Coilgun – v.0.1
As noted before, Ze Local Awesome-blowing-stuff-up club, of which I’m the Benevolent Dictator for Life, has created the initial iteration of a coilgun. Behold!
I can already hear the complaints about the lack of video of the thing actually firing, but I have an excuse: our benevolent email-writer for life, managed to kill a vital component while trying to make a would-be version 0.2 (this also explains why nothing is connected to anything else). So, no video until we finish up version 0.2, which should be soon.
For those of us unfamiliar with *what* a coilgun is, and who are familiar with physics, a coilgun is essentially a big electromagnet. For those of us who are not in the physical conspiracy, but still want to know what they’re looking at, a quick physical primer: first, the big cylinders are capacitors, which store electricity, only to quickly dump all that electricity through the coil. With all this electricity moving around in circles through the coil, a magnetic field is created, which then draws magnets or pieces of metal through the coil, sending them flying.
Well, okay, you should forgive me: this is the first iteration of the documentation associated with the coilgun, too. I’ll try to update the descriptions and inner workings better as we go, especially since we managed to do very little math on this coilgun. We’ll probably do more and more math/analysis as we go, too.
So, finally, some gory details: we have a capacitor bank of 4 capacitors in parallel, rated for 200V and 1200uF. The coil was made with 24 gauge magnet wire, for a coil density of who knows what, since we weren’t keeping track, and we’ve already taken most of it apart. The coil is wrapped around some 6 inches of 1in diameter PVC piping, and we used a high voltage, high current rated thyristor as a switch. With the capacitors charged up to 195V, we shot a magnet around 70cm straight up into the air, which is not too bad for doing absolutely no math. Maybe I’ll talk about our throwing-together process in later posts.
For the next iterations, we’re thinking about using a high-voltage transistor instead of a thyristor, for better control of the current: once a thyristor is turned on, it passes current, and continues passing current until there’s not enough voltage to keep it turned on. A transistor passes current only when there’s some voltage applied at the base. (Note: I know this is a bad explanation, especially when I use terminology on several different levels. As I hinted at before, I’m trying to apply some agile methodology to blogging, and maybe it’ll stick). Also, we’re looking into thicker magnet wire, and a way to power the circuit directly from the AC grid.
And I’m sorry about the crappy photos: the camera phone idea is good, but the cameras still don’t hold up well when you want crisp details.