Data Sheet

-105-
229. Sampling
Replace the switch (62) with the press switch (61) and replace the speaker
(93) with the lamp (76) in project #213. Connect points C and D with a 4-wire
(4), press the press switch (61) and you will see the lamp (76) is ashing
quickly. Sampling is a method for digitally encoding sound signals including
music. The idea is to sample the amplitude of the sound signal at regular
points in time, and then encode these samples into a binary bit stream that
can be stored and retrieved for future recreation of the sound signal.
230. Nyquist Theorem
Replace the switch (62) with the press switch (61) and replace the speaker
(93) with the lamp (76) in project #213. Connect points G and H using
4-wires (4), press the press switch (61) and you will see the lamp (76)
ashing slowly. The Nyquist Theorem relates to the minimum sampling
rate needed to perfectly be able to reconstruct the original signal from
the samples. The Nyquist Theorem states that if sampling is performed
at least at twice the highest frequency component of the signal, then
theoretically the signal can be perfectly recovered from the samples.
231. Digital to Analog Reconstruction
Replace the switch (62) with the press switch (61) and replace the speaker
(93) with the heart LED (69) in project #213. Connect points C and D with a
4-wire (4), press the press switch (61) and you will see the heart LED (69) is
ashing quickly. While the Nyquist Theorem states that it’s theoretically possible
to recreate an analog signal from its samples (assuming the samples meet the
Nyquist Criteria), it turns out that the lter needed to exactly reproduce the
original analog signal is practically impossible to implement. However, practical
smoothing lters can be used to reproduce a very close replica of the original
analog signal. Think of this as like connecting the dots between the amplitude
samples to get something that looks very much like the original analog signal.
232. The 3-in-1 Module
Replace the switch (62) with the press switch (61) and replace the speaker
(93) with the heart LED (69) in project #213. Connect points G and H with a
4-wire (4), press the press switch (61) and you will see the heart LED (69) is
ashing slowly. The 3-in-1 module (11) has the music and sounds it produces
stored in an IC in a digital format and uses techniques discussed in the
previous projects to create the audio signals it sends to the heart LED (69).
+
–
[ 229 - 232 ]