# Simple Coil Gun

Discussion in 'Electronic Projects' started by Someone Electro, Sep 3, 2005.

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1. ### Someone ElectroNew Member

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What is an coil gun? Its an prety fancy way of shoting projectiles out of an tube.It uses magnetic force to do it.Its simply just an coil of wire around an tube that has an iron rod in it.

Heres how it works:
The rod is siting before an coil.Then a pulse is run trough the coil.The magnetic force will try to pull the rod in the midle of the coil.So that makes the rod move.Then we need to thurn off the coil right before the rod has reached the center.Its still moving so it will fly out of the tube.

In order to make it go fast we need lots of curent.And becose it only needs to be a pulse an capacitator is the right component for the job.It will store the charge and then release it all at once in the coil.We also need farly high voltage to get enugh curent trough the coil.

I made an simple coil gun.It needs the corect balance betwen the capacitence and the coil resistance.

Here is what speeds i got:
-12 Km/h whith only 2 capacitors and 1Ohm coil
-27 Km/h whith 2 caps and an 0.2 Ohm coil
-30 Km/h whith 4 caps and an 0.2 Ohm coil

I have made a video of the gun shoting at varius oobjects.(Excuse my crapy webcam)
http://media.putfile.com/coil-gun_PC

The video is 2MB,27 seconds and at 30 fps(So you can do freze frames)

Ok next is the construction.
The transformer i used outputed 50 V I then have an voltage dubler that then outputs 100 V.(Each cap is craged to 50V)Then there is some work to be done whith the "FIRE!!!" switch.Do not use an normal stitch becose it will be destroyed! In my case the switch has to take an 500 amp pulse.So i made my own switch fom scrath Its aculy a pice of thick wire that contats an chunk of coper wen i push down the fire button.This all was closed in a cardboard box becose wen i hit the switch an spark almost as bright as an photo flash is made that will blind you.(The switch is not in the photo)

Now the hart of the coil gun! The coil it self.
The coil must be low resistance in order to get enuugh curent trough it.And it also must be made out of thick enugh wire or the coil will overheat.I used 2 m of 1mm coper wire.

Good luck if you try to build it

Oh and here is the part list:
-1: 40 - 70 V mains transformer
-2: 1 Amp diodes
-2 or more: big electrolic capacitors rated for 60 V or more
-1:switch for charging
-Coper wire,cardboard box and duck tape for the fire switch
-Coper wire and a small plastic tube for the gun
-1 or more:Iron rod for an projetile.

Objects fired at in the movie:
1 Litle cardboard box
2 Dry kitchen sponge
3 Platic bag
4 Crunched togeter alu foil
5 Whiteboard marker
6 CD

This is dengerus if you launch it in your eye!!!And be avare that your handeling high voltages (100V)!!! Safety first!!!

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2. ### Jay.slovakActive Member

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Hmm I see you made it an official project

3. ### Someone ElectroNew Member

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Just in case anyone wants to build it.

Right now i just got some magnet wire from my grandpa as he worked in electrotehna (Thay make a lot of electric stuff,including high power motors) He has lots and lots of this stuff.And the wire i got is perfect.I got 10 m of 1 mm wire and 15m of 1,2mm wire.

Im going to make taps in the coil so i can experement a litle.

Also wod paraleling coils work?(Thats what im goignt o try too)

The new coil whithout center taps is 0,6 Ohm and gets the projetile to 29,5k m/h

Its about 3-4 times biger than the old one.

Il post how it thurns out!(I hope it thurns out good)

btw: The new coil is also so heavy the rig tips over to the front.

4. ### DaveNew Member

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Nice work Someone Electro.

6. ### Someone ElectroNew Member

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Thanks.

Il probobly make an beter SCR version whith timing and stuff.I hope i get it right since i never switched 500A solid state.

I also learned not to shoot it in the celing becose it will bouce back.It almost hit my head.(Same same story whith furniture.
Also an leson is to conect the corcodile chips good.The clip was siting on insulationand just an litle bit was contacting the wire.Wen i fired sparks ware flying evryware! :lol:

Many also be a MOSFET since i found one that can take 110A continues and 320A peak for \$2.60.Its an uhh IRF3205

Hmm wait a minute this cant be asembeld on a bredboard,sice 500A trough a bredboard translates in to big sparks if you ask me.And big sparks = bye bye breadboard.

7. ### audioguruWell-Known MemberMost Helpful Member

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You won't get anywhere near 500A through crocadile clips or a breadboard. Look at the size of a car's booster cables and huge strong clips for about only(!) 100A.

Coils in parallel reduce the inductance because they must share the current.
Put coils in series to increase the inductance but their resistance is added reducing the max current.
The current in an inductor builds slowly at first, therefore a large inductance is slow. :lol:

8. ### Someone ElectroNew Member

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It dosent need to take continues 500A.It only needs to take an short pulse of 500A.

If the clip is contacting the wire good then it will be able to take it.

I wired the whole thing up whoth crocodile clips and its workign well.Oh and the clips had an higher curent wire betwen them.(The original can bary take 1A continues)

Im still staying whith crocodile clips.

Wod you imagene what wod hapend if i didnt solder the wires in the clips.

The clip the sparked cut the wire that it was on in half.You know that prety much scared me becose it just sudenly hapend in one fireing.

Corocdile clips seem to take huge pulses prety well.

9. ### danielsmusicNew Member

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did you use "livewire" to draw the diagram at the top?

10. ### Someone ElectroNew Member

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Yep thats LiveWire.

Anyway i orderd some SCRs a wile ago and i shod get them today or tomorow.But the IRF3205 is out of stock! :cry: They shod get them in about 14 days

The SCR is orderd is an 2N6509 Its an 800V and 200A for 10 ms

11. ### Someone ElectroNew Member

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Wooohooo

I got the SCRs.

So lets get down to busnis.

12. ### audioguruWell-Known MemberMost Helpful Member

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Wait a minute!
I must nail some plywood over my windows first.
Please shoot in the other direction and I hope your projectiles don't circle the globe. :lol: :lol:

13. ### Someone ElectroNew Member

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The simple coil gun V2 is now operational.

I toght i wod give the beradboard a chance and tryed to asemble it on that.

Then i slowly incresed the voltage evry fireing and at full charge no sparks or pops or anything like that.Yea i just run 500A trough an breadboard.

Lets see canada if north west from here Il try to aim in that direction. :lol:

But the SCRs have made an problem.The thing is now so silent im woryed about the microphone picking up more noise than the fireing sound.So how an i going to meshure the speed now? Il try to put the mic directly on the coil so it will hear the silent click.

The "control panel" is still prety much the same.One button to fire and one to charge.

Il probobly make an new video too.

14. ### audioguruWell-Known MemberMost Helpful Member

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I want to see a video of 500A going through a breadboard. It will go off like dynamite.

15. ### Someone ElectroNew Member

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Nope

All i get is a slight click from the coil wen fireing.

16. ### Someone ElectroNew Member

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I found an nother fun thing to do whith it.

I cut narow pecis of aluminium foil and conected where the coil shod be.The thing goes off in a huge flash.

Ive put thins in a box since wen it waporises the amultinium there are pecis of burning foil flying around.

Prety nice to watch.

17. ### Clyd3New Member

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so i take it that firing too much in short succession would result in dynamite breadboards and dodgy croc clips as a result of heat buildup?

18. ### Nigel GoodwinSuper ModeratorMost Helpful Member

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I think the 500A figure is only complete guesswork?, and certainly if it's wired on a breadboard the resistance of the connections and wires will limit it to far less than that. As well, the high current will only be a very short pulse, which rapidly falls away.

Building it correctly, with heavy wires and good connections, will probably improve performance?, by allowing a much higher current pulse.

So, short thick wires, and the absolute minimum of connections in the current path, would be the way to go. A breadboard and croc clips are about as bad as you could possibly find!.

19. ### audioguruWell-Known MemberMost Helpful Member

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I agree that the decimal point is missing. He would be lucky to get 5.00A with those flimsy connections. :lol:

20. ### Someone ElectroNew Member

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You ceranly wodnt be able to blow an hole right trough 8 sheets of alu foil whith 5A.

And til now i didnt have any sparking on the joints.

It clocked 31km/h for the small projetile and 22.5km/h for the big projetile.

Nope evryting seems to work fine. If the joints had resistance they wod cetanly spark.

But if an wire is contacting somting whith its tip it makes an big flash and makes an hole.The breadards contact seem to "hug" around the wires enugh to give virtualy no resistance to it.

So breadoards give low enugh resistance joints to take 100s of amps

21. ### Someone ElectroNew Member

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Oh and heres an comented photo of it.

The fire switch is stuck to a bell whith duck tape.(The bell was perfect becose its heavy and dosent tip ower likely)

Meaby il also make an video of it.

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