112
2.36 Metronome
Circuit 87:
Metronome with discreet unijunction transistor
Setup information
Install the two transistors, the four resistors and the two electrolytic capacitors as shown in
Fig. 2.87.
The
nine 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. You can significantly increase the sensitivity of the Piezo ele-
ment by using a sound plate or even a sound box. Read more about it in Chap. 1.2.3
Components required:
1 x 2N3904 transistor,
1 x 2N3906 transistor,
1 x 1 k
Ω
resistor,
2 x 2.2 k
Ω
resistors,
1 x 220 k
Ω
resistor,
1 x resistor, see box Experi-
ment, 1 x 1 μF electrolytic
capacitor, 1 x 10 μF elec-
trolytic capacitor, 1 x Piezo
element, 1 x breadboard,
1 x 9V battery with clip
connector
Fig. 2.87:
Metronome with
discreet unijunction transistor
Experiment
If everything is wired correctly, you will not hear anything once the battery is connected. Up to now you still
don’t know the value of resistor R2. This resistance defines the metronome pulse. Details are listed below:
Resistor R2
pulse
47 k
Ω
50 bpm
22 k
Ω
80 bpm
10 k
Ω
180 bpm
If you use a potentiometer (value 50 k
Ω
or 100 k
Ω
) instead of a fixed resistor, you can adjust the pulse
continuously. On a side note: The two transistors are wired in a way that they will function like a unijunc-
tion transistor.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.87.
Содержание ELECTRONICS EXPERIMENTS BOX
Страница 4: ......
Страница 251: ...253 Fig 3 27 Circuit 27 4 seconds switch off delay Fig 3 28 Circuit 28 20 seconds switch off delay...
Страница 258: ...260 Fig 3 42 Circuit 42 Active 8 5V battery monitor Fig 3 43 Circuit 43 Active 7 8V battery monitor...
Страница 260: ...262 Fig 3 46 Circuit 46 Meters for 1 5 V Zener diodes and higher Fig 3 47 Circuit 47 Discreet 2 2V Zener diode...
Страница 261: ...263 Fig 3 48 Circuit 48 Discreet 2 9V Zener diode Fig 3 49 Circuit 49 Discreet 3 7V Zener diode...
Страница 265: ...267 Fig 3 56 Cir cuit 56 Audio limiter Fig 3 57 Circuit 57 Amplifier for a storm detector...
Страница 269: ...271 Fig 3 64 Circuit 64 Stabilizer for 1 9 V Fig 3 65 Circuit 65 Stabilizer for 2 5 V...
Страница 275: ...277 Fig 3 80 Circuit 80 Quiztimer 30 seconds Fig 3 81 Circuit 81 Handy diode tester...
Страница 290: ...292 Fig 3 118 Circuit 118 HF watch dog with LED indicator Fig 3 119 Circuit 119 HF watchdog with moving coil instrument...
Страница 295: ...297 Fig 3 130 Circuit 130 4 seconds switch on delay Fig 3 131 Circuit 131 15 seconds switch off delay...
Страница 298: ...300 Fig 3 136 Circuit 136 NAND gate with moving coil instrument Fig 3 137 Circuit 137 Input level Mixing console...
Страница 300: ...302 Fig 3 140 Circuit 140 Electrometer with moving coil instrument Fig 3 141 Circuit 141 Simple AM Radio...
Страница 315: ...317 Fig 3 179 Circuit 179 HF generator 150 kHz Fig 3 180 Circuit 180 HF generator 420 kHz...
Страница 324: ...326 Fig 3 202 Circuit 202 3 seconds switch on delay Fig 3 203 Circuit 203 7 seconds switch on delay...
Страница 325: ...327 Fig 3 204 Circuit 204 Piercing siren sound with Piezo element Fig 3 205 Circuit 205 Discrete Operational ampli fier...
Страница 328: ...330 Fig 3 210 Circuit 210 Discreet 5 2V Zener diode Fig 3 211 Circuit 211 Discreet 7 4V Zener diode...
