Elenco Electronics 202 - Manual (Page 62)

-61-
Project #123
OBJECTIVE: To make a
circuit that buzzes when the
lights are off.
Buzzing in
the Dark
Project #125
High-Frequency
Touch Buzzer
OBJECTIVE: To build a high frequency
human buzzer oscillator.
Now place the 6V lamp (L2) across the points
marked A & B (in parallel with the speaker,
SP). Now touching your fingers between B1
& D1 creates a higher frequency sound.
Project #126
Mosquito
OBJECTIVE: To build an oscillator
circuit.
Place the photoresistor (RP) into the circuit in
project #126 across where you were
connecting the jumpers (points B1 & D1 on
the grid, and as shown in project #123). Now
the buzz sounds like a mosquito.
Project #127
Loud Mosquito
OBJECTIVE: To build an oscillator
circuit.
Now place the 10 μF capacitor (C3) across
the points marked C & D (in parallel with the
0.1
μF capacitor, C2) and remove the 6V lamp
(L2). Now the sound is much louder.
Project #124
Touch Buzzer
OBJECTIVE: To build a human buzzer
oscillator.
Remove the photoresistor (RP) from the
circuit in project #123 and instead touch your
fingers across where it used to be (points B1
& D1 on the grid) to hear a cute buzzing
sound.
The circuit works because of the resistance in
your body. If you put back the photoresistor
and partially cover it, you should be able to
make the same resistance your body did, and
get the same sound.
This circuit makes a high-
frequency screaming sound
when light shines on the
photoresistor (RP), and makes
a buzzing sound when you
shield the photoresistor.