136
2.49 Glass breakage detector
Circuit 111:
Glass breakage detector
Setup information
Install the three transistors, the diode and the six resistors as shown in
Fig. 2.111
The twelve jumper wires
come next. Last but not least connect the Piezo element. Check the placement on the board again and only
then connect the battery.
Components required:
2 x 2N3904 transistors,
1 x 2N3906 transistor,
1 x red LED, 1 x 1 k
Ω
resis-
tor, 2 x 10 k
Ω
resistors,
1 x 47 k
Ω
resistor,
2 x 470 k
Ω
resistors,
1 x 1 μF electrolytic capaci-
tor, 2 x 10 μF electrolytic
capacitors, 1 x Piezo ele-
ment, 1 x breadboard,
1 x 9V battery with clip
connector
Fig. 2.111:
Glass breakage
detector
Experiment
If everything is wired correctly, the small signals of the Piezo element, which in our case represents a micro-
phone, will be strongly amplified. At a certain threshold the red LED indicator turns on. The circuit is very
responsive to the noise of breaking glass. If the circuit is used for real, the Piezo element should be glued
to the glass pane that you wish to monitor. You could also use a relays instead of the red LED, which would
then trigger an alarm.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.111.
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...
