led vu meter=lots of noise??

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MrDEB

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this circuit may be what I am looking for BUT I fear all them transistors may produce alot of noise seeing how the amp is connected to the filter outputs
https://www.electro-tech-online.com/attachments/audio-spectrum-analyzer-en-pdf.15065/
also thought of 10 LM3916's but now were $30+ just for a display (chips only)
my thought was use several uln2803 and maybe an Aleghro A6279EA-T
just rambling ideas
theres got to be a way to build a LED vu meter but at a low cost using modern chip technology.
any input would be helpful
 
MrDEB said:
this circuit may be what I am looking for BUT I fear all them transistors may produce alot of noise seeing how the amp is connected to the filter outputs
Click to expand...

Your fears are completely groundless!.


There is, you use a DSP and FFT to do it all.
 
what is a DSP and a FFT?
I was looking at quad bi lateral switches to take the place of all the transistors (20+)
 
MrDEB said:
what is a DSP and a FFT?
Click to expand...

If you don't know, than it's not much help to you! - but it's how anything like this remotely modern works - but VERY complicated to design and program.

FFT is Fast Fourier Transform if you want to look it up.

I was looking at quad bi lateral switches to take the place of all the transistors (20+)
Click to expand...

Why?, what have you got against transistors?.
 
proposed design sch.

this is just starting. parts may not be oriented correctly.
need to clean up but idea may be better than a bunch of transistors etc.
may need diodes to isolate outputs of 4016 to 3916?
not sure if the 4017 will drive both the 3916 and the 2801?
any input?
transistors seem old fashion, low tech
 

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circuit description of vu meter

In put from audio feeds the 10 band-pass filters - LM837’s
Outputs from filters feed the cd4016 quad bi lateral switches and are isolated from each other using diodes that feed the output to the amp.
The cd4016’s are cycled using the 4017 set up as a count to ten then recycle
The outputs from the cd4016’s feed the LM3916 dot/bar driver. The LM3916 outputs sink the X half of the 100 led array
The outputs of the cd4017 also cycle through the cd4069 inverters then turn on the transistors which control the Y half of the led array
In theory this should work??
 

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Your bandpass filters and the circuit in the article are wrong.
You seem to be shorting together most of the LEDs.
 

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oups I see where I crossed up

the op amp inputs are backwards.
The LED array I drew is probally deceiving.
The leds are connected from the transistors to the outputs of the 3916 in an array type setup
one connected to the X and other end of LEDs to the Y
agfter looking at diagram I see what your talking about being shorted.
Thanks for the heads up
need to redra the array and switch the op amp inputs around.
I guess it was all the cutting, pasting then mirror the schematic.
 
Instead of using many CD4066 transmission gates (they are better than a CD4016) you could use two CD4051 which is one input to one of 8 outputs. the CD4051 is also the improved version.
 
revised filters

I changed the inputs and re drew the led array
its basically the same circuit as
https://www.electro-tech-online.com/attachments/audio-spectrum-analyzer-en-pdf.15065/
this circuit calls for a C1815 but its a pnp transistor. I used the complement as stated in the data sheet. wish there was a better way?
the bi lateral switches I don't think would handle the current-need to look at that.
Was hoping to use say a 2803 or ? but the logic level is backwards.
 

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