Elenco 130-in-1 Electronics Playground - Manual (Page 125)

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This circuit produces light and sound when it detects
your voice or any other sound. The earphone acts as
a microphone. IC 1 amplifies sounds picked up by the
microphone. Diodes Da and Db rectify the amplified
signal - that is, they convert the sound signal from AC
to DC. The signal travels through IC 2, the
comparator, and activates the LED and the speaker.
When you complete the circuit, rotate the control fully
counter-clockwise, and set the switch to position A.
Then rotate the control clockwise while speaking into
the microphone, and set the control in a position
where the LED only lights when you speak into the
microphone. Stop speaking and the LED turns off.
Now disconnect the wire between 57 and 62, and
reconnect it between 57 and 32. See what happens
to the speaker and LED when you blow into the
microphone (earphone).
Notes:
EXPERIMENT #105: SUPER SOUND ALARM
Wiring Sequence:
75-63-28-131
29-76
30-47
31-64
46-86
56-77-110
58-59-60-79-78
85-80-61-109
66-83
67-90-73
68-89-71
87-69-113
74-111
84-91-115-127
112-129-128
49-50-51-53-54-135
114-13-EARPHONE
122-132
27-65
57-26-121-130-48-116-70-92-88-62-33-72-14-EARPHONE
119-124-134
Schematic