Thanks Dave
I'll try what you suggest..

The reason I use this 3pins ECMs'is because the other kind (2pin) are not so
sensitive.
I try them in some circuits but the sensitive was poor.


Regards

Tal Bejerano
AMC - ISRAEL


-----Original Message-----
From: pic microcontroller discussion list
[mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Dave Tweed
Sent: Sunday, June 09, 2002 4:12 PM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [EE]: Identify ECM pins


Tal --

> I am holding 2 Electret condenser microphones but can't tell the pinouts.
> I assume the pin that connected to the body it's ground.

Yes.

> but I know one is +v and the other one is output.
> are there a way to know for sure?

The only key difference between the two is a resistor -- the load resistor
of the internal FET preamplifier.

Try applying a voltage (+5VDC or so) to one pin through a 2200 ohm
resistor. If both pins measure the same voltage with a high-impedance
voltmeter, then the pin you're powering is the output pin and the
unconnected pin is the power pin.

If the unconnected pin is a lower voltage than the one you're powering,
then you're powering the power pin (you can take the resistor out now), and
the other pin is the output pin.

Many ECMs have only one pin besides the ground. This simplifies the wiring,
but you have to supply an external load resistor.

-- Dave Tweed

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