Elenco Snap Circuits® Deluxe Sound & Light Combo - Manual (Page 156)

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This project requires a smart phone with an internet connection, so you can
download a free app. Find and download a “spectrum analyzer” app that
lets your smart phone view the frequency spectrum of a signal. Visit the
Snap Circuits ® Sound product page at
http://www.elenco.com/downloads/scc350/ to find a few suggestions.
A spectrum analyzer is an instrument that engineers use to look at the
frequency content of electrical signals, and shows which frequencies have
the most energy. A pure tone will have all its energy at a single frequency,
while a tone with overtones will have the most energy at the main tone,
but also have energy at multiples of the main tone. A complex sound will
have its energy spread across many frequencies.
Spectrum analyzers usually show data as a chart of energy content versus
frequency. Energy is usually shown in dB (decibels), a logarithmic
measurement, so the strongest frequencies have much more energy than
the weak ones shown. There is always a “noise floor” of background noise,
which can make weak signals difficult to observe.
Start the app and talk into the smart phone’s microphone, and watch the
frequency content of your voice on the screen. Try making a single tone
at different frequencies, or whistling.
Next, use the one of the keyboard (U26) circuits such as projects 186, 191, or
210-211. Make sound with the keyboard and see what its frequency content
looks like.
See the Spectrum Project 368
Project 369 Blinking Colors
Build the circuit as shown and turn on
the slide switch (S1). The white and
color LEDs (D6 & D8) are blinking.
Push the press switch (S2). Now the
red LED (D1) is blinking but the white
LED is off.
If you swap the locations of the red
and white LEDs, then the red LED will
be blinking and the white LED will be
off, and pushing the press switch
won’t change anything.
Red light is easier for LEDs to produce than
white light. When the red and white LEDs are
connected in parallel (which happens when S2
is pressed), the red LED will dominate because
it turns on more easily.
SCC-350_Manual_Part_C.qxp 7/25/14 2:11 PM Page 44