If your intention is to detect AC but not DC then use capacitive coupling 
from the transimpedance amp or FET, which ever you intend to use.  The AC 
will pass through the capacitor (not literally of course) but the DC level 
will not. You can also put a band pass filter in so that you select the 
spectrum you choose.


----- Original Message ----- 
From: "Forrest Christian" <forrestc@imach.com>
To: "Microcontroller discussion list - Public." <piclist@mit.edu>
Sent: Thursday, July 05, 2007 6:49 AM
Subject: [EE] Very low power khz IR detector


>I need to build a circuit which will detect the presence of "modulated"
> IR... aka the type that comes out of almost any remote control.  The
> output will wake a PIC10F to blink a led in a predetermined pattern.  I
> don't need to decode the IR, but it does need to discriminate modulated
> IR from DC IR (light) and ~60Hz IR (Fluorescent).  It is ok if this just
> doesn't work when DC or 60Hz light is present as this device will
> typically only be used in low light conditions.
>
> The catch?  This needs to be battery powered, and small, and be able to
> idle waiting for an IR signal for months at a time without battery
> changes. I've been trying to figure out an option for this, but all of
> the modules I see takes around 1-2ma, which doesn't equate to "months at
> a time" on either 9V or 4AA's.
>
> Any ideas?
>
> -forrest
>
>
>
>
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