Elenco 130-in-1 Electronics Playground - Manual (Page 107)

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Here’s another siren that alters its pitch. The siren we
built in our last experiment alters pitch from low to
high, but this one alters its pitch from high to low and
finally stops making any sound. When it stops, press
the key and the siren sound will start again.
Set the switch to position B and put together the
circuit. When you finish the wiring, slide the switch to
position A to turn on the power. You hear a high-
pitched siren sound that becomes progressively
lower, it sounds like a falling bomb. Press the key to
start the sound again.
Like the siren in our last experiment, this siren uses
IC 1 as a buffer and IC 2 as an astable multivibrator.
The capacitor C and the resistor R change the pitch
of the siren sound. The pitch adjusts slowly when you
increase the values of C and R, and adjusts quickly
when you decrease their values. Try using the 3.3
μF
capacitor for C and notice how the pitch changes.
Notes:
EXPERIMENT #88: FALLING BOMB
Wiring Sequence:
1-29
2-30
3-116
5-84-94-106-70-121
63-113-131-138
64-90-92-115
65-105-89
66-82-83-91
68-67-81
93-69-114-137
119-124
122-132
Schematic