How about two rubber flapper valves, one to allow airflow during inhale and
one during exhale.  Perhaps an optical sensor could be used to sense which
one is open.

-----Original Message-----
From: A.J. Tufgar [mailto:tufgaraj@MUSS.CIS.MCMASTER.CA]
Sent: Tuesday, April 23, 2002 2:57 PM
To: PICLIST@MITVMA.MIT.EDU
Subject: [EE]: Source of pressure sensor.


Hey everyone,
             I'm looking for a source of cheap pressure sensors like the
one below it's $32 CAD seems expensive for what it does.  I need to tell
if someone is inhaling or exhaling (into a tube), anyone have a better
idea or source?  Simple on or off is okay don't really need to monitor
pressure nothing fancy.  But it needs to be sensitive.
I was thinking of something like a small diaphram with two wires that
touch when there is a slight negative differental (inhalation) of
pressure (with respect to atmospheric pressure) in the tube and pull
apart when someone exhales (positive differental) this would be ideal
but where whould I get such a device?

http://canada.digikey.com/scripts/ca/dksus.dll?Detail?Ref=16003&Row=179460

Thanks,
Aaron

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