# LED VU Meter That Dances to Computer Music

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## Introduction: LED VU Meter That Dances to Computer Music

This is a cool LED project I am undertaking. The heart of this project is using the LM3914N (or similar) LED driver. Once completed this can be connected to your sound card or can be connected via a microphone element (still working on this part) for some really cool effects lto light up your room. I connected this via 4xAA rechargables. Guilt free power.

This is my first project and my first instructable so bear with me.

Also this is still a work-in-progress since there is so much I plan to do with this project. I will keep updating this if possible with updates such as not relying on a microphone, driving more LEDs, ect.

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## Step 1: What You Need.

First her is what you will need.
1 - LM3914N LEd driver
1 - 1k resistor
1 - 1M resistor (the picture shows a 10k resistor but I got best results with 1M, play around with this value to get best results)
1 - 1uF electrolytic capacitor
10 - LED (your choice of colors)
Some wire
Solderless bread board or whatever else you want to build on
4 AA batteres

Switch is optional

## Step 2: Build the Circuit and Connect the Sound Source

So I followed this schematic when I build the circuit. I used a 6V source (4AA).

Pin 5 may get a little confusing. What happens there is pin 5 goes to node "A". Node "A" attaches to a resistor (1M) which goes to ground. Node "A" also connects to the negative of the capacitor.

Other than that it is straight forwards. The negatives of the LEDs face the chip. The positive ends of the LEDs are connected to the source.

The Input. Now this is porbably the most important step. The input comes from sound card on my computer (to be able to listen and view this effect you need to get this: http://www.monoprice.com/products/product.asp?c_id=102&cp_id=10218&cs_id=1021802&p_id=667&seq=1&format=2&style=

The male end of the above goes to the sound card where you speakers are now. One female end is connected to the speakers you just unplugged. The other end will be this:
http://www.monoprice.com/products/product.asp?c_id=102&cp_id=10218&cs_id=1021802&p_id=644&seq=1&format=2&style=

You take 1 end of this and cut it and split the wire to look like the picture shown.

## Step 3: Turn on Some Songs and Sit Back and Watch

The final circuit is shown here.

This is a note from where I got the circuit drawing: "I like to see lights move to music. This project will indicate the volume level of the audio going to your speakers by lighting up LEDS. The LEDS can be any color so mix them up and really make it look good. The input of the circuit is connected to the speaker output of your audio amplifier. You want to build two identical units to indicate both right and left channels. The input signal level is adjusted by the 10k ohm VR. If you wish to make a very large scale model of this unit and hang it on your wall there is an optional output transistor that can drive many LEDS at once. The unit I built drove three LEDS for each output. The sequence of the LEDS lighting are as follows Pin 1, 18, 17, 16, 15, 14, 13, 12, 11, 10."

I only did this for 1 channel but plan add improvements.

Take a look at the video for results.

Some things I need to fix are:
All of the 10 LED's do not light up. I need to make an amplifier of some sort but dont have too much expierence in this.
Make this work with a microphone element
Add multiple LED's in place of each 1 LED (maybe 3x10 = 30LED)
Also figure out how to connect the microphone element as I have no idea what the picture below shows

## Step 4: Possible Additions to Project

Here is the mic and other possible 'mic' I have. I wish to implement one of these with the current circuit.

154 11K
89 8.4K
200 13K

## 59 Discussions

Hello,.
Can i use 1.5uF 50v capacitor instead of 1uF?i have a couple of 1.5uF's but not 1uF...

Great tut. I have done the same thing using LM3914'S in my project. you can connect as many leds to each pin as you can can supply voltage for (max20v) as the ma are user selectable (see data sheet). mine has two leds on each pin at the moment and works fine! during testing I had 4 leds on each pin to see how far it could go!

This may be a stupid question by where can I buy the LM3914N LEd driver? radio shack doesn't sell them :-/

Some Lm3914's Are selling as Cheap as 5/\$2.50 or 50 cents each.... No Kidding!!!( On E/BAY)

if any other ic is there like LM3915 because in india bangalore this ic not available please help me.

thank you sir for this interresting project
please can you help me to realise it for 120v because i want to see the different voltage between 120v and 0V on bar graph vu meter
thank you sir all my regards

Great project! take a look my blog!!

http://candelectronica.blogspot.com/2011/12/led-vu-meter-en-un-hcs08-freescale.html

This does not work. I have tried this with 6v and 12v as a power source. I hooked this up exactly the way you have it. I still can't get it to work.

I see that the LED's are connected directly to power (12v in the schematic). Is there some sort of limiting device inside the LM3914N? I don't want to end up blowing up my LED's.

I just found this schematic and built it using the LM3914N chip instead of the LM3916. https://www.instructables.com/files/orig/FX5/67GS/FLROK12R/FX567GSFLROK12R.gif
Took 10 minutes and works a charm! I tried the schematic on this page your reading now and was disappointed with the result. All LEDs were lighting up at the same time and I nearly gave up altogether! Removing the capacitor from pin1 to 8 makes it less sensitive. This is the gain controller of the LM386 btw.

I'm a newbie to electronics but am fascinated by all of this and want to make a larger unit using more LEDs. There are loads of variations using the TL071 and others.
My questions are, how do I add more LEDs? Do I need a bigger supply? Do I still use the same circuit but add different components? How do i use RGBs with this and how do i control them using different preset programs? I.e. ALL ON, STROBE, FLASHING, KNIGHTRIDER, etc. Looking at VU meter towers on youtube i am smitten with concept and want to put this into something different.
I know I ask a lot of questions but I feel like an electronics vampire recently...my thirst for knowledge is getting stronger and stronger the more I delve into this stuff!
VU Tron costume would be awesome in a night club, lol. Maybe more suited for party's though.

Anyway, if anybody can help me with suggestions on building something amazing using a VU meter apart from the norm I would love to hear your ideas. There must be loads of things you can put this stuff in.

Maybe the first helium balloon with a VU meter on it to 100'000ft with a camera on it.lol
I think too much!

Any help appreciated. Sorry for going on.

Cheers!

one question for the part that shows a PNP, where does it connect to? does it add a longer string of leds?

The base of the transistor goes (through the 1K resistor) to the IC pins(1-18) that drive the single LEDs. That portion allows the IC to turn on more LEDs. That could be used to make each segment brighter. You could also use it to make a longer string, but that wouldn't increase the resolution of the display.

The output of the transistor is where each PNP is used to connect multiple LEDs. For example output 10 would be connected to the PNP via the 1k resistor. Each output can have a PNP circuit if you chose to add that many LEDs.

can i use 1watt luxeon leds here, what transistor can i use? the output is very low to drive the luxeon tnx
im using a cell charger at 8v

i tried using 2 3904 driving a tip31c but the leds are litted even without sound and the other leds just stay lit only 1 is working

Try adding a 4u7 capacitor going from the positive rail to pin 7 of the LM3915 in this project? It should give some rather pleasing results especially in LED intensity for this project! It will hopefully sort out the fact that only 3 LEDs are lighting! Let me know how you get on.