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Circuit 106: Whistle buoy
Setup information
Install the two transistors, the five resistors, the ceramic capacitor and the electrolytic capacitor as shown in
Fig. 2.106. The ten jumper wires come next. Finally, insert one end of the jumper wire, which will function
as switch (shown dashed) and is labelled with Start. Last but not least, connect the Piezo element. Check
the placement on the board again and only then connect the battery.
You can significantly increase the sensitivity of the Piezo element by using a sound plate or even a sound
box. Read more about it in Chap. 1.2.3
Experiment
A whistle buoy is used to produce a loud and prominent warning signal. Our circuit is at least capable of
accomplishing the second point. Close the Start switch. You do this by inserting the end of the wire jumper.
The generator howls. But unlike the previous circuit, here a deep howl sound is produced. Open the switch
again, by pulling out the appropriate wire end. The whistle buoy slowly reduces its frequency again. Repeat
this play as often as you like.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.106.
Components required:
1 x 2N3904 transistor,
1 x 2N3906 transis-
tor, 1 x 10 kΩ resistor,
2 x 10 kΩ resistors,
1 x 47 kΩ resistor,
1 x 100 kΩ resistor,
1 x 100 nF ceramic capaci-
tor, 1 x 10 μF electrolytic
capacitor, 1 x Piezo ele-
ment, 1 x breadboard,
1 x 9V battery with clip
connector
Fig. 2.106: Whistle buoy
131
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