AUDIO POWER METER circuit WITH LM3915

This VU (volume-unit) meter is capable of monitoring and displaying

power levels present at the speaker terminals of a stereo audio

power amplifier.


The levels are displayed in ten discrete steps. This meter is not

designed to give an accurate display of the power levels.It is

designed to give an approximate visual indication of the audio

power output of each channel. For many situations - disco, parties this

is all which is required: the flashing LED's add atmosphere to the

situation.

LM3915. This is a monolithic Dot/Bar Display Driver IC made by

National Semiconductor. It takes an analog voltage input on pin 5

then drives 10 LED's providing a logarithmic 3dB/step analog display.

When measuring power, a 3dB increase means that the power input

has doubled. As the power doubles, an additional LED will be lit until

the maximum is reached. The display can be bar or moving dot

depending on the connection of pin 9 to the positive supply. The LED

drive current is regulated which eliminates the need for current

limiting resistors.

The supply voltage can be between 3V to 25V.