VU meter circuit Stereo/Mono 20 LED with PCB

Here are LM3914/LM3915 VU meter circuit projects. They can display with 20 LEDs on stereo, or mono with 10 LEDs for all audio system.

Also, we can easily build and cheap. We will be happy when use them.

Do you believe it or not? I have seen VU meters for more than 40 years. Until now, it is still very popular. Why is that? Read below.

VU meter circuit Stereo_Mono 20 LED with PCB

I have made a lot of amplifiers. Because I like to listen to music. Also, I like the VU Meter circuits, too. They show the power level of the audio. It is so beautiful.

Many friends may prefer them same me. When you go to an electronics store to buy a VU meter KIT. In pattern, assemble the various parts by their own and ready usage.

Why should build the LM3914 VU Meter circuit?

Most freiends choose the LM3914 VU meter circuit. Because it is convenient, easy to modify in many form.

Today I assemble these circuits using this IC. Sometimes you are looking for ideas on this

For example:

The flashing lights by the music, to decorate the Christmas tree, exotic, and unique.

This project is very easy. Because of use alone IC only and a few external components.

The display system can drive directly LED up to 10 LEDs and display as light running is DOT or BAR as you want. See the circuit below.

The working principle

LM3915/ 20 LED VU meter circuit


Electronic VU meter circuit diagram using LM3914 / LM3915

The main of this circuit is LM3914N or LM3915. Which the external circuit is the same.

Difference of LM3914 & LM3915

  • LM3914N will display an amplitude of a signal in Linear form.
  • LM3915N will display the signal in Logarithm form.
  • LM3916N: Update The outputs can drive, LCDs, vacuum fluorescents, and incandescent bulbs, as well as LEDs of any color

Normally if using the amplitude of the sound signal. We should use the LM3915N.

Thanks ODX: we can use LM3916 for this circuit, too.

See in the circuit above again.

The input signal from the power amplifier will be entered through to Voltage Doubler circuit consists of C1, C2, D1, D2.

They will convert sound signal voltage to DC voltage and have amplitude are 2 times of the input signal.

Then, insert a single to input pin 5 of IC1.

And next IC will compare the signal amplitude, to drive LEDs display follows the amplitude of input signal as above.

The Mode selection in working of the circuit. To display in DOT or BAR form. We can select switch S1 to control pin 9 of IC1.

Which if release the switch S1, it will display the bar form.

But connected pin 9 through switch S1 to a positive voltage of the circuit. It will display in the DOT form immediately.

The power supply

This circuit requires 9V to 12V power supply. we have 2 options to do easily.

Build this project

First of all, make the PCB layout in stereo or mono as you want.

Stereo VU meter PCB layout

Then see Mono form here.

Mono VU meter PCB layout

Secondly, Soldering all components into the PCB, as you see in (stereo form).

Components layout of Stereo VU meter

and Mono form.

Component layout of mono VU meter LM3915
The component layout of Mono VU meter

Caution:

Polarity of LED must be placed correctly. If you reverse the polarity, the LED does not light.

The Shopping lists


IC1: LM3914N, LM3915N, LM3916 Dot/Bar Display Driver
D1, D2: 1N4148, 75V 150mA Diodes

0.25W Resistors, tolerance: 5%
R1: 10K
R2: 2K
R3: 3.9K

Electrolytic Capacitors
C1, C2: 1uF 50V
C3: 47uF 16V
LED1-LED10, LED 2x5mm LEDs.

Note:
1. If you need to print the PCB layout please check 200 dpi per inch on the image scale.

2. In PCB layout does not have C3. But we can add it power supply terminal. Or if you use a regulator. You may not use it.

3. If you not like this circuit please look at:

Transistor VU meter

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I always try to make Electronics Learning Easy.

Apichet Garaipoom

I love the electronic circuits. I will collect a lot of circuit electronics to teach my son and are useful for everyone.
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