LED Spectrum Analyzer

[4pyros]

trying to get the SMD LEDs on one side of a pcboard with the other side to mount the LM3916"s and resistor arrays.

This would be a one sided board. LEDs on bottom side.

No that would be a double sided board with feedthroughs.

 

[MrDEB]

The SMD LEDs would be mounted on the "bottom" traces with the LM3916, resistor arrays "through hole type" on the top.
1x board.
been configuring on different designs. Looks like I might get by with one board for displays and display driver circuitry.
Don't really want to do a 2x board but the FILTER section board will have to be 2x.

 

[MrDEB]

REASON for the LM3916's = Got at a bargain price.
Hoping to have a reference signal to adjust each display. Thinking maybe a 555 outputting a pink noise or ??
any suggestions??

 

[audioguru]

Pink noise is many frequencies from 20Hz to 20kHz. How can a 555 do it?
My pink noise generator uses a digital IC that is not made anymore.

 

[MrDEB]

perhaps I used wrong terminology.
suggestions for calibrating the led displays/filters

 

[irbirb]

perhaps I used wrong terminology.
suggestions for calibrating the led displays/filters

log-sweep sine tone

 

[MrDEB]

LOG SWEEP SINE TONE??
going to have to research and how to produce.

 

[audioguru]

Take a variable frequency sine-wave oscillator and sweep its frequency with a sawtooth waveform. It feeds the input of an amplifier. The output of the amplifier feeds the vertical input of an oscilloscope.
You can see the frequency response of the amplifier on the screen of the oscilloscope when the same sawtooth waveform is driving its horizontal amplifier.

 

[ronsimpson]

https://www.electro-tech-online.com/custompdfs/2011/03/MSGEQ7.pdf
I made a PCB using this as the filters. A PIC does the LM3916s job and drives the LCD display.
I have not had time to do the software.
I noticed the putput of the MSGEQ7 has an offset. 0 does not equal 0. This can be fixed in the metering section. The MSGEQ7 does not have the best filters. Only 7 filters. You can run two parts in parallel. By changing the RC on pin 8 you can set the frequency range. Running two filters at different frequencies might give better proformance.

 

[irbirb]

Take a variable frequency sine-wave oscillator and sweep its frequency with a sawtooth waveform. It feeds the input of an amplifier. The output of the amplifier feeds the vertical input of an oscilloscope.
You can see the frequency response of the amplifier on the screen of the oscilloscope when the same sawtooth waveform is driving its horizontal amplifier.

yeb. and with a dual-trace scope you might compare two of your filters.

LOG SWEEP SINE TONE??
going to have to research and how to produce.

computer would do the trick in a pinch (for audio frequencies anyway)
plenty of software for generating test signals i think.

 

[d3dreaper]

It's quite amusing to find that i had forgotten about this forum only to relocate it after revisiting the velleman schematics online. It's also quite amusing to read the lack of knowledge i had before lmao.
AudioGuru (as well as everyone else helping me then): Thanks for your assistance (felt i should say that since it was long overdue haha)
I will definitely try to keep up with updates on my projects and such...

 

[JimB]

d3dreaper said:

It's also quite amusing to read the lack of knowledge i had before lmao.

JimB says:
A brave and honest man!
Welcome back to the forum.

JimB

 

[audioguru]

Years ago, I made hi-fi speakers and purchased coils for the crossover network from a local high-end speaker manufacturer. My latest speakers did not sound correct so I used a high quality audio spectrum analyser from work with my pink noise generator and saw that the value of the coils in the crossover were incorrect.

I took the audio spectrum analyser and pink noise generator to the manufacturer and showed that the speakers in their demo room also had incorrect crossover coil values.