Sound Detector Hookup Guide

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Contributors: Byron J.
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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.

Schematic

We connect those parts as follows.

Fritzing Schematic

Which translates thusly onto a solderless breadboard.

Fritzing Breadboard

The assembled, operational version looks like this.

Physical Breadboard

Listening to "The Lonely Bull" by the Ventures

Sound picked up by the microphone is now translated onto the bar graph. The louder the sound is, the more LEDs light up!

A few of notes about the circuit.

  • It uses two power supply rails. An external supply was used as a source of 13 VDC. The 13V is further regulated down to 5V using an LM317 adjustable regulator. This provides the recommended minimum of 12V for the bar-graph driver, and a stable source of 5V for the Sound Detector.
    • The 5V is connected to the + rail at the top of the breadboard. It is used to power the Sound Detector, and as the anode supply for the LEDs.
    • The 13V is on the lower + rail, and is the power supply for the LM3916.
  • The 100K Ohm resistor between pins 6 and 7 of the LM3916 sets the reference for the scaling of the bar graph. If the meter seems to be too sensitive, it can be reduced to 10K or lower.
  • Pin 6 of the LED bar graph is at one of the covered-over positions on the power rail. The leg was folded over to make contact with pin 5.
  • Pin 9 of the LM3916 sets the chip for dot or bar modes. As shown above, tied to the 13V rail, the chip is in bar mode. If pin 9 is left unconnected, the chip will be in dot mode.