Picture of Battery Powered Portable VU Meter
What follows are instructions for constructing a battery powered portable VU meter, as well as detailed instructions for the construction of the PCB needed to complete this project. It was designed to illuminate from 0-10 LEDs depending on ambient sound levels. I designed it to be attached to a wristband, clothing, or a necklace if the design is scaled down somewhat. Its purpose is to be worn in a nightclub or similar locale where music is playing, as an animated alternative to a glow stick. It can be used, however, for a variety of alternative purposes.
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Step 1: Materials Required

Picture of Materials Required
SMT Components.JPG
UV Exposure Board.JPG
Processing Chemical Bottles.JPG
For this project, you will need the following materials:
1. 1 LM3916 IC
2. 1 LM386 IC
3. 10 LEDs
4. 1 UV Reactive PCB Board
5. 1 18 pin IC socket
6. 1 8 pin IC Socket
7. Various SMT Resistors
8. 1 Dremel tool
9. 1 UV Exposure box
10. Developing chemical
11. Etchant (I use Ferric Chloride)
12. 1 Fine soldering pencil
13. Fine silver-bearing solder
14. 4 3v coin cell batteries
15. 2 Sockets for 2 coin cell batteries each
16. 1 switch
17. 1 electret microphone
18. 3 (1 uf SMT capacitors)
19. Denatured or Isopropyl alcohol
In a pinch some of these components may be purchased from Radioshack but your best bet is to buy them from or from Frys Electronics, or other equivalent local electronics parts retailer.

Step 2: Preparing the PCB Artwork

Picture of Preparing the PCB Artwork
Transparent PCB Positive.JPG
I created the PCB artwork in a program called ExpressPCB, which is available for free download and is surprisingly functional. The resultant artwork is pictured on this page. Next, I printed out the PCB artwork on a transparency. When printing the top copper layer of he PCB within ExpressPCB, the yellow component outlines are not printed, only the red traces are printed. I then cut out the printed portion of the artwork. This will define the size and shape of the PCB. The third picture is a screen shot of ExpressPCB showing labels for all of the components.
 if you use the ''large'' sized smd components, it's really easy...
yeah, but i dont hae any smd omponents, just regular ones
 you can bend a nd cut the leads on through hole components, i have an eduino completely assembled with through hole components, on an smd board.
Zem Vlorbschnat4 years ago
zack2474 years ago
can i swap out the microphone with an audio jack for an mp3 player?
Vlorbschnat (author)  zack2474 years ago
That should work fine, the voltage output from an mp3 player is going to be higher than the voltage from the microphone, though. It could work if you just connect the mp3 player output directly to the LM3916 IC rather than passing it through the LM386 amplifier.
thanks. and do you know where i might find the lm3916 without purchasing it over the internet? (like in old electronics, cd players, etc)
Vlorbschnat (author)  zack2474 years ago
I'm not really sure. You might be able to find one in an old piece of equipment with a VU meter, but it would probably have to be old enough that it still uses DIP chips. You also might be able to find one at Fry's Electronics, or some other electronics store, but it is a pretty obscure IC, so it will probably be tough to find that way.
zack247 zack2474 years ago
Vlorbschnat (author)  zack2474 years ago
That looks like it should work fine, I think.
nak6 years ago
Howdy, I've been drawing out a schematic from your PCB design, and was just wondering if there was a reason for the 2x(1 uF) capacitors in parallel instead of using a single capacitor?
Vlorbschnat (author)  nak6 years ago
No, I just happened to have some 1 uf capacitors on hand so it was easier to parallel two of them than buy some new ones
nak Vlorbschnat6 years ago
ok dokie, I'll post a modified schematic sometime for the community, I want to test it all out first before I do that though!
We've been waiting...
du fox nak4 years ago
what components would i need to swap out if i wanted to run this off +6v?

thanks, awesome instructible!
Vlorbschnat (author)  du fox4 years ago
I think it should run fine off of 6v, I believe that in the circuit board version I powered it by two 3v lithium coin cells in series, so I was just supplying it with about 6v.
even though the resistor and capacitor values are different? thanks
Vlorbschnat (author)  du fox4 years ago
I believe the circuit is tolerant enough to component values that it should work fine, but if it doesn't just tell me and I'll try to get some new values to you.
sweet well parts are on the way, ill let you know what happens!
Vlorbschnat (author)  nak6 years ago
Sounds good, people have been asking me to put together a schematic for a while but I haven't had the time
happywatt4 years ago
This looks great and I'm a novice just getting started. Before attempting to do this I'd like to see if I could build it on a breadboard and test it before trying to build it on an actual working model, do you have a schematic for the circuit that you could send me? Also, will a LM3916 work just as well or do you need to stick to the LM3914? Thanks,
Vlorbschnat (author)  happywatt4 years ago
Both the LM3916 and the LM3914 should work fine. Another Instructables member made up a schematic for this circuit and posted it here:
Demircat5 years ago
Hello again, and my apologies for the many questions. I put this together on a solder less circuit board, and it works very well! I am curious however, how would I power more than one LED per junction on the IC (I guess properly distribute milliamps somehow)? I want to make a board that essentially pulses a line of several LEDs at each junction. Thank you for any advice!
Use a transistor .
thals19925 years ago
Is there any way you can post the files you used for ExpressPCB (the SCH file and the PCB file?)
drlitzen5 years ago
Could I use a potentiometer to vary the resistance and tune the sensitivity of the display so that it only displays higher volumes, or is it a function of the microphone that affects how sensitive the display is?
alnorwich5 years ago
good project but can you list the values of resistors used please, i want to use larger radial resstors if poss. thanks
coletrain5 years ago
what kind of microphone did u use? i dont know anything about mics
Vlorbschnat (author)  coletrain5 years ago
Any kind of 2-electrode condenser or electret microphone should work, it doesn't need any internal circuitry, it just need to be in effect a tiny speaker.
baadn3wz5 years ago
What is the voltage rating of the cap?
Vlorbschnat (author)  baadn3wz5 years ago
I don't remember the exact voltage rating, but it doesn't need to be much, it only needs to be more than 6V. I'd say a 10V capacitor would be a good choice, that shouldn't be too hard to come by and it should give you a pretty good safety margin.
Thank you very much! I am a beginner in electronics and I just can't figure out on my own the specs for soe parts.
Vlorbschnat (author)  baadn3wz5 years ago
No problem, I'm glad to help
matija_cro5 years ago
I need correct name of switcher!!Please
Vlorbschnat (author)  matija_cro5 years ago
The NKK-M2024SS1W03 toggle switch, sold at Frys Electronics, should work. Any toggle switch with PCB pins should work in this application. There are a great many toggle switches that would work well sold at, but I did a cursory search and came across one that is similar in form factor to the one I used, part number 563-1150-ND. Send me an email or leave a comment if you need any more help.
carlos-felo5 years ago
It's good!
mccloudm5 years ago
Do you still have the Artwork for this PCB saved on ExpressPCB? I would like a copy of the file.
KT Gadget6 years ago
sry this might sound like a stupid question but what is the differnce between SMT resistors and the resistors with the leds on them? is just the amount of voltage drop or is there something im missing? cause im just wondering if resistors with the leds on them would work just as well.