VU Meter Project

This circuit uses the popular LM3914 IC, a monolithic dot/bar display driver. It senses an analog voltage level and drives ten LEDs, providing a linear visual display. It's a simple way to create an impressive audio visualizer.

1. Understanding the LM3914: This IC contains a set of 10 comparators that compare the input voltage to a reference voltage. As the input voltage increases, more comparators turn on, lighting up more LEDs.
2. Assemble the Circuit:
   • Connect Pin 9 (Mode Select) to Pin 3 (+9V). This puts the IC in "Bar Graph" mode. For "Dot Mode", leave Pin 9 disconnected.
   • Connect Pin 3 (V+) and the anodes (+) of all 10 LEDs to the +9V supply.
   • Connect Pin 2 (V-) and Pin 4 (R_LO) to Ground (GND).
   • Connect the cathodes (-) of the LEDs to the output pins of the LM3914, starting with LED 1 to Pin 1, LED 2 to Pin 18, LED 3 to Pin 17, and so on, down to LED 10 at Pin 10.
   • Create the reference voltage divider: connect the 1.2kΩ resistor between Pin 7 (REF ADJ) and Pin 8 (REF OUT). The potentiometer is used for sensitivity control.
   • Connect the audio input (from a 3.5mm jack) to Pin 5 (Signal). Connect the ground of the jack to the circuit's ground.
3. Calibrate and Test: Power the circuit and play some audio through the input jack. You should see the LEDs light up in response to the volume. Adjust the 10kΩ potentiometer to change the sensitivity of the display.