first coilgun / Gauss rifle i built, let's call it v1.0

it has 8 stages, all independent from one another. Each stage switches on its coil as soon as the projectile breaks the IR bridge in front of the coil and shuts it off when the projectile exits the IR bridge, when it is in the middle of the coil.

Steel projectiles are stored in a "rubber loaded" magazine wich attaches to the gun with a pair of neodymium magnets.

A solenoid in the rear pushes the topmost projectile into the first coil, wich in turn pulls it out of the magazine and propelles it forward to the next stage.

It is capable of semi-auto fire with a pretty high fire rate. Each projectile weights about 14g and carries almost 3J of kinetic energy, enough to punch through cans and shatter ceramic tiles and glass bottles but nothing too serious.

The circuit design is fully discrete, and i plan to keep it that way for v2.0.

In v1.0 each IR photodiode signal is fed into a totem pole transistor pair, which in turn drive the gate of the big MOSFET that switches on the coil. Pretty simple stuff.

The problem is that the signal from the photodiode is quite a slow ramp, and the BJTs are feeding the exact same signal to the MOSFET, this causes the MOSFET to work in the linear region for a relatively long ammount of time (just a few ms, which sounds like nothing but is actually quite long). At the current levels that each coil operates (~100A) this means a lot of power dissipated in the MOSFETs, which caused them to often fail rather spectacularly.

This is one of the aspects that i have planned to change. I've designed a whole new circuit that will drive the MOSFETs' gates up way quicker, and hopefully solve the unexpected fireworks problem.

In between explosions i had enought time to use the rifle on a lot of targets. I definitely had a lot of fun building and using this coilgun, and so did my friends. I leave you a couple of clips that illustrate the v1.0 in action