Elenco Snap Circuits SOUND &reg - Manual (Page 86)

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/scs185/ 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 1, 6, or 25-26.
Make sound with the keyboard and see what its frequency content looks like.
See the Spectrum Project 188
Project #B1
See the Sound
This circuit uses the color organ module (U22) from the SCL-175
set. Build the circuit as shown, turn off the left slide switch (S1),
and turn on the right slide switch. Press keys on the keyboard to
make sounds and change the light on the color organ. Turn on the
left slide switch to add optical control, and wave your hand over
the photoresistor to also change the sound and light. If desired,
add one of the SCL-175 LED attachments on the color organ.
BONUS CIRCUIT FOR SNAP CIRCUITS ® LIGHT OWNERS
-85-
If you own Snap Circuits ® LIGHT (Model SCL-175), then
you may also build this circuit. Do not connect additional
voltage sources from other sets, or you may damage
your parts. Contact Elenco
® if you have any questions.