Digital Sound Meter

...hey anyone der can help me how to contruct this project...i decided to use pic16f877 to display the value of a sound in dB into the LCD...please help me how to program..thanx...

There are a number of projects on the net where people use small micros to make a db meter.

There are several ways to do the ‘analog’ part of the project. One is to use op-amps and diodes to change the audio signal to rectified, filtered DC. Look for db meter information and then replace the meter with a micro.

The other way is to send the audio directly into the ADC and let the software do the rectifying and filtering. That worked for me for average reading and peak readings but I had to move up to the PICF18xxxx to get speed for RMS readings.

Driving LEDs is simple and fast. When I used a LCD the time it takes to talk to the LCD is too long to do the RMS conversion and up data the LCD. If you use the analog rectifiers and filters then the computer is not very busy and can talk to the LCD just fine.

**broken link removed**
Low cost SP/DIF level meter and audio monitor
Microchip Technology User Forums
AN #107 - Logarithmic bar graph (LED and LCD) - MCS Electronics

Funnily enough, the first question I ever asked on here was how to generate a log scale for an audio meter - I was building a PIC stereo replacement for an LM3914/5 - and required to be able to switch it to either lin or log.

The design used a 16F876, and fed two rows of 16 LED's, used two pins as analogue inputs, a third one to select lin/log, and a fourth as a 2.5V reference.

Anyway, that post generated no immediate answers - and I had to work it out myself

Basically I used a loop in Delphi using the log command to print a sequence of 16 values out for voltages from 0 to 2.5V.

...really?..it is possible to do the rectifying and filtering of the audio input?...actually i'm experimenting the rms detector...but until now it doesnt work yet...

eliamex said:

...really?..it is possible to do the rectifying and filtering of the audio input?...actually i'm experimenting the rms detector...but until now it doesnt work yet...

Click to expand...

Oh yes. See the image.

You can do something with the DC level to get at your RMS value.