Coil gun project.

Discussion in 'The Guru's Pub' started by Xbrain, Jun 28, 2011.

1. XbrainMaster Guru

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Hello fellow gurus.

I'm doing, for fun, a real coil gun. I went through many websites looking at what people do and what schematics they use.

The goal is simple, use a coil to generate a magnetic field badass enough to throw something metallic. I've seen most people use big capacitors to generate enough current.

I'm looking for advice as my electricity knowledge is a little old...

So ! Magnetic field formulae for a coil is :

B = ยต0 * N * i / l

http://en.wikipedia.org/wiki/Solenoid

The only part that one can really increase is intensity then. As U = RI, a low resistance means you can use low voltage right ?

Starting with that, I made a coil and put an old PSU on it on the 3.3V rails, rated at 30 Amps. Might have done something wrong or it's not pulling any power... I had no magnetic field at all.

Can someone give me some info about capacitors and how to integrate them ?

And just about anything I should know would be cool.

Once finished I'll stick a GURU3D sticker on it if you help me ^^

2. ChoujiAncient Guru

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Use neodymium magnet rods as the projectile, and use a high speed switch to alter the polarity of the multiple coils you'll need inline. If done right, and fast enough, you'll pull the projectile through, turn off the coil, then reverse polarity and use it to push the magnet out.
http://en.wikipedia.org/wiki/Coilgun

It adds a pull then push to a single coil.

Capacitors are simply batteries that can charge and discharge rapidly, especially the discharge. Your biggest problem with those would be stopping them from feeding back into your power supply, so you'll need some really heavy diodes.

Sadly i haven't tried these first hand, and last one i did play with was in highschool and i don't have those details.
Just be careful not to fry your coil. or power supply for that matter. Since you're essentially creating a short with the coil.

3. XendanceAncient Guru

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Why not make a railgun? To me it seems more simple to build than a coilgun.

4. BLEH!Ancient Guru

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One word: Heat. You'd burn the rails out after every shot like the US navy do . Tempted to try a coilgun myself though, some awesome builds on youtube.

:biggun:

5. XbrainMaster Guru

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I want to make a coil gun because... It sounds cool ^^. Might be because of fallout 2.

Couple of questions :
- If I make a circuit with my PSU from a GND to a 3.3V (like pin 2 and 3), how high is intensity ? Is it at maximum rated, meaning 30 amps ?
- If I draw 30 amps from psu, should I get a noticeable magnetic field ?

- Is this schematic correct ?

6. BLEH!Ancient Guru

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Depends on the coil resistance as to whether it'll blow or not. There are better ways of doing it than using a PSU, such as trickle-charged banks of massive capacitors wired in parallel to give a HUGE burst current through the coil. Youtube "Coilgun" for some examples. Theres one on there that looks amazing.

7. JhetskiThe Lonely Guru

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Post frags later.

8. XL_enceMaha Guru

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With the way you have your circuit in your drawing, as soon that switch closes, you may end up overloading your power supply. You'll get a burst of current from the capacitor, but there's nothing to stop the current from being drawn from the power supply as well. Most likely the coil resistance will be low enough to try to draw more than 30A from the power supply.

So you may need a switch instead of a diode to disconnect the power supply from the system fully when the coil turns on.

Edit: After re-reading your post, I see that you wanted to use the power supply as the main source of power when the coil turns on. Like "BLEH!" said, you will probably be better off using large capacitors in parallel to get the burst of current for the coils. If you do this, make sure that the coils can handle 3.3 V, or else they'll melt!

Also, you will need to use a high power resistor to limit the current drawn by the capacitors to below 30A as they are charging.

Last edited: Jun 29, 2011

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