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
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
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+)
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
This guy programmed a PIC Micro to take care of the VU meter side. He's basically using a set of bandpass filters to make a crude spectrum analyser - but the result is pretty impressive if you like that sort of thing!
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??
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.
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.