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PICList Thread
'Tilt Switches'
2005\03\11@063742 by Russell McMahon

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>I am looking for a tilt sensor that can be rotated in the plane
> perpendicular to the ground without
> switching but will switch when horizontal to the ground (in any
> rotation
> that is horizontal to the ground).
>
> Imagine a ruler that is horizontal to the ground.
>
> I want an output as long as the ruler's long side is horizontal to
> the
> ground, even if it is rotated 360
> degrees around the horizontal plane.
>
> If it is standing up, (long side perpendicular to the ground), I
> don't want
> an output if it is rotated about the vertical
> axis, or is flipped end to end. (of course it would give an output
> as it
> gets horizontal to ground when rotated end to end).

The "modern" way to do this is probably with accelerometers.

But you could design a custom mercury switch to do this.
A pair of adjacent metal rings arranged vertically sit in a circular
"well" - like two parallel donuts inside an enclosing glass donut. A
mercury blob makes contact with both rings. (Or you could have a
single ring inside a conducting donut housing). This donut's axis of
symmetry is the same as the long axis of the ruler. Tilt the ruler too
far off axis in any direction and the mercury breaks contact.

Using accelerometers (or a single bipolar accelerometer) arranged with
its/their axis of sensitivity in line with the axis of the long ruler,
the accelerometer  will see maximum acceleration when the ruler is
vertical in either orientation (polarity changes). Process output
accordingly - ie horizontal when acceleration is below a certain level
with either polarity. This would be almost trivially easy to
implement.



       RM




2005\03\11@081511 by pic

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Russell,

Does the accelerometer give output for static conditions ?

It needs to switch when in the position rather than just changing of
position.

{Original Message removed}

2005\03\11@095153 by Herbert Graf

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On Sat, 2005-03-12 at 00:13 +1100, pic wrote:
> Russell,
>
> Does the accelerometer give output for static conditions ?
>
> It needs to switch when in the position rather than just changing of
> position.

Absolutely. When oriented the correct way an accelerometer measures the
Earth's gravitational field. Change the orientation and that reading
decreases (assuming the sensor isn't accelerating in another direction).

TTYL



-----------------------------
Herbert's PIC Stuff:
http://repatch.dyndns.org:8383/pic_stuff/

2005\03\11@154956 by pic

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Thanks for the information guys.

Regards

David.

-----Original Message-----
From: spam_OUTpiclist-bouncesTakeThisOuTspammit.edu [.....piclist-bouncesKILLspamspam@spam@mit.edu]On Behalf
Of Herbert Graf
Sent: Saturday, 12 March 2005 1:52 AM
To: Microcontroller discussion list - Public.
Subject: RE: Tilt Switches


On Sat, 2005-03-12 at 00:13 +1100, pic wrote:
> Russell,
>
> Does the accelerometer give output for static conditions ?
>
> It needs to switch when in the position rather than just changing of
> position.

Absolutely. When oriented the correct way an accelerometer measures the
Earth's gravitational field. Change the orientation and that reading
decreases (assuming the sensor isn't accelerating in another direction).

TTYL



-----------------------------
Herbert's PIC Stuff:
http://repatch.dyndns.org:8383/pic_stuff/

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