Go Down

Topic: MEMS ADMP401 microphone for Voice Samples Recording  (Read 3899 times) previous topic - next topic

naidu003

hi , recently i have brought a MEMS microphone ( https://www.sparkfun.com/products/9868 )
for my project to record voice samples  , ADMP402 data sheet (attachment)

as this brekout board shows 200 milli Volts o/p

IS IT POSSIBLE TO record the voice samples with 200 m V range

DVDdoug

Quote
IS IT POSSIBLE TO record the voice samples with 200 m V range
That depends on what you plug the board into...    200mV is a little low for a line-level audio signal (or for the Arduino), and a little high for a microphone-level signal, but it might work in either application depending on the hardware you plug into.    (Most microphone preamps can handle 200mV.)

Of course, the actual voltage level will depend on the loudness of the sound and how close the microphone is to the sound.

Grumpy_Mike

An input voltage of 200mV on a 5V 10 bit A/D converter corresponds only to 42 different levels. So your sound will be recorder to a resolution of less than 6 bits. This means the quality will be crap.

naidu003

The thing is i have to replace the ADMP401 MEMS microphone instead of MAX9814 Microphone amplifier AGC
https://www.adafruit.com/products/1713


First prototype I have used MAX9814 microphone board to record the voice samples
https://www.adafruit.com/datasheets/MAX9814.pdf

It was good enough

I have done recording by connecting ADMP401 MEMS microphone to arduino mega

for code see the attachment 

but .wav files doesnt have any voice samples
 

naidu003

this is the recorded file at arms length with my voice


Grumpy_Mike


naidu003

find the attachment

i am thinking to do in this way

1. amplify the output of MEMS microphone 200 m V  using suitable op amp 

suggest me which op amp  can amplify properly 200mVolts to 2 V Peak to Peak with 20dB gain (voltage gain is Av=10) 

then 200m*10=2 Volts, hope this is enough to record the voice samples

 


naidu003


Grumpy_Mike


naidu003


Grumpy_Mike

Thanks.
I can see that you haven't got the hardware right. Most of the file consists of zeros. It should consist of around 512 for silence. The input needs biasing up to 2.5V.

The size of any change is only very small, less that 16. This means that the signal you are getting is way smaller than the 200 mV you are expecting.

Finally I am not sure that the header file is correct. When I loaded it into Audacity it thought it was a 32bit floating point sample.

naidu003

Thanks.
I can see that you haven't got the hardware right. Most of the file consists of zeros. It should consist of around 512 for silence. The input needs biasing up to 2.5V.
i have the solution for this , i have designed a op amp circuite which will bring the 200 milli volts to 2.5 base with 0-4.5 Pk-Pk

please reffer the attachment of circuit designing 

The size of any change is only very small, less that 16. This means that the signal you are getting is way smaller than the 200 mV you are expecting.

I have tested the miceophone at silence and playing some song at arms length , both sampled bit values and analog voltages are appearing to me as a same 

please reffer the attachment of .CSV file and pic shows the pulse processing output


Finally I am not sure that the header file is correct. When I loaded it into Audacity it thought it was a 32bit floating point sample.
I have no idea about this header file i got from APC digital recording project

naidu003

circuit designing attachment


.CSV file attachment  & pulse proccesing pic

Grumpy_Mike

The prcn picture shows that you have too much gain and therefore clipping of the audio, this will cause a great deal of distortion.

The CVS file shows you still have not got the DC offset correct. The silence recording should show values of 512 not zero. Also there should not be such large noise spikes.
I am not sure what the difference here is of the data columns and the recording columns.

What software are you using for recording?

naidu003

#14
Feb 06, 2016, 06:32 am Last Edit: Feb 06, 2016, 08:22 am by naidu003
The CVS file shows you still have not got the DC offset correct.
 
CSV file containing  the ADMP401 MEMS microphone output values i.e, 200 milli volts of output values
 
those values at COM port i have copied and paste it in a csv file , i have not done the amplification till now
 
using TL072 op amp is my next step to go for Av=10 with DC offset

THA VALUES IN CSV FILES SHOWS 0-98/0-3.3 volts WHAT DOES IT MEANS ?

 
What software are you using for recording?
Arduino mega2560 , with 2 button interupts , SPI - microSDcard  module
for code please reffer the earlier attachment above mentioned "APC_Digital Recording V 6.1"

Go Up