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2.16 Electronic potentiometer
Circuit 41: Electronic level control with large control range
Setup information
Install the two transistors and the five resistors as shown in Fig. 2.41. Then install the ceramic capacitor and
the two electrolytic capacitors, followed by the eight jumper wires. 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
Experiment
With an electronic level control you can define the weakening of an audio signal by means of a control
voltage value. In our case, at 0 V control voltage, the audio signal will be amplified by the factor 10; at
-7V control voltage, it will be muted by factor 1.000. The maximum output voltage is about 1 V. As sources
for (negative) control voltage you could use batteries such as 1.5V, 3V, 4.5V batteries or a suitable variable
power supply.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.41.
66
Components required:
1 x 2N3904 transistor,
1 x J111 FET transistor,
1 x 100 kΩ resistor, 1 x 10
kΩ resistor, 1 x 4.7 kΩ
resistor, 1 x 2.2 kΩ resis-
tor, 1 x 1 kΩ resistor,
2 x 10 μF electrolytic
capacitors, 1 x 100 nF
ceramic capacitor,
1 x Piezo element,
1 x breadboard, 1 x 9V bat-
tery with clip connector
Fig. 2.41: Electronic level con-
trol with large control range
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