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NH USA
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so i did some reading but have not found every thing i should be knowing for this project

i have 10 caps with 10 flash camra chargeing pcb boards  and so far for testing  i have a 1/4 inch plastic drinking tube with some hand wond coils useing 22 gauge wire with a relay ( relay is not rated for this kind of power not sure what to do that for contacts to discharge the caps.)
then im useing an arduino atmaga to time the discharges threw the relays
one relay per cap so far i have move ment with just one relay one coil and one cap ran by the arduino .

i have many qutions to the math behind building this  i belive  that its 12 inch of coil and barel
from breach to end of tube .

timeing will be a factor but in till i know what the oz of the round i plan to shoot is i know i cant set it in stone

but i have no idea what a good coil wiinding would be and how to make it to spec .. like say langth of wire guage of wire and how meany times  to wind the wire per coil with a 1/4 inch tube in the center . so far i have a reading of 280 v in one cap with multi meter  not sure how people are geting there reading becuz the draw seems to drain the cap and at one point frid the fuse in my meter and welded the contacts in my relay and turned one of my rails in my bread board black so im going to guess i have to much resistance in my coil cuaseing alot of heat in the spark or sdischarge let me know if you have any help-info on this..
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EZ8MMPRO

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I don't think you connected the grounds, Dave.
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Is there somewhere in the International section that could help you?
Or maybe try Google Translate.
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NH USA
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what are you saying ?  you dont understand what im asking ?
im on the fourm on my android soo im limited to typeing on small keys
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EZ8MMPRO

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I don't think you connected the grounds, Dave.
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Quote
you dont understand what im asking
Pretty much, yes.

Like this:
Quote
i know what the oz of the round
and this:
Quote
i have many qutions to the math behind building this 
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Gosport, UK
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My guess was 'weight, in ounces, of the round', but I couldn't decide between 'equations' or 'questions'.
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New Hampshire
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Based on my experience trying to build coilguns. So what I believe your saying.

1 you built a few coils yourself with some 22 gauge wire.
2 Your firing something down a 1/4 in tube for your barrel (what are you gonna use for projectiles?)
3, You've got your capacitor bank built out of disposable cameras, as well as the charge circuit.

Ok so what your planning on doing is making the arduino trigger the relays on in series to accelerate the projectile more efficiently.

That means turning on the first relay, then as the projectile passes shutting it off, and turning on the next. ANd having an individual capacitor bank for each coil.

Its not surprising you broke your multimeter, caps they have in disposable cameras can store more then enough power to hospitalize someone. Odds are, your relays wont trigger fast enough to get the series right (unless you lengthened the barrel, but then theres more friction). And with that much power as your first coil project, theres a very high chance your gonna hurt yourself. You say 22 AWG wire. How much voltage can the insulation take though?

Try something simple. 1 Coil, 1 cap/charger, and 1 relay (get something with high voltage and current ratings). Get that to work off your arduino (jsut have like a fire button on the arduino) Then move up to adding more coils and caps.

To note, its a lot easier to have a pair of coils on top of eachother each getting less power then it is to have 1 coil with 2x the power in it. And its safer. Now go experiment. I don't wanna see a news report of some guy hospitalizing himself with a homebrew coilgun though.
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Regarding the discharge triggering:

My initial "solid-state" thought was IGBT or TRIAC - something of that nature; might not be cheap, though.

A non-solid state method might be to use a spark-gap discharge trigger; basically, you set up a pair of electrodes separated by a small gap; this is your "switch" (hooked between your coil and cap bank for the coil). Rig up a 555 timer or something as an async multivibrator (you could also experiment generating the waveform with an Arduino). Use an optocoupler to output this into a transistor/mosfet controlled voltage booster circuit (like the simple ones used for homemade stun devices), the output of which is connected across the air-gap electrodes. When the 555 is triggered (by the Arduino, or you output the waveform directly), you generate a spark-discharge across the terminals of the air-gap, which ionizes the air and forms a path for the main cap-bank to trigger. You could place the spark-gap in a vacuum for better efficiency, but if you keep the gap small, it shouldn't be a big issue.

That's my thought anyhow; I've never done this (or played with HV circuits). Needless to say, such circuits and arrangements with a coilgun are very dangerous and should be respectfully handled. One hand in pocket rule at all times.
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NH USA
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ok thanks sorry about all the type'os im useing my phone and running a cnc at work at the same time so im not to good at multi tasking ..
so your saying cut down on my banks and coils from 10 to say 3 would be a good place to start . i have only tested one so far .and it only moved the round 6 inchs .. with one cap .. witch seemed to have way more out put then i expected .. useing that 30amp 12volt auto relay ...
haveing the arduino with one coil would be a waste i would think  .. but spread the 3 coils and time the relays with arduino would be ok right .. and im not worryed about hurting myself i do see the dangers but its just for fun and i plan to use my ushal coman sense.. soo if you think 10 is to many ok but 1 is not not going to do it with what i have for a setup in less i did my coil winding wrong and should make a new coil becuse im geting plenty of power and spark and burnt out stuff with lil progress on moveing the round threw the tube . 

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EZ8MMPRO

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heres a quick pic oh what i got..


* 0422122217d71185.jpg (100.71 KB, 480x640 - viewed 23 times.)
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EZ8MMPRO

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Well what are you using for a projectile. One thing you should probably do is make the coils themselves a bit bigger (the look from the picture like they onyl have about 20 turns in them). Also since I'm assuming your projectiles are probably nails with the heads ground off, you might want to switch the nails themselves. Some nail steels aren't as magnetically active as others. Though that will come down to trail and error.

If you've got a few working coils though, and aren't too worried. What you can do, take 3 coils, and place them right next to eachother. Then a little down the line do another bank of 3, and farther down another 3. Set them all up with their own relay, but in a manner so each bank of 3 will trigger at the same time.
(With doing this, itll give you the power of 9 coils, but the complexity of 3) then it comes down to doing testfires and trying different timings. Probably will have to use micros in the timing really.
You might be helped severely by throwing together a chronograph (actually im gonna ask advice on the forums about how to make one here in a few mins) And testing the speed of the projectile at several steps of the firing.


Another experiment you might try, do 3 banks of coils. 1,2,2, coils. Hook it up so that on firing, first all the coils are triggered, each having its own cap to run. After passing coil 1, the second 2 banks are triggered again, drawing power off a second set of caps (also taking another few couple relays). As it passes the second bank, the last 2 coils trigger again, along with another set of caps. That means that at initial, the projectile will have the highest acceleration, and then as it moves through the barrel, gets sped up again by the new fresh charge from your second cap bank. Then right before it leaves the barrel, gets another last burst of significant power. This can only work though if you have measured out the speed at several points and can trigger the coils at the right time.

Also it lets you use all your coils. If the explanation isnt clear, later on ill draw a diagram. I tried to do this once with my own coilgun. But as it would happen, there was too much current going through the projectile, and it had a habit of melting the plastic I made the barrel out of.
(I was using it as a conductor to make the contact for the subsequent coils. To alleviate needing computer timing, note this was long before learning of arduino lulz) Yeah it was a dumb idea, but charging single coils at a time, it worked great.
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Pittsburgh, PA, USA
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Maybe you can build a circuit that has the 2nd, etc, coils detect the one before energizing past some level to trigger itself and use FETs instead of relays and a controller. If you can detect the movement of the projectile then that would be even better.
It is current, not voltage that powers the magnetic field, you even might be able to pump up a big external field and collapse that to feed the gun.
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Examples can be found in your IDE.

NH USA
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ok well you were right about needing bigger coils im so suprised at the complex ness of this project .. i was relly wondering why it is soo hard due to the fact that relays them selfs are coils and have a great response and pretty good pull on the contact spring .. so itt crossed my mind to take some of the relays my dog chewed on .. (lil brat.) and take the coils out and line them up now with say 6 of those fired at the right timeing should advance a steel bb ball threw the tube advanceing it every time it fire anothrr coil right ? not alot of power but results right ? dident do this but im having a much harder time with supply some the coils with  the relays.. i belive they may be welding them selfs in side but not sure every 5th try i get some kind of action out of it i bought 100 ft of wire and used about 60 so far to make 3 coils  20 feet in each 6 or 7 layers tall 8 wraps wide soo they are taller then wide ..seems to work much better ... but even in crud use  like just doing one coil and one relay and one cap with the charger and one aa battery all hooked up and a   big push switch .. im only getting a scrw driver bit to move 6 inchs ... my hopes are to only need enough  power to use steel b.bs from a bb gun and some how control the timeing that will = power with the arduino in the end ... relays work but not well the 3 coils seems much better then the complex 10 setup  ive burnt up 3 relays and 5 flash cammras and a multi meter and some pcb board its becoming expensvie hahaha...

soo i have to ask couls i get some specs on a good working coil to make and may be i can mod my relays to handel  more current..  i was also gonna ask would chargeing the caps with say 12 volts 20 amps have the same affect as useing the chargeing transfomer ? 
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im not sure how the forum here work but im hoping this topic is still open i had some more time to work on my coil gun project and using some basic arduino functions with a pot have it working with 2 coils so far not much power building a new set of coils to night and have a cnc made barrel stainless steel 20 inch's long .245 od .205 id with .040 thick wall and that leaves me .005 clearance on the inner wall to my steel round not sure of the type or quality of the ammo but its a drill bit for my  small screw driver set seems to fire the best with weight and size..

soo my setup had some issues with over power at first using 6 caps to a single coil but i figured out how to use a relay and the arduino safely  by taking the hard hitting punch out of the discharge by useing the the flash tube of the disposable camera and useing the discharge circuit thats already there i was able to hook a much smaller relay to the switch on the pcb bord discharging the caps threw the coil in to the flash tube and with a poorly made single coil lost  a little bit of punch doing it this way but with only 3 caps now i got about 4 feet of distance i dont believe the camera board can handle more then 5 caps burnt a cupple out trying .... after that i moved on to completing a second matched to this one added a second poorly mad coil and relay with charging circuit adding a pot to the arduino that will manually  adjust the timing between coil discharges  it has been varey tricky to get the timing right due to the cap are not always deliveing the same amount of distance but it did add about 3 feet with the best i have gotten the timing
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EZ8MMPRO

NH USA
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so my problem now is a discussion on witch way to go with building it to full working scale i have a rail a made for this with 10 caps ( not connected parallel or sires they are individual )  ill add a photo .. now i mnot sure if i want to try to time 10 discharges if i will benfit more from geting the timeing right and punching the round 10 times down the tube or if i should try to build a set of 2 big coils and use 5 caps and chrgers per big coil   i think not knowing what i need for a coil desin to mact what i have is the biggist problem but this is where im at  cant decide if i want 10 small coils like i have that are working now and accelerating the round with each one down the tube or just try to punch it twice with 2 coils that would be approximately 6 inches long each  and use 5 and 5 to do this
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EZ8MMPRO

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SORRY IT DIDENT UPLOAD THE FIRST TIME HERE IT IS


* 0422122217c73215.jpg (88.43 KB, 480x640 - viewed 24 times.)
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