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PICList Thread
'Cheap Accelerometers'
1997\09\23@125215 by John Shreffler

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For output and size, nothing beats Kynar film
produced by AMP in Valley Forge PA.  They
have a demo device which is a 1/2" x 3"
piece of film, laminated between two sheets
of light mylar, and a neon bulb riveted on one
end.  You hold it between finger and thumb
and wiggle, and the neon fires about ten times
in each direction, causing an arc of orange flashes
in a dark room.  I used the stuff for sensitive
microphones, hydrophones (buried in urethane)
and motion detectors.  It is not a static pressure
detector, only works on derivatives.

I have had comments in the past that my postings
contain weird trailers.  Could someone let me know
if this problem has been fixed?

John Shreffler
New Directions

1997\09\23@150946 by Matt Bonner

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John Shreffler wrote:
<snip>
> I have had comments in the past that my postings
> contain weird trailers.  Could someone let me know
> if this problem has been fixed?
If you mean that MS Mail attachment - gone!  (Let the other MS users
know how you did it.)

1997\09\24@031857 by Peter Baines

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Firstly "Thanks to all who responded to this thread so far" Your Ideas have
been an insperation. In fact I have now concluded that I probab;y don't
actualy require an Accelerometer but a 3 DOF movment detector, I am trying
to build a small device that I can attach to my snowboard that will sound a
LOUD alarm if anybody tries to "Borrow" it without my permission. It will
have a small keypad to arm/dis-arm it and must be about the size if a
ciggarett packet. it will run of a 9V battery. I have most of the keypad
and I/P O/P code sorted so far it's based on a 16c84. So if anybody has any
ideas on motion dectection please let me know. It dosent have to be linear
just digital will do. IE motion /no motion but the sensivtivity must be
quite good.

Thanks again for all the help so far .......


Cheers Peter ............

1997\09\24@035147 by Pasi T Mustalahti

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On Wed, 24 Sep 1997, Peter Baines wrote:

> Firstly "Thanks to all who responded to this thread so far" Your Ideas have
> been an insperation. In fact I have now concluded that I probab;y don't
> actualy require an Accelerometer but a 3 DOF movment detector, I am trying
> to build a small device that I can attach to my snowboard that will sound a
> LOUD alarm if anybody tries to "Borrow" it without my permission. It will
> have a small keypad to arm/dis-arm it and must be about the size if a
> ciggarett packet. it will run of a 9V battery. I have most of the keypad
> and I/P O/P code sorted so far it's based on a 16c84. So if anybody has any
> ideas on motion dectection please let me know. It dosent have to be linear
> just digital will do. IE motion /no motion but the sensivtivity must be
> quite good.
>
> Thanks again for all the help so far .......
>
>
> Cheers Peter ............
>
PTM: Make a small cage of wires that are insulated of each other. Three
wires should be enough. Connect the to a sounder. Put a metal ball in the
cage. When you move the cage, the ball rolls and makes new connections.

--------------------------------------------------------------------------
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Mail: Turun Yliopisto / Fysla, Vesilinnantie 5, 20014
Pt 02-3336669, FAX 02-3335632 (Pk 02-2387010, NMT 049-555577)
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1997\09\24@042648 by Keith Dowsett

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At 08:20 24/09/97 +0100, you wrote:
>Firstly "Thanks to all who responded to this thread so far" Your Ideas have
>been an insperation. In fact I have now concluded that I probab;y don't
>actualy require an Accelerometer but a 3 DOF movment detector, I am trying
>to build a small device that I can attach to my snowboard that will sound a
>LOUD alarm if anybody tries to "Borrow" it without my permission.

I have several suggestions.

The traditional tilt switch is a mercury switch. It comprises a ball of
mercury and some contacts. If it's tilted the mercury moves breaking the
contact. The main disadvantage is that it only covers a small range of
angles so you would need to stow your board the same way each time.

Another neat trick is to use a spring and weight system, similar to those
used in pinball machines to detect tilting. These are particularly sensitive
to sudden movements. You need a piece of piano wire which is fixed at one
end, and passing through a ring at the other. In the middle you attatch a
sliding weight, and adjust it so the wire doesn't quite touch the ring. Any
sudden movement and the piano wire touches the ring.

I'll try and sketch it here...

     ____                   .
     |  |---------WWWW-----(-)-
     |  |                   |
------+--+-------------------+-----

This will detect motion along two axis, and two of them, along each side of
a box for example, should detect acceleration along any axis. Main weakness
is that they don't detect very small forces.

Hope this helps,

Keith.



------------------------------------------------------------
Keith Dowsett         "Variables won't; constants aren't."

E-mail: kdowsettspamKILLspamrpms.ac.uk  or .....kdowsettKILLspamspam.....geocities.com

WWW: http://kd.rpms.ac.uk/index.htm
    www.geocities.com/CapeCanaveral/Lab/8979

1997\09\24@065828 by mikesmith_ozNOSP*M

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On 24 Sep 97 at 8:20, Peter Baines wrote:

> Firstly "Thanks to all who responded to this thread so far" Your
> Ideas have been an insperation. In fact I have now concluded that I
> probab;y don't actualy require an Accelerometer but a 3 DOF movment
> detector, I am trying to build a small device that I can attach to
> my snowboard that will sound a LOUD alarm if anybody tries to
> "Borrow" it without my permission. It will have a small keypad to
> arm/dis-arm it and must be about the size if a ciggarett packet. it
> will run of a 9V battery. I have most of the keypad and I/P O/P code
> sorted so far it's based on a 16c84. So if anybody has any ideas on
> motion dectection please let me know. It dosent have to be linear
> just digital will do. IE motion /no motion but the sensivtivity must
> be quite good.

There's something like that built into my alarm clock - its a 2 part
one - slides apart - one side is conventional quartz clock and
'normal' pip pip type alarm - other side is an 'industrial strength'
- "747 at 10 metres" variety.  Anyway, when you split it, the
industrial strength alarm has a slide switch on it, and a short
length of cord.  Idea is - you hang it on a motel door, to warn of
onexpected entry.  I suspect the device is using the very loud piezo
as both a mike and a sonalert - cuts down on parts.  Its
ultra-sensitive, there's absolutely no way you can remove it from
door without triggering it.  (it has a long attack envelope for the
volume - otherwise it'd be impossible  to disarm.)
MikeS
<mikesmith_ozNOSP*M.relaymail.net>
(remove the you know what before replying)

1997\09\24@114338 by kotay

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>
> On Wed, 24 Sep 1997, Peter Baines wrote:
>
> > Firstly "Thanks to all who responded to this thread so far" Your Ideas have
> > been an insperation. In fact I have now concluded that I probab;y don't
> > actualy require an Accelerometer but a 3 DOF movment detector, I am trying
> > to build a small device that I can attach to my snowboard that will sound a
> > LOUD alarm if anybody tries to "Borrow" it without my permission. It will
> > have a small keypad to arm/dis-arm it and must be about the size if a
> > ciggarett packet. it will run of a 9V battery. I have most of the keypad
> > and I/P O/P code sorted so far it's based on a 16c84. So if anybody has any
> > ideas on motion dectection please let me know. It dosent have to be linear
> > just digital will do. IE motion /no motion but the sensivtivity must be
> > quite good.
> >

Pasi Mustalahti wrote:

> PTM: Make a small cage of wires that are insulated of each other. Three
> wires should be enough. Connect the to a sounder. Put a metal ball in the
> cage. When you move the cage, the ball rolls and makes new connections.
>
You can buy this type of tilt switch at many discount parts
distributors.  Check out: http://www.allcorp.com/sw008.html#TILT
This is the All Ecectronics web page.  They sell this switch
for 50 cents.  I think Marlin P. Jones also carries this switch
but it is only in their catalog not on their web page:
http://www.mpja.com/

Keith

Keith D. Kotay
Ph.D. Candidate
Dartmouth College
EraseMEkotayspam_OUTspamTakeThisOuTcs.dartmouth.edu
http://www.cs.dartmouth.edu/~kotay

1997\09\25@134056 by Nic van der Walt

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> LOUD alarm if anybody tries to "Borrow" it without my permission. It will
> have a small keypad to arm/dis-arm it and must be about the size if a
> ciggarett packet. it will run of a 9V battery. I have most of the keypad
> and I/P O/P code sorted so far it's based on a 16c84. So if anybody has any
> ideas on motion dectection please let me know. It dosent have to be linear
> just digital will do. IE motion /no motion but the sensivtivity must be
> quite good.
>

Try this:

Take two concave glas circles. (Used in chem labs, don't know the
fancy name). I used ones about 1" in diamiter. Put a drop or two
of mercury on one and cover it with the other.

Now you have a conductive liquid runing around in an enclosed space.
Now you slip a couple of dozen contacts inbetween the two edges and
glue everything shut. As this gets bumped and tilted it makes and
breaks contacts like mad.

I read this with a PC where I  could dedicate 32 lines, but there
must be an trick with resistors and A-D's that lets you get away with
less. Or just put in only say 12 wires. Hook them up alternatly to
+ , input , gnd, input. Gives you six I/O's used and probably more
than enough sensitivity. Keep scanning the pins and when it moves
the bitpattern will change.

Nic

1997\09\25@174220 by Jean Mercier

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It seems that you need a cow bell !
Use one built for little kitty cat.
The inside metal ball hanging from a fine copper wire passing through an
isolated hole in the metal cup !

1997\09\25@185609 by TONY NIXON 54964

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Try

http://www.assemtech.co.uk/index.htm

They make all sorts of motion / vibration sensors.

Regards

Tony


Just when I thought I knew it all,
I learned that I didn't.

1997\09\25@211215 by athan Jhonson......KC7JHO

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A thermostat for an airconditonar has a mur. switch and will do exactly what the setup below will do.

KC7JHO
It's not just for radio any more!

{Original Message removed}

1997\09\26@141215 by Tim Kerby

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Hi
What about using a piezo electric cable or bi-morph element (available in
the RS sensors section) or more cheaply, use a mercury based vibration
sensor (like a tilt switch) these work in any orientation (3 DOF) and cost
about £1 UKP.


Tim

At 08:20 24/09/97 +0100, you wrote:
{Quote hidden}

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'Cheap Accelerometers'
1997\10\01@123454 by Christof
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On 26 Sep 97 at 19:02, Tim Kerby wrote:

> At 08:20 24/09/97 +0100, you wrote:
> >Firstly "Thanks to all who responded to this thread so far" Your Ideas have
> >been an insperation. In fact I have now concluded that I probab;y don't
> >actualy require an Accelerometer but a 3 DOF movment detector, I am trying
> >to build a small device that I can attach to my snowboard that will sound a
> >LOUD alarm if anybody tries to "Borrow" it without my permission. It will
> >have a small keypad to arm/dis-arm it and must be about the size if a
> >ciggarett packet. it will run of a 9V battery. I have most of the keypad
> >and I/P O/P code sorted so far it's based on a 16c84. So if anybody has any
> >ideas on motion dectection please let me know. It dosent have to be linear
> >just digital will do. IE motion /no motion but the sensivtivity must be
> >quite good.
> >
> >Thanks again for all the help so far .......
> >
> >
> >Cheers Peter ............
> >
> ------------------------------------------------------------------

How about a Mercury Switch?

Regards,
Christof

1997\10\02@165832 by jorgegf

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Hi everybody

...
Christof wrote:
>
> On 26 Sep 97 at 19:02, Tim Kerby wrote:
>
> > At 08:20 24/09/97 +0100, you wrote:
...
> > >ideas on motion dectection please let me know. It dosent have to be linear
> > >just digital will do. IE motion /no motion but the sensivtivity must be
> > >quite good.
...

       How about a paltform with 2 or 3 mercury bubble switches (organized on
an ortogonal structure). When arming the device you can read the current
status of the switches, and them react to any change on taht staus.


       best regards

       Jorge F

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