Manual

-107-
Here’s another siren that alters its pitch. The siren
w
e 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 3.3mF capacitor for C and notice how the pitch
changes.
Notes:
EXPERIMENT #88: FALLING BOMB
Wiring Sequence:
o 1-29
o 2-30
o 3-116
o 5-84-94-106-70-121
o 63-113-131-138
o 64-90-92-115
o 65-105-89
o 66-82-83-91
o 68-67-81
o 93-69-114-137
o 119-124
o 122-132
Schematic
EP-130_62315RevC.qxp_EP-130_062812 6/23/15 11:17 AM Page 107