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continuous camera tazer

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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continuous camera tazer

Unread postAuthor: big_boom » Mon Jun 06, 2011 4:26 am

hi
so i was trying to make an ignition source from a disposable camera, but somehow, sometimes as soon it is sparks, it just keeps recharging. on some occasions, it starts charging as soon as i put in the battery. any ideas about what's going on??? i'm 100% sure i'm not hitting the charge button on the front. would appreciate any help.
cheers
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Unread postAuthor: Technician1002 » Mon Jun 06, 2011 6:32 am

Some camera flash units auto start the charge cycle when the cap is discharged by taking a photo. If you don't use it for a long time the cap will run down and it won't auto recharge so it does not run the battery down keeping it charged all day.

Use a flash from another brand of camera to avoid the unwanted auto start.
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Unread postAuthor: Ragnarok » Mon Jun 06, 2011 7:12 am

Technician1002 wrote:Use a flash from another brand of camera to avoid the unwanted auto start.

Or buy a 1-cell holder and a switch, wire the switch in between the cell and circuit, solder the "front switch" closed.

Turn your new switch on when you want to charge, turn off when you don't. Simples.
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Unread postAuthor: jimmy101 » Mon Jun 06, 2011 4:20 pm

Ragnarok wrote:Turn your new switch on when you want to charge, turn off when you don't. Simples.
But don't expect that new switch to act as a "Safety". Turning the switch off after charging up the main cap wont "safe" the circuit.

To sort of safe the circuit you could use a multi pole switch to discharge the cap to ground (through say a 250 Kohm resistor) when the switch is turned "off".

EDIT: wreally bad engwish
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Unread postAuthor: Technician1002 » Mon Jun 06, 2011 5:54 pm

For a faster safety, a lower value resistor can be used. It needs to be able to have enough thermal mass to accept the entire amount of stored energy. Discharging at 1/2 amp will limit the current to safe levels for the switch and other components. A 2 watt wire wound or thin film non fusible resistor of about 470-1,000 ohms will do the job nicely.

250K is high enough value it won't need a switch, but will continuously bleed the capacitor down at a slow rate.
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Unread postAuthor: big_boom » Mon Jun 06, 2011 11:07 pm

the switch is an idea, however the camera should work, it's a kodak, and i've seen it work in videos before. any thoughts about how there could be something i did to the circuit, i left it unchanged, well i tried to. i did notice that the button to take a picture doesn't work or the wheel that you turn to take a new picture isn't turning anything. does anyone know if they were at all connected to the circuit?
thanks
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Unread postAuthor: jimmy101 » Tue Jun 07, 2011 4:22 pm

Technician1002 wrote:250K is high enough value it won't need a switch, but will continuously bleed the capacitor down at a slow rate.

Not for a typical disposable photoflash board. A typical photoflash board would have a hard time keeping up with the discharge through the 250Kohm resistor. You would probably end up limiting the max voltage on the cap to something like 200V.
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