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# making a coil gun help Answered

when i make a coil with magnet wire,i have enamelled wire, do i have to sand the whole thing so the copper touches in the coil, or just the ends going to where im hooking it up? EDIT: i changed my title, because i have more questions about coil guns in general.

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## Discussions

is there a way that I could charge some 200v 330uf capacitors from an old PC power suppy with the camera flash circuit? because it charges up to around 330 volts and i don't want to hook up my other capacitors to that much voltage

if my capacitors are rated at 330V and i have a 250 V switch, will it lessen its power?

lets just say this switch will fuse and won't work. you need to use an scr

yea i know what fuse means. what about a switch rated at 350V? but the amps you go the lower the voltage rating, and i dont know how much amps 20 capacitors will generate.

high current rating is more important than voltage current is what fuses stuff

well its 20 capacitors, but its only powered by a d-battery, so the voltage is only 1.5 V, i think i should switch to a 9 volt to make the coil more powerful, my firing swtich its rated at 50A 12VDC and 25A 24VDC so i think im good.

the voltage in the capacitors depends only on the inverter circuit. you can make 300 V and more with either D or 9 V battery the D battery stores more energy than 9 V. it will last longer (more shots off 1 battery) the current of the switches is not bad but the voltage may be too low. 300 V is at all not 12 or 24 can you give photos of the switches from inside ? maybe they are isolated enough for 300 V after all

i cant take the switch apart, but the guy at radio shack said if im charging the capacitors with - lets say - 1.5 volts, the charge that comes off the capacitor will be 1.5 volts. he also said that there is no such thing as a switch that is rated at 330V or higher. he said try online, but normally nothing requires that much. whats an inverter circuit?

why you cant ? an invrter is a circuit that changes voltage. its basically built of transistor and transformer. sometimes more components in a coil gun it converts the battery voltage to 300 V that are charged into the capacitors they are used also in lcd screens / computers (the power supply is basically an inverter) / flash cameras / emergency lighting systems and other stuff you can get high voltage high current switch in industrial electrical parts center. but you often can use smaller switch

but the coil gun will still shoot if i just use a battery to charge it without an inverter, right? will it still be able to shoot strong?

i doubt it. you need huge capacitance (probably way beyond farads) and very low rsistance of wires and capacitors (which is a problem) for a realistic solution you need volts and lot of them. use an inverter

ok, but if i use an inverter then i need a switch that can stand up to 330V and there is none, let alone the amps.

you need a semiconductor called an SCR. It's not that I don't trust your knowledge on the subject, but you have to really know what you're doing when your messing around with 300 or so volts at nearly infinite current. I'm just saying, 1.5 volts or 9 volts is a lot different than 300. Also, to all those people that have been shocked my a camera capacitor (as have I), this settup is much more dangerous, imagine 20x the current going through your body, because in this situation the capacitors have a total of 20x less esr.

the current is about the same cause your body resistance >>>> capacitor esr but it is more dangerous cause the amount of energy is higher. its sufficient for longer electrocution ams is harder to discharge with flash cap you can atleast pull it out with your other hand

where do i buy, or make an SCR, and where would i put it in th ecoil gun? between the capacitor bank and the camera PCB?

scr is a generic name to a type of electronic component. there are lots of different scrs and you should use one that matches to your circuit get scr in the same place as any other components - trashed electronics or electronic component shop the scr replaces the fire switch and it goes between the capacitors and the coil

what about an inverter, also electronics store? where does that go?

interesting... see, i did not know that. well then i guess all i need to get is the SCR but as in your PM to me, i think i might put the project aside until i get more electronics knowledge.

well thats the thing, i dont have that much knowledge this is my first electronics project, i got really interested and wanted to make more things and thought htis is good place to start, im basing my project from this:

http://matthack.com/category/coil-gun-v20/

many 240 V and 110 V switches actually can hold 330 V and more. it depends on how they are built inside just look for switch with huge amps hint - look in industrial supplies center (one that sells equipment for factories and construction sites)

i think thats right. is it true that if im charging the capacitors with 9 volts the current when i turn the switch on is only 9 volts? or will they charge the voltage to 330V

most switches withstand over 2 X their voltage rating if your switch is for appropriate current and it does not have touchable metal parts its likely to be ok use a switch for as high current (A) as you can and bother less about the voltage

Where should i place my coil on the barrel? at the end where it leaves the barrel (assuming the coil attracts) or will the coil repel? meaning i need to place it near the bottom.

thanks, thats very helpful, but some parts are very confusing

do all the capcitors in my coil gun have to be the same voltage and uF?

you are limited to the most low voltage and dont get the most out of the capacitors some electrolytic capacitors perform better when charged closer to their maximum

so wouldnt i be limiting the uF if i use some higher than others? sorry, i dont know that much about this stuff

sorry for double post, but uF is the capacitence, so if i use some with higher compacitence than others wouldnt it be worse than using all the same. and why am i limited to the one with the lowest voltage? an electronics website that explains this would be useful.

one last thing. how many capacitors should i use? i have 13, 330V 120uF capacitors and 9, 330V 80uF capacitors

do you have some polyester caps for the same or higher volt as well ? they dont have much capacity but low resistance which might boost performance a bit. try it im interested if it works

the lowest voltage capacitor limits you to hom much power you can charge it with say you have 3 90v caps and 1 5v cap you want to charge the bank, and you can't charge the 5v cap with more then 5v, or it will bloww up uF doesn't matter

how long should the coil be and how many layers? im making a coil gun that will shoot small nails

depends on wanted power

magnetic force = current X num of turns

for low voltage use few turns of thick wire

for high voltage use lots of turns of thin wire

coilguns may have different designs. see how other coilguns with the same power source are built

ONLY sand where you connect to the battery wrap the coil tightly, and one way