A problem regarding my Slayer Exciter circuit?

Question

I have made a Slayer Exciter circuit for my school project. I'm going to be assessed on it. Now, it works just fine. But if I have to light a tubelight or something, I have to touch the terminal to the wire sticking out of my secondary coil. Then I can move the tubelight about, close to the coil and it won't go off. But why do I have to touch my light to the wire initially? Because in most Slayer Exciter circuits that I have seen on the internet, the light only has to be brought close and not actually touched. Can someone please give me a technical explanation? The examiner may ask me this and more than that, I want to know.

Answer 1

But why do I have to touch my light to the wire initially?

You need to create a situation where the electric field across the tube is big enough to start ionization. Your circuit is battery powered and appears to have very little ground capacitance hence your body makes a very feeble connection to the "current return path" of your circuit. Given that your body is actually part of the circuit, this feeble connection is the weak link in my opinion.

I would connect the negative terminal of your battery to a piece of tin-foil (aluminum foil) that forms a 12" ground-square under your base board. Now you have a significantly increased ground capacitance and a less-feeble AC connection to your body. This will improve things.

However, there is no guarantee that your circuit is producing enough voltage so although the ground-square may improve the situation, you may still need to adjust the output coil.

Answer 2

To start discharging in the gas needs stronger field than your system generates without touching the wire. It continues more easily if there's some ionization left. Fix: get higher output voltage or more easily ionizing tube.

Answer 3

It takes more energy to ionize the gases in the first place than it does to keep it ionized. Therefore in your low-power setup you need that initial direct high voltage connection in order to transfer enough energy to the tube to "ignite" the gases. Once "ignited" it will take significantly less energy to keep the tube lit, which is why you can move it around the coil without touching it.

If you wanted to improve the output of your coil so that the tube lights without even touching it, you could increase the supply voltage. You'd need to make sure your circuit can handle the new supply voltage though.