61
2.14 Acoustic continuity tester
Circuit 36:
Acoustic continuity tester
Setup information
Install the two transistors and the four resistors as shown in
Fig. 2.36.
Then install the two electrolytic
capacitors and the four resistors followed by the eight jumpers. Finally connect the Piezo element. Check
the placement on the board again and only then connect the battery.
You can increase the sensitivity of the Piezo element significantly by using a sound plate or even a sound
box. Read more about it in Chap. 1.2.3
Components required:
2 x 2N3904 transistors,
2 x 1 k
Ω
resistors,
2 x 10 k
Ω
resistors,
2 x 100 nF ceramic capaci-
tors, 1 x 10 μF electrolytic
capacitor, 1 x Piezo ele-
ment, 1 x breadboard,
1 x 9V battery with clip
connector
Fig. 2.36:
Handy continuity
tester
Experiment
Even if everything is wired correctly, nothing will happen at first. But when you move a resistance between
the probe tips (the ends of the jumper wires which serve as substitute), you will hear a sound. If short-
circuited, the frequency is high; at 100 k
Ω
, the pitch is low. When you use this circuit to test devices, you
don’t need to read the display. Your eyes won’t get distracted, and your ears will hear whether a short cir-
cuit or a high-impedance connection is present.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.36.
Summary of Contents for ELECTRONICS EXPERIMENTS BOX
Page 4: ......
Page 265: ...267 Fig 3 56 Cir cuit 56 Audio limiter Fig 3 57 Circuit 57 Amplifier for a storm detector...
Page 269: ...271 Fig 3 64 Circuit 64 Stabilizer for 1 9 V Fig 3 65 Circuit 65 Stabilizer for 2 5 V...
Page 275: ...277 Fig 3 80 Circuit 80 Quiztimer 30 seconds Fig 3 81 Circuit 81 Handy diode tester...
Page 315: ...317 Fig 3 179 Circuit 179 HF generator 150 kHz Fig 3 180 Circuit 180 HF generator 420 kHz...
