Instructables
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

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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)

There is a bunch of sellers at ebay.com ;)
nitrox0275 years ago
can i jsut use a PIC?
MROHM nitrox0274 months ago

You Don't Need To Program a 3914

spasha3 years ago
if any other ic is there like LM3915 because in india bangalore this ic not available please help me.
anuraj spasha6 months ago
easily available at S.P. road.
kikouu1 year ago
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
12V on schematic is connected to ground, not a good start on the project
candelo2 years ago
Great project! take a look my blog!!

http://candelectronica.blogspot.com/2011/12/led-vu-meter-en-un-hcs08-freescale.html
Wally_Z2 years ago
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.
Wally_Z2 years ago
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. http://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!
KT Gadget5 years ago
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.
supes (author)  KT Gadget5 years ago
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.
burton26633 years ago
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
andrewj413 years ago
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.
much better!!!!! but still not perfect.
phevtron3 years ago
so? how can we add the mic?
truck564 years ago
Hello,,I have built this unit a couple ways now. First,,if you use the actual speaker output from your sterio amp instead of the sound card on your pc,,all of the leds light up no problem!! I have also used a transistor on the out put pins of the chip instead of connecting them to the leds and can drive 11 leds off the transistor!! Its totals 110 leds and when connected to my sterio amp speaker output they all light up as the volume is increased. Only thing I would like to do is add an amp to the circuit board with a mic so it dosent have to be connected to a speaker at all,,just the sounds in the room should light it up !! Im NEW at this and dont really no a whole lot about electronics but if you would like any info on what i have just posted,,e-mail me at  cntruck56@hotmail.com          and i will try to help asap ! I also have a video but dont no how to put it here ??
johnybody4 years ago
All the light are reversed. The ground must be at the cathode. the ship will give a HIGH so the anode have to be by the ship.
hugoola24 years ago
Is it possible instead of using the sound output, use the hdd led ?
Werewolve5 years ago
Why did only the first 3 Led's light up?
each that LED, lights up on different frequency. first 3 LED's are probably for lower frequency's like 30 to 160 Hz other LED's are for higher frequency's 200 Hz to 16Khz. If there is a signal from 30 to 160 Hz than that 3 LED's will light up and if there is a signal from 200 Hz to 16Khz other 7 LED's will also light up so the other 7 LED's didn't light up because there wasn't higher frequency's to light them up. sorry for the bad English I'm not good at it
i think the reason they all didnt light up i believe is because the resistor value is a little high for led's i'd try a 330ohm. colors are orange orange brown gold... i used those for my led's in my speakers and with them, the leds haven't burnt out or gotten over powered even on 100% power from my 105x7 watt receiver.. nice job!!!!! im gonna try to get one built by next week and install it in my computer case
finky5555 years ago
Nice little circuit. You might want to correct the schematic, it shows the diodes connected to both +12 at the top of the string and ground at the bottom effectively shorting the power input. I like the idea of using the mic to make it portable.
Demircat5 years ago
For the optional output for multiple LEDs, does the input (point after the resistor) lead into pin 5, or somewhere else? With that, is there a recommended limit as to how many LEDs to use? Thank you!
pjahster5 years ago
3 things: 1. So I should just leave the white wire alone? It's not needed? 2. The cable shown is the M/M cable? 3. The 2 stereo jack cable isn't altered in any way, right? I am thinking of doing this for a school project, so any help would be appreciated.
I don't know about the other 2 but for #1 you do only need the two he has, I think the uncoated one is the negative and you need either the red OR the white, one goes to the left ear the other goes to the right ear but if you want separate VU meters for each ear double out the negative and run this with the red and the negative and the white with the negative
Zauk5 years ago
Which is the positive and which is the negative? I'm pretty new to electricity, so please help me out. It says '12 volts', but is it Positive or Negative?
amper665 years ago
Nice job For this circuit really work, you need an RF amplifier. I did this for me and it works very well !!! Good luck
amper665 years ago
I Just downloading and trying. I will use a LM3915 any difference with LM3914 ? thank you
this schematic did better for me. and I got all lights to display, but it was an LM3915. Ill replace it with a 14 when I get one.
audio-level-meter-1.gif
oh and by the way. i used 5v from inside my computer and the Motherboard sound output. (soldered wires on the underside of it [not recommended for the novice])
audio-level-meter-1.gif
*NOT* recommended for the novice (dumb formatting)
audio-level-meter-1.gif
Hmmm, in the Audio input, wich one is positive and wich one is negative? I guess 4 is negative but I want to be sure Thanks
4 is negative cause its tied to ground at pin 2.
RodgerE15 years ago
I built one of these. I put it in a glass flower vase with broken glass inside.
Video here
http://www.zoominternet.net/~rodgere/vumeter.avi

Video
invalid movie: http://www.zoominternet.net/~rodgere/vumeter.avi

digitalrox5 years ago
I have a problem with this, only the first 5 leds light up, i don't know why...
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