Fog Horn - Maker Factory ELECTRONICS EXPERIMENTS BOX Manual

2.34 Fog horn

Circuit 85: Fog horn
Setup information
Install the two transistors, the five resistors and the two electrolytic capacitors as shown in Fig. 2.85. The
nine jumper wires come next. 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
If everything is wired correctly, you will hear a slowly rising raucous sound similar to a foghorn once the
battery is connected. When you switch off the battery, the sound slowly fades away. However, over the Piezo
element the sound is not as powerful as the original, but sufficient for your tests.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.85.
110
Components required:
2 x 2N3904 transistors,
1 x 1 kΩ resistor,
2 x 2.2 kΩ resistors,
2 x 47 kΩ resistors,
2 x 100 nF ceramic capaci-
tors, 1 x 10 μF electrolytic
capacitor, 1 x 1000 μF elec-
trolytic capacitor, 1 x Piezo
element, 1 x breadboard,
1 x 9V battery with clip
connector
Fig. 2.85: Fog horn