User manual

not only mechanical pressure can charge the piezo panel, but a temperature change as well. Warm up the panel by touch with open contact. As a result, it will
charge and generate noise when discharging. After a while, cooling can produce a crackle again.
Mission: Put the entire model for
some time into the cold out-
doors. Take it back into the
warm indoors and obtain at least
five clearly audible crackles in a
row: 3 points.
3 Charging and discharging
Behind the third door, there is a 2.2 k

(2.2 kohms) resistor. It is labelled by three colour rings (red, red, red). The fourth, golden ring indicates the 5% accuracy
class. Connect this resistor in parallel to the sound converter. It will ensure quick discharge. Therefore, a simple contact is enough this time. The noise is generated
each time when the contact is closed or opened. The resistor consumes energy so do not leave the switch closed for a long time. However, if possible, the battery
should last until the end of the experiment.
Info: You can easily estimate the moment of the battery discharge. The amperage is 9V divided by 2.2 k

i.e.
around 4 mA. For the alkaline battery with the capacity of 500 mAh it makes 125 hours or about five days until the
battery goes flat.
Mission: Make two touch-contacts and connect your skin resistance in a row to the available 2.2 k

resistor. The
skin resistance is some 100 k

, so that with small current the discharge is much slower and quieter. The resistor
only plays a protective role and restricts the current in case of an inadvertent direct contact of the sensor contacts.
Resistance can be changed by touch of different strength. The purpose is that the crackle is only generated with
every closing, but not opening the switch: 4 points.
4 Light and sound
Behind the door number 4 you will find a red light diode (LED). Integrate the LED into the positive lead of your model so that you know, when the switch is closed
and the current flows. When installing an LED, you need to observe correct polarity.
The LED has two different connectors. The short wire is the negative (cathode), and the long wire is the positive (anode) pole. Once the LED is integrated, it is
difficult to see which wire is the short one. There is, however, an additional marking. The broader lower edge is flattened on the cathode side. Besides, the bigger
bracket in all LED across this calendar is connected with the cathode inside the LED.
Info: In a series connection, the battery voltage of 9V is divided to a single load. Now, a voltage of about 2V is
applied to the LED, and 7V to the resistor. Since the voltage at the piezo sound converter is only at 7V, the crackles
caused by switch touching are now a bit quieter. Since our ears are accustomed to a much broader range of sound
levels, the difference is practicable unnoticeable.