Audio Level Meter

[Peter1960]

Hi, I'm trying to read the adc in to create an audio vu (level) meter, but the input is unstable.
Any suggestion on how to increase its stabilty, but maintain fast conversions, so the dsiplay doesn't lag the audio level ?
thnks
Peter

[penelopepug]

Hi! I'm not sure what you mean by the input being unstable? Is it too noisy to sample reliably via the analog input of your pic? Perhaps you need a sample and hold circuit or an active full wave recitifier which uses an opamp and an RC filter. Can you post your code and add some more detail to descibe the problem?

[PJALM]

Hi,

Is your audio source line level or speaker level? If it is from a speaker output then the signal levels will be too high for the pic and cause the instability, try adding a resistor (or a pot) between the PIC input and your audio source to bring it down to a level the pic can handle. You may even want to try using a voltage divider circuit.

I hope this helps.

Peter

[sougata]

Hi,

Please post the schematic and code with the PIC details. Otherwise it might be waste of time for both of us.

Regards

Sougata

[ritvarsrizikovs]

ADC for PIC is very stable!
I use 10bit ADC and max error ir one bit.
Need to use 7805 for stable 5V power, inductors and capacitors for smaller pulsation.

If You need simple Audio level meter, then use rectifier, resistor and capacitor. And Use Vref pin on PIC, to set max value. Thats all.

For More advanced level meter use OpAmp and create band filter or band filters and build up to 8 band spectrum analyser. With 16 OpAmps it is very simple to build. And for example 16F877 or 18F452 works fast. You can read all 8 channels and display. By software You can add peak detectation and build log scale.

[Excelcier]

I'm fairly new so be gentle, but could someone provide some sample code as a reference for me to build on? I'd really appreciate it.

[savnik]

and build log scale.

How i build log scale.
I use linear scale now.