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A couple of questions about coil guns

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rp181

Tue Oct 16 2007, 10:55PM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529

I have recently become interested in making coil guns, so i set out to make one. I made one with a flash camera circuit without much difficulty that coul shoot BB's about 40 ft in a arc. I am trying to make a optically triggered multi staged one, but i dont get how to set of the SCR. Im thinking: a IR led on one side, and a IR sensor on the other, but how does it set of SCR with a increse in conductivity past the sensor? The only way i can think is if the LED makes 100% resistance, will that work?

My second question is about boost converters. I want to make one from a 555 timer, but i cant find a decent design ( im no good at designing my own circuits). Any schmetics or links?

I have searched for info about coil guns for about 2 weeks now, so i have done my homework =). Ive seen all the websites i saw linked from here.

rupidust

Wed Oct 17 2007, 12:37AM

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

Thanks for make nearly every thread in the forum section go to waste.

Bauerb2

Wed Oct 17 2007, 01:09AM

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

uhh... i used these three sites and they answered all of my problems.

< all info on CG's here

< boost converter found here

< beacause this should be your first place to find help. ALWAYS AND FOREVER. OBEY GOOGLE!!

careful, these can be rather dangerous, and explosive. protect yer eyes, wear contacts

they'll stop anything. (i obviously found out the hard way.)

good luck
Bauerb2

Simon

Wed Oct 17 2007, 04:47AM

Registered Member #32 Joined: Sat Feb 04 2006, 08:58AM
Location: Australia
Posts: 549

Ignore Rapidust.

Any boost convertor schematics or links? Don't ask here (check the rules). If someone wants to publish a schematic, it'll be on the web, so always search for that kind of thing.

About triggering the SCR, I suggest having a look at the simple nightlight circuits out there (the ones with LDRs) and adapting them. If you're still confused, you'll need to research how an SCR and a phototransistor works and possibly study some electronic circuit theory. You can ask us about that stuff, but read what's on the web, first.

rp181

Wed Oct 17 2007, 09:36PM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529

Ok, thx, sorry for the rules. Nice idea to look at night lights, ile take a look.
ive seen rupidust's reply on other newbies threads, will not judge you all by 1 or 2 people.

Overclocked

Thu Oct 18 2007, 10:20PM

Registered Member #1056 Joined: Thu Oct 11 2007, 11:15PM
Location: CT, USA
Posts: 27

Look at the Max1703. Ive built that circuit myself and it works great! It boosts a 3V cell to 5V, Enabling you To get more power from your batteries to Power the 555 Timer.

As for Inductor Values for the 555 Timer, you will have to experiment with values that suit your needs.

rp181

Sat Oct 20 2007, 03:54PM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529

OK. first off thx for all your help one last question about this boost converter:
If i cut the right part off, starting right after the FRED, and cut down, will this portion give me +500VDC?

cut at red line, would blue dot be + 500vdc and green dot ground?

IMG from anothercoilgun site

Overclocked

Sat Oct 20 2007, 04:12PM

Registered Member #1056 Joined: Thu Oct 11 2007, 11:15PM
Location: CT, USA
Posts: 27

rp181 wrote ...

OK. first off thx for all your help one last question about this boost converter:
If i cut the right part off, starting right after the FRED, and cut down, will this portion give me +500VDC?

cut at red line, would blue dot be + 500vdc and green dot ground?

IMG from anothercoilgun site

Yes it will. But you may have to have one cap hooked up to filter the DC and get a reading on your meter. Ive noticed that without a Cap, My output hovers at 30V. Hook up a cap and it starts to go up to 50V.

Marko

Sat Oct 20 2007, 04:20PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

rp181, boost converters are bad choice for sucha high voltage stepup ratio.

I can hardly think of a better capacitor charging converter than a Royer.

Search over the forum and ask...

rp181

Sat Oct 20 2007, 04:21PM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529

so if i cut after cap, ile get 500VDC, but when theres a volatage drop the cap will fill the power in? If so, will a lower voltage cap do,will it need more capacitince?

O.o fast reply. ile look for a royer, never heard of one.

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