Loud Foghorn - Maker Factory ELECTRONICS EXPERIMENTS BOX Manual

2.40 Loud foghorn

Circuit 95: Fog horn
Setup information
Install the three transistors, the seven resistors and the two electrolytic capacitors as shown in Fig. 2.95.
The twelve jumper wires come next. Finally 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 loud raucous sound like that of a fog horn once the battery is
connected. The sound coming from the Piezo element is not as powerful as the original, but it is sufficient
for your tests.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.95.
120
Components required:
2 x 2N3904 transistors,
1 x 2N3906 transistor,
1 x 1 kΩ resistor,
2 x 2.2 kΩ resistors,
4 x 220 kΩ resistors,
2 x 10 nF ceramic capaci-
tors, 2 x 10 μF electrolytic
capacitors, 1 x Piezo
element, 1 x breadboard,
1 x 9V battery with clip
connector
Fig. 2.95: Fog horn