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Audio Spectrum Display

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andyb

New Member
Hey guys, first time poster here. Just wondering if anyone would be able to help me make an Audio Spectrum Display (for those who want an example,


I don't want to use LED's, instead I want motors to push pieces of perspex upward which fall back down by their own weight. What I'll need is a way to get the volume levels of about 10 different frequencies and use those levels to move the bars. It is hard to explain as I don't know much about electronics and even less about audio systems, but if anyone could help it would be very much appreciated.
 

ericgibbs

Well-Known Member
Most Helpful Member
hi andy.

My concern would be the poor response time of the perspex bars driven by motors and falling down due to gravity,
compared to the response time of audio waves.

What sort of audio frequency range did you have in mind.?
 

andyb

New Member
Thanks for the advice Nigel. And Eric, it's only for visual effect when listening to music, it's not like it needs to be accurate or anything.
 

j.p.bill

New Member
Have you looked into the "original" visual audio display - the color organ? Three or four banpass filters and some lights (or LEDs) that vary in output along with the associated musical frequency. There's probably any number of designs on the web.

Yep - 1,910,000 hit on google. The first one is a kit.
 
i want to do something like this myself in future, while i havent been doing masses of research into it what ive learnt so far is that bandpass filters with http://www.national.com/pf/LM/LM3914.html ICs would do the trick. apparently theres a logarithmic version of that IC, i dont know how it would affect the output but its an intresting thing to look at.

does anyone have a link for a good bandpass filter schematic? this would be useful for me too.
 
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audioguru

Well-Known Member
Most Helpful Member
Google has many links to bandpass filter circuits. Most use a single opamp in an inverting filter.
 
oops sorry i didnt see that :)

Edit:

after looking at that link does it mean you would have to use 4 op amps for each frequency? and to get a certain frequency output you need to change the values of the capacitors in the feedback loop of op amps 3 and 4, is there a calculation for what values = what frequency?
 
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agent420

New Member
I'll just add that if a pc could be part of this project, you could always write some code to get the fft (spectrum) data out of Winamp or something... That would additionally allow for coding some averaging or integration functions that may be easier (and more easily experiemnted with) than hardcoded circuits, especially for the unknown display properties (movement time, etc.)

Maybe motor control though parellel port or usb?

And I'll just say bless you guys with the visions of projects like this, but no knowledge of electronics! A goal like that can certainly be a motivation to learn LOL. I used to strive just to learn how to bias a transistor switch ;)

edit -

I am also thinking some type of servo control might be the way to go with the display motors...
 
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