First there was this: LINK

Which led to this: VIDEO

So I thought I'd try to make one.

Attached is the schematic as given on the site associated with video.

I drew it in LTSpice, also attached.

Op Amps were substituted from original based on the TI crossreference
recommendation, and availability from DIGIKEY. I hope these are suitable.

Also attached is the .SUB files for the Op amps.
If you need to know how to use them, which I didn't either, look HERE.
Big thanks to RonH.

And a link to DATASHEET.

I am looking for any comments on, component selection, basic circuit,
improvements, or even the drawing or simulation.

I haven't worked with audio, or Op Amps much and thought this might
be a fun little project. End use probably hooked to an MP3 player or
I-Pod in tandem (parallel) with an amplifier driving some speakers.

Thanks for looking.

 

What do you intend to do with it? I had thought of trying to make a stereo version (left and right channels), make each output dependent on volume (more LED's lighting up as freq. level increase) and placing the diodes in a pair of sunglasses. I'd then pop some good music into headphones, put the goggles on, close my eyes, of course, and really zone out!

 

What do you intend to do with it? I had thought of trying to make a stereo version (left and right channels),...

Prabably just a knick-knack (sp.?) to plug a small music player into.

stereo version (left and right channels)

As soon as bugs are worked out.

 

Speaking for myself I'd go PWM and keep the heat down. It would add a little more circuitry, but the power savings might be worth it.

 

Speaking for myself I'd go PWM and keep the heat down. It would add a little more circuitry, but the power savings might be worth it.

Do you have a quick example you can post? Just the basic idea would
be enough.

 

Just so you can see the frequency response, I added the Modulate function.
See the upper left corner of the schematic.
Modulate is in the Special Functions directory. There's an example of how it's used in pll.asc in the Examples\Educational directory.
I right-clicked on the Modulate symbol and added the "mark=20k space=20" on the Value line, and X'ed the box to the right of it by left-clicking on the box.

space=20 tells Modulate that when the FM input is 0 volts, to output 20Hz.
mark=20k tells Modulate that when the FM input is 1 volt, to output 20kHz.
I set the AM input to a constant 0.2v; the output is 0.2v; 0.4v p-p.

I'd changed the simulation to run for 2 seconds, but that proved excessive; I stopped the simulation when it was around 12k-13kHz
v(n001) is the output voltage from v2; the input to FM.
The lowpass on D4 drops off at around 340Hz, same as where the passband of D5 starts.
D5 is on from around 340Hz to about 1.55kHz.
Then D6 cuts in around 2.5kHz, and starts fading out around 6.6kHz.

You might want to increase the passband for D5, or add another bandpass filter between D5 and D6.

 

Do you have a quick example you can post? Just the basic idea would
be enough.

Actually I do...

LEDs, 555s, Flashers, and Light Chasers

Chapter 12 deals with pulsating LEDs, I make reference to a single channel color organ. If you were at the filters in front (as suggested) you could have a very bright piece of equipment indeed.

 

SgtWookie:
That's the kind of tip I was hoping for. As usual you are most helpful.
I'm going to try to close up the "gap" you spoke of, this project for me
is about understanding, not just an exercise in copying someone elses
design.

Bill Marsden:

Speaking for myself I'd go PWM and keep the heat down. It would add a little more circuitry, but the power savings might be worth it.

I like the idea of power savings, I'll probably try to add that in at some point.

Thanks

 

Let me know if I can help. This is the kind of project that fascinates me. In the old days it was light bulbs, now it is LEDs. In the scheme of things it doesn't make much difference.

I remember several of folks coming out with audio spectrum analyzers, if I can find it I'll post it here. They are all variations of the same things.

**************

One of our other members, mik3, came out with such a audio spectrum analyzer. He is a regular, but hasn't been in for around 6 weeks.

http://www.youtube.com/watch?v=j-4h3l9O4fc

 

Let me know if I can help. This is the kind of project that fascinates me.....

Thanks for the support. I may be in touch.

Just a warning though, sometimes my progress on these projects
is stop and go, although I intend to keep updates in this thread.