VU Meter Speakers

A VU meter is a standard measuring instrument which measures volume in audio equipment. If you open up your recording devices on Windows, you can see a digital Volume Unit (VU) meter which shows the audio level. You get analog and digital displays and each level is typically marked off with a dB value and this corresponds to the input audio level. In analog displays, the dB value is written on the back and a needle shows the current audio level. With digital displays, we use LED's and each LED that lights up, is a dB value. These values are given by the datasheet.

I decided to build my own speakers and incorporate a VU meter to add something extra to my set of speakers. We only make use of a few components, mainly a speaker, amplifier and a driver for the VU Meter, it all works out to be pretty cheap and produces good sound quality at an acceptable volume level.

We will be using a 3D printer to print the housing for our speakers and any extras that we may include. You are welcome to build your own case if you dont have a 3D printer.

In order to build our VU meter speakers, we will need a few parts that are listed below:

• 2 Watt Speaker x 2(Stereo)
• TDA 7053 x 1 (Stereo 1 Watt Amplifier IC)
• LM3915/3916 x 2 (VU Meter Driver)
• LED's (5mm) x 10
• 5k Ohm Resistors ~ 4.7k is close enough
• 1.5k Ohm Resistors
• 8.2k Ohm Resistors
• Ripcord/Speaker Wire
• Hook up wire
• 4 Way Speaker Connector x 2 (Optional)
• 1 x 3.5mm Stereo Audio Jack (Female)
• 3D Printing Filament
• Non-Slip Rubber Feet

The speakers are a bit of a problem considering every store around the world sells different sizes that may not be compatible with my design. I have removed the speaker holder in my 3D files so you can simply glue or bolt your speaker directly to the cover. If needed you can scale the model to accommodate your speaker size.

The LED's should all be diffused since it shows a nice even colour at all angles and doesnt hurt your eyes in the dark. I used 4 green, 3 yellow, 2 orange and 1 red per speaker.

The 4 way speaker connector is optional. The 3D model doesn't include holes for it since I'm assuming many people will have difficulties finding the connector that I used. You can use any connector or jack you like, or just make some holes and hard wire the speakers.

The best thing to do first is to print out the speaker housing and cover. In the files Iv'e included multiple cover designs and 2 variants of the main speaker housing. The choice of material and colours are up to you, I used 1.75mm PLA WoodFill filament which looks pretty good on my wooden desk. Some print statistics and ideas are below:

Speaker_Housing:

Speed - 50 mm/s

Infill - 25%

Raft and Support - None

Print Time - ~5 Hours

Speaker_Cover:

Speed - 50 mm/s

Infill - 50%

Raft and Support - None

Print Time - ~2.2 Hours

Speaker_Cover_2:
Speed - 50 mm/s

Infill - 25%

Raft and Support - None

Print Time - ~2 Hours

These settings worked really well for me and my printer. No supports are needed and all 3D stl files are rotated correctly and will print in the center of your bed. They are immediately print ready files.

I used a 4 way speaker terminal (http://www.mantech.co.za/ProductInfo.aspx?Item=72M...) so I will show how to mount the terminal in the above link.

If you look at the Technical Data provided on the link, you can find the measurements for the terminal. If you have a different model, I suggest using a digital caliper to measure the distances. Measure your Speaker_Housing and simply minus the length of the speaker terminal, divide that result by 2 and you have the distances from the edge that the terminal should be mounted at. With my terminal, it was around 2.5mm on each side. Then simply measure the center of one pin to the center of the next pin and mark that distance off on your housing. Once you have all the marks on your case, just line up your terminal to the marks and make sure everything is properly aligned and spaced correctly before you drill. See the 1st image to get an idea.

The next part is to drill the holes. I used my Dremel tool with a 6mm drill bit. The pins on my terminal are about 5mm but make sure to drill a larger hole because we will have to add a wire and we need the clearance. Now Dremel's don't have a collet that can handle a 6mm drill bit, the highest is 3,5mm but Dremel does make a nice set of bits from 3-6mm that fits. If you dont have one, you can order one from here. You can see a picture of the set that i have, it is the official Dremel product. Once the holes for the pins are drilled, mark off and drill the holes for the mounting screws. I used a 3mm drill bit and it worked out quite well. At this point you'll notice burs around each hole, to remove the burs, use a larger drill bit and just hand turn it and it will scrape off all the burs around the holes. This method works for removing burs on any material but for certain metals, you might have to use a drill press. You're ready to test fit your terminal, use a 3mm nut and bolt and make sure everything is lined up correctly and everything is flush to the housing. Don't tighten it just yet, we still have to add some wires.

The last step to finish off our housing is to add some non-slip pads on the base. If you look at the pictures above, I used a soft rubber pad and it holds really well on my smooth wooden table. You can use any furniture pads that are non slip, make sure to use them because the cables can pull the speakers off your table.

Something I didn't do that will help in the final steps is to sand down all the edges on the front of the housing so that everything is flat and glues nicely when you finish off the speakers.

I provided two speaker covers, I will be working with the Speaker_Housing provided in the stl files but the only difference is the grill design.

Okay so the holes located on the top of the housing are meant to hold 10 5mm LED's. The colours are up to you but I used 4 green, 3 yellow, 2 orange and 1 red, all the LED's are diffused.

The first step is to mount the LED's, I used some hot glue and put a generous amount of glue to hold each LED in place. I inserted and glued each LED one at a time. When inserting the LED's, make sure all the anodes of the LED's are in the same row, this makes it easier to connect all the anodes together. Keep in mind, this cover will need to glue to the housing so you don't want to glue on the sides otherwise it wont fit flush on the housing. If you mistakenly apply too much glue, it isn't a problem, just use a knife and trim off some glue. As you can see in my first image, I cleaned up all the sides of the glue.

Leave the glue to dry for a few minutes and make sure all the LED's are straight. Bend each anode of the LED, the anode is the longer leg, so it joins with the next LED's anode. Solder all the anodes together so we get a single common anode. This makes it easier to wire since we only need a single wire to provide the 5V to all the LED's. Do this with the anodes ONLY. The cathodes will connect to our VU meter driver.

The last step is to add wires to all the cathodes of every LED. Use some nice flexible stranded wire so you can route them in the housing nicely.

Let's get started with the wiring. The first thing we will wire up is the speaker terminal. Just solder some speaker wire to each terminal, the length doesn't matter but make it long enough so you can work comfortably. Always add heatshrink tubing to every joint. Feed each wire through their respective holes and mount the terminal permanently with two M3 bolts and 2 M3 nuts.

Because we have two speakers, since we are creating stereo audio, one speaker will house the amplifier and driver and the other speaker will just house the driver. Its your choice which speaker you want to house the amplifier, I used my right speaker. We will call the speaker which holds the amplifier the Main Speaker and the other will be called the Secondary Speaker.

For the Main Speaker there are 2 pairs of positive and negative terminals. The 1st pair is for the power and ground. The second pair is for the other speaker. Both these pairs are actually outputs however you can use the power and ground pair as an input as well. You can drill an extra hole in your housing if you want to add a dedicated power cable but thats just extra wiring which I didnt want to do.

For the Secondary Speaker, the design so far is exactly the same however the terminal wiring is a bit different. Both the pairs are inputs. The 1st pair is power and ground and the second pair is the signal from the amplifier which drives the speaker. Take a look at the images to see a simplified block diagram.

Now that the explanation of the terminals are out of the way, lets wire the Secondary Speaker. I used my left pair of terminals, looking from the front, as my audio signal. Solder the red terminal wire to the positive of the speaker and the black terminal wire to the negative sign on the speaker. Now make sure you solder 2 extra wires on the speakers, reason being is because we will use the same signal to control the LED VU meter. Check the images above.

We will not do the same steps for the main speaker because we need to connect the amplifier first and then wire the output to the speaker.

For the amplifier we will be using the TDA7053. Its a really simple stereo amplifier with a 1 watt output per channel. Its more than loud enough for any small desktop or portable use.

When making this on a vero board, strip board or PCB, make the board as small as possible, it should be small enough to fit somewhere inside the speaker housing. My board was about 2 columns wider than the IC itself when I built mine on the vero board.

I've attached the circuit diagram above, taken from the datasheet which works perfectly. The polarized capacitor on the voltage supply is for filtering and I used a 220uF cap. The other cap is a smaller non polarized cap and i used a 100nF ceramic capacitor. I used both 16v capacitors. The smaller cap is to help filter higher frequency noise on the voltage supply.

You can build this circuit as shown in the diagrams however for pin 2 and pin 6 which are the two input signals, we will be using the signal coming from our 3.5mm audio jack. Pin 1 and 7 will share the common ground signal from the audio jack which is then connected to the ground of our power supply.

On a typical 3.5mm male audio jack, the signals are left, right and common for a stereo cable. The image above shows which part of the jack carries which signal. Looking from the very end of the jack and reading backwards, we have the left, right and common channel in that order. You will need to look up the datasheet for you female jack as some pins can differ. If you dont have a datasheet, just use the continuity function of your multimeter and probe the pins to see which one corresponds to which terminal on the male plug.

Lastly you can wire up your 3.5mm female jack, solder it onto your PCB and then mount it to the case. Its fairly easy to mount, just use the nut provided with you panel mount jack and tighten it as best you can.

The VU meter is really simple to build. We are using the LM3915 bar graph display driver and the datasheet example is almost exactly the circuit we will be building. We can see that each LED's cathode is connected to a certain pin on the IC, therefore we have a common anode and each LED is driven by the IC pulling that pin to ground. As you can see, we dont need current limiting resistors since this IC is programmed to deliver even current to all LED's by using some resistors on pins 7 and 8 of the IC. For resistor R1, I used a 1.5k Ohm resistor and for R2, I used an 8.2k Ohm resistor. This will deliver about 12-13mA per LED. I know this seems low but do you really want a bright red LED shining in your eyes running off 20mA while youre on your PC at night? Also it's a waste of power, this is also meant to be practical to use in portable applications.

The signal source is what comes from the speaker, pin 5 is connected to the '+' of your speaker and pin 4 gets connected to the '-' of the speaker. In the datasheet, it says to ground the '-' signal, DO NOT do this. The TDA7053 states not to ground the output signal of the amplifier.

There is no need for the tantalum capacitor because our LED's arent 6" or further from our IC.

Pin 9 is the mode select pin. This allows it to function in either bar graph or dot display mode. I have mine set up to operate as a bar graph display which is what you've seen in the video. The dot mode basically only turns on one led and that bounces left and right. Its better for lower power applications. If you want bar graph mode, tie pin 9 to 5v or VCC. If you want dot mode, then leave pin 9 floating, basically just leave pin 9 alone.

We're almost ready to finish up and display our speakers. You want to test everything out to make sure all the LED's and the audio actually works before we enclose the case.

At this point all you want to do is stuff the wires and the board into the sides of the enclosure. If possible, try fit the board behind the speaker holder to save space and make it easier to glue. basically just make sure youre able to close the case and have all the wires safely tucked away as well as the circuit board that you made.

Next you want to use your choice of glue to stick the cover to the case. In the future I will modify the design so you can use bolts instead but for now gluing is good enough. I used a 2 part epoxy since it holds better than hot glue but if you want it to be removable, hot glue is a good choice and its simple to remove if you need to open up the case.

And....thats it, your speakers should be done and now you can use them with your iPod, phone, computer or even add some batteries and make them portable. Now you can use the terminals on the back of your speaker, wire up some power and connect it to the other speaker. You should be good to go.

Thanks for reading this instructable, please report any typos or errors so I can fix them ASAP :)