You can use a microphone to detect sound. Here we
will make a circuit that lights the LED when the
microphone detects sound, using the speaker as a
microphone.
Slide the switch to position B and assemble the
circuit. When you finish the wiring, turn on the power
by sliding the switch to position A. Then speak into
the microphone - the speaker - or give it a light tap.
The LED flashes in response.
Look at the schematic. IC 1 acts as a microphone
amplifier - a non-inverting amplifier with a gain of
about 100. IC 2 works as a comparator. Its positive
(+) input terminal receives a reference voltage from
the battery. The output of the microphone amplifier
goes to the comparator’s negative (–) input terminal.
When this input voltage is higher than the reference
voltage, the comparator’s output level becomes low
and the LED lights.
Notes:
EXPERIMENT #95: VOICE ACTIVATED LED
Schematic
-114-
Wiring Sequence:
o
1-29
o
2-30
o
3-110
o
5-76-74-80-70-121
o
85-31-63-132
o
33-64
o
79-65-112
o
73-86-66
o
90-67-111
o
89-68-115
o
69-109
o
75-116
o
119-124
o
122-131
Содержание EP-130
Страница 11: ... 11 I ENTERTAINMENT CIRCUITS ...
Страница 26: ... 26 II BASIC SEMICONDUCTOR AND COMPONENTS CIRCUITS ...
Страница 36: ... 36 III LED DIGITAL DISPLAY CIRCUITS ...
Страница 41: ... 41 IV A TOUR THROUGH DIGITAL CIRCUITS ...
Страница 49: ... 49 V MORE ADVENTURES WITH DIGITAL CIRCUITS ...
Страница 64: ... 64 VI THE WORLD OF TRANSISTOR TRANSISTOR LOGIC ...
Страница 77: ... 77 VII APPLICATION CIRCUITS BASED ON THE OSCILLATOR ...
Страница 88: ... 88 VIII BASIC OPERATIONAL AMPLIFIER CIRCUITS ...
Страница 116: ... 116 IX MORE ADVENTURES WITH OPERATIONAL AMPLIFIERS ...
Страница 129: ... 129 X COMMUNICATION CIRCUITS ...
Страница 136: ... 136 XI TESTING AND MEASURING CIRCUITS ...