Another nembie Q:

[rp181]

when DYI said overly powered ignition system, i think he was talking about high energy arcs from capacitors.

[DYI]

How do you class powerful? My ign system draws on a 12v 300amp battery.

If it can't detonate TNT directly, it ain't high powered
I believe you're using an induction coil to create the HV, so you don't need to be worried about getting any decent energy out of it.

And FAEs do detonate. Not very quickly of course (I believe well under 4km/s on average), but if you see a really slow motion video of one going off, you'll understand. They set off the fuel/air mix with an explosive charge in most cases, that goes off a preset amount of time after the burst charge.

[jimmy101]

How do you class powerful? My ign system draws on a 12v 300amp battery.

You really can't gauge the power of the ignition from the power of the voltage source. How much current does it actually draw? It almost certainly doesn't draw the full 300A the battery is capable of.

And, if it is any type of capacitive discharge system then the current rating of the power supply is pretty much irrelevant. A 1.5V AA battery (sources ~10A, 15 watts) charges a photoflash cap to about 6.5J in several seconds. The phtotocap will dump that charge in ~1mS. That's 6,500 Watts (1J = 1W*S). Basically, the photocap discharge system compresses a couple seconds worth of power from the battery into a ~1mS long pulse. That 6,500 watts is about twice what a 12V, 300A battery can do continously.

Propane + air at 1 ATM requires a few hundred microjoules for ignition.

[McFear]

you just answered a question i was about to ask., thanks very much:P

[SpudFarm]

i just started to think about ignition.. a wire from the tungsten electrode on a tig welder to the spark gap and then the other (don't know name in english) on the chamber..

[McFear]

cathode? thaty what your looking for
positive terminal or have i got it wrong way around

[jimmy101]

i just started to think about ignition.. a wire from the tungsten electrode on a tig welder to the spark gap and then the other (don't know name in english) on the chamber..

I'm not familar with TIG welders, but don't regular arc welders require contact between the electrode and the work to "ignite" the spark? A standard arc welder wouldn't work as a spark source for a spudgun.