Instructables
Picture of LM3915/LM3916 VU Meter
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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

Picture of 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

Picture of Wire the LM3916 Circuit
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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

Picture of 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

Picture of WIre the LEDs
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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

Picture of 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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i tried out the circuit but only one of my LED's is working. I used a 12v adapter the one led blinks with reapect to music but others do not
Mathieu55552 years ago
Since co'callaghan1 have not been answered, I still do not know what is the Vref, so I put a 10K potentiometer in place of 2 7.5K and 1.3K resistor.
Now I Can ajust the VuMeter. If the sound is not very loud I can raise the level. So its work perfect.
Pot 10K, first pin go to #7
Second to #8 on chip
and third on ground.
Sorry about those last three posts. I've only got one question. Can you please explain what Vref is and what I'm supposed to do about it? Do I connect it the way it describes or what? It's just confusing because it does not appear to be connecting them. Do I have to do that?
wootwootman4 years ago
is it possible to add a potentiometer in there somewhere to vary the sensitivity of the input?
Werewolve5 years ago
I have 12V car battery. Where can i get the 3V for the Led's? or can i use 12V with a 620Ohm Resistor? Led: 2,25V 20mA
you can use 12 volt... but use a 330ohm 1/2 watt 5% tolerance... they work great for led's
get a 3v (or so) regulator..