Elenco Electronics EP-130, Руководство пользователя

Страница: 103 / 160

The electronic buzzer we built in project 82 can only
make a continuous beep, but we can make a similar
circuit that produces various siren sounds.
Now we’re going to make a siren that gives out a
sound with a variable pitch. When you move the
switch, this siren wails and then makes a continuous
high-pitched noise.
Slide the switch to position B and assemble the
circuit. When you finish the wiring, turn the power on
by sliding the switch to position A. You hear the
speaker give out a sudden, roaring siren sound. The
sound is low at first and becomes higher, then
changes to a steady tone in about 3 to 4 seconds.
When you press the key and release it, the capacitor
discharges and starts the siren sound again.
Refer to the schematic. IC 1 works as a buffer and IC
2 as an astable multivibrator. The pitch changes
when the 100k
Ω
resistor increases the voltage
applied to the 10
μ
F capacitor.
Notes:
EXPERIMENT #84: HAND OPERATED SWEEP OSCILLATOR
-103-
Wiring Sequence:
o
1-29
o
2-30
o
3-116
o
5-84-70-106-114-137-121
o
89-63-131
o
64-88-92-115
o
65-87-105
o
66-82-83-91
o
68-67-81
o
90-69-113-138
o
119-124
o
122-132
Schematic