Six LED stereo VU display circuit built with IC LM3915

The figure below is a scheme diagram of a six-LED three-dimensional VU display circuit built using the dot/bar display driver IC LM3915. This VU display should be connected before the amplifier module circuit. You can connect this circuit to a preamp output, tone control input/output, or equalizer input/output. This circuit is powered by 12V DC power supply.

About LM3915:

The LM3915 is a monolithic integrated circuit that senses analog voltage levels and drives ten LEDs, LCDs, or vacuum fluorescent displays, providing a logarithmic 3 dB/step analog display. One pin changes the display from a bar graph to a moving dot display. LED current drive is adjustable and programmable, eliminating the need for current limiting resistors.

The LM3915's 3 dB/step display is suitable for signals with a wide dynamic range, such as audio level, power, light intensity or vibration. Audio applications include average or peak level indicators, power meters, and RF signal strength meters. Replacing traditional gauges with LED bar graphs allows for faster response, a more robust display and high visibility, while maintaining the ease of interpretation of an analog display.

The LM3915 is very easy to apply. In addition to 10 LEDs, a 1.2V full-scale meter requires only one resistor. An additional resistor sets the full-scale range from 1.2V to 12V, independent of the supply voltage. The brightness of the LED is easily controlled with a single potentiometer.