diy - DIY & Electronics

>>204

Uh, I've never made one before so I don't have any tips. Do you have experience doing things like this?

Also, post results when you have them please!

I've actually had about a billion thoughts about coilguns. I could talk about them all night.

Some thoughts:
Don't kill yourself. The energy stored in a capacitor is 1/2CV^2, so higher voltage is how you get the most energy, and unsurprisingly the highest current as well. Don't kill yourself with that voltage, take reasonable precautions.

Build good instrumentation and experiment. There's any number of ideas to try with coilguns, from different sized projectiles and coils to fancier switching electronics, to more stages, and in order to build a good coilgun you will probably need to try all kinds of stuff. Build good instrumentation to measure projectile speed and other things you might need, like high currents. If you don't have good instrumentation you'll wind up guessing.

The worst part is the start. Going from zero velocity is the most inefficient part of the coilgun. Play with ways to make the beginning more efficient and the performance of your gun will increase significantly.

Post videos on the internet. Coilguns are the most awesome thing ever so there should be lots of videos on the internet.

make it thin, with thin wires
wrap the wires in the same direction, even when you layer them
make sure there are no kinks / etc
you can get a good activation mechanism from digital cameras (or any switch if you buy one)
don't shock yourself fuarrrking with capacitors.

>>209
Yes, you need to wrap the wire in the same direction. As to the wire size, that depends on the current they are going to have to handle. Whatever the current, it will be instantaneous, so probably erring on the side of making the wires thin is good. However, if you get a monster capacitor the size of a soda can and charge it to 450 volts, then discharge it through 24AWG wire, the wire will probably vaporize.

Pick the wire diameter to survive the current it will see. What current will it see? Break out your differential equations book and read about RLC circuits.

Is it possible to use a mechanical start of the projectile, and then using the coil-gun to get a better performance?

>>211
Almost certainly. I would recommend it.

>>205
no, first time working with electronics and magnets and stuff.
>>209
sure thanks. I already wondered why my electromagnet didn't work. So i need to wrap it ~120 times around again… Or should i just buy an electro magnet?
>>211
i will try this out

>>215
so, i opened some spare cd-drives and disassembled them. i think i'll use the cases for the trigger and some attachments. the thing in the middel is the first coil, i will use it to get the projectile moving (i still need a big coil though). I will use the two things on the top for adjusting of the coils, so that i can use different projectile sizes. And on the far right are some spare parts.

some more ideas?

>>215
Wrap it using an electric motor since you are already dissembling things.

I always think DIY weapons are so cool.

Poetic even; the advantage of the human is obviously the brain, and with DIY weaponry the individual man is using his brain to a very high capacity in order to make tools for domination.

I dunno it's just something I think about and can't even articulate right,

>>218
I just finished my weapon. Well, i couldn't make a coilgun, but i was abled to make a taser.
I will link to the video of me using it when it finished uploading

>>218
>>390
here it is:
https://www.youtube.com/watch?v=wTkId7JnBgs

>>395
It's probably too late, but you should learn about how to increase the voltage with inductive elements like inductors and transformers to avoid using batteries in series.
http://www.instructables.com/id/Capacitor-charger-60-400V/ this circuit I made might be useful next time, it can charge caps from 60 to 400 volts, stopping when reaching the desired voltage and recharging them automatically when empty.
I also wanted to make a coilgun, but there are many variables involved, including timing and how to switch the load stored inside the capacitors without blowing everything up. There is also some math behind the coils arrangement and the shape and size of the projectile. The bad thing about coil guns is they're very inefficient, specially if you don't design them properly.
Here's a neat example https://www.youtube.com/watch?v=TWeJsaCiGQ0

If you want to build a real taser look for transformers and voltage multipliers, they're really simple to make, combined with a 555 (or any resonant circuit), a mosfet and a small transformer you can get well over 10000 volts.
https://www.youtube.com/watch?v=WRjSyTrhq8g

>>765
neat!

>>207
>The worst part is the start. Going from zero velocity is the most inefficient part of the coilgun.
The most obvious response to that problem I can think of is to use some other form of propulsion at the beginning, like a mechanical flick. Even just storing up the energy of pulling the trigger would allow production of noticeable speed, slight as it may be when contrasted to the desired target velocity.

There is a design that does not need any switching or triggering mechanism:
Use multiphase current (like, from an electric outlet, not a battery) and wire each phase wire to a different coil.
With a little fiddling (varying space between coils and weight of the projectile) it is possible to have an "ideal" coil gun, i.e. one where the coil switches off exactly when the projectile is near the middle of it.

The coils will have to be spaced increasingly as the velocity of the projectile increases but the switching frequency stays the same (50 or 60Hz).
You might want to look up the design of drift tube particle accelerators as the design is the same.

A nice bonus is that with a decent feeding mechanism your coilgun can be fired at full auto up to 60 times per second (or 3600 rpm, 3 times as fast as the MG42 and only 50% slower than a full blown Gatling canon).

A word of warning: Such outlets are usually found in industrial environments and easily output several kW of power (400V and many Amps). This is not at all the same as your average handheld coilgun.

Tripod mount advised.

Like >>765 said, timing on these is notoriously difficult. You can use and inductance circuit to try to determine when to shut the electromagnet off/start up the next one. The system response is generally limited due to the large electric and magnetic fluxes created by the magnet itself. Some designs have used a shielded circuit and light-probes, but your best bet is to manually tune the timing bit by bit.

You're going to wear out a lot of capacitor arrays getting one of these working properly.

Just build a rail-driver.