Elenco Projects 102-305 - Manual (Page 20)

-19-
Project #134
OBJECTIVE: To make a circuit that
buzzes when the lights are off.
Buzzing in
the Dark
Project #136
High Frequency
Touch Buzzer
OBJECTIVE: To build a high frequency
human buzzer oscillator.
Replace the speaker (SP) with the 6V lamp
(L2). Now touching your fingers between B1
and D1 creates a quieter but more pleasant
buzzing sound.
Project #137
High Frequency
Water Buzzer
OBJECTIVE: To build a high frequency
water buzzer oscillator.
Now connect two (2) jumpers to points B1 and
D1 (that you were touching with your fingers)
and place the loose ends into a cup of water.
The sound will not be much different now,
because your body is mostly water and so the
circuit resistance has not changed much.
Project #138
Mosquito
OBJECTIVE: To make a buzz like a
mosquito.
Place the photoresistor (RP) into the circuit in
project #137 across where you were
connecting the jumpers (points B1 and D1 on
the grid, and as shown in project #134). Now
the buzz sounds like a mosquito.
Project #135
Touch Buzzer
OBJECTIVE: To build a human buzzer
oscillator.
Remove the photoresistor (RP) from the
circuit in project #134 and instead touch your
fingers across where it used to be (points B1
and 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.