First, using the external interrupt facility, the Arduino observes the gate output, and sets the onboard (pin
13) LED to follow the gate status.
Second, in the loop() routine, it uses an analog input to periodically sample the envelope signal. That value
is interpreted into a message indicating the current loudness via a series of thresholds.
Analog Example
As a purely analog circuit, the Sound Detector isn’t limited to strictly being a peripheral for a microcontroller. To
illustrate an alternate application, we’ve wired up a completely analog example. We’ve tied the envelope output to
an LM3916 VU bar-graph LED driver, to make a visual sound level meter. For this application, the Sound Detector
is configured with no resistor for R17, and the default 100K in position R3.
Materials
Again, we start with the Sound Detector, then add the following parts.
Dot/Bar Display Driver - LM3916 (VU Taper)
(2) Electrolytic Decoupling Capacitors - 10uF/25V
Voltage Regulator - Adjustable
Resistor Kit - 1/4W (500 total)
10 Segment LED Bar Graph - Red
Wall Adapter Power Supply - 12VDC 600mA
Schematic
We connect those parts as follows.