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low voltage coil guns?

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tod

Mon Sept 10 2007, 03:03PM

Registered Member #987 Joined: Thu Sept 06 2007, 06:45PM
Location:
Posts: 3

HI Guys,

Myself and a friend have a contract to build a coil gun and are wondering about the pros, cons or possibilities of making a 120v DC coil gun. I am the fabricator side of it all and my friend is the electornics side (not yet registered on 4HV)and we are wondering if there is a fundamental resaon why people do not seem to make them (relatively) low voltage.

Thanks

Tod

WaveRider

Mon Sept 10 2007, 03:15PM

Registered Member #29 Joined: Fri Feb 03 2006, 09:00AM
Location: Hasselt, Belgium
Posts: 500

I made one that used 100V. Worked well, given the low voltage. Take a look here.

tod

Mon Sept 10 2007, 07:20PM

Registered Member #987 Joined: Thu Sept 06 2007, 06:45PM
Location:
Posts: 3

Thanks for that, I have forwarded it on to Phil, my electronics man and hopefully it will mean more to him than me, but thanks for posting it. I forgot to mention that it will be a multi stage.

My question is really why in general do people make high voltage ones? Do they work better? Is it cheaper? Is it easier? etc Which of course leads to why do people not really make low voltage ones?

Thanks

Tod

Dr. Dark Current

Mon Sept 10 2007, 08:09PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

tod wrote ...

Thanks for that, I have forwarded it on to Phil, my electronics man and hopefully it will mean more to him than me, but thanks for posting it. I forgot to mention that it will be a multi stage.

My question is really why in general do people make high voltage ones? Do they work better? Is it cheaper? Is it easier? etc Which of course leads to why do people not really make low voltage ones?

Thanks

Tod

I believe you need a lower pulse current rated switch for higher voltage (also there's lower loss in the switch with higher voltage)

Barry

Tue Sept 11 2007, 01:00AM

Registered Member #90 Joined: Thu Feb 09 2006, 02:44PM
Location: Seattle, Washington
Posts: 301

I made a dandy little portable coilgun (the Mark III) which charged a 12v capacitor from a lantern battery. But then, I like to work at low energy anyway.

Me too, Phil; I'd like to hear how/why other people have chosen kilovolts and up.

Barry
When my ship came in, I was at the airport.

rupidust

Tue Sept 11 2007, 01:03AM

Banned
Registered Member #110 Joined: Fri Feb 10 2006, 12:23AM
Location: Banned City
Posts: 85

tod wrote ...

In general why do people make high voltage ones?...

Tod

An existing PFC (Photo Flash Capacitor) architecture of 330v coupled by a ready availability (and sometimes free) is the general answer. Next would be fast pulses. Next exist chargers for 330v.

tod

Tue Sept 11 2007, 07:25AM

Registered Member #987 Joined: Thu Sept 06 2007, 06:45PM
Location:
Posts: 3

Is it really as straight forward as...........the components are easily available for higher voltages and less so for lower but given component availability and a fat budget there is no intrinsic reason why we can't make a low voltage gun?

Tod

Steve Conner

Tue Sept 11 2007, 09:07AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Yeah, when I was at uni I remember some of the other students making a coilgun that ran off 12V gel batteries. If I remember right one of those students was James Paul:

and there are details of his low voltage guns on that site.

Bauerb2

Tue Sept 11 2007, 10:59AM

Registered Member #973 Joined: Tue Aug 28 2007, 07:32PM
Location: Pittsburgh, PA
Posts: 66

i have mine running off of 250V at a grand total of 180J with a quad triac switch and a very blunt tipped projectile at 10grams. shot through a pop can and cracked my drywall wall 10 more feet away. :D

anyway, i first started on my first gun at 28v with a 2200uF cap. i guess if you go multistage with such low voltage and precision timing you could get it working pretty well. as for 120v, if your rectifying mains, the cap voltage will be about 180volts. thats how i ran my second coil. worked pretty well. i had the wrong wire (too thin) and it got hot and melted the plastic barrel. if you are using higher voltage there are definite decreases in resistive losses in the coil and switch. and , as mentioned above, most switches (scr's triacs etc. ) can handle higher voltage than lower voltages.

my coils based off of barry's coilgun. thx!

andrew

Bjørn

Tue Sept 11 2007, 11:23AM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

Any voltage will work in theory, in reality a medium voltage is much more cost effective and easier for simple designs.

if your rectifying mains, the cap voltage will be about 180volts.

That depends on where he lives and I think he lives someplace where that is not correct.

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