LM3915/LM3916 VU Meter

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Introduction: LM3915/LM3916 VU Meter

About: I like to tinker with just about anything, sometimes it works out in the end. Have fun looking at the projects, try tearing something open and let me know how it goes. cheers, -Joe

The LED VU Meter was the height of late 80s boombox technology. This instructable will build one out on the breadboard. Who doesn't like blinking lights...

I have a bigger project in mind and will post instructables of each piece and tie it all together at the end.

Here is the live action video:



Step 1: Parts

You will need either the National Semiconductor LM3916/LM3915/LM3914, 2 for stereo...

-2x 1.2k Ohm Resistor
-Wire
-2x 10 LEDs or a 10 Segment LED Bar graph
-2x Breadboard, or just one big breadboard
-2x Stereo 1/8" jacks
-Optional 2.2uF capacitor
-Power supply anywhere between 3-25v

Step 2: Wire the LM3916 Circuit

You will wire up the circuit following the diagram attached. For a bigger version you can check out the page at N.S..

I skipped two things, I did not use the capacitor as it is only necessary if you have more than 6" of cable between the LEDs and the chip, and I also did not use the 7.5k resistor in the diagram going to pin 6/7. your mileage may vary.

Step 3: Pass Through for Sound

I wanted to be able to listen to the music while looking at the flashing lights, novel idea I know...

So I wired up two 1/8" stereo jacks wire the two together, and then hang 3 wires off of one, the negative will go to pin 4 on both chips, while the left signal will go to pin 5 on one chip, and pin5 on the other chip.

Step 4: WIre the LEDs

Remember the LM3916 switches negative not positive. So hook the positive up on all of your LEDS to positive in your breadboard.

Then pin 1 should go to the first pin on the LED, followed by pins 18-10 so they will light up in order.

As you can see in the second pic, I got a little sloppier on the second set of LEDs and just used wires from a jumper kit so its a little messy.

Step 5: Radio Raheem

Now you can live large like Radio Raheem, this would fit nicely in the ipod nano box wouldn't it...

Except you can't fit 20D batteries in a nano box...


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    user

    We have a be nice policy.
    Please be positive and constructive.

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    81 Comments

    Can you please give the applications of the Audio VU Meter

    I recently made one of these and I'm pleased with the result, but there is a problem. I did not see anywhere to be mentioned this circuit does not work if you connect it in parallel with an amplifier or even headphones...I supposed the signal is too weak to work with 2 devices so I added an amplifier...same result. If you guys have a solution to this I'm happy to hear it...else the audio source is compromised during vumeter use.

    Trying to get this working but I'm having a problem getting the circuit to recognise and input. I did skip the capacitor as the LED's are directly on the board. When I apply power to the circuit, all 10 LED's light in bar mode or just the last one in dot mode.

    I've connected a 1/8" jack stereo cable to the circuit. The red/white wires I've connected to pin 5 with the ground going to pin 4. Now what's interesting (to me anyways) is if I pinch the plug with my finders, the lights drop down so only LED 1 is lit. As I apply and release pressure, the LED's respond.

    I'm a total newb with regards to this stuff and I'm not entirely sure I have an understanding of what the input signal should actually be. I've assumed an iPod would work but upon connection, all the LED's are extinguished and there's no response to the iPod at all, regardless of volume level.

    Any help would really be appreciated!

    For those looking to add a "power level" meter to a small amplifier (like a boombox) this circuit might be worth trying:
    http://www.bowdenshobbycircuits.info/page11.htm#vumeter.gif

    It uses the LM339 quad comparator. It needs more parts, but is overall much cheaper and easy to find.

    1 reply

    I have made one of those with LM339N with 16 leds and added a microphone to work without cables, more portable and also reacts to voices.

    http://www.youtube.com/watch?v=hLSS5CipBLc

    http://www.youtube.com/watch?v=Y8_KJ0PjmDk

    Works great on voltages between 5 and 12V. I've powered it on a scrap power supply found around the house that gives 6.2V. I don't have a video on it working on microphone but there is no difference between the functionality. I am planning to make 10 bands as this one (but I want to work with smaller, smd components) and then make some active filters to make a spectrum analyzer. If anyone knows a working schematic that I can modify the res and caps to change the frequencies properly I would really appreciate it.

    Also if anyone is interested in my schematics or any other piece of info about this project I am happy to share and explain. (tiberiusvinczi@gmail.com)

    I built one with 10 levels of plexiglass with LEDs drilled into them. Each level has 2 LEDs in parallel and I get questioned a lot on how did I managed since the driver only outputs 30mA for each pin, and I have 2 20mA LEDs in parallel for each pin(so 40mA in total) and the only aswer I have is my LED aren't at full brightness. Right? I'm not an expert in electronics. Is it ok, or has an effect on long term.....

    Here is my vu meter.

    1 reply

    can you give me your schematic of VU led meter ? please .. my email: thanthanhspkt@gmail.com

    hello aneamtu .... i need help for that plexi glass vu meter.... i need that circuit please....

    user

    Do I use the leds as they are on the schematic or I put a resistor for them ? I am using 10x1,8V LEDs

    3 replies

    as long as the supply voltage is greater than the LED voltage by a volt or two, it'll work. so 10V and up is fine. This chip has internal current limits, so you don't need resistors.

    yeah little information here...
    (:D one lesson a day)

    because they are 8v LEDs, and the chip only outputs at the most 5 volts (because we can't output more than we are given. (well we can, but that is WAY more advance than what we are doing here...) and under-powering an LED will not do any harm. Except mental harm because if the LED doesn't turn on, then you get confused out your mind of why it isn't...
    (UH OH im breaking my one a day rule...)

    THE SIMPLEST ANSWER IS ALMOST ALWAYS THE CORRECT ANSWER, AND MOST OF THE TIME, IT IS THE ONE MOST OVER-LOOKED!

    user

    as they are works

    i want to know 2x 1.2k Ohm Resistor -W=?
    -Optional 2.2uF capacitor =v=?

    1 reply

    when in doubt with resistors, use 1/4watt, that's the most common size. With capacitors, as long as the voltage rating on the cap is higher than the supply voltage, you're fine.

    im currently building a circuit like this; but the input isnt strong enough so im gonna use the LM386 to boost the input so more lights turn on... without it, only the first three lights turn on at maximum sound

    3 replies

    the sensitivity is influenced by the resistor values, try using 10k liner sweep pots instead and play with them until you get good brightness and sensitivity.

    I have the same problem with an LM3914, but I didn't know what an LM286 is nor how it works, any advise?

    Respectfully, and to state the obvious, simply use google. Also do the same search on on you tube. The LM386 is a small audio amplifier.

    im looking for an actual schematic of lm3915 vu meter using 1w luxeon leds, im trying to use tip31c as a driver but the output of the 3915 is so little to drive the transistor. im using this cell charger than goes up to 8volts

    1 reply

    for that kind of thing, you'll want to use a FET (field-effect transistor), not a BJT (bipolar junction transistor). BJTs require current to turn on, whereas FETs only require voltage, the gate pin acts like a capacitor, not a diode. High-power BJTs can require substantial amounts of current (too much for the 3915 as you found out) and would need cascading with small-signal transistors to work (complicated and spendy). With a P-channel FET, you can just hook the gate up to the output and then have a 500-ohm resistor as a drain to V+.