Multiple Electret Mics

Forum 2005-2010 (read only) Hardware Interfacing
#1

I'm trying to hookup six electret mics to my Arduino (one into each analog input). I spent a lot of time searching this site (and google) for circuits and I found links to a circuit using a 386 op amp and that works great (this site has a good photo of the circuit I'm using: http://www.berio.alg-a.org/spip.php?article105) .

Now that I have gotten one mic to work, I'm trying to scale it up. I made two amp circuits, each with their own mic, but for some reason both op amps are outputting the same voltage from either mic (even if the other mic is clearly not receiving any sound input). For my project I need separate outputs from each mic. Any ideas on what I'm doing wrong or suggestions for a better circuit?

Thank you in advance for your help.

#2

Has your mic 2 or 3 pins ?

#3

My mics have two pins.

#4

Ok, are your circuits wired as seen on these shematics :

http://www.josepino.com/circuits/index?mini_amplifier_lm386.jpc ??

Try something like that :

#5

Thanks for the help. Yeah, I have it wired like the circuits in the link. I’ll try it with the circuit you posted and see if that works.

#6

Please tell us if that works, or how you managed it.

#7

Hey

there's a schematic at the link below for an electret mic preamp, inside the zip file. This one is used for sound level detection, which is I assume what you are trying to do. You may have to play with the op amp resistor values, depending on the microphone used. I designed this one, and with the stated values it will amplify a whisper from across the room into something detectable by analogRead(). Gotta stress though that different mics have different qualities- the optimum setup is to use an oscilloscope on the output while tweaking the op amp values for maximum gain/lowest noise/highest stability.

http://www.glocal.ca/downloads/glocal_camera_trigger_june26_08.zip

Also, if what you're after is to mix six mics into one signal, then just look up "resitive audio mixer" in google image search, and pump the six op amp outputs into the resistive mixer.

D

#8