SpudFiles

SEAKING9006 wrote:It was made about a year or two ago in response to a thread I made on spudtech about the construction of cartridge based combustions.

jackssmirkingrevenge wrote:No need to use a capacitor, just hook up the two points of the piezo to your bolts.

TurboSuper wrote:Your problem is simply that the caps don't have enough voltage behind them. They only have about 300V or so- not nearly enough to jump a gap.

You'd need to either wire the 3rd, really high voltage lead on the board in between them to ionize the air, or put some steel wool in between the electrodes. Or you can wire the caps to an ignition coil to step the voltage up to a few kV.

I'm with JSR though- go with a piezo. You don't need any fancy electronics whatsoever, just wire the two leads to your spark gap and you have an insta-kaboom

These Mickey-Mouse camera ignition circuits are usually more trouble than they're worth, the only real advantage I see to them is they make that cool sci-fi whining noise when the caps charge.

markfh11q wrote:Actually, they're good for making hybrid ignition systems, since you generally need more voltage. A camera capacitor dumping through a Nissan ignition coil made one of the biggest sparks I ever generated...

jrrdw wrote:Go with the 100,000v stun gun circuit from www.bcarms.com

jimmy101 wrote:Like turbo said; you doubled up on the wrong capacitor. The big-ass cap is charged to 300~330V by the circuit board. That voltage will only jump a gap of about 0.2mm (~1/100"). There is a lot of energy in the cap but the voltage just isn't high enough to spark. (Two photocaps would contain about 12 joules of energy when fully charged.)

The high voltage (about 10KV) needed to trigger the phototube is created by dumping a second, much smaller cap (see photo), through the HV trigger transformer. The output of that transformer is carried by a wire to either the metal reflector around the flashtube or to a wire wrapped around the flashtube. That wire is the only source of high enough voltage to jump a gap. You can try to use that wire as the spark source. The other side of the gap would be wired to the circuit boards ground contact. Though the spark is up around 10KV the current is extremely low because the cap that supplies the power is only something like 0.02 MFD, total power when charged to 320V is 0.5millijoules (just barely enough to ignite propane+air).

So, it is that small cap that you might try doubling up using the cap from another board.

Or, dump the big-ass photocap through a car ignition coil. You might think you could dump the big-ass cap through the trigger transformer but I suspect you would destroy the transformer with that much power going through it.

Or, try a trigatron, which uses the two leads from the big-ass cap plus the HV lead in a three electrode spark gap. That'll give a huge spark, but is a PITA to keep working becuase the alignment is tricky and the electrodes get burned up.

Or, like others sugested, just use a BBQ piezo or buy a stungun.

TurboSuper wrote:That third wire would either go in between the gap of the capacitor leads to act as a trigitron of sorts, or act as the spark itself by placing it near the ground.

I've never really tested this setup, but some dude got it working on a website I read.


And yes, even the small spark from the piezo will be enough to ignite the cannon...it don't take much.

DYI wrote:I also live in a country where self-defense is illegal, but you don't need to worry about getting a stungun from BCARMS to New Zealand, as he removes the case and ships the bare circuit, without a battery, as a voltage regulator. Technically, it's not illegal to bring the bare circuit through customs, only when it's in the case do you have a problem.

Discharging a low voltage cap (like the ones on a camera board) through an ignition coil is of use sometimes, but it's an overly bulky system for a basic combustion gun. Either use a BCARMS high voltage pulsed DC circuit, or a basic piezo sparker for starters. Unless you're building an EBW or Marx generator to set off a high-mix hybrid, capacitor based systems are kind of overkill.

iisthemuffin wrote:Im pretty sure it doesnt matter how big of a spark you create.

Think of it like this: If you have a towel soaked in gasoline and you light it with a lighter it will light just like if you lit it with a big propane torch.

Your not trying to make a huge spark. Just burn the fuel. If your ignitor is sparking, then it will catch the fuel inside of the chamber and your good to go.

If i were you i would just leave out the capacitors all together as JSR said.

The tiny sparker coming from the sparker is enough to igntie your fuel. Just make your gap a bit bigger and you should be fine.

How would i wire in the Piezo? As now i have the holes from the bolts? Just poke in the wire from the piezo?

And just make a case? It sounds like youve done this before

Stun guns are illegal here, I'm from New Zealand

Silentone wrote:Something i can do to make it work? Too much deodorant? Not strong enough spark?

starting fluid

Silentone wrote:Right i've wired up the Piezo starter.. It sparks fine..

I put in the potato *grin* and did a 2 second spray of deodorant and put on the end cap.. Clicked the piezo but no joy, Any ideas?

Something i can do to make it work? Too much deodorant? Not strong enough spark?

ammosmoke wrote:Actually, a bigger spark/more ignition locations is more effecient and therefore more powerful. But, this being a simple gun and a first timer, I don't think I would bother.