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Spectrum analyser Equalizer project how to go about it?

Maglatron

Jul 12, 2023
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Actually I think for me it's easier for me to use a mic and a pre-amplifier then drive a row of bar graph LED's using an LM3914,
and then after that, put a filter inand try to get that to work at the specified frequency, say 45Hz, make another filter for column two and so on. The reason I am not doing the FFT and muxing is because nobody could tell me how to get it to work with the code I supplied to alter and modify for my needs and so I'm following the advice from anouther member who says this:

step-by-step approach.

build a signal amplifier that picks up the aufio signal from the source you are going to use (microphone, line-i, ...?) and amplifies it to a level the LM3914 can handle. You'll probably have to learn a lot while building tjis circuit. Opamps are deceptively simple when you look at the standard circuits, but opamps can nevertheless be tricky to handle when it comes to the fine details like e.g. stability of the amplifier without ringing or, worse, self-oscillation due to improper feednack circuits.
Build a single channel VU-meter to display the signal from the amplifier by the LM3914 in a way that pleases your estetics.
If necessary (very probable) debug these circuits and tweak components until it operates as your expect.
Build a first single filter e.g. for the bass range. Insert the filter into your signal chain and check that the response displayed by the LM3914 matches your expectations, which in this case should be a display of the bass tones' volume only.
Once this works go on and build the remaining filters and display circuits for the remaining channels. You may even consider designing a modular PCB with filter and display circuit which is customized to different frequencies by populating the filter with different components. The have 20 or so of these PCBs manufactures (not so expensive nowadays). The simply assemble the PCBs (solder components to them) and combine with power supply and signal amplifier (step 1 from above list) for the full spectrum analyzer.

In my opinion your chances to complete this project to your satisfaction are much better using such (or similar) modular approach.

That being said I am still open to suggestion, if you can come up with arduino code, or modify the one I suggested earlier, I have got esp32 dual-core arduino powerful enough and I have two T74LS257BI 88506 multiplexer chips. I have also ordered some quad-op-amps (TL074) I'm going to be using 16 columns by 20 rows. can you get the LM3914's to work with multiplexing? and back to the original question is it possible to split the current between regulators from a battery?
 
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Maglatron

Jul 12, 2023
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but I dont know if it's possible to use muxxing with this idea, ie in conjuntion with LM3914
 
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Maglatron

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Hello,

I see that you made the stopband more narrow. That will lead to an extra stage in the filters.
I also see you are mentioning the LM3914, wich is a linear voltage indicator.
The LM3915 would be more suitable for audio as it is logaritmic.

Bertus
 

Maglatron

Jul 12, 2023
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Is it possible to use the LM3914 in conjunction with muxxing chips?
 

Maglatron

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I want to have the led's running on 1 milliamp how do you set this up with the LM3914
 

Martaine2005

May 12, 2015
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I want to have the led's running on 1 milliamp how do you set this up with the LM3914
Each channel outputs 10mA current so one would presume a current limiting resistor in series with each LED.
EDIT: I just read that its current is programmable so no need for resistors.

Martin
 

Maglatron

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ok could you explain that in further detail
Each channel outputs 10mA current so one would presume a current limiting resistor in series with each LED.
EDIT: I just read that its current is programmable so no need for resistors.

Martin
 

Martaine2005

May 12, 2015
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The data sheet shows an example of linking pin 6 to pin 7 and then pin 7 to Ground via a single resistor. Changing that resistor to a potentiometer will allow for LED brightness to be controlled. Not sure how that makes it programmable!! :)
 

Martaine2005

May 12, 2015
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what is lower limit and upper limit? thanks
There is no upper limit. Each output can control a transistor or many other switching/amplifying devices.
The standard output on each channel is 10mA. This can be further controlled by the use of a potentiometer as described above. But you can also use series current limiting resistors with each LED to get your requirements.

Martin
 

Maglatron

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Ok in this video at 6:30mins it states that the upper and lower limit
 

Martaine2005

May 12, 2015
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That video is …… I don’t know what.
The data sheet tells a different story and I believe the data sheet.
You should read it too!
The questions you ask are in the data sheet or on the example circuits within the data sheet.
Please read the data sheet before asking us to read it for you and then type it here for you to read.
Please identify a section that you don’t understand and ask questions about that section.
I feel for you, but nobody is going to walk you through a complete build or reverse engineer somebody’s code to make it work for your project.
If you read the whole thread through, you have a multitude of ways and great examples, links and circuits.
Just my 2 cents .
 

Maglatron

Jul 12, 2023
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so I bought some old IDE ribon cable to keep the board neat and tidy promiss to have some updates soon!
 

Martaine2005

May 12, 2015
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Ribbon cable is perfect for keeping it neat and tidy. Always try and use the multi coloured cable too. It makes it so much easier than deciphering ‘all’ grey cables.
 
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