How do I connect a electret microphone to a PIC pin?

[Windmiller]

Hi!

My idea is to connect an electret microphone without preamp, with the output directly to a PIC pin.
I believe it should be possible without the preamp just because I'm only interested in getting the frequency, not the dB(volume)

My first question is..
Am I right? Will I get enough signal without preamp to count the frequency, or is it to low for the PIC to notice it?
I made my "googling", but ended up here asking my question instead.. hopefully someone knows by their own trial and error.

My secound question is.. this one's stupid I know..
The output signal from an electret microphone varies from 0V and up? It is never a negative value here? :roll:

Thanks!

Regards,
Morgan

 

[ard]

Yes, I think you should be able to connect the electret directly to a pic pin, thru' a capacitor. Just remember that the signal would rarely be a ttl-level swing, so chose an input pin that can be configured as an opamp, and count every time the signal goes higher than your refernce. Alternately, configure an input as an ADC, and again decide on a threshold, to detect the signal. With this, you should be able to measure frequencies of a signal with an amplitude of a few 100s of mV. I would also use a clamping diode, just in case the mike gives a high pulse.

Regards,

Anand

 

[Easyrider83]

I think, trying to attach mic directly to ADC input is a very bad idea.
First of all, you should find a CPU with the operational amplifier on-board.
Second, you need to apply at least low-pass filter.
And the last one - it is a very hard mathematics you should use - Fourier conversion. I tried to do that on a low range PIC MCU. The results was not very clear. I will send you my schematic tomorrow from office. It stored on my computer. Anyway, I used external operational amplifier with a low-pass and hi-pass filter.

 

[AKENAFAB]

Hi

Maybe some of these schematics could be helpful :-D

 

[poorchava]

You might want to consider using MSP430 series from TI. Some of them have integrated opamps or variable gain amplifiers. They are generally advertised as mixed signal controllers

 

[Windmiller]

Ard! Thank you for your answer, I'll try this, you made my believes even stronger now

---------- Post added at 21:56 ---------- Previous post was at 21:29 ----------

Eayrider83, thank you very much, i'm very interested in your schematics that would be very nice of you

Though, I don't need FFT in this one or DST because i'm going to use it in a place with no/little ambient sound where the microphone is going to pick up one single sin wave and test if it's around 220 Hz (A tone) by using timer and counting.. Still I'm very interested in your schematics. I'm starting to think that I need a preamp here.. maybe find a CPU with the operational amplifier on-board like you said.

---------- Post added at 22:03 ---------- Previous post was at 21:56 ----------

Akenafab, yes the 2-wire schema seems to be a good template to use, thanks!

---------- Post added at 22:16 ---------- Previous post was at 22:03 ----------

Poorchava, I'm going to take this chip into consideration, thanks for telling me about it.

 

[Easyrider83]

Schematic:

R9 and R10 may be excluded. They was needed to connect wires on one-sided pcb.

 

[joeyla]

Check this out:

https://www.olimex.com/dev/images/msp430-169stk-sch.gif

You could use the Mic section which is for Stereo input. Just use one part for Mono