SpudFiles

I made a little mini combustion with an airsoft barrel. It is very ghetto, but I like it. Anyway, the sparker is just the one out of a long nosed lighter. To make the spark gap (I think that's what it is) the part where you see the spark, I put two holes in opposite sides of the chamber, put the wire around the screws, and screwed them in. The tips of the screws are perfect distance apart. The only problem is that when there are screws on both ends, red and black, there is no spark. When I only have the screw on one wire though, it works fine. Can anybody help with this?

For current to flow, there must be a voltage differential in the gap.

Sometimes it is miss-understood where the differential is in some spark sources such as a piezoelectric from a lighter. They come with only one wire.

If you hook this one wire up to both screws, there is no differential between them and thus no spark. If you connect to only one of them, one that is not connected has capacitance to it's surroundings so a voltage pulse will arc to it, thus a spark.

The piezoelectric from a lighter has a striker hammer spring assy. The HV element is in the small cylinder that has the wire sticking out of it. The metal body of this element is the other terminal. Connect a wire from the metal parts of the unit such as the spring, metal case, etc. In the lighter it came out of, this was connected to the metal ground of the lighter. The HV lead was connected to the gas tip so it would arc from the gas tip to the shell to ignite the gas.

Connect one screw to the HV lead and the other screw to the metal mechanical parts and it should work fine.

Ok thanks, but it would be rather difficult to get a screw hooked up to one of those components... they are very tiny. I found out that if I put one end on a nail then another end on a screw then it sparks.

Like tech said, the long handled lighters I've used have two wires, well actually, the metal pipe is one of the conductors and replaces one of the wires. There are two wires connected to the piezo element, one permanently and one kind of haphazardly to the top of the piezo. One of the wires connects to the metal lighter barrel and the other runs up the barrel. The tip of this second wire is one element of the spark gap. The entire "muzzle" of the lighter is the other gap element.

http://www.inpharmix.com/jps/Hacking_lighter.html

There must be a complete circuit for the spark to work. The second "wire" attachment to the piezo is on the plastic hammer button of the piezo element.

The full length wire, in the case of this particular lighter, runs inside the fuel supply hose. I suspect that is to increase the insulation on the HV wire and to reduce the chance of a spark jumping someplace other than at the spark gap (like through the wire's insulation to the barrel).

In my experience with piezo sparkers there are always two contacts. Often one is a wire glued to the piezo's body and the other is a metal cap at the end of the piezo.

Below is an image from Wikipedia showing a typical lighter piezo wired up to spark to itself. One wire and one metal end cap.

BTW, if your chamber is metal then it won't work if you use metal screws. One of the screws must pass through the chamber without making electrical contact with the chamber.

On metal barrels, Nylon or Teflon washers and bushings work well.