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coil gun help! Answered

i am building a coil gun and i need help. what is a good material to use for the barrel? a Pen tube? i did a test using on cap and it went about six inches with barely any wire for its coils. how fat do you think i can get a small nail going with 4 caps at 300v at 450 uf? also, does the projectile have to fit snuggly in the barrel. i am using magnetic wire from a motor taken apart. so, how many windings should i have?

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50 Replies

user
tech-king (author)2008-03-29

i hate say it, but the diode will probably not protect the circuit and will steal power from the coil gun. thats why i said safety gap.

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user
guyfrom7up (author)2008-03-28

To Tech-king: I promise I will not make any HV projects. What's RCRL? Resistor Capacitor Resistor Inductor? I'm making a wireless power inductive power transfer device thingamagij, that doesn't count, right? Tank Circuits, yummy.

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user
tech-king (author)guyfrom7up2008-03-29

resonant capacitance, resonant inductance. basically a tesla coil or other resonant transformers or frequency generators.

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user
guyfrom7up (author)tech-king2008-03-29

ohhh, you mean to resonatley (the adverb of resonant) step up voltage to insane levels. I'm just using resonant coils to transfer power without wires efficiently.

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user
guyfrom7up (author)2008-03-28

i dunno, well I have an idea, but ask tech-king I know he's not as quick to respond as me ;) but do you really wanna risk saftey?

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user
tech-king (author)guyfrom7up2008-03-29

im not that slow! i was asleep. it was 10 oclock easter time.

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user
tech-king (author)2008-03-29

you dont. the coil goes to rf ground, the caps to charger circuit ground

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user
tech-king (author)2008-03-29

you have to charge it to full power, and you need to discharge it through the coil

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user
guyfrom7up (author)guyfrom7up2008-03-28

well I don't wanna give you any more info cause I don't want you to die ;)

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user
tech-king (author)2008-03-28

no, to earth. not nothing

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user
tech-king (author)2008-03-28

i told you: a ground spike or alternative earth

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user
tech-king (author)2008-03-28

no. the neg side of the caps go to the neg side of the charger

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user
tech-king (author)2008-03-28

its an alternative ground, like a ground spike

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user
tech-king (author)2008-03-28
user
tech-king (author)2008-03-28

i cant seem to make it bigger. sorry

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user
tech-king (author)2008-03-28

why arent you using an scr? you will weld your switch closed. and the part where the wires come near but dont join is the safety gap.

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user
guyfrom7up (author)2008-03-28

ok, I'm going to take on more crack at this wont the kickback damage the capacitors? Yes, and the spark gap is there because the kickback is a higher voltage than what you putted in, thus with the higher voltage it will be able to jump the spark gab and your capacitors are saved. The coil and spark gap are in parralel, just like my image below (instead of a diode, it's the gap)

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user
tech-king (author)guyfrom7up2008-03-28

last crack results.........calculating.............25%....... ........50%...............75%.............90%.........95%.........critical system error......... system shut down to prevent damage....... back online.....calculating results............ error error error error........ initiating system shut down....... printing grade.......ejecting paper... paper jam!!!.... error error.......... paper ejected. you get: question one: right answere, partly right reason part about spark gap working: missed small part last paragraphe: epic failure results: you are not allowed to build a tesla coil, or any other RCRL circuitry. you are also not allowed to build a marx generator. so, lets correct the errors: the part about kickback: everything right but a small bit: its the volts that bridge the spark gap, the amps that sustain the arc. so dont worry about the high amperage causing problems. placement of spark gap: here were you messed up, and this would probably cost you the caps or nst if this were a tesla coil. the spark gap has one side attached to the positive side of the circuit between the caps and scr, and the other side goes to the RF GROUND!

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user
tech-king (author)2008-03-28

the gap protect the charger circuit from kickback from the coil, not spark failure.

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user
Goodhart (author)2008-03-27

There is, if I remember correctly, and inductance problem with using steel or iron.

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user
tech-king (author)Goodhart2008-03-28

the resistance of steel goes up with the frequency. it shoudnt be a problem though with a coil gun. so yeah, screws are fine as long as you keep an eye on the tips. eventually, they get worn or pitted and the screws need replacing

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user
Goodhart (author)tech-king2008-03-28

so you don't predict any significant "loss" using steel as electrical junctions?

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user
tech-king (author)Goodhart2008-03-28

its a safety gap, not part of the wirring. it could be okay.

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user
Goodhart (author)tech-king2008-03-28

oh ok, my bad, I didn't read carefully enough *blush*

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user
tech-king (author)2008-03-27

screws are fine, but try to find copper ones. anything but steel is preferable

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user
tech-king (author)2008-03-27

not necessarily. but mostly yeah. the worst part: a lot of people survive the shock and die of heart failure within 24 hours of the shock.

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user
tech-king (author)2008-03-27

useful. read the entire thing before posting.

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user
guyfrom7up (author)2008-03-27

IT's mearly 2 uninsulated wires that are close together!!! Usually people use something like copper balls as electrodes.

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user
tech-king (author)guyfrom7up2008-03-27

no! thats not it. aside from the something like copper balls for electrodes part that was completely wrong! you can get seriously hurt if a safety gap fails. to build a safety gap, construct a u shaped box out of plywood drive an object with a pointed tip through each side. attach one side to your rf ground (not house ground or 3rd wire) and the other end to power after what you want to protect. test fire. pull the electrodes apart until when test fired, the prongs just dont arc over. do not back them out so far they dont arc period. just a little at a time until the arcing stops.

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user
guyfrom7up (author)tech-king2008-03-27

I have now been officially wrong on all HV things, lol, actually it's not a laughing matter, but yeah...

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user
tech-king (author)guyfrom7up2008-03-27

bit off topic, but feel free to wade in on the "how does a CPU read signal inputs from a game controller and translate it to an image on a screen that shows the performed function?" we need your wit. actually, you really should read up on this sorta stuff.

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user
tech-king (author)2008-03-27

hmm. a diagram would help you. ill work on one. in the mean time, do you mind wadding in on the "how does a CPU read signal inputs from a game controller and translate it to an image on a screen that shows the performed function?" topic please. your input and wit are needed.

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user
tech-king (author)2008-03-27

nope. you need no arc spray or silicone sealent

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user
tech-king (author)2008-03-27

if you use crappy 22 gauge radio shack wire, yes, you need real insulation. not hot glue

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user
tech-king (author)2008-03-27

thicker is better. dont forget the wicking effect of amperage.

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user
tech-king (author)2008-03-26

22awg magnet wire????!!!!!! nononononononono. thats a horrible choice!! you need real wire. 10 awg. rated to 1kv at high amperage. or nst wire with extra insulation. but not magnet wire!!! get real wire!

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guyfrom7up (author)tech-king2008-03-26

yep, techking is right. A figure you could look at for magnetic power (I don't know if this is a real unit) is number of coils x amps. 22 gauge wire would have too much resistance, You want close to infinity (lol) amps going through.

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user
tech-king (author)guyfrom7up2008-03-26

22 is too thin to safely handle the current. guy, you are wrong about the resistance, because you have forgot about the wicking effect (please dont take offence, but you should probably revise the hv part of your workbooks). you have forgotten the wicking effect, were current travels on the outside of the wire. hence, the area of the wire that can carry power is reduced from pi x (RxR) to 2 x R x pi. a lot less. thats why you need better wire in thickness and insulation.

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guyfrom7up (author)tech-king2008-03-26

that makes more sense. I want to do HV stuff, but I need edumacation on the subject I've never takin a formal electronics course, sigh... I was going to take electronics 1 and 2 when I get into highschool (I'm in 8th grade) but I passed out of them and now I get to do an independent study, eh oh well ;)

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tech-king (author)guyfrom7up2008-03-26

*education* maybe ill do an instructable on high voltages later.

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user
guyfrom7up (author)tech-king2008-03-26

that'd be awesome Please include the safety speach ;) kruser's right, it was a joke.

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user
tech-king (author)2008-03-26

you shoudnt need insulation, assuming you already have good insulation on the wires. (you did use neon sign wire right?) assuming you didnt, what did you use? anything under 10 awg is bad. look for wire rated to 1kv at high amperage

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guyfrom7up (author)2008-03-25

I cannot find your comment, please start up here lol

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user
guyfrom7up (author)2008-03-22

usually it's just 2 copper balls that are really close to eachother (couple millimeters) I'd say you'd be able to get by by having 2 wires (no insulation on the tip) close to eachother that can be adjustable, but one jiggle when moved, adjust it so that it's the right distance apart to work I never made one.

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guyfrom7up (author)2008-03-22

a safety gab is 2 really close electrodes. WHenever the normal voltage is aplied across the coil the gap doesn't arc, but when the EMF comes back it is much higher than the applied voltage, and will jump the spark gap, shorting out the coil, protecting everything else.

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user
tech-king (author)2008-03-19

from charger to caps-ok from caps to coil- no go to make coil- no go

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guyfrom7up (author)2008-03-19
user
tech-king (author)guyfrom7up2008-03-19

he wants to know if magnet ire, like in transformers, is good enough. the answer is no. look for the highest gage you can use.

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tech-king (author)2008-03-19

any other questions? or should i start the safety speach now?

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