RE: Sat on a Toilet Sensor ?

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

Ian..



Nice to hear from you again... not so nice to hear about your impending
"no job" situation.



I had a look at the loo seat last night, and there ain't much space to
mount a wireless button press... only probably 4mm tops..



So, thinking about the ultrasonic solution again;



There is already power since the fan itself is mounted next to the
cistern behind the panel, ISTR it's a 9V transformer so the ideal would
be a controller that used the same power supply and simply tripped a
relay to power the fan (with a small overrun). I think the idea of a
timer that delayed activation is a good idea to avoid it tripping as
someone simply lifted the lid etc. In fact that's something I'd have to
check.. how high up the seat lifts, since the sensor would HAVE to be
mounted above this height to prevent the seat lid triggering it. My
concern would be the height would be such that it if you sat on the
toilet and was leaning forward (reading a book ?) , the detector would
have to be detecting at the same distance (i.e between your shoulder
blades) as someone simply stood in front of the toilet having a 'P'



Best solution may still be a strain gauge but does anyone have more info
on how they work.. i.e. do the just present a variable resistance on the
wire that is proportional to the strain on them ?

I would think it would be fairly simple to have a small hole in the
panel, that was at the bottom/back/underneath of the wall mounted toilet
bowl, and have a strain (compression) gauge mounted behind so that the
slight  leverage effect of the toilet bowl against it when someone sat
down would be detectable...???



Marcus

________________________________

From: ukha_d@xxxxxxx [mailto:ukha_d@xxxxxxx] On Behalf
Of ian.bird@xxxxxxx
Sent: 12 July 2007 10:07
To: ukha_d@xxxxxxx
Subject: Re: [ukha_d] Sat on a Toilet Sensor ?



I think the beam break is a bit of a non starter. The Maxbotix sensors
though hold the most promise and are far less prone to toilet humour too

;-)

You would need some brains behind it though as it effectively measures
the
distance from itself to something. When this changes the next read of
the
sensor will reflect the new distance. You would need to remember the old

distance and possibly implement a timer so it only activated the fan
after
a delay. That should stop false alarms. Any PCB and micro solution would

need power and a serial interface to change config (the latter in an
ideal
world).

Shout if you want more help. I could even build you something but you
would have to cross my palm with silver as time is now money as I head
towards no job :-( ----- I even have a sensor here too

Thanks

Ian

"Tim Hawes" <timsyahoo@xxxxxxx
<mailto:timsyahoo%40googlemail.com>
>
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11/07/2007 12:05
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Re: [ukha_d] Sat on a Toilet Sensor ?

I think what you need is a "strain" gauge... (snigger) ;-)
Seriously though, perhaps a better term would be "load cell".

As an alternative, Ian modified a Maplin beam break sensor to indicate
traffic through a doorway (IIRC), maybe you could mount one firing
across the toilet seat and include a timer so it only activates the
fan if the beam is blocked for 10seconds say, to avoid false triggers
due to the seat being lifted etc.
Also IIRC, there's some details on his site at: www.mollyology.com

There's a lot of this beam-break stuff used on industrial machinery as
interlocks instead of physical guard rails/barriers. RS
(http://rswww.com <http://rswww.com> ) has a
selection, but at
industrial prices :-(

One final off-the-wall suggestion, put an electrode on each side of
the toilet seat, when the person sits down they make the circuit and
you can use that signal to start the fan (a bit like the battery
testers that were fitted to the sides of some duracell batteries).

HTH,

Tim.

On 7/11/07, Marcus Warrington <marcus.warrington@xxxxxxx
<mailto:marcus.warrington%40mis-es.com>
> wrote:
> 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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