That's cool.  Is this a commercial system or did you build it yourself.

John Dammeyer



> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Brian Taylor
> Sent: Wednesday, April 24, 2002 3:29 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: [OT] sensitive inhalation or pressure sensor
>
>
> I have an oxygen system for my sailplane that provides a
> short burst of
> oxygen at the start of each inspiration cycle.  The oxygen burst width
> varies with altitude and by firing the oxygen in at the start
> of the breath
> intake, the oxygen gets right through the lungs.  The over
> all system is
> extremely frugal with its oxygen use.  The system uses no
> mask, it has two
> tiny cannula that poke 10 mm into the nostrils.
>
> The pressure sensor is a capacitor fabricated on the PCB as a 50 mm
> diameter disk of vacuum aluminised plastic (looks like wine cask
> material).  This is vented to atmosphere one side.  When you
> inhale the
> small pressure drop in the cannula moves the capacitor plate
> and a '555
> (yep - it should be a PIC) changes frequency. This is sensed
> and the oxygen
> valve is opened for the required milliseconds.
>
> It all runs on one 9v PP9 battery and works to over 25,000 feet.
>
> Hope this helps.
>
> Cheers
> Brian
>
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