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10 LED VU Meter Project by LM3915 and LM324

Project Summary

VU (Volume Unit) meters are often included in analog audio equipments to display a signal level in Visual Units. We are building a mono input VU meter in this project. You can build one pair to use them in stereo mode.

Project Description


Figure 1 

Input sensitivity is about 1 Volt rms, up to +6dB. You can adjust the input amplitude by using the multiturn 50k linear potentiometer (POT1). Circuit needs symmetric ±12V power supply because of the LM324 opamp. We used metal film resistors (1% tolerance) so accuracy is sufficiently high. Visual duration can be adjusted by using linear 10k potentiometer (POT2). LEDs should be 5mm x 5mm in size for best fit. But we used standard LEDs and this caused a little shift as you can see from the image. Dot/Bar switch determines the operation mode of LM3915.


Figure 2 

The PCB file is provided in pdf format. You can apply it to the board by using the ironing method.

Click here to watch the project video.

Project Files

File NameFile Size
Schematic, Layout and PCB files510.22 KB
Tags: LED, Volume, Unit, Meter

Comments on this Project:

By humprey gikungu 0Score: 

7 years ago:  How can i get access to the actual circuit diagram

By s.h -1Score: 

7 years ago:  you can see the download link above

"Click here to download schematic, layout and PCB files."

By Jass 0Score: 

7 years ago:  what are the components please...?

By Hi 0Score: 

7 years ago:  When you download the schematic, you can see the components on it.

By alp 0Score: 

7 years ago:  thank you my frend

By Diogo 0Score: 

6 years ago:  have a problem using one or lm324n a lm324 opamp?

By Jun 0Score: 

6 years ago:  how is it connected? what is the input?

By mathew 0Score: 

6 years ago:  so can u hook it up to speakers? if so wat wattage cuz i dont understand the whole volts to watts thing. or can u hook it up to the rca pluggs on a car amp?

By mian 0Score: 

6 years ago:  Need schematic Diagram of this circuit.

By Nick 0Score: 

5 years ago:  Can you please tell me where you bought all of your components? Did you get them from a single online store?


By Alexandre 0Score: 

5 years ago:  People is lazy to even read, what a shame!!!

By tech 0Score: 

5 years ago:  VU does not stand for "voltage unit". It stands for "volume units". Please correct this.

By aiza siguerra 0Score: 

5 years ago:  i'm just wondering, where is the input stage for this circuit? :)

By zaza pachulia 0Score: 

5 years ago:  This is a nice project! I will ask my students to make modifications on this based on their creativity :)

By hinder 0Score: 

5 years ago:  it can be adjust the glowing of light or maybe it can be stable to glow, when the audio signal is fed into it?

By bluwy 0Score: 

5 years ago:  how the entries on this circuit? whether using mono jack socket?

By egm 0Score: 

4 years ago:  Hi, any idea if instead of leds, I connect triac's to 220V lamps, so as to make a giant VU meter, will it work?
Any specific triac code you wanna propose?

By Jessica Miller 0Score: 

4 years ago:  Hi
Nice project!

I would like to know how many watt does the potentiometers need?
10k ohm
50k ohm

Because there are different potentiometers with different watt numbers, so I dont know whitch one i should buy..

can I also use blue leds? 3.5V

what does LED's optocoupler in your shematic means?
can i also put two leds (blue) in series on every of these 10 channels?

By mark 0Score: 

4 years ago:  hi!i am building the same project as my final project for logic circuit...i use the pdf version of the pcb layout and it is not working properly...when i turn on the power supply all led turns on...even w/out audio signal..hwat should i do??plz replay!!i really need help.any suggestion will desperate.i dont want to fail...HEEELLLP!!asap ..thank you!!

By Zeraphine 0Score: 

4 years ago:  @ Mark, the PCB layout on the PDF is not mirrored so if you use the Toner transfer method without mirroring it first, the circuit wont work at all, I think the author should upload a pdf that has a mirrored PCB layout :)

By M28 0Score: 

3 years ago:  Hi

Nice project. What type of LEDs did you use?

By Dr. Electron 0Score: 

3 years ago:  People, are you retarded? All is listed and explained. M28 What type?! He used 5mm blured LEDs... OMG! :D

By Christian 0Score: 

3 years ago:  I noticed your capacitor in your schematic diagram, the one connected to the negative supply is in wrong polarity. That should be corrected, and so far that's all i have noticed.

By JP 0Score: 

3 years ago:  Hi guys , sorry if this is a stupid question , but would it be possible to modify this so that the input voltage will work of around 2.5 millivolt to a maximum ( all leds on ) @ 40 millivolt ? I want to connect this to a " K thermocouple " to make a custom EGT gauge .

Thanks , JP

gam Aziz
By gam Aziz (0) 0Score: 

1 year ago:  please can you help me to realize this project sir??
my signal have 120V max and i want to see this signal on bar graph led

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