Which translates thusly onto a solderless breadboard.
The assembled, operational version looks like this.
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.
Resources and Going Further
