Audio - Arduino Sketches: Tools and Techniques for Programming Wizardry - page 299

documentation states that the +Vs pin must have at least 4 V, but the Arduino
Due is powered only by 3.3 V. On the Arduino Due, there are two voltage pins:
3.3 V and 5 V. For this example, the LM35 will be powered by the +5-V pin.
For other components, this might have been a problem; the Arduino Due is
powered at 3.3 V, and the inputs expect to have 3.3 V or lower; applying 5 V to
an input could damage the microcontroller. The LM35, however, can safely be
powered by +5 V in this application because the output is equivalent to 10 mV
per degree Celsius, or 1.5 V for 150 degrees. Therefore, the LM35 can safely be
powered by +5 V because it will not output more than 3.3 V.
The button will be connected to digital pin 2. It will be powered by 3.3 V and
connected to ground through a 10-Kilohm pull-down resistor. When the button
is open, the input will be connected to the ground, resulting in a logical zero.
When the button is pressed, the input will be connected to 3.3 V, resulting in
a logical 1.
Finally, the audio output will be connected to DAC0. Remember, this is only
a signal; it is not strong enough to power a speaker. Using too much power will
result in damage to the Arduino. To output audio, the schematic uses a jack con-
nector. Most home Hi-Fi systems or mobile speakers use a jack input, usually
by using a male-to-male jack cable. It uses the same connecter you would use
to connect your MP3 player to the speaker.
Figure 18-3 shows the layout for this design.
Figure 18-3: Hardware layout (Image created with Fritzing)