Elenco Electronics 202 - Manual (Page 70)

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Project #153
OBJECTIVE: To build a circuit that makes a loud whine.
Whiner
Project #154
Hummer
OBJECTIVE: To show how adding
capacitance reduces frequency.
Now place the 0.1 μF capacitor (C2) above
the 0.02 μF capacitor (C1) and vary the
adjustable resistor (RV) again. The frequency
(or pitch) of the whine has been reduced by
the greater added capacitance and it sounds
more like a hum now.
Project #155
Adjustable
Metronome
OBJECTIVE: To build an adjustable
electronic metronome.
Now place the 10 μF capacitor (C3, positive
“+” side on right) above the 0.02 μF capacitor
(C1) and vary the adjustable resistor (RV)
again. There is no hum now but instead there
is a click and a flash of light repeating about
once a second, like the “beat” of a sound. It
is like a metronome, which is used to keep
time for the rhythm of a song.
Project #156
Quiet Flasher
OBJECTIVE: To make a blinking
flashlight.
Leave the 10 μF capacitor (C3) connected but
replace the speaker (SP) with the 6V lamp
(L2).
Build the circuit, turn it on, and move the setting on the adjustable
resistor (RV). It makes a loud, annoying, whining sound. The green
LED (D2) appears to be on, but it is actually flashing at a very fast rate.