this is my first project and im confused about microphones, i want to conne ct four electret microphones to the Raspberry Pi and i dont know where to c onnect them, am i supposed to use analog/digital convereters ADCs, do i hav e to use amplifires with them or not.
i have figured everything else but im stuck at this point, please help me
I _think_ you won't need much, if any, amplification to use an electret microphone. If you do, simple op-amp circuits should work OK.
You _do_ need to use an ADC of some sort.
Does the Rasberry Pi have four analog input channels of sufficient speed, or do you need to add them?
-- Tim Wescott Wescott Design Services http://www.wescottdesign.com
On Fri, 25 Jul 2014 20:02:21 -0500 in sci.electronics.basics, Tim Wescott wrote,
Raspberry Pi does not have any analog inputs. A USB sound adapter could work for microphone input.
The FAQs say that you can add "any supported USB microphone". That probably means mono, possibly stereo, but certainly not 4-channel. There is at least one stereo input audio device available from Wolfson, but I don't see anything beyond that.
So you'll need to use an I2C device. Do a Google search for
"A/D input raspberry pi" (without the quotes) to see your options. My quick review turned up multi-channel devices that sampled at rather slow rates (3300 samples/sec for example on the Adafruit 4-channel 12-bit board).
So you need to decide how low a sample rate your project can tolerate, then see if there are any devices that can support it. As I noted on the DPS newsgroup, the *multi-channel* sample rate may be slower than the single-channel rate you see in advertisements. And you'll need that rate to be much faster than the highest frequency you want to measure. (At least 2x, but more would be better.)
Best regards,
Bob Masta DAQARTA v7.60 Data AcQuisition And Real-Time Analysis
my project requires about 8K sample/second for each channel, i couldn't find any A/D converter with that rate. is there a way or another ADC to obtain that rate ?
Can't use something like this;
Here is another idea which requires you to use a secondary small uC because I am sure the PI can not keep up with the data flow, with a helper processor you can buffer up the incoming and get packets of info in compressed form. Of course be prepared to pay the price! :)
Also with example, two of these will give you 4 in and 4 0ut.
Jamie
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