Build Your Own 8-LED VU Meter Circuit – Power Levels Explained

Description

The circuit presented below employs two dual comparator modules (LM339) to control the brightness of a series of eight light-emitting diodes, thereby visualizing volume levels. Each of the eight comparators is configured with voltage dividers adjusted to progressively increasing voltages. This arrangement causes the rightmost LED to activate initially when the input signal reaches approximately 400 millivolts, corresponding to roughly 22 milliwatts at a 8-ohm system. The dividers' settings ensure that each LED represents approximately twice the power level of the preceding one, extending the scale from 22 milliwatts to about 2.5 watts when all LEDs are illuminated. The system's sensitivity can be reduced via the input control to accommodate higher signal levels. It's important to note that this circuit has not been constructed or evaluated by the author; therefore, feedback regarding its functionality is greatly appreciated. The expected power distribution amongst the LEDs is as follows:

Circuit diagram