Signal Tracker - Maker Factory ELECTRONICS EXPERIMENTS BOX Manual

2.69 Signal tracker

Circuit 145: Simple signal tracker with Piezo element
Setup information
Install the two transistors, the four resistors and the three electrolytic capacitors as shown in Fig. 2.145.
Insert the eight jumpers. 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
Even if everything is wired correctly, nothing will happen at first. If you are familiar with the relevant safety
guidelines as per VDE and know how to observe them when working with devices that are to be connected
to the mains, you can now interconnect the circuit and an external circuit.
When you then touch the individual points at the input that have the audio signals of the circuits to be
tested, you will hear the response coming loud and clear from the Piezo element – no matter if the ampli-
tude is just a few mill volts or several volts. This tool comes handy, if you need to quickly locate a broken
level in an audio circuit.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.145.
Components required:
2 x 2N3904 transistors,
1 x 4.7 kΩ resistor,
1 x 10 kΩ resistor,
1 x 220 kΩ resistor,
1 x 1 MΩ resistor,
1 x 1 μF electrolytic capaci-
tor, 2 x 10 μF electrolytic
capacitors, 1 x Piezo ele-
ment, 1 x breadboard,
1 x battery, 9V battery with
clip connector
Fig. 2.145: Simple signal tracker
with Piezo element
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