Sat on a Toilet Sensor ?

["Marcus Warrington" <marcus.warrington@xxxxxxxxxx>]

OK.. I need some ideas for a little problem I have.



I am currently refitting our bathroom and I need a way of activating a
fan but ONLY when some is SAT on the toilet. The fan is a "pan
fan" that
extracts air from the toilet bowel to prevent.. err.. smells.. pervading
the room. I did a mini bulk buy of these a few years ago.. which reminds
me, Kevin.. I still have yours in a box somewhere.. let me know your
address and I'll get them sent to you!



My first thought was a PIR but that would be difficult to restrict to
only "sitting" on the toilet i.e. it would detect if someone
reached
down and lifted up the seat , or maybe even some one standing there to
pee etc.



Next thought was use an ultrasonic sensor mounted on the wall behind the
toilet bowel (the cistern is concealed in the wall) and adjusted to
point down at a 45 degree angle so that it covered the rear half of the
toilet. Problem is I'm not too sure how "focused" the beam can be
made
on these devices.



Another thought was to use a stress sensor (or weight sensor ?) on the
toilet bowel. In some ways this would be the ideal since it would not
rely on proximity to trigger. Problem is I have no idea what I'm looking
for, how much they are, how easy they are to integrate with a relay etc



Anyone got any ideas ?



Marcus



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