Coilgun Handgun

Step 2: General Details

Capacitors:
Connect the capacitors Via bare Solid wire and solder (Line up the negative with the negative!).
The capacitors should be rated 300 VDC to 900 VDC for best results.

The energy found in a capacitor can be calculated based on this formula:

1/2 x C x 1e-6 x V²

or

0.000005 x C x V x V

Where C is the capacitance in micro-farads (uF) and V is the Voltage the capacitor is charged to in Volts.

Coil:

Here is a good video that shows you how to wind your coil:
How to Wind a Coil

-Bolt of an appropriate length and diameter
-Large diameter washers and nut to fit on the Bolt
-Electrical (usually black) tape or preferably super glue or epoxy
-Straw or paper to create a space between coil winding and the bolt
-Magnetic or Enamel wire
-I use Plexiglas washers created via a hole saw and drill press. This allows you to super glue each layer to the plastic washers that way the coil is more structurally sound when taken off the coil. If you choose to have plastic washer you can feed the starting wire through a grove or hole cut in back plastic washer, this aids greatly in winding.

    Now, get your straw or piece of paper and cut it about 1-2 mm longer than the desired length of your coil. Put the end washer(s) on the bolt and place the straw or paper on the bolt as shown in the picture, if the straw doesn't fit on the bolt simply cut it length wise.fit the remaining washer and nut on the bolt as shown.

    Feed the end of your magnetic wire though the center of your end washer and allow about 2-3 in of the wire to come out the other side. Wrap the wire that was put through the end bolt around the head of the bolt to secure it in place. Now start to wind the coil in a clockwise or counter-clockwise manner around the bolt. DO NOT switch from counter-clockwise to clockwise or vise versa, always wind in one direction around the bolt, otherwise your coil will not work. Continue to wind until you have reached the other end, secure the wire with your thumb and if you have tape tap the layer down tightly, if you are using super glue DO NOT glue the first layer, this will glue the wire to the straw or paper.
To make a second layer simply continue to wind, rotating in the same direction you started and making you way back to the other end of the coil on top of the first layer. Once you have reached the other side glue or tape the assembly and continue to wind in the same clockwise or counter-clockwise direction back and forth along the length of the coil. Wind the coil as perfectly as humanly possible and keep the wire as perpendicular to the bolt as possible.

Once you are done with your coil tape or glue the assembly as tight as possible and let it sit for few hours. Then, take the coil off the winder as carefully as possible and remove the inside of the straw or paper with pliers.

To Make the Guns grip open the plastic handle and hot glue in the roller switch so that the switch is triggered by, well, the trigger. Drill holes in the back and attach wires to the switch (1,3) and then put the wires through the holes. Close the Handle and if you can hear a click when you pull the trigger it should work.

RELAY
A relay has two working elements in it, an electromagnet and a mobile contact.

First a little Vocabulary:
-  NC-Normally Closed-When no current is applied to the electromagnet C and NC are connected
-  NO-Normally Open-When current is applied to the electromagnet C and NO are connected
-  C-Common- Connected to either NC or NO based on state of electromagnet
-  SPST- Single Pole Single Throw- Either NC or NO is included in this relay, not both

       This relay will have 4 connections, Although some appear to have more, If the location of the electromagnet is unknown apply a 9V-12V source to each connection combination possible until a click is heard, this is the electromagnetic and when the relay is hooked up as in the diagram in the subsequent step the gun will fire when a proper voltage is applied to these connections again.

-  SPDT- Single Pole Double Throw- Both NC and NO are included in this relay(Shown in Picture below)

    This relay will have 5 connections, Again If the location of the electromagnet is unknown apply a 9V-12V source to each connection combination possible until a click is heard, this is the electromagnet and when the relay is hooked up as in the diagram in the subsequent step the gun will fire when a proper voltage is applied to these connections once more.

For this Project either a SPST or SPDT Relay can be used, we only use the C and NO connections so a SPDT will have an unconnected Lead.

Opening the Relay will allow you to find these connections more quickly, but put the cover back on when your ready to install the relay.

Also Below is a picture of the semiautomatic configuration.

Comments

[bodacioushammer]

I have been following your extensive guide and have been able to make a fairly simple design. since i am not shooting for anything fancy i am working with the bare minimum. I am using a 20 AWG magnetic coil with 4 layers and a Gauge wire linking everything together. I have 8 capacitors in my bank. I can get a big charge, but i cannot get it to pass through to the coil. does the wire have to be the same gauge as the coil? or do i need more layers on my coil to make it work?

[Hav0c]

if you use metal washers when winding the coil do you have to take them off after or can you leave them on for strength.

[ngunarathne]

why not use a good 'ol neodymium magnet as a "hammer" that goes thru the coil and strikes a non-ferromagnetic projectile? that would eliminate any back firing effect and you wouldn't even have to time when the coil goes off. right?

[tinker234]

wow thanks i will try this when i make one

[bogigang]

Where can I find cheap disposable cameras?

[FetterChiller]

if u ask kindly in a local shop, they give you the used ones (free).

[Hav0c]

Can I use caps with different capacitance values. I have some ranging from 80uf-200uf

[Dragon Shades X]

You probably could, but it would mess with the pulse time and it would not work nearly as well as it would if you used, say, all 120 uF 330V capacitors. The different uF values mean that each capacitor will have a different discharge pulse time, so if you graphed the charge put out over time the line would be all squiggly and not like the ideal curve that a uniform bank would have. In a worst case scenario the coilgiun might end up shooting the projectile backward, but I don't think that that could actually happen. It probably will just shoot it really slow.

[Hav0c]

OK thank you.

[padmanabhapsimha]

If you use capacitors in parallel, they will act as a single capacitor with a total capacitance equal to the sum of their individual values. Just make sure that the voltage rating is equal to or above your charger's output. And about what Dragon Shades X mentioned about the backfiring and the other stuff, that's nonsense. If you time the pulse properly, any coil gun will work. You just have to make sure that the current in the coil is switched off when the projectile reaches the center of the coil in order to prevent the suck back effect.

[mbrown9412]

Yes, caps do add up when in parallel, but if they all have different voltages it can be squirrelly - the lowest voltage sets the voltage for all of them. for eample, if you have 3 500V caps in parallel with one 100V cap, the ma is gonna be set at 100V

[padmanabhapsimha]

absolutely..
all the capacitors must be able to tolerate the emf output of the charger bank. the different capacitance values are not critical.

[padmanabhapsimha]

16 to 20 AWG wire worked best with me

[Dragon Shades X]

Just so you know, I'm only an amateur. Nobody was really answering comments, so I'm doing the best that I can. But you sound like you know what you're doing, so I'm hoping you can help me. I built a coilgun to rwilsford's specifications, the exact gauge wire he recommends, 11 capacitors of 120uF 330V, parallel, with a seven layer coil 3cm long with the same gauge magnetic wire as he used, and 4g rounds. rwilsford says it should shoot about 40m/s, but I can barely beat 10m/s. When I use 1g projectiles I get 30m/s, but they don't work that well. I have tried switching the current direction through the coil and tried moving the projectile around inside the barrel, but it does not change anything. Do you have any ideas?

[padmanabhapsimha]

your capacitor bank can store around 143 joules of energy. maybe you could try using a smaller bank. It maybe taking longer for all the current to discharge through the coil. If you are using the same ferromagnetic projectile for repeated shots, try lightly hammering the projectile in order to destroy the magnetic field it has built up (you know it could be creating some sort of a suck back effect). Are you using an SCR to trigger your coil?? I would suggest a TRIAC which is practically the same as two SCR connected in opposite directions. Using a TRIAC will reduce the error of you connecting the capacitors in the wrong way as it works like a two way SCR. If you still can't improve performance, try increasing the length of the coil to 4 cm. It has worked best with my design. Also try to improve upon his triggering circuit. (decreasing the time the current flow through the coil)Worst case scenario- your coil's resistance is too high. Try using a thicker enameled copper wire for your coil. or try decreasing the number of layers. (18 SWG would be the best 21 SWG works quite well)
Most likely your coil is taking too long to discharge the caps. if you could decrease the resistance of the coil to around 0.3 to 0.1 ohms by using a thicker wire, you could vastly improve it's performance. for a 0.3 ohm coil I would recommend 4 to 5 caps of 120uF 330 v parallel. If nothing works buy 2 to 3 caps of 12000uF 63 volts. They worked the best with me because the amt of charge stored is high even though the voltage is low. Basically for a low power single stage coil gun the energy for each stage should be around 50 to 75 joules if your coil resistance is greater than 0.1 ohms

[padmanabhapsimha]

if you use a system named "low voltage cutoff system", you can increase the voltage output of the boost converter. when the cap charges to its max extent, the system automatically cuts off the power supply to the capacitor.
I get faster charging rates due to this.

[padmanabhapsimha]

PS if you can decrease coil resistance you can as well dump more energy into it.

[darkade7]

would it be better to have a short coil with a lot of layers or a long coil with only a couple of layers?

[padmanabhapsimha]

short coil with lots of layers is always stronger than a long coil with less layers

[Spaceman Spiff]

Have you considered building a coil cannon and going for a height record? Give the projectile a GPS tracker and maybe even a camera for even more fun! I think this would be a fun physics project; keeping safety in mind of course. A projectile this large could do some damage when falling from those heights.

You mentioned not using a capacitor with capacitance greater than 2nF. What would be wrong with using a supercapacitor, of say 1kF, besides the danger of handling such loads?

[lakevista5]

I made a Coil gun using 15 capacitors with a total 300v and 1880uF with a single stage coil.  My coil is 39mm long  and 5 layers thick, using 24gauge magnetic wire.  the problem i am having with the gun is that it shoots backwards.  at 100v it shoots forward, at 125v to 175v it does not shoot at all and 200v to 300v it shoots backwards. 

what should i do... should i decrease the number of capacitors, increase the voltage or change the coil.  if the coil is the problem what size would you recommend?

[BobTheEngi]

did you apply the "right thumb up" concept wrap the wires according to the direction of your fingers. Check online if I'm not clear. Hold the barrel with your right hand, and with your thumb pointing to the up and up should be the direction of the projectile. Should wrap left to right and then back again. If that fails, then maybe the positive or negative charges

[brain in a jar]

Hi, i'm no professional but i think you should move the bullet a little further away from the coil before firing. or move the coil forward. My guess is this should work, but...

[leven]

Yes, it sounds as if the pull gets to strong at the higher voltages, so the projectile is pulled trough the center of the coil, and as soon as it passes that, it starts to accelerate backwards. The magnetic field doesn't die out fast enough, so one thing is to move them further apart, or maybe use thicker wire, so you will get more current, and thus a stronger field with more pull, but that will die out faster.. but i'm just guessing :P 

[Lenny24]

Thats Called "Suck-Back".

[mbrown9412]

yeah. you can fix that with a longer coil, or with wiring your caps for less uF, meaning it'll fire for a shorter period of time.

[riku1]

how well would a 15-25 layer coil work ifit was about 2-3 cm long on a straw and was out of 20 gage wire that is in most down step transformers and how many micro-ferads at 330v would it take to launch the round at least 20yds as a single-stage coilgun?

[syndicate26]

It was a very nice looking circuit. I just couldn't figure out what all is attached to what, except what looked like a 5v source for the LED and a reset + a bunch of other stuff that I don't know how to use like the 555 or a 556. I understand these are timers but I dont know how to use them. I don't quite understand. Do you have a simple view or 2 -D diagram of the guts so I could see how everything was fitted? I'm not much of a schematics kind of guy. If it helps I have MOSFETs, 1-556, 2 pairs of LED T&E, Camera charging circuits, with 3 120uf 330v per coil @ 2 Coils + 2 160uf 330v injector stage. I have a high voltage trigger instead of the relay you suggested. Could you help me with a diagram I might understand? Thank you for your patience with a difficult person.

[moshee]

www.doctronics.co.uk/555.htm is a good place to learn about the 555 and how it works. Just high voltage won't work - the trigger needs to be high current rating as well (like around 30 or so amps). If you have difficulty just reading schematics then i don't suggest trying to implement a multi-stage just yet. Learn how to read them, it'll make everything a lot easier.

[syndicate26]

I built a coil gun via disposable cameras and I was wondering if it is possible to incorporate pairs of L.E.D. infrared sensors into my triggering for a multi-stage design? If so, how do you attach the sensors so they trigger the next stage without being fried to pieces? I'm a bit inexperienced but I understand what you were doing in your diagram of the pa-III-B and most of your others.

[moshee]

 they're not going to get fried to pieces... the photogates aren't connected to any of the high voltage wiring

look at the pa-iv schematic, it's got a good photogate circuit you can look at

[SaNjA2659]

Hello, rwilsford07! Could you help me, please? I am going to build a 3 - stage coilgun. I have 3 x 400v 470uF caps (1 per coil) and I am going to use them at 350v. my barrel will have 6mm inner diameter and projectile - 2cm long. Could you tell me please how many layers of what wire should I have and also how long must be the coil?

[rwilsford07]

via the simulator the best coil is 20mm long and 16 layers with 22 gauge wire. After that measure the exit velocity and get back to me.

[SaNjA2659]

ok. Thanks!

[jeremy_smith]

what is the item number of the optical sensors, sfh309 and sfh409, i can only find things similar to them.

[moshee]

mouser.com/ProductDetail/Optek/OPB815WZ/ was the one used in the PA-IV

[generalxcypher]

Does mixing capacators of different capacatance and voltage matter? i have 4 circuits with100uF 330v capacator circuits, 2 120uF 330v circuits and one 80uF 330v circuit would you reccommend just using the 4 330v 100uF capacator circuits? or is it ok to mix and match?? :/ also if i were to use the 4 circuits, what would be the optimum length of coil to use?

[rwilsford07]

As long as your connecting the capacitors in parallel (+ to + and - to -) any capacities can be connected. No capacitors that have different voltages should be connected in any way. so you can connect all the capacitors you have without worry. The coil properties will depend on you final capacitor bank and projectile properties. I would suggest getting some more cameras to have a total bank capacitance of 960uF or more.

[dlcoates1]

the more microferads or "uF" the better.

[generalxcypher]

Also before you said i could just connect all the positives and negatives of both the capacators and the battery terminals to their respective like poles on the next circuit to make a charger circuit.... do i need to remove certain things from the board in order for it to work? ie. the flash bulb etc. this was because i cant get any cameras like the ones in the description.... whilst yes they will be bigger and not "mini" charger circuits... but i do want to know.... will it work just fine doing as you say and just connecting the terminals to the same terminals on the other circuits?

[SaNjA2659]

Please, answer my questions: 1. what lenght should coil have? 2. how many layers should it have? 3. can i make barrel from a pipe made of iron? thank you!

[rwilsford07]

1,2 The coil properties are going depend on your projectile and capacitor bank properties.Once you figure out the projectile diameter and length and figure out how many capacitors you can afford to get let me know and I'll help you figure out an optimum coil design. 3. No the barrel must be made of non-ferromagnetic material, preferable non-conductive, and as thin and strong as you can get it.

[Nattwood]

so technically if i were to make a rifle out of pvc it would work if i had large cappacitors.

[SaNjA2659]

If this works well, I will build coilgun for same projectiles but on 8 400v 470uf caps.

[SaNjA2659]

Thanks! I wanted to build coilgun with 12 disp. camera caps. My projectile will have 4 cm lenght and about 1 cm in diameter. Thank you very much for your help!

[rwilsford07]

What are the capacitors capacitance?

[SaNjA2659]

I don't rather know. Can you better give me a formula for coil?

[moshee]

the ratings are usually printed on the side of each capacitor. if not, then using a multimeter is the only way to find out (and not many multimeters do capacitance...)

[SaNjA2659]

In Estonia nobody is using disposables or other film cameras any more, so I am going to build rwilsford07's booster and buy 4 to 6 400v 470uF caps, because you said that 8 of them is too many and I don't want to make timing circuit.

[moshee]

I think using 2 or 3 per accelerator coil is good enough. at a certain point, the amount of capacitance doesn't affect the speed any more. it just retains more energy for more shots per charge (which would require timing each shot to only release a controlled amount of energy into the coil), not to mention a greatly increased charging time. so, that many capacitors would be good for a multistage gun, or 2 - 3 guns, depending on what you want to do.

[SaNjA2659]

OK, I have bought two 400v 470uF caps. Now I need a charger, a barrel, a projectile and coil. I also have LED optical sensor from old printer(!). I have some more questions. 1) Is it neccessary to put a diode to coil inputs? 2) Is it neccessary to put an optical sensor into the barrel? 3) How many and what type of charg. circuits I must use?

[moshee]

I will answer these to my best knowledge. hopefully rwilsford07 can help 1) it is not necessary but it prevents damage to the capacitors and circuitry from back EMF from the coil. according to rwilsford's experiments it seems to cut down the efficiency a lot. 2) If you're going to make a semi-automatic or multi-stage gun then you must put the optical sensor around the barrel such that the infrared beam goes through a hole or gap. If you're not doing either then an optical sensor is not needed. 3) for high rated capacitors like these it would be best to make your own, rwilsford has an instructable for a very nice charger circuit.

[the_lark]

I have some questions too... if i'm using a 400v capacitor bank with 500uf total capacitance, a single charger circuit that charges the bank to 300v , a 220v 30A rated relay, and 9-layers of 27 AWG for the coil is that going to work or am i just epic failing?

[moshee]

27 awg is a bit thin, but otherwise just be ready to wait a really long time... also, have some spare charger circuits ready. You'd probably burn them out really fast...

[the_lark]

thank you dude you really helped here

[SaNjA2659]

thanks!

[nomooremr.niceguy]

Let's say I had 100,000 volts at 80uF. How well would that work? Or would it be better to put less voltage and more capacitance?

[coilsinamotor]

a coil gun works by voltage not capacitance. I made a coil gun with 12 capacitors in parallel at 500v. I also made the same one more time but this time in series. the same product but the one in series will perform better

[nomooremr.niceguy]

Ok. Thank you. Check out this Idea I had. (I haven't done any experimenting But from what I'm picking up, you don't want more than about 900-1000 volts on your coil gun) My idea is to take capacitors and put them in series until you have the optimum voltage, and then you duplicate that hawever many times you find necessary. So now you have X chains of capacitors wired in series. Take them all and wire each series in parallel, So now you not only have the optimum amount of voltage, but also a higher capacitance for your coilgun. How would that work?

[rwilsford07]

For a reluctance coilgun, which is what this is, I recommend a voltage between 300V and 900V, you proposed voltage would likely be good for an induction coilgun, but that amount of energy (400kJ) would fill up a room with capacitors.

[kjjohn]

what is an induction gun? It sounds interesting.

[rwilsford07]

An induction coilgun has the same basic part as a reluctant coilgun, but the projectile is non-magnetic and conductive, they usually use aluminum. Basically when the capacitor bank is discharged into the coil it produces a changing magnetic field where the projectile is, that changing magnetic field produces opposite currents in the projectile, much like how a transformer works, these are known as eddy currents and are the reason reluctant coilguns will never be used in the military, among other reasons. The eddy currents work against the coil and projectiles magnetic attraction, so non-magnetic projectiles are used. The Eddy Currents produce there own magnetic field and the opposite magnetic fields repel each other. The military has been working on one that can propel a very large projectile several kilometers per second and doesn't have as many efficiency problems as reluctance coilguns. The reason the normal coil-gunner can't make one is that you need a capacitor bank with several kilovolts to tens of kilovolts, those capacitors are far more expensive than electrolytic. And The projectile has to be relatively big. Google "induction coilgun" for more.

[nomooremr.niceguy]

Ok. That makes sense. Is there anyway to give this more power? I'm looking through this instructable and it's soo cool! I'm wanting to get as much into the gun as I possibly can. I'm just trying to figure out how I can do that. Thank you for your help.

[rwilsford07]

There a number of site out there. If you are really interest I recommend you read all the articles HERE.

[eggman]

first off, how are you planning on having 100KV? do you have 100KV caps, and do you have a 100KV source?

[nomooremr.niceguy]

I'm intending on taking apart a stun gun and modifying it for this purpose. It actually has considerably more than 100KV. But I want to get a general idea of how powerful this could be. Any advice is greatly appreciated.

[nomooremr.niceguy]

The stun gun actually has 950KV to be precise. Is there anyway to incorporate that into this at all? I'm assuming not. That's not what I really want to hear but if it's the truth I'd rather be told now than find out later, the hard way. Again any help is appreciated. Thank you.

[rwilsford07]

Unfortunately No, you need a lower voltage, 300V-900V. Even if you did have a large capacitor bank the stun gun would not charge it as when a load is applied to it the voltage drops significantly. But any new idea are welcome, keep thinking.

[nomooremr.niceguy]

I'll do that. Thank you very much for your help. What would you think about explosive rounds?

[rwilsford07]

Very possible given you have the materials, time, and energy; It would certainly be very cool and make the coilgun more effective, Electromagnetism and Explosions, I like it.

[eggman]

hmm, how big does an EMP have to be before it starts wiping out transistors? cause it would be sick if you could put a timing circuit inside of the round to detonate an explosive.

[nomooremr.niceguy]

I have the plans to make a round that will detonate on impact. The only problem is it requires aluminum tubing as the housing because it's easy to get(it requires an arrow shaft to be precise, but I think I can shrink the length down. unfortunately, the diameter must remain the same). Is there anything more sturdy than a straw with approximately the same outside diameter that is also non-metallic(or anything that won't conduct electricity)? And to answer your question. The way most EMP generators work is, they run an electric current through a wire and overload it with electricity to the point it super heats and explodes, "throwing" the magnetic field everywhere. So while I don't think they have to be particularly strong, let me be the first to tell you, if your coil explodes, you have bigger problems than a fried transistor. The charge circuits you've been using use transistors, so you might need a little protection because it will be in close proximity to your coil, but you can make "shields" if you like. You might try surrounding your transistor in a ferrous material like iron. Making the tube out of iron could do the trick. You'll have to do some experimenting on that one. But the U.S. Military has a grenade that can be fired out of a shot gun, it then has a rocket and pop out fins included to propel it farther and drive it through walls, and on top of all that it can be set to detonate a certain distance from the wall it was shot through. So say you expect everyone to be sitting at a table in the middle of a room, 5 feet from the wall you're behind. You set it for 5 feet and it blows up above the table. It's crazy. I'm sure there are other countries that have the same thing, but I don't know who else does and who doesn't. Anyway, if you're looking to build something like that you might try searching around to find out if anyone has the plans for it. If you get them, send a copy to me. I know I went way off topic there, but I just thought I'd throw out a few ideas. I hope that was what you were looking for.

[Defaultio]

How did you mount the handle to the rest of the body?

[rwilsford07]

I cut the front side to be perpendicular to the top and mounted it with .25in Plexiglas on either side for support. THIS picture of my PA-IV show the setup well.

[coilsinamotor]

good jod on the coil gun

[Defaultio]

Ok. I just drilled holes through the handle and the body and used some sheet metal to put across the handle and body on both sides and bolted it together.

[skiz1989]

what I don't understand is how you have only used one piece of wire. If you go left to right on the bolt, then right to left as mentioned above, wouldn't that screw the magnetic field up?..IE. current travels through the wire in one direction so if you went left to right and started propelling the projectile when you come back to the left you would be pulling it towards you again? Basically I don't see how your projectile doesn't oscillate?

[coilsinamotor]

no because like a permenet magnet an eletro magnet also has an south and north pole so as current passes through one side will be magnatized into the north pole and one the south the north drives the projectile forward and south backwards. so thus the position of the projrctile is very important if you have any ?'s you can ask me.

[rwilsford07]

(removed by author or community request)

[skiz1989]

No not babbling at all. I know what your saying and I don't doubt you, I just still don't see how it doesn't affect polarity as I thought winding the coil back onto itself would cause oscillation. Anyway that aside I'm currently winding my coil now ( taking it slowly as hands cramp up not to mention letting the glue dry) but I noticed I will run out of wire before I can complete it. I. Ill only manage to get about 6 layers out of it. Would it be ok to then use another wire aslong as I wrap it around the same direction as the other? Ie. The wires would run in parallel to one another.

[coilsinamotor]

yes,but make sure do not connect the wires in series or the magnetic field will not be as strong. so connect the coils in parallel. what you will end up with is 2, 6 layer coils and 4 wire leads

[kjjohn]

he means not to wrap it clockwise, then stop, then wrap it conterclockwise. Changing "linear" direction, if you will, doesn't affect it, however, changing "rotational" direction does.

[coilsinamotor]

worng changing nether of these elements will efect on how the proformence of the final coil. but you can try.

[skiz1989]

Ahhh that kinda makes sense....but I don't quite see how that works still. If current only flows in one direction through the wire, even by following the coils in the same direction wouldn't it do something along the lines of: >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> etc, thus continually reverse the poles?

[kjjohn]

I don't know exactly what happens, but that is the way it works

[GIBBERATOR]

Hey Im working on getting the relays but not all the cameras are kodak and some of the transformers are a lot different then the kodak ones so would it be a bad thing if I just had less relays then capacitors or does it have to be the same amount?

[markubiak]

Hey, on my coilgun i'm using, everything works except the coil. When we try to use it , it wont pick up a single thing. Can someone help?

[eggman]

what do you mean, "pick up"?

[moshee]

I tried to make a coil gun following these instructions as closely as possible with the materials I had available (I bought a relay and flip switch). When I finally got around to testing it, something weird happened. As I began charging the capacitor bank, I heard the high-pitched noise that would normally happen. It only lasted for a few seconds, however. Near the end, its pitch lowered slightly then completely disappeared. The LED never came on. The transistor on the circuit I was using started smoking, though.

[rwilsford07]

What battery arrangement do you have and are you using the circuit boards I recommend in the instructable?

[moshee]

Also, if you don't mind, I have another question (sorry!). Where did you get that board to mount the capacitors on, as shown on your website (the PA-IV, 2nd image below schematics)? or did you make it yourself? I'm having a lot of trouble putting my capacitor bank together.

[rwilsford07]

The board that fried is done for, but 2AA should not damage the board, either the charger circuit was bad, which happens, or you might have not connected the circuit right, try again with another charger, check your connections several times, and if your still having problems let me know. I used a printed circuit /copper clad board to mount my capacitor bank, MPJA.com or electronicgoldmine.com has them, I cut it to size and then split the copper down the middle to make two large traces for the capacitors to be soldered on to.

[moshee]

Tried with new circuit, new capacitors, new wires attaching everything, checked and double-checked the connections, still nothing. Is the charging usually accompanied by a burning smell?

[rwilsford07]

Do the capacitors charge to there rated voltage?

[moshee]

I think the highest they have gotten is about 200V before I got scared and turned it off. They're rated at 330V. Also, this time I did not hear a noise but it was still charging. They reached about 120V.

[rwilsford07]

Try charging the capacitor again and see how hot the transistor gets, if the transistor does not burn your fingers then let it charge to the full voltage.

[moshee]

it was my capacitors, some of them were faulty. I decided to just get a couple of the ones (470 uF 400V) linked in the instructable so hopefully it will work now.

[moshee]

alright, so the transistor is not hot, but after I charge it a while and check the voltage with my multimeter, the needle goes backwards. Could this mean that I soldered the battery pack on backwards? Also, the voltage is pretty low considering the amount of time spent charging, and I used new batteries (probably about 20 volts in 2 minutes)

[moshee]

Alright, thanks for the info!

[moshee]

I'm just using one normal camera flash circuit (Kodak, I think) and 2 AA batteries. Would linking several flash circuits together help with this?

[270168]

Can you explain in detail how to make the coil because i am not getting it. thanks

[eggman]

look through the comments, this question has been answered before

[Ganjipanda]

Ok...this might me stupid question. But what I'd relay?(just reminder I am a Korean secondary who stayed Canada for a year) and what does replay do? Also,in other coilgun guide,they don't show about relay of thecharger circuit.so I think I don't need them and last, I don't get the picture or charge circuit that looks like stick and the schme... Thinghy.

[Ganjipanda]

Sorry wrong spelling. What is relay do?

[moshee]

A relay is a type of switch that uses an electromagnet to move a piece of metal from one side to the other. It is used in this design instead of a normal switch because under high voltages a normal switch would get welded shut and become unusable.

[kjjohn]

just out of curiosity, how would coil performance be affected if the barrel was not only surrounded by the coil, but also a ferromagnetic layer, say, steel, in between the coil and the barrel

[rwilsford07]

It really depends on your set of variables: coil properties, Capacitor bank properties, switching element etc.I have not experimented in depth with this but theoretically it should increase the total force exerted on the projectile, but you'll need to separate the iron into small strips, spray them with electrical insulation, and then place them axially around the coil, there should be no long conductive path around the coil. This should only work for low level coilguns, but my PA-IV uses this method and it has a pretty good efficiency compared to other SCR switched coilguns at that energy level.

[mdgnys]

A relay has two working elements in it, an electromagnet and a mobile contact. First a little Vocab: NC-Normally Closed-When no current is applied to the electromagnet C and NC are connected NO-Normally Open-When current is applied to the electromagnet C and NO are connected Its Auctually the opposite NC is Normal Closed and means the cricuit is closed mean ing current flows through it.

[blablabla123]

Would it be suitable (i already made this), making a coil with 24 AWG magnetic insulated wire (not stranded) with 12 layers? Btw, i would like to know whether the strength of capacitance is prefered over amount of voltage? if so whould it be suitable to use 9 330V caps @ 80 uF WITH a cpacitor that is 16V @3300 uF? and how would i go about individually charging it?
Thanks :D

[eggman]

Do not hook up different size capacitors in series and do not mix different voltage capacitors in any way.

[kjjohn]

couldn't you wire different size caps in parallel, though, just not series?

[blablabla123]

Thanks you. I had researched it the next day and realized what a stupid thing that would have been :o . Thanks, btw what gauge wire would you suggest? i made one with 4 layers of 24 awg and one with 12 layers of 24 gauge and surprisingly i came out with mixed results, all of which pointed to the 4 layered coil as a better one... I am quite confused. I have not taken physics yet (excited to but stay patient with me :P) so please help me out :D! (other sites i have looked at explain things in terrible ways... not that i can do better but yeah thanks! :D

[rwilsford07]

The properties of you optimized coil will be based on you capacitor bank properties, the 12 layer coil with 22 gauge wire worked exceptionally well with a 400V 470uF capacitor but never worked well for the best setup of photo flash capacitors I could get. The optimum gauge wire really once again depends on your capacitor bank voltage and capacitance, basically for a coilgun there is no easy equation that will point to an optimum anything, but on the first page of this instructable there is a coilgun simulator link, download it and you can play with all of the variables to get an optimization for any set variables, like a capacitor banks properties. My best advise is to use it and also read the second to last page of this instructable, it gives some pretty good generalizations to help you understand why a 4 layer coil can be better than a 12 layer coil. And yes you can wire different sized capacitors in parallel, but they need to be the same voltage.

[raedonchar]

Would it be possible to use a 1000v .1Mf capacitor?

[Defaultio]

Im not sure if you said anywhere in this, but what did you use for your barrel? And how does your loading/ reloading mechanism work, or is it just manual projectial insertion through the front of the barrel?

[rwilsford07]

It does in my instructable. I used to just use a straw inside my coil but now I don't use anything inside the coil and just have a barrel outside the coil made of PVC to guide the projectile out of the gun. Basically the auto loading system for my PA-III-B is just a ammunition magazine and an auto loader. If you search through the comments you'll find a picture of it. My rifle, PAR-1, just uses a bolt action loader. My SDPA-1, which can be seen on the last step, is a muzzle loaded coilgun. So I've use most types.

[Chris94]

You can also use a pen tube their both about the same size, but the pen tube is better because it is sturdy!

[Defaultio]

But i don't think a pen tube would be long enough. Something like that but longer would be great.

[Chris94]

Glue a couple together with a glue gun that's what I did.

[Defaultio]

I'll try it.

[Defaultio]

thanks, one more quick question, what do the dotted lines in the circuit diagram mean?

[Defaultio]

thanks. one more quik question, what do the dotted lines in the circuit diagram mean?

[rwilsford07]

They represent all of the components in the series. As an example the capacitors in parallel are Named C1, C2, C3, ... Cn, where "..." means the Capacitors C4-C(n-1) an is equivalent to the dotted lines in the schematic.

[Chris94]

For the coil I used 24 gauge wire(not magnet), 5 centimeters long, and 10 layers. Do you think it will work pretty good?

[hardwarehacker]

You can salvage some pretty good power caps from old computer power supplies. You want the primary side caps, Most supplies will have something around 450uf at 350 volts. as always, YMMV

[wise_guy42]

Have tried or considered a shaped coil? If so, what have your findings been thusfar?

[Crimson-Deity]

Will this work as good coilgun capasitors?

[rwilsford07]

Yes but you can get them at electronic goldmine for much less.
Goldmine Capacitor

[Crimson-Deity]

I live in Norway. Goldmine ships only to:

Australia
Brazil
Canada
Hong Kong
Japan
Republic of Korea (South Korea)
Mexico
New Zealand
South Africa
United States (including U.S. protectorates)

=(

[rwilsford07]

I'm pretty sure your can get them here and they can ship them to you.

[sakabato777]

I am trying to build a duel stage gun ( 2, 2" coils 1 9v battery 1lbs. AWG 30 mag wire 12 1.0uF 450V Radial Electrolytic Capacitors and 2feet of pipe is my shopping list ) how do you fix the capacitors for this??? should i go 4x4 or 6x2? also how many capacitors do i really need

[rwilsford07]

Those capacitors are to small to be used in a coilgun, you need at least 400uF for a gun to be useful and larger magnetic wire, at least 24awg.

[sakabato777]

why larger? smaller will make it go faster right?

[rwilsford07]

Smaller magnetic wire has more resistance, and less current( which means a smaller magnetic field) and can easily burn out since a coilgun pumps a few hundred amps through the coil.

[cool man 66]

would Narva Auto Cable Red 0.3mm do the job please tell fast

[rwilsford07]

You must use magnetic/enamel wire for best results. If your cable has thick (greater than .2mm) insulation then it is not magnetic wire, it can be used (depending on the value of your capacitor bank), but it will not be near as efficient.

[cool man 66]

ok so were do you get magnet wire from in new zealand i cant find it

[cool man 66]

what wire did you use i need to know fast like 1 hour fast please

[eggman]

22 gauge magnet wire is the standard. make sure that it has an enamel insulation on it.

[blablabla123]

Quick question, I destroyed a couple of old Adapters and found some pretty large capacitors of which measure 400V and 150uF. Would using the capacitors from the adapter be acceptable or should i stick to the Photo-Flash capacitors? Thanks :D

[rwilsford07]

Sorry for responding so late. The Larger 400V 470uF Capacitors I use are for computer power supplies and they work much better than twice the energy in photo flash capacitors, so yes it would be fine.

[blablabla123]

Great, thanks, i made myself an Emp while screwing with this stuff :P. Thanks great instructable by the way. :D

[1-0_1-6]

I built the charger circuits. Do you know what the maximum input voltage is? You mentioned 3V but do you think 4-5 volts might work? Last question: if i had 450V capacitors, could the charger circuits easily charge them up?

[rwilsford07]

I recommend 3V input, 5V is pushing it so monitor the temperature of the chargers if you do use a higher voltage, but I wouldn't, and yes the capacitors will charge to there full voltage, likely to 500V.

[montmorency]

you could use a cooling fan, just get one of those small cpu ones and use those, they work pretty well for me.

[1-0_1-6]

Thanks for the your help.

[MicRoelelectronica]

cool thingy but how do you read: "-UM:12 Layer, 29mm L, 8mm InDia 940uF 400V 31m/s 8g(2*400V 470uf)"?

[rwilsford07]

Not Maximized(Not tested to the full efficiency): Coil Dimensions-12 Layer, 29mm Length, 8mm Inner Diameter; Capacitor Bank Value:940 micro Farads, 400 Volts; Output Velocity: 31meters per second; Projectile Mass: 8 grams; (Number of Capacitors: 2; Individual Capacitor Values: 400 Volts 470 micro Farads)

[srobot]

By "Wind it tightly, in the same direction", do you mean wind it left to right, then right to left, then left to right, OR do you mean left to right, then left to right, then left to right? I just finished my coil, but I went left to right, then right to left, also my coil is a bit lumpy and smaller at one end (smaller by about 1/8 inch). Do you think this will be fine, or do I have to buy more wire and redo? Thanks!

[rwilsford07]

What I meant by wind it tightly in the same direction is that the current in the wire needs to always be traveling in the same direction and it needs to be as close to the center of the coil as possible, therefore the winding should not reverse direction at any point, aka left to right, left to right... So unfortunantly a redo will be necessary.

[emuman4evr]

Uh... If its going left to right how are you going to do multiple layers? I understand that the negative has to be in the back and the positive has to be in the front or the projectile shoots backwards into your face.

[rwilsford07]

Actually the electromagnets polarity(ie positive/negative) doesn't affect the direction it shoots, the projectile is just pulled toward its center. Left to right or right to left really isn't a great description for the way you wind a coil, just wind it in a circle going one direction, nothing special, you don't need to stop and turn around or wind from the front to the back then start at the front again. Once you wind one layer just wind directly over it, that's it.

[squirt8500]

so you would wind in one direction in a circle but you could go back and forth?

[srobot]

I think you mean, "reverse direction at any point, aka [it should be] left to right, left to right..."? As soon as I get your reply I'll start working on the coil. Thank you!

[srobot]

hmm, I made a link, here is the comment again: I think you mean, "reverse direction at any point, aka (it should be) left to right, left to right..."? As soon as I get your reply I'll start working on the coil. Thank you!

[rwilsford07]

I'm not sure how you could reverse direction at any point, but left to right or right to left really isn't a great description for the way you wind a coil, just wind it in a circle going one direction, nothing special, you don't need to stop and wind it the other way or wind from the front to the back then start at the front again. Once you wind one layer just wind directly over it in the same direction, that's it.

[martini161]

ok, im still kinda confused here, so you wind around the straw from the begining to the end like this: | | |(((((((((((((| | | Start here end here do you then go from where you are now, on the right and wind it going towards the left, or do you go back to the right again and then start winding toward the left agian?

[martini161]

sorry illustration should have looked like this instead:
|`````````````|
|(((((((((((((|
|`````````````|
LeftRight

[paulm]

you just have to wind a coil, forwards until you fill the row tightly, laminate then go backwards, laminate repeat. hope your less confuzzled now

[Killa-X]

Yeah. It really isn't hard to understand how to coil it, I my self see it as wtf how cant u, but that's cuz i take apart so many things and uncoiled these things all the time. Maybe we need a 123 :P 1. Leave your self a few inches of wire to connect to your capacitors 2. (Me) Start on the very left side, and start coiling tight together towards the right. 3. When you hit the right, depending the set up, it should layer on top, and your on your second layer. Now, Coil to the left! 4. its on the very left side now isnt it? and didnt it layer it self to layer 3? Coil to the right!! 5..6...7...8.... 10. Leave your self extra wire.. cut if needed, Enjoy.

[blablabla123]

thanks for explaining Killa-X :) (helped me quite a bit :D )

[sgtmik]

yup

[montmorency]

where do you get the wire and the hand grip from?

[anubreed]

The magnet wire an get in a 3 spoll set at radio shack. the hand grip well from a toy gun or power washer hand or some thing like that.

[GuitarLord66]

The wire can be bought from stores, if you wanna go cheap you could take it from old car ignition coils (that's what Ive done) and I think you could also get magnet wire from old transformers. If you had read the instructable you would have seen he said "A spray paint "can gun" handle or other handle." You can get plastic handles from lots of things like toy guns.

[montmorency]

thanks guys I appreciate it.

[cerwinthedoc]

also, what would the specs be for a barrel and loading system? do you just feed it into the coil or what?

[Trilby]

sorry but i'm still REALLY confuzzled, could someone make a video or something of what to do when you fill the row. i really don't want to be screwing this up. -- Trilby - Mad as a hatter, sane as a judge

[cerwinthedoc]

do i need to get EXACTLY the 160uf capacitors or could i use something bigger? for example: say instead of using 8 160uf capacitors, i just took 2 200v 470uf capacitors and 1 330v 160uf and 1 330v 120uf capacitors and hooked them up to the charger circuits?

[eggman]

it'd be best for you not to mix and match voltages, but you can use as many different capacitences as you want to reach your desired level

[lager]

Wait if i wire up capacitors like so id multiply the voltage im getting?

[eggman]

if you wire your caps in series, it multiplies the voltage and halves the capacitance

[pillbox]

did you ever consider using a pig-iron toroid (iron ring) to wind your coil around instead of plain air? you'd get a much stronger magnet that way

[Killa-X]

You mean make it like a transformer kinda to keep the fields in? I was actually told on 4-HV or w/e Coilgun forums, that Washers on the outside actually DOESNT help, makes it worst... Quote: I wouldn't use a washer; you read this on barry's coilgun site that washers, despite directing flux lines toward the projectile, external Iron is subject to heavy hysteresis losses. What you could try is cutting the washer in fourths, covering them in enamel, and then assembling the quartered washers nearest to the projectile's end of the coil just as if it was another washer. The coil and washer will act like a transformer, inducing current flow in the washer which reduces from the overall current available in the magnetic field, but quartering it in this way should reduce those losses significantly.

[pillbox]

no, a toroid electromagnet is when you wrap the wires in-and-around-and-around a doughnut shaped piece of iron (or any ferromagnetic material). This has absolutely nothing to do with the washers, although there won't be a need for those anymore since the shape is continuous.

In the current design, the wires are wrapped around a piece of straw, which means that the coefficient being used is for air. By wrapping it around a nail instead of a straw for example, you'd get a much stronger magnet than if there was no core at all.

[eggman]

your missing the concept completely. the projectile has to pass through the middle of the coil. so there has to be an air core

[pillbox]

no, you are. the "barrel" goes through the "doughnut".

[eggman]

wait, so you're suggesting just putting a barrel through the middle of a toroid?

[Killa-X]

Yeah I was going to say, This instructable, The coil has a Air core. A straw / plastic does not effect the field, thus when its turned on, it brings in the metal object fast enough to fire it out with a lot of momentum. Now maybe when You (Pillbox) mention your idea, you thought eggman was talking about your idea (pillbox's) not the actuall instructable :S

[pillbox]

yes, ok, granted in the instructable rwilsford07 uses an air core, would using an iron ring make the bullet go faster?

[rwilsford07]

No, the coil can not be wrapped around a toriodal core. The only way to increase the output of the coilgun is to have Iron surrounding the coil, which usually does nothing anyway unless you use a high level of capacitance or lower voltage to make the voltage change over time slower to make eddy currents that are very low.

[rwilsford07]

BTW, the reason a toriodal core will not work is because the magnetic field is carried within the toriod, and not the center of the toriod. But keep thinking of ideas and don't be afriad to post them.

[pillbox]

thanks, that was the answer i was looking for is there any shape that could introduce a core into the electromagnet? like a cylindrical core but with a hollow space in the middle for the barrel to go through

[rwilsford07]

Any ferromagnetic material that is in the center of the coil will concentrate any magnetic field lines on itself. So if a core with a hole is placed in the center with a whole, the projectile will not be drawn into the center, but will be drawn to the core, and not the center, (it would effectively shield the center of the coil from the magnetic field lines). Keep thinking though, it takes only one way to make something work, and a trillion not to.

[guitardenver]

What kind of tap do you laminate with for each row? Glue seems like it would take to long to cover a hole row of wire for that many rows.

[Killa-X]

Electric tape. Did the same

[fred21]

am all ready done with the charger circuits how much 400V 470uF Capacitors should I use to make a powerful coil gun?

[paulm]

he has ratios listed in the instructions

[crazy_jim]

instead of putting 5 470uf 400v capasitors in parallel you can put 1 capasitor 2350uf 400v or something familiar to this?it is the same isn't it?

[martini161]

it would, but good lucky finding one of those, and if you do, good luck fitting it in a hand gun sized profile

[Andruha1123]

(removed by author or community request)

[TheMadScientist]

isn't that adding the capacitance? wouldn't you want to add to the voltage instead by putting them in series, not parallel?

[rwilsford07]

While the more voltage you have the better, maximizing capacitance for a certain coil is neccesary to obtain worthy effeciency. So capacitance is needed.

[comodore]

This is the capacitors bank, isn't it?

[rwilsford07]

It is an example of a capacitor bank.