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Camera flash circuit with no ignition coil

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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Unread postAuthor: LikimysCrotchus5 » Wed Oct 22, 2008 8:38 pm

After looking at this topic, I have been wondering if the voltage from this is enough to have 3 good spark gaps for a advanced comubstion?
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4SPC, My 4" piston 3" porting cannon
Memo:
Fix up copper cannon
Fix up 4SPC
Start Stirrup pump
Start Toolies piston bazooka
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LikimysCrotchus5
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Unread postAuthor: microman171 » Wed Oct 22, 2008 10:52 pm

How about a knife switch? That way you have the leverage to unweld it.
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Unread postAuthor: CpTn_lAw » Mon Nov 10, 2008 6:31 pm

jimmy said something but i can't agree...
On a camera circuit, with the two caps, one big, one small, the small one is wired to a tranformer, and the HV end is in contact with the glass of the flash tube. Big capacitor is wired to both "poles" of the flash tube, but current can't pass because it hasn't enough energy.
The role of the HV wire in contact with the flash tube is to ionise the gas inside, reducing it's resistance, allowing for the big capacitor to discharge almost entirely through the gas, ceating a blinding flash.

When you do a 3 electrodes setup (required for this kind of power) basicly your HV wire does not touch the two wires from the big cap. The small energy from the small capacitor through the HV transformer is only a small fraction of the total energy release. In fact, when you trigger your setup, the HV wire ionises the air between the two big wire from your big cap, allowing the current to jump from one wire to the other. This is a full 6.5 joules discharge.

Doing this, you don't need to have a big switch, because you don't short circuit the big cap. The air between the two big electrodes has a high enough resistance to make this setup a "circuit-like" setup.

Now i recorded a while ago in high speed what would happen. you clearly see that the HV wire does not produce a spark in this particular setup, the spark is between the two electrodes from your big cap.


Concerning the plasma globe circuit...you can change the high voltage coming from the flyback transf. by changing the transistor and putting a higher voltage input. i did put a 2N3055 transistor, and send 14volts, 10 amps input in short burst. HV output was approximately 15kv, and the arcs were , well, noticeably bigger.


I took an old transformer from a voltage generator...look at the size of the beast...(the penny is a 1 cent of euro) Image

I haven't done any testing with it so far, but after my electrostatics/magnetics exam on tuesday, i should have more time to play with it...
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"J'mets mes pieds où j'veux, et c'est souvent dans la gueule."
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Unread postAuthor: jimmy101 » Tue Nov 11, 2008 1:49 pm

CpTn_lAw wrote:jimmy said something but i can't agree...
On a camera circuit, with the two caps, one big, one small, the small one is wired to a tranformer, and the HV end is in contact with the glass of the flash tube. Big capacitor is wired to both "poles" of the flash tube, but current can't pass because it hasn't enough energy.
The role of the HV wire in contact with the flash tube is to ionise the gas inside, reducing it's resistance, allowing for the big capacitor to discharge almost entirely through the gas, ceating a blinding flash.

When you do a 3 electrodes setup (required for this kind of power) basicly your HV wire does not touch the two wires from the big cap. The small energy from the small capacitor through the HV transformer is only a small fraction of the total energy release. In fact, when you trigger your setup, the HV wire ionises the air between the two big wire from your big cap, allowing the current to jump from one wire to the other. This is a full 6.5 joules discharge.

Doing this, you don't need to have a big switch, because you don't short circuit the big cap. The air between the two big electrodes has a high enough resistance to make this setup a "circuit-like" setup. ...

I believe that is exactly what I said. The little cap and the HV transformer ignites the tube. It will generate a spark across a small pointy gap all by itself but that spark is probably not enough to ignite porpane + air since it is very weak. The low ESR trigger cap is typically something like 0.02MFD charged to 300+V just like the big cap. Since the capacitance is only about 1/6000 the photocap's it only has about 1/6000 the energy Roughly 1mJ.

The typical trigatron setup uses the very small energy but high voltage trigger to ionize the air between the two main electrodes. Basically exactly the way the phototube works. The only difference is that the Xenon in the phototube has a much lower ionization voltage than does air so the gap between the main electrodes can be much larger (typically a half inch or so for a xenon tube of a disposable camera).

BTW, "Big capacitor is wired to both "poles" of the flash tube, but current can't pass because it hasn't enough energy." is wrong. It can't pass current not because there is insufficient energy (there is more than enough energy), it can't pass current becuase the voltage isn't high enough to break down the xenon gas in the tube. You need higher voltage, not higher energy, to trigger the tube.
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