Acoustic Continuity Tester - Maker Factory ELECTRONICS EXPERIMENTS BOX Manual

2.87 Acoustic continuity tester

Circuit 186: Acoustic continuity tester
Setup information
Install the two transistors, the four resistors and the two ceramic capacitors as shown in Fig. 2.186 followed
by the eight jumper wires. Finally connect the Piezo element connect the Piezo element. Check the place-
ment 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
Even if everything is wired correctly, you won't hear anything at first. But by bridging, the test leads become
low-resistance and you will hear a loud tone. This makes continuity measurements easy and straightfor-
ward.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.186.
Components required:
2 x 2N3904 transistors,
2 x 2.2 kΩ resistors,
2 x 220 kΩ resistors,
2 x 1 nF ceramic capacitor,
1 x 1 μF electrolytic capaci-
tor, 1 x Piezo element,
1 x breadboard, 1 x 9V bat-
tery with clip connector
Fig. 2.186: Acoustic continuity
tester
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