LM3915N -LED VU Meter weekend project

Okies

It's pretty long time since I've been looking forward for building an LED Level Display using LM3915N(Lot impressed by AG's sound level indicator, lols).

So this was my last weekend project needless to say. Ya know, it's very exciting to build something interesting on lazy sundays. So just went to electronics market on saturday to procure couple of cute LM3915N's and started building the circuit on breadboard.

Coupled with my NuForce uDac Line level output(I use this excellent DAC with 2v output for interconnecting my Laptop and Creative T40 speakers.) this gives me an awesome rhythmic level display option, in fact I'm pretty impressed on the performance of this chip.

Soon I'll be assembling and integrating this with my home theater system.

Here's the pic and video of the same. Thanks for watching

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Either there is something very wrong with your video or the circuit. That VU doesn't come even close to to representing via vision anything I'm hearing.

Sceadwian said:

Either there is something very wrong with your video or the circuit. That VU doesn't come even close to to representing via vision anything I'm hearing.

Click to expand...

Not even close, but that is the actual representation of the music levels we're hearing.

Scead, I think it made an audio visual illusion because of the kind of music I played(maybe LM3915 little confused on how to dance with this music, kinda stuff LOL).

Ok, I've analyzed it closely to understand what you actually meant.

There's a .1uF cap at input pin 5 along with 1n4148 as a simple peak detector which actually delays the response time a bit, but without that the display won't be eye catching one. For eg, if first 5 LED's are ON for a moment, the in between one's will be blinking and they won't be at a constant illumination level and the response is very fast. The input cap keeps the LED's ON for a moment at good brightness so that our eye's can catch it properly.

I've reduced the cap value to 473pf now the response is better but the LED brightness decreased a bit.

If you look on to the below video with op-amp peak detector, you can see that the response is much slow( see LED's goes off one by one slowly). We can configure this according to our testes is the essence

https://www.youtube.com/watch?v=-mHOWARP6lI

The datasheet for the LM3915 shows three Peak Detector circuits.
My Sound Level Indicator uses a transistor emitter-follower to quickly charge the 0.33uF peak-hold capacitor through a 100 ohm resistor. Then the capacitor discharges slower through a 330k resistor when the signal level is low.

Not even close, but that is the actual representation of the music levels we're hearing.

Click to expand...

It doesn't track the beat, the vocals the clapping, nothing psyco-acoustical in the song, it may represent course average power levels but this is visually unappealing. Try tossing in a low pass to only catch the bass so it will track the beat, or a high pass so it will catch the claps, or the mid range so it will track the vocals.