So How Does It Work?

It was indeed a challenge to come up with a method of demonstrating Electrostatic sources of electricity in such a way that it could be used in the field and trigger a system that could provide the Geocacher with the clue to the coordinates of the final stage. Electrostatics are quite finicky in respect to humidity. It was determined that the "Magic Tape" Positive Charge Generator approach would be the most reliable. But how to use that charge to trigger the system? Electrostatic charges are not like batteries or thermocouples. You can't draw current from charged plastic strips. We made use of a fairly new device called a MOSFET. (Metal Oxide Silicon Field Effect Transistor) shown in the diagram. It will turn on only if its gate (G) in the diagram is charged positive. When it is off there is no current flowing through the 1K resistor so the voltage at D and the input of the microprocessor is at +5 volts. When a positive charge is on the gate the voltage at the microprocessor drops close to zero as shown in the little graph pointed to by the red arrow. The system will then activate and pulse the piezo buzzer beeping out the coordinates.

You may click on the diagram to enlarge it.

When the positively charged tape is brought near the charge plate the electrons in the charge plate, wire and MOSFET gate will be attracted as close as possible to the positive charges on the tape...leaving the gate with a lack of electrons thus looking positive and this turns on the MOSFET.

So, actually there is not charge exchange between the tape and the plate. Just the proximity of the positive charge on the tape induces a negative charge on the area near the tape leaving the other end at the gate positive. Taking the tape away will return plate and gate neutral again...but by that time the system has already been triggered.