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Spectrum analyser Equalizer project how to go about it?

Maglatron

Jul 12, 2023
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Spectrum analyser Equalizer project, how to go about it? any idea of where to start I want some led dot matrix's and recreate what old stereos used to do, with red LED's. I have arduino chips and I want to put a microphone near so it and have high pitch sounds on the right and deep bassy on the left with the rest inbetween. I think this would be a right good little project and maybe have a 3.5 jack in and a 3.5 jack out without altering the sound but takes the signal and displays it in bars according to frequency range and have linear resistors to interact with how high up the bar goes exactly like old stereo systems, I had one when I was young and loved it. I would stare at it for hours any input valued!
 
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Maglatron

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bassically this is what I want to make but with red LED's instead of green
 

Maglatron

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to include what you pointed me to with the arduino nano I have a spare mega 2560 knocking about, for more out put pins and have decided I want to run it from an interception between the line from the rca jacks (white and red) apart from that its a blank canvas!
 

Harald Kapp

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Ask your favorite search engine for "arduino spectrum analyzer". Lots of projects available on the internet.
 

Maglatron

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i found this but I wanted to keep the "old skool" led look and not a screen!
 

Maglatron

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heres another
so now I know what i want any ideas on how to build a driving circuit for it?
 

kellys_eye

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I'd suggest you go 'analogue' with this. Do some research on the use of audio filters built around a simple op-amp. You'll learn an awful lot about electronic principles.

Design and construct a series of filters - as many bands as you see fit - and use the outputs to drive columns of LEDs based on the LM3915/6 (3915 is the linear display and 3916 the log display version).

Electronics Today International (Magazine) did such a project - amongst many similar done by various others at the time - in their June 1978 issue. I have a PDF of the project but it's too large to include as an attachment here but here's a screen cap of the first page <edit - ALL the pages!>:

The principles are sound and it's scalable to whatever size display you want - LED colours of your choice of course. If you just used the filter section you can drive the LM3916 (stackable to as many LEDs as you want) you can go 'nuts'!
 

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Maglatron

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what is linear and log? and did you say that you included the entire article in screen shots many thanks?

That pretty cool especially the antiqueness of it but I dont understand it to be honest can you draw me us a spice model asy file with 32 columbs and 15 rows of red led if you have the time?
 

kellys_eye

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If you take the analog filter section then all you need is the input circuitry and as many filter channels as you desire. The article shows 8 and each section has an output pin - a varying voltage. You can spice emulate a single channel very easily.

Feed that varying voltage to an LM3916 (LED column driver - Google the datasheet for it) and that filter output voltage will bounce the LEDs in either a 'dot' mode or 'column' mode (your choice) according to the signal level at that particular frequency.

You don't need to build the whole circuit - just adapt the parts you need (probably just the filters) and the reason for posting it is that the article explains how it all works and is definitely worth a read.

Audio signal levels follow a logarithmic law (sound pressure levels) so you must show the result in that way else the display will not follow the actual sound being produced. The LM3916 is the logarithmic version of the 'linear' LM3915 - again, check the datasheet as this explains it very well.
 

Maglatron

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I want column mode and I have read it but I shall go over it a few times how in spice do you simulate music?

So I still dont understand properly it's fuzzy when zooming are there any newer pdf's that I can reference, I think I learn better when I see the same thing written in more than one way, thanks

yeah can't make any sense of it any other litrature about these things?
 

kellys_eye

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yeah can't make any sense of it any other litrature about these things?
PM me your email address and I'll forward the original PDF files to you. 8.4Mb in size so you need a decent internet connection.
 

Delta Prime

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So I still dont understand properly it's fuzzy when zooming are there any newer pdf's that I can reference, I think I learn better when I see the same thing written in more than one way, thanks
 

Maglatron

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I like that article any tips on how to make it into say 30 band spectrum and "dance" to the music? do you need to have a chip for every frequency? is there a 20 LED bar driver, because the LM3915 only supports 10, also what are the flat LED's in stacks of 10 or possibly 20 called to find and buy?

 
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kellys_eye

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because the LM3915 only supports 10
They can be connected in cascade to any number you want.

Each 'band' requires it's own filter but the filters themselves have a 'band WIDTH' which, if you make too many, result in them overlapping and the columns will start to dance in pairs rather than individually.

This is where a digital version comes into its own. Whilst you CAN make analogue filters with VERY narrow pass bands they become increasing complicated and component-dense but with a digital filter you can derive practically any band width just by programming.

If you want to learn about analogue electronics then starting with the filters shown in the article (and understanding how they work) is a great learning exercise but if all you want is an end result then purchase a kit of parts that achieves the multi-channel result you seek.
 

Maglatron

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No probs - except an email address issue??? See my PM reply.
I cant access email but I had a similar problem on another thread, one guy split the file with 7-zip and uploaded it through this website. it would be great if you can do that for the pdf
ps he changed the extension to .txt so that he could upload!

what do yo call the flat LED's in stacks I would like to learn about the filters analogue and bandwidth and all that cool stuff

PM me your email address and I'll forward the original PDF files to you. 8.4Mb in size so you need a decent internet connection.
can you split and upload? I'd appreciate it if you can thanks in advance
 
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