# COMMUNITY : FORUMS : BURNING QUESTIONS

## electromagnetic gun

can anyone help me makig an electromagnetic gun, to shoot projectiles at high speed using magnetic wire, capacitor etc,

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ayushdubey12 (author) 5 years ago
what r ur opininions about levitating ing gun ???
Orngrimm5 years ago
I got a case full of new 400V 470uF caps from eBay at a reasonable price a few months back.
Google for "coilgun" which yields a HUGE array of information.

However, i warn you:
- Playing with such voltages at such enrgy-levels is not only dangerous it is potentially LETHAL!
- If you dont have a good knowledge of powerelectronics, fiddling with such stuff is a desaster waiting to happen! I am an electronics engineer and belive me: I have made small versions of such contraptions and i am MORE than respectfull with them to say the least.
- The capacitor is your smallest problem... To control such voltages with those energy-desnities and transients is a challenge worth studying for... A V-Switch is the only viable thing for small \$ if you ask me. However, it needs a secondary cap to shut off the first at the right moment.
- This brings us to the next: Without proper sensing or timing, you cannot shoot anything. If you simply turn on the coil, the projectile rushes to the center of the coil and sticks there. You need to shut off the coil at the exact right moment.
- Also the charging is a problem since you need high voltages DC. There are multiple topoligies for doing this: Flyback, Ladder, ... The problem is again with the speed of charge eg. the power-deliver-capability of the charging circuit.

ayushdubey12 (author)  Orngrimm5 years ago
can u pls tell me how can i charge a capacitor ?????
5 years ago
You simply connect it to a DC-source.

Now to the question you MAY wanted to ask:
"How do i charge a capacitor with 400V DC? And how do i generate such a DC-Voltage in the first place?"
Well... The boards here are for sure not the correct place to talk about self-made DC-HVDC-Converters or alike... Also to be honest such things are VERY difficult and complicated and even i as electronic engineer do not claim to be a master in it... But i know my ways around such lethal (!!!) voltages and the savetymeasures needed to be in place.
Also if we talk about speed and efficiency of the charging, thats worth more than 1000 pages of literature...

What i now explain is LETHAL and VERY DANGEROUS and i DONT TAKE RESPONSABILITY in injury or death of one who trys it or comes by and touches it.

That said:
Get a high (!!) currect rectifier or build one yourself with 4 diodes. Wiki helps you on that with "Bridge rectifier".
Now you have a pulsating "DC". If you hook up your Caps to the outputs of the rectifier, it gets loaded to ACvoltageeffective*sqrt(2).
So if you have 110V AC your cap will be charged to 155.56V DC.
If you have 230V AC thats 325.27V DC. You can subtract twice the forward-voltage of one of your diodes from that if you want exact values...
However: Since the active (Active as doing charging-work on your cap) voltage if fastly reduces, it will take longer and longer for the voltage to go up a volt.
Also you really should connect a series-resistor (But please one you calculated for resistance and WATTAGE!!) as a current-limiter... An uncharged ideal cap is a short-circuit for the current.
Also it is always good to tripplecheck the polarity of your caps. Inverse-loading a cap on an unlimited rectified AC-line will blow up almost instantly. Hurting you along if you are unlucky to be in its path...

Again: The principle layd out here is simple, but you are diddling with powerline-currents and thats something you should NEVER do.

Also the method you can find in the web where they scavenge old single-use-cameras and simply use the flyback-circuit to charge your own big cap are nowhere save to say the least!
ayushdubey12 (author)  Orngrimm5 years ago
thnx dude , , , , ,
5 years ago
+1
5 years ago
Like those on ebay: http://www.ebay.com/itm/10-EPCOS-Electrolytic-Capacitor-470-uF-400V-470uf-/360502162741?pt=LH_DefaultDomain_0&hash=item53ef9a7535
StumpChunkman5 years ago