Introduction: Simple 20 LED Vu Meter Using LM3915

The idea of making a VU meter has been on my project list for a long time. And finally I can make it now.

The VU meter is a circuit for an indicator of the audio signal strength. The VU meter circuit is usually applied to an amplifier circuit so that the level of audio power can be determined by certain parameter settings which will be displayed in the form of light from the LED.

The number of LEDs used for indicators varies depending on the manufacturer. For the VU meter that I made, I used 20 LEDs. To make it more interesting, I divided my led colors into 3, namely 12 green, 5 orange, 3 red.

Step 1: Watch the Video!

The video gives you all information you need to build this project. But in the next steps you can find a parts list, schematic and reference pictures for your convenience.

Video : https://youtu.be/stXMA4m1m-o

Step 2: What Do You Need??

Of course, what is needed to make this project is an electronic component. And below are the components needed along with a little explanation:

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 regulated and programmable, eliminating the need for current limiting resistors. The whole display system can operate from a single supply as low as 3V or as high as 25V.

LM358 is a dual op-amp IC integrated with two op-amps powered by a common power supply. It can be considered as one half of LM324 Quad op-amp which contains four op-amps with common power supply. The differential input voltage range can be equal to that of power supply voltage. The default input offset voltage is very low which is of magnitude 2mV. The typical supply current is 500uA independent of the supply voltage range and a maximum current of 700uA. The operating temperature ranges from 0˚C to 70˚C at ambient whereas the maximum junction temperature can be up to 150˚C. in this circuit, I use the LM358 op-amp to raise the audio signal level.

• 20*LED

In simple terms, LEDs are electronic components that can emit light. in this circuit I use the LED to display the audio signal strength level.

• 1*Mic

there are two sound sources for the VU meter that I made. The first comes from the music amplifier input and the second comes from the Microphone. by using a microphone vu meter can measure the audio signal that comes from the surroundings, for example, human voices and so on

• 1*Trimpot

trimpot including variable resistor type. in this circuit I use it to control the audio signal from the microphone to the LM3915 IC input

• 1*PCB

PCB has an important role in this project. PCB is used as a place for components and circuit lines. So that the VU meter can work as desired. For the process of making PCB I will explain in the next step

• Pasif Componen

An IC sometimes requires supporting passive components such as resistors and capacitors. Including IC LM3915 and LM358 which require passive components. The following is a list of the passive components used: - 2*100n, - 5*2k7, - 2*0R. - 2*470uF

• Cable

several cables are needed to connect the audio input and the VU meter module

Step 3: PCB Schematic and Layout

Here you can find PCB schematics and layouts. Schematic and layout can be seen in the image above. Besides images, I also provide them in PDF form which can be downloaded below:

Step 4: Order PCB on PCBWay

To make PCB 2 layer PCB with good quality. I use PCBWay services to make a 2 layer PCB for this VU meter project. You can see the finished 2 layer PCB in the image above.

The gerber file to make this VU meter PCB can be downloaded below

Step 5: Inserting Components

This VU meter module has several modes that can be used.

• 20 LED Mono Vu meter.
• Streo VU meter (10 LED / ch).
• Music VU meter.
• Mic VU meter.

In each mode, it is necessary to adjust the components installed.

In this article I will make a VU meter with 20 LED Mono VU Meter mode with audio music input. For component configuration see schematic. For schemes that are marked with a cross means that they do not need to be installed

Step 6: Results and Testing

The image above is a form of the VU meter module that I made.

For examples of other series you can visit my youtube channel here: https://www.youtube.com/c/mrsottong

or my other platform here: https://www.pcbway.com/project/member/?bmbno=E204445A-DE2C-40