Electrical – Troubleshooting a round fluorescent bulb with 4 pins in a square formation

I thought plasma balls were capacitively coupled and verified that "A standard plasma lamp device uses an electric current having an oscillating frequency of 35 kilohertz and a voltage ranging from 2 to 5 kilovolts"

The light emission in the globe from ionization uses different inert gases to yield different colors. The electronic ballasts in fluorescent lamp (FL) tubes require less current to ignite than older versions with heaters, due a similar high frequency trigger and then current limit once the tube resistance drops.

The current thru the globe is low but increases with capacitance coupling to the glass sphere and brightness increases with current density from higher capacitance per square cm.

Holding the glass is safe since the capacitance across the glass insulator is low. But once the gas inside has ionized the impedance to the electrode pin is lower than the impedance thru the glass and also being a conductor, the current density from contact is much higher, so a sensation is easier to detect.

The sensation of creating static electricity walking across a carpet with a door key in hand and zapping the door the knob, which has almost no sensation yet creates a strong arc. Yet touching the door knob has a much stronger sensation. The difference here is not current here but rather current density.

But this is just a static discharge where the peak current can be more than an amp in less than a nanosecond then sustained at lower level for several uS or more. In the case of the FL contact pins, the finger contact creates a high current density sensation and also since it is AC, it can be sustained at a lower level if squeezed.

So in short ( no pun) it is the capacactive coupling of the glass tube to the globe that creates the glow with the capacitive coupling of the hand. Bypassing the capacitive impedance of the hand-to-glass with a lower resistance contact to the tube pin bypasses the flow thru the body with much higher density. The body leakage capacitance to air (free space) then completes the circuit.

Overall current is limited by the flow from the plasma globe. But human sensation is a combination of current density and current level as well as pulse rate.

Maybe to try to add pullup resistor to the reset pin. Or to redesign your board so that power lines are more distant from arduino.