5-Level VU Meter

LED VU meter provides visual indication of audio signal strength. Aside from audio applications, a lot of people find this device useful for other purpose, such as sensor indicator, battery charge monitor, and countless of others. But measuring signal strength is not the main motivating factor why most experimenters would want to build this. It is, well, for the light show!

For whatever reasons you may have, here is one VU meter you can build with just a few components.

Photo 1. A 5 level VU meter using AN6884 assembled on a perforated   prototyping PCB. 

Schematic diagram of the simple V.U. Meter. R resistance value  depends on the supply voltage. A 47 ohms resistor will make the circuit work nicely with a supply voltage ranging from 8.0V to 12.0Vdc. The VU meter has a logarithmic response in relation to the signal input. Pin6 LED is the topmost led and will light if the input signal level is raised to about 6db. Pin 4-1 levels are as follows:

            Pin 4 – Yellow, 3dB
            Pin 3 – Green, 0dB
            Pin 2 – Green, -5dB
            Pin 1- Green, -10dB

If you want the VU meter to respond do DC voltage as well, you can omit the 2u2 input coupling capacitor.

Left photo shows the component layout of the VU meter. The prototyping board I used to construct this has isolated pads for each mounting holes. This allows me arrange the component in any way I want.

copper and wiring side is shown with a large photo to enable you to examine the wirings in detail. The red and black wire in the photo goes to a 9V source. The circuit will work on a wide power supply voltage range, as such, it does not require a regulated power source.

Bill of Materials

AN6884 IC - 1pc
RED LED d5mm - 1pc
YEL LED d5mm - 1pc
GRN LED d5mm - 3pcs
RES 10K - 1pc
RES 47ohms - 1pc
VRES 10K - 1pc
ECAP 10uF/16V - 1pc
ECAP 2u2u/16V - 1pc
Prototyping PCB 5x7cm - 1pc
Battery Sna - 1pc

Approximate cost of parts: P80.00
Parts available @ e-Gizmo.com