Maker Factory ELECTRONICS EXPERIMENTS BOX Manual page 96

Circuit 73: RC low pass 3 kHz
Setup information
Install the transistor and the electrolytic capacitor as shown in Fig. 2.73. Last but not least, connect the
Piezo element. Check the placement on the board again.
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
We will use electrical filter circuits, among other things, to suppress the noise. The basic circuit that serves
this purpose is a RC or LC filter consisting of a resistor/inductor and a capacitor. Depending on the wiring,
this creates a low pass or a high pass. In our case, we are using an RC low pass filter; the cutoff frequency,
up to which signals can pass, is 3 kHz If you have an mp3 player connected to the input, it will sound as if
the music comes from a handset.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.73.
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Components required:
1 x 47 kΩ resistor,
1 x 1 μF electrolytic
capacitor, 1 x Piezo ele-
ment, 1 x breadboard
Fig. 2.73: RC low pass 3 kHz