SpudFiles

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

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.

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.

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

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.

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

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.