Wiring Diagram

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VU METER 10 LED CIRCUIT SCHEMATIC DIAGRAM

The LED VU meter is simpler and smaller than it's analogue counterpart, and is very common in audio equipment. This version is based on a National Semiconductor IC, and uses the logarithmic version. Each LED operates with a 3dB difference from the previous one, and a jumper is provided to allow dot or bar mode.

The circuit is completely conventional, and is based on the application notes from National Semiconductor. The circuit is shown picture below and as you can see it uses a single IC and a few discrete components. DC to the LEDs is almost unfiltered - C1 is included to make sure the IC does not oscillate, and is not a filter cap. This allows a higher LED current with lower dissipation than would be the case if the DC were fully smoothed, and full smoothing would also require a much larger capacitor. This increases the size and cost of the project - especially important if it is to be used in larger numbers as may be the case with a mixer or analyser.