LM3915/LM3916 VU Meter

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

Comments

[faki]

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

[lasermaster3531]

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.

[reverser514]

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!

[nak]

as they are works

[tqnata_1]

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

[lasermaster3531]

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.

[chainsawz]

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

[lasermaster3531]

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.

[happywatt]

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

[static]

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.

[burton2663]

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

[lasermaster3531]

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+.

[Mitsukai]

go to http://www.datasheetcatalog.com/ to get the actual schematic for lm3915

[chirag parmar]

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

[radiorahim]

 Radio Raheem!!!!!!
Living large. Man, he even walks in stereo.
Love it.

[radiorahim]

 What is the red thing in each of the photos?

[reverser514]

well son, when a photon likes a diode A LOT, they make whats called an LED. haha the "red thing" in the photos is a bar graph, simply a bunch of LEDs in line with each other and packaged as one item instead of a bunch of LEDs.

[radiorahim]

Well old man, I think what we have here is a failure to communicate. Step 1, bottom of the frame, a red plastic thing. Is it some sort of probe?

[offtherails2010]

lol x 2 @ old man !!!

yaa i know this is a real-old post but just in case you were still scratching your head about this asked question, your right that little red thing is a probe for digital multimeters, here is an example of a set!

[JohnBailey]

Yes. It's a hook probe. Same use as a crocodile clip, but much smaller.
Press the button (big end) and a little hook slides out to clip on a component lead or wire. Release it, and it pulls back gripping the wire.

[Mathieu5555]

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.

[uhclem]

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.

[co'callaghan1]

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?

[co'callaghan1]

(removed by author or community request)

[co'callaghan1]

(removed by author or community request)

[Werewolve]

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

[reverser514]

OH THANK YOU FOR ASKING THIS QUESTION!

I had a couple of tweeters left over from a sub box I scrapped awhile ago. I took some good old wood, cut a circle out of it for the speaker, and left room for LEDs. My only problem is I don't feel like running a wire from the front of the car to the trunk.. maybe I'll just splice it in with my trunk light... :D then it will only turn on when the trunk is open!!! and the crowd goes wild on the thought!!!

[likeastone9999]

you can use 12 volt... but use a 330ohm 1/2 watt 5% tolerance... they work great for led's

[charlieb000]

get a 3v (or so) regulator..

[microOhms]

i love to invent or to make a device w/o planning like of those people who make an electric devices!!!!!!!!!!!!!!!!!!!!!!!11

[yashfau]

can u please show how you have connected the audio to this device ?

[bror89]

hey what's the difference with these two chips?
LM3915 IC chip LM3916 IC chips

[the_don125]

Both are logarithmic display drivers, the LM3916 is just better tuned for audio.

[zcrank]

N o Way. You Rocked the Siouxsie in the Video! Way Kool!!!

[Raiden19]

I was thinking, could you get this to run off a usb port 5 volts? If so you could use it on your pc. House the electronics in a seperate box and just have the visulisers showing, either side of your monitor for both channels.

[wootwootman]

is it possible to add a potentiometer in there somewhere to vary the sensitivity of the input?

[grampafish]

this same chip ie 3914 can be used along with a 555 and 4017 to make an led oscilloscope see schematic

[chance313]

I am interested in building something like this to put on my guitar, so when i play it on a dark stage it will light up. does anyone know a way to do this where i can wire it to the audio output. If it helps, i have active pickups.

[spinynormann]

how large is your input signal?

[alex7street47]

can u cascade the ic to 5(50 led) with 1 single input.... how the schematic?