flash capacitors and rail guns(help pls)

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flash capacitors and rail guns(help pls)

Postby Webbed_Toes » Mon Jun 22, 2009 9:26 pm UTC

My friend and I have been making a wrist mounted rail gun and we have run into an issue. The flash circuit we took from a disposable camera is a jerk-face and we can't get it to work. We have the capacitors and what I am wondering is, is it possible to charge the capacitors fully and keep them charged until we complete the circuit without using the flash circuit. And when we do complete the circuit we want the stored electricity to be released at once in an instant.
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Re: flash capacitors and rail guns(help pls)

Postby Sir-Taco » Tue Jun 23, 2009 5:26 am UTC

Um, I may be absent minded here, but a RAIL GUN? As in firing magnetically accelerated particles/objects at multiple times the speed of sound right? I believe only the military has those, and not even in usable format, just for speed tests. Or do you mean a "simple" magnetic coil gun (aka Gauss gun)? If so I would say grab/google a guide on a coil gun, there's got to be a diagram of the circuitry required for that sort of release of energy. Sorry about the clarification, but hey if youre that far in building a rail gun that small, nice! If so, a coil gun is easier, not needing a massive current to fire the gun instead using magnetic to accelerate the projectile.

Edited due to a missing half of a sentence, whoops.
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Re: flash capacitors and rail guns(help pls)

Postby Webbed_Toes » Tue Jun 23, 2009 7:38 pm UTC

yeah but "rail gun" catches peoples attention better. But yeah it is a Gauss gun. My issue is all those tutorials have a flash circuit involved and those little buggers never work. If you have any tips on getting them to work that would be great too
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Re: flash capacitors and rail guns(help pls)

Postby JoeyJo0 » Tue Jun 23, 2009 7:42 pm UTC

Hey, I have experience in making coilguns.

So, what exactly is your problem?
For one, I recommend you use the camera flash circuit, it's the easiest way.

Please state your problem further.
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Re: flash capacitors and rail guns(help pls)

Postby Webbed_Toes » Tue Jun 23, 2009 10:59 pm UTC

well when I try to use flash circuit from disposable cameras I cant figure out how to connect everythin to the flash circuit. also when I take the flash out to allow maximum electrical flow towards the coil it doesnt seem to work
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Re: flash capacitors and rail guns(help pls)

Postby mrbaggins » Wed Jun 24, 2009 3:48 am UTC

Just leave everything in tact on the flash circuit (including the capacitor).

There will be a node or something you push to charge the capacitor (with a lovely high pitched wiiiiiiiiiiiiiiiiiing noise).

Work out what button/switch/pair of contacts makes the flash work (charge the capacitor, then press stuff until the flash goes off).

Then, take out the bulb, and rig whatever you want (The coil) between the two points that previously went either side of the flash bulb.

Then, charge the capacitor with the flash charger button, and fire the coil with the "shoot the flash" button.

If you don't like the size/shape/safety of the circuitry (shorting it can be quite painful, and they are often bad sizes/shapes for a given task) then feel free to remove each component and rewire your own. You only need to establish what pieces you need, as the rest can be bought at an electronics store very cheaply, and you have more leeway with how stuff gets laid out. If you do this, make sure that you get heat shrink tubing as well, to guarantee to can't short the lines to the coil.
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Re: flash capacitors and rail guns(help pls)

Postby hotaru » Wed Jun 24, 2009 6:28 am UTC

Webbed_Toes wrote:yeah but "rail gun" catches peoples attention better.

i hate when people lie just to get attention. it's really annoying.

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Re: flash capacitors and rail guns(help pls)

Postby Sir-Taco » Wed Jun 24, 2009 2:21 pm UTC

hotaru wrote:
Webbed_Toes wrote:yeah but "rail gun" catches peoples attention better.

i hate when people lie just to get attention. it's really annoying.


But hey it worked, and with what mrbaggins said sounds like it would work. Now I'm gonna try to build one of these. (I still think Gauss rifle sounds just as cool, too much Battletech/Mechwarrior for me.)
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Re: flash capacitors and rail guns(help pls)

Postby Webbed_Toes » Thu Jun 25, 2009 2:49 pm UTC

hotaru wrote:
Webbed_Toes wrote:yeah but "rail gun" catches peoples attention better.

i hate when people lie just to get attention. it's really annoying.

to be honest i didnt really know the difference. sorry if i made you mad. and also thank you mrbaggins but i wanted to ad more capacitors. should i use a series or parallel?
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Re: flash capacitors and rail guns(help pls)

Postby Magilla » Thu Jun 25, 2009 3:05 pm UTC

Putting resistors in series increases resistance. Putting capacitors in parallel increases capacitance. They work opposite to each other (easiest way to remember it).
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Re: flash capacitors and rail guns(help pls)

Postby mosc » Thu Jun 25, 2009 8:34 pm UTC

1) the capacitor in a flash has a limited "maximum" charge. The energy required to accelerate even a single atom to relativistic speeds is immense. The concept of a railgun implies massive energy which, quite frankly, you're not going to store in a fucking camera flash on your arm
2) Any capacitor discharges gradually. how gradual is determined (in the most simplistic case) by an RC circuit. This is a circuit with a resistor and a capacitor. In other words, there is no such thing as zero resistance so you will always have some time constant for the discharge of the capacitor. You may, for example, get 90% of the charge after 100ms but you're not going to get 99% after 1ms. You get the idea.
3) If you wanted to increase the capacitance, you'd want to wire them in parallel. Capacitors work as short circuits to DC and closed circuits to AC (high level). In other words they charge when there's a difference in voltage between their two nodes. If you daisy chain them, you split up that voltage difference. Parallel will put the most voltage across them.

I could do some math but I would wager the number of camera flashes required to accelerate a single atom to, say, .5C or so would be in the millions. That's assuming you actually have some apparatus to transfer the energy in the first place (GL with that it doesn't exist). Anyone?
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Re: flash capacitors and rail guns(help pls)

Postby darkspork » Thu Jun 25, 2009 8:40 pm UTC

On coil guns in general: how much do you usually get from one camera? How far can you fire a nail, for example?
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Re: flash capacitors and rail guns(help pls)

Postby mrbaggins » Thu Jun 25, 2009 10:29 pm UTC

You'd launch ball bearings, not nails. I made one that launches a .5mm (.25") ball bearing with the capacitors from two cameras, on one camera circuit, and it would break a glass window from the opposite side of the room. Yes, I learnt that the fun and "Get yourself grounded" way.
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Re: flash capacitors and rail guns(help pls)

Postby darkspork » Fri Jun 26, 2009 4:49 am UTC

mrbaggins wrote:You'd launch ball bearings, not nails. I made one that launches a .5mm (.25") ball bearing with the capacitors from two cameras, on one camera circuit, and it would break a glass window from the opposite side of the room. Yes, I learnt that the fun and "Get yourself grounded" way.

Yeah... ball bearings...
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Re: flash capacitors and rail guns(help pls)

Postby dasada122 » Mon Jun 29, 2009 10:29 pm UTC

I would love to see what you have so far, any plans.

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Re: flash capacitors and rail guns(help pls)

Postby mrbaggins » Tue Jun 30, 2009 3:10 am UTC

I don't know about the OP, but I'm going to throw some cash at some pieces and make some circuitry over the holidays, including a Gauss gun... Not sure on wrist mounted... maybe remote control car...
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Re: flash capacitors and rail guns(help pls)

Postby darkspork » Wed Jul 01, 2009 8:19 am UTC

I'm amazed at how easy it is to get flash circuitry. A local pharmacy offered to give me a whole box of used disposable cameras for free, as they normally have to pay shipping to get rid of them. Coincidentally, on that same day I went to the Radio Shack immediately next door. The guy there let me have some free crap because it was broken.

I have a half-built coilgun downstairs made from those parts. I never got to finish it because of college. I should go find it.
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Re: flash capacitors and rail guns(help pls)

Postby Themata » Fri Jul 03, 2009 8:42 am UTC

Even if it does grab attention, railgun is a completely inaccurate term. A railgun uses moving rails to create a magnetic force on an object and uses very high amounts of electricity passing through the projectile to create a resisting magnetic force, causing the projectile to travel at incredbily high speeds, often much higher than the speed of sound, hence all the disbelieving comments. A coilgun (what you're making) relies on a completely different principle and passes a charge through a stationary solenoid (coil) to propel a metallic object without charging the object itself like a railgun does:
Spoiler:
Image



Safety: Make sure you test it WITHOUT putting it on your wrist first. You need to make sure it's firing the right way before testing it on yourself, as these can be incredibly dangerous. Also, make sure to enclose the capacitors in a box where all the circuitry is kept, as exploding capacitors are not very pleasant at all. Finally, ALWAYS discharge the capacitors before toying with them (do this by placing a screwdriver across the two metal contacts of the capacitor (don't touch the metal of the screwdriver). And make sure your circuit is GROUNDED, especially if you're looking to arm mount it (mount it on your right arm so that in the event of electrocution, the electricity does not pass through your heart while seeking ground).

I've seen coilguns using at least 8 capacitors in parallel, linked to a flash circuit like most simple ones are these days. Can get some hefty results out of them.

Safety aside, time for the fun stuff.

Image
(image found here)

Make sure you're wiring like that, and making a short between the connections where the shutter mechanism was connected before. In case you hadn't already worked out, you need to put a switch between the circuit and the coil for the instant discharge, and you should also put a switch somewhere inbetween, either where the shutter mechanism was previously connected (I'm not sure if a switch here will work, just theorising, correct me if I'm wrong somebody), or between the capacitors and the circuit itself if you have a seperate capacitor bank. This way you'll have a switch to begin the charging process, and then a switch to discharge and fire. You can probably manage to put a light in this too which will indicate when the capacitors are charged, assuming there isn't a light on the flash circuit already.

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Re: flash capacitors and rail guns(help pls)

Postby mrbaggins » Fri Jul 03, 2009 10:11 am UTC

Themata wrote:(don't touch the metal of the screwdriver)
Not really a big deal. More to the point is don't touch the metal between the two points it's contacting, but given it's only a 5mm gap, that's hard to do. You can short it (and a bunch of other similar situations safely with a key, whilst holding the key metal with your hand. It will not zap you at all.

Themata wrote:making a short between the connections where the shutter mechanism was connected before.
Not necessary. In fact, probably counter intuitive, depending on the make of the camera. You're only stealing the voltage from the capacitor, and this is charged by a separate circuit to the one that discharges it to the flash bulb (much like how it will discharge to the different circuit of the coilgun).
Themata wrote:This way you'll have a switch to begin the charging process
This should already be on the camera. Depending on the make, it could be better to solder your own in it's place though. A lot are just two slightly separated pieces of metal you push together, and this isn't near as nice a fancy push button you can buy for 20c.
Themata wrote:put a light in this too which will indicate when the capacitors are charged, assuming the flashbulb on the circuit doesnt already do so

There should be one already. It's usually orange.
Themata wrote:then a switch to discharge and fire
This is shown in your pic, however, it's also a bad way to do it, as the wonderful sparks you make playing with capacitors will be made AT THE SWITCH. Where your fingers are. The switch in the pic is realistically a fun way to zap/scare people. Anyone who pushes that switch will either get zapped, burnt, or scared by a big bang.

If you want to make this work without burning yourself, you'd be better off doing the following.

Pull apart camera. Get circuitry all out, and either rewire/remount a better battery connection. Tip: 2 D-Cell batterys will charge quicker, usually not break the circuitry, and will last MUCH longer. A single D-Cell will not break the circuitry (unless the AA would), will last longer, but will take longer to charge the capacitor.
Remove the flash bulb, noting the two points that it was connected to. Connect these two points to either end of your coil, using wires that won't deteriorate with whatever voltage you are storing in the capacitors. There does not need to be a switch in this circuit, unless you want a safety (The gun will not fire if said switch is off, the capacitor can still be discharged though). If you do put one in, make sure it has reasonable size connections to handle the voltage. Small connections/wires = high impedence = heat = not fun.
Depending on make, probably remove the charging switch. On a lot of cameras, calling this a 'switch' is being generous. Again, note the two points, but instead wire on a switch of your choosing. Either a toggle (Push once to start charging, push again to stop), a single press switch (press and hold to charge, let go to stop) or a flick-switch (turn on to charge, turn off to stop).

This will work fine now as a single capacitor coil gun.

To add more punch:
Remove the capacitor from both this camera and a bunch of others, noting polarity before removal on THIS camera.
Solder them all on (in the same polarity) onto two long thick copper wires. (Get insulated stuff, strip the little section where you connect the capacitors, then heat-shrink back over the top on either side to reduce exposed areas).
Connect the copper wires to where you removed the capacitor, with the same polarity direction as before. You now have however many capacitors acting like one big one.
Note: Don't do too many, as it is possible to end up putting too much voltage across the prefab circuitry doing this. If you go a long way like this, rewire the whole thing, stealing the pieces you need, or research how to make one and do it yourself.

Edit: A quick picture... I'm going to movies soon else it would be better. In this pic (because it's unfinished) the little switch for actually firing the flash (usually two bits of metal at the end of 2 little wires) will fire the coil. You can replace the two little bits of metal with any type of switch, preferably with a "Magic" or "More magic" label. It is NOT shown in this picture. The switch shown charges the capacitor.
Spoiler:
firemylazer.png
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Re: flash capacitors and rail guns(help pls)

Postby Themata » Fri Jul 03, 2009 11:31 am UTC

The switches I was talking about were flick switches and wouldn't result in a zap, and two was mainly for safety's sake, especially if he wants this on his wrist. If the camera already has a switch on it, then win. The optional switch you indicated in your diagram was the same as the one shown in mine which you said would zap. I also mentioned light probably already being on the circuit as well in my edit, but you ninjad me :P

The way you mentioned joining them in parallel was what I've seen and it ends up with pretty damn cool results, but things just start getting dangerous at this point ;).

Tip: Put a diode in the circuit after the capacitor bank in order to stop current running back to the capacitors and possibly blowing them.

Thanks for the corrections though Baggins, I haven't actually made one before, I'm just going by knowledge/research. I intend to experiment with one these holidays without actually using a flash circuit and see where that goes.

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Re: flash capacitors and rail guns(help pls)

Postby mrbaggins » Fri Jul 03, 2009 1:36 pm UTC

Themata wrote:The optional switch you indicated in your diagram was the same as the one shown in mine which you said would zap.

I might have misunderstood, but it read like it's meant to be the firing switch, at which point it would bring the pain. Using it as a safety (It's either on for the entire discharge, or off preventing it) means it never has top act as a 'contact point' allowing it to cause hurtage. You want to abuse the camera's already in build circuitry as much as possible, because it does the job we want.

Edit: With a little knowledge, and the inverters from a camera, this schematic can be used to make the gear into any shape you need:
Spoiler:
Image
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