Manual

-105-
T
he operational amplifier (op amp) works well as an
oscillator. In this experiment, you will build an
electric buzzer that makes a continuous beep. By
r
otating the control you can change the tone of this
buzzer.
When you finish the wiring, set the control to the 12
o’clock position and press the key. From the
speaker you hear a continuous beep. Turn the
control as you press the key; the tone of the buzzer
changes.
The electronic buzzer only makes a beep, but it can
be used for many different purposes, as you’ll see
later.
This circuit is an astable multivibrator working as an
oscillator to produce a square wave signal for the
speaker. Adjusting the control changes the
frequency, so the tone of the sound is different. The
frequency is determined by the resistors and
capacitor connected to the input terminals of the
operational amplifier. Try changing the capacitor to
0.02mF or 0.1mF and see how the tone changes.
N
otes:
EXPERIMENT #86: BUZZING WITH THE OP AMP
Schematic
Wiring Sequence:
o 1-29
o 2-30
o 3-116
o 5-84-70-106-121
o 63-27-138
o 28-81
o 67-90-92-115
o 91-68-105
o 69-82-83-89
o 119-124
o 122-137
EP-130_62315RevC.qxp_EP-130_062812 6/23/15 11:17 AM Page 105