Project idea(s) for this year. I’ve been fiddling lately a lot with electromagnetism and solenoid structures at work – but how to do something more entertaining with electromagnetism? One of the first things I can think of would be by shooting projectiles. Of course, there’s nothing new in creating a coilgun – besides the fact that I’ve never built one myself. But what I’m actually interested about in this, is to make it more efficient and not to waste any unnecessary energy to heat. Typical approach seems to be single stage coilgun where awful energy storage is converted to heat with every shooted projectile. That’s just silly.
My first approach to this topic would be multi-stage coilgun with ”energy recovery”, so energy stored to magnetic field of coil will be stored and used again in further stages. At least couple of easy ways to do this come to mind at this instant, either charge the energy straight to a capacitor through the coil (and so on…) or use the coil-stage as boost generator for next phase.
So basically increasing efficiency would mean couple of things, coils cannot be very ”thick”, because we want to keep the magnetic flux path under control and airgaps short without sacrificing too much of the mechanical simplicity. Also resistance losses is something we want to avoid (heat), so this eventually leads to figuring out the optimal capacitance and finding semiconductors to survive the quite high current pulses… More on that when I have time to do some calculations 🙂
Anyway, this leads straight to another cool side-project. When you need lots of coils, hand-winding is awful and boring task, at least I don’t like the calculation part at all – you’ll lose it at some point anyway! There’ s ofcourse option just to measure the overall length of wire and use some approximation for nominal radius of coil, but I’ve found that this is way too inaccurate for inductors. And ofcourse there can be lot of other cool uses for this toy, how about custom-made guitar pick-ups? So my ”to be” winding machine would be uc controlled dc-motor with smooth speed control, winding round calculation and some sort of automatic spreading for the available core-area. Controller part will be piece of cake, but making this suitable for different kind and sizes of coils and wires will need some thinking on the mechanical construction. Meanwhile I had to do a number of similar hand-wound coils, so I built up a little helper for the task. This was constructed in couple of hours from scrap parts and it uses old pedometer for round calculator.

Not pretty, but it works as a charm!