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Disposable Camera Ignition

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Unread postAuthor: Ragnarok » Sat Jan 24, 2009 12:28 pm

sputnick wrote:When you attach capacitors in parrallel like that, the voltage stays the same, but the amps increase. This is why it is lethal.

Afraid not. The internal resistance of the capacitors is utterly negligible compared to the resistance of a person, so combining them in parallel does next to nothing - those capacitors can probably deliver currents of a couple of thousand amps, but when, and only when, the resistance of the load is exceptionally low.
If a person is the load, they have resistances so high that any changes in the peak currents that the bank can supply is irrelevant - because the person's resistance is the deciding factor in the current.

Put it this way. A Lead Acid battery is about 12V, and one made for it (a powerful diesel engine starter battery is a good example) can chuck out upwards of 300 amps - but touch that, and absolutely sod all will happen to you, because your resistance prevents the 12 volts pushing more than microamps across you, not even enough to feel.
The maximum current a source can give out is pretty irrelevant to whether it will be fatal to you - it just needs to be MORE than is fatal to you - and in terms of current, stacking capacitors in parallel only increases the maximum current that can be drawn, so has little effect on it's lethality.

What kills you is a mix of amps and energy. However, it's only the amps actually flowing, and the energy actually transferred that counts, and you need voltage for that to be possible.
Also, while I'm on that point, the concept that stunguns and tasers use low currents is fallacious. They actually use high currents - for it's that which causes the pain. However, they are short bursts of current, and individual shocks lack the energy to be fatal. On average, over a second or two, the current is low, because a lot of the time it's not giving any current - but the peak currents are high.

However, that is not to say the bank couldn't be lethal under extreme circumstances - ANYTHING can be lethal under extreme circumstances.
But trust me, I've touched banks at both higher voltages and capacitances than yours, and last I checked, I'm not dead.
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Unread postAuthor: rp181 » Sat Jan 24, 2009 12:57 pm

Theres nothing else to be said, you can decide if you are going to stick to your own false idea. Back on subject,
Remove the camera circuit from the camera and just put in on top of the box, it will be more compact.
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Unread postAuthor: jimmy101 » Sat Jan 24, 2009 1:51 pm

So this is just a contact spark? How will you use it in a spudgun?

The extra caps are really a waste of time for an ignition system. It takes about half a millijoule to ignite propane in air. A single 120 MFD photocap at 300V is about 5J, roughly 10,000 more energy than is needed for ignition. Using say 5 caps just gives you 50,000 more energy than needed but who cares, if 10,000X isn't enough it is unlikely that 50,000X is going to work any better. (A BBQ piezo is down in the range of a couple mJ).

For comparison, a 100g spud moving at 100m/s (~300 FPS) represents 500J of kinetic energy. Figure a typical combustion spudgun is 10% efficient, that means there is about 5,000J of energy in the chamber. A single photocap represents just 0.1% of the energy in the chamber. Five caps would be just 0.5% of the energy of the chamber.

So the multiple caps don't help with ignition and they don't contribute a significant amount of energy to the chamber.

It is much more impressive if you use a single cap and set up a trigatron type spark gap that can actually be triggered electrically using the photoboard's HV trigger circuit. That'll give you a non-contact spark (across a gap) that is triggered with a switch. When I've done this the resulting spark sounds nearly as loud as a firecracker.

As to lethality, well, it's just 300V. The bodies resistance is high and extremely variable. Shorting a pair of smooth surfaces with your finger tip probably won't produce much more than a tingle. Jab it into your skin and you may well blow the tissue out'a your finger between the two contact points. Jab it into a finger on one hand then make the other contact with a jab to the other hand and your muscles will lock up and you may well be dead. A 120 VAC household circuit (typically limited to 15 Amps by the breakers) can easily kill when applied across the body. A photocap will eventually discharge so you might survive, depends on if there is enough current, and lasts long enough, to actually stop the heart.
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Unread postAuthor: john bunsenburner » Sat Jan 24, 2009 2:15 pm

And could you theoretically get the heart you stopped with the device beating again with the same device?
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Unread postAuthor: sputnick » Sat Jan 24, 2009 2:25 pm

RP181, THAT IS WHAT I HAVE BEEN SAYING THIS WHOLE TIME never have I said that voltage kills you, are you even reading what I am sending you?
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Unread postAuthor: Ragnarok » Sat Jan 24, 2009 4:49 pm

sputnick wrote:never have I said that voltage kills you

And that is exactly the problem. Voltage cannot be ignored when considering the potential lethality.

@John Bunsenburner: A De-defibrillator is rather more complex than that.
They use somewhere above 100 Joules at around 1000 volts, but it's inductively damped, and has to be applied in the right places.

It's also worth saying that not all heart stoppages can be fixed with a De-fib. However, you'll be extraordinarily lucky to restart a heart without one.

Forget any ideas of external heart massage doing the job (like the crap you sometimes see on TV and in film) - that's only up to keeping someone from dying until a de-fib gets there.
Even then, I've only ever personally known of three cases of someone successfully being revived after a heart failure. One of those was a friend who's heart stopped on the operating table, and the De-fib was already there. Both of the others were people (neither of whom I knew, but I was there at the time) who were "lucky" enough to be at major events when it happened, and with first aiders literally right next to them ready to help instantly and de-fibs nearby.
One of the second two later died a few days later in hospital, but the revival on site worked.
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Unread postAuthor: john bunsenburner » Sat Jan 24, 2009 4:57 pm

Isnt it true that is you are in the same room as the LHC in CERN and one of the electrons hits you it has so much energy it would kill you in an instant. If i am not wrong then amerage is the amount of particals per unit of time(amount mesured in coulombs) and voltage is the amount of energy per unit of charges(energy mesured in Joules). If a single electrong(negatively charged partical) hits you then the amerpage, current, but in the LHC the energy of this partical is extremly big, therefore it has a high voltage. This partical is able to kill you that means that een voltage along can be lethal in the right does, i ai correct or way of?
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Unread postAuthor: MaxuS the 2nd » Sat Jan 24, 2009 5:15 pm

Since when did this turn into a discussion on how electricity can kill you?
Jees guys, keep it in your pants next time!

Nice work on the disposable camera flash ignition. :)
Neaten it up a little and you've got yourself something to work with.
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Unread postAuthor: sputnick » Sat Jan 24, 2009 5:17 pm

Thanks, It started out as a high voltage experiment, but the sparks inspired me, being hot enough to weld and all :lol:
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Unread postAuthor: rp181 » Sat Jan 24, 2009 5:18 pm

Its better to know what your dealing with.
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Unread postAuthor: MaxuS the 2nd » Sat Jan 24, 2009 5:24 pm

Indeedy, you might want to build a high voltage circuit next time - Now you're hooked!

It's much better to have an spark/arc between two points than to have to touch the two terminals together. It cuts out so many complications.
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Unread postAuthor: Ragnarok » Sat Jan 24, 2009 5:30 pm

john bunsenburner wrote:Isnt it true that is you are in the same room as the LHC in CERN and one of the electrons hits you it has so much energy it would kill you in an instant.

No... because the LHC accelerates protons. :tongue3:
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Unread postAuthor: rp181 » Sat Jan 24, 2009 5:35 pm

Any way, that is kind of pointless for ignition. Look up a triggered spark gap. come to think of it, i have a explanation up:
http://rp181.110mb.com/index.php?p=1_12_Switching
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Unread postAuthor: jimmy101 » Sat Jan 24, 2009 7:00 pm

rp181 wrote:Any way, that is kind of pointless for ignition. Look up a triggered spark gap. come to think of it, i have a explanation up:
http://rp181.110mb.com/index.php?p=1_12_Switching

AKA a Trigatron (as I posted eralier).

See 6Mhz's example;
http://www.angelfire.com/80s/sixmhz/trigatron.html
http://www.angelfire.com/80s/sixmhz/camera.html
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