Signal/intensity LED indicators - Question.

[spectreman]

Hello all,

I'm looking for a way to add 1 (or more) "signal/intensity" LED indicators to an already existing board...purely for aesthetic purposes.

For example, Dead Astronaut has a pair of clipping LED's on his X Fuzz circuit that function in the manner i would like, but i'm not sure how to incorporate this same LED effect into an existing board.

Ideally, I would like to create a "signal/intensity" LED daughterboard that i can add to any existing project so that as the intensity of the signal increases, the LED gets brighter, and as the signal decreases, the LED gets dimmer.  Is something like this possible?  Am I even making any sense??

Thank you for any help!

[mth5044]

Sure is possible! Check out the midfi clarinot schematic via google. I'd link it but photobucket is being photobucket. There's an IC driving an LED which shines on a LDR. You want the ic up through the LED part!

[Rob Strand]

Search for "electronic vu" or "electronics vu meter". 
You can get special IC's, some IC's are cheap like those in car radios. 
There's also simple BJT versions.

Wire-up like
Signal ->  Filter ->  (Buffer) -> Rectifier ->  Attack Decay Time Constants ->  Electronics VU

You might want to add a "filter" that emphasizes frequencies above 1k (or 2K) upto 10k (to 20k).
This weights the intensity or annoyance level we perceive.  You could also cut below 100Hz.
You will need to play around with it.

[GibsonGM]

"Dead Astronaut" did a thing called "sound 2 light" (search here) which used an LM386 to flash a couple of LEDs in sync to your playing.  Extremely simple, and might be something you could use, if you are not looking for some sort of micro precision....other than that, I'd go with a transistor type VU meter, if you need more lights, more sensitivity....

Edit:  Here you go, the pic should be explanation enough.  If not, ask Rob! 

[spectreman]

OK!  I think this will work...I'm gonna try it out.  Thanks!!

[GibsonGM]

Cool.  I've use it here and there - very handy when you just need a quick blink! 

[R O Tiree]

...or you could go mad and think about an LM3914 dot/bar 10-LED driver chip?  If you want to go down that route, give me a shout, because they're not quite as simple as the datasheets would have you believe.