Studying a TV image capture works. Barcodes can be extracted from PAL or
VGA images pretty easily once the software can determine their orientation.
The big problem with that is that image arrays draw a lot of current, and
they have to be on all the time.. Not workable for battery systems.

There's more to PIR (long wave, i.e. heat radiation) than meets the eye. In
an outdoor setting, for example, a very sensitive PIR detector can easily
pick up the steady radiation of the BIG BANG, and anything that interrupts
that radiation, even if cold, will be detected. That's not well know, but
is the reason persons and animals with heavy fur can be detected.

--Bob

At 10:31 AM 6/30/2003 +1200, you wrote:
> > Yeah, it would need amplification, that's 4 sure. I've noticed birds
> > don't seem to emit much IR ..................SNR wrt background IR is
> > quite high in winter
>
>Have you Googled for something like +murata +PIR ?
>
>A project of a couple of years ago involved using Murata piezo
>sensors to detect people in a room 10m away with a battery-
>operated micro. The sensors on their own are pretty limited to
>a lot of movement under metre but adding a Fresnel lens makes
>a huge difference. Amplification is TLC271s at low frequency/
>low current setting. As the unit had a timeout period after detection
>the V+ for the amps was supplied by a PIC pin. From memory the
>PIR part of the circuit used around 20uA. The range that needs
>boosting is at most a few Hz. I found that the simple circuit used
>was fairly insensitive to air movements. Common security light
>circuits I looked at were more complex and usually based around
>a quad amp like an LM324. Their complexity helps to prevent
>false triggering, but in our app that wasn't too much of an issue
>so we just went with amplication. PIRs themselves are pretty good
>filters anyway. The Fresnel lenses were got from a local alarm
>supplier. As only a narrow horizontal band of detection was
>needed it was found that using just a 15mm strip from the middle
>of the (originally 50x50) lens was sufficient. Be aware that lenses
>are available for particular applications - eg curtain, long range,
>short range etc - and you may need to optimise. And not all plastics
>are transparent to PIR so watch out for that. Some lenses found
>weren't intended for PIR
>
>I would expect that small furry animals don't emit much heat. Fur
>is, after all, a very good insulator. Have you considered something
>more sophisticated, eg a motion detector based around a camera ?
>A webcam and an IR spotlight would do. By comparing frames it
>should be quite easy (on paper) to detect a new object. Plus you
>get a picture of it. The resolution of the comparison could possibly
>be used as a filter to focus on a particular size of aminal. eg
>
>http://home.earthlink.net/~apendragn/gbcam/
>
>or Google for "artificial retina"
>
>--
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