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'[EE] About capacitance sensitive schematic'
2007\07\17@114415 by Andre Abelian

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Hi to all,

last night some one stole my 2 security cameras by going on the roof.
Since there is an alley I put cameras just in case. now after 7 years
of living there without seeing any problem this is our first problem
seen. no thing got lost but this could be sign of some thing else.
My plane is:
any time some one goes on the roof turn alarm on

My question is:
around the roof there is 24 square feet metal that is isolated
thinking to add capacitance sensitive circuit if any once wants to
go on the roof it will trigger the alarm or any kind of sound.
The reason for capacitance sensitive is if they wear gloves it still
will sense it.

I know cypress PsOC does this but I am not good at PsOC and my
choice is PIC so far. Does any one have any capacitance sensitive schematic
that I can add to pic?

I can only see hand how he is removing the camera by bending the camera around
but what purpose I do not know.

thanks

Andre

2007\07\17@115652 by Xiaofan Chen

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On 7/17/07, Andre Abelian <spam_OUTaabelianTakeThisOuTspammason-electric.com> wrote:
>
> I know cypress PsOC does this but I am not good at PsOC and my
> choice is PIC so far. Does any one have any capacitance sensitive schematic
> that I can add to pic?
>

Check with Microchip and they should have already application notes
for the cap-sense application.

Xiaofan

2007\07\17@121325 by Bob Blick

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--- Andre Abelian <.....aabelianKILLspamspam@spam@mason-electric.com> wrote:

> last night some one stole my 2 security cameras by
> going on the roof.

Ouch! On the bright side, at least they didn't break
into your house afterwards, but that really sucks.
It's hard to sleep when you know people consider you a
target 24 hours a day.

> around the roof there is 24 square feet metal that
> is isolated
> thinking to add capacitance sensitive circuit if any
> once wants to
> go on the roof it will trigger the alarm or any kind
> of sound.

Capacitive sensing works because the sensor is
dramatically smaller than the object being sensed. So
I don't think it'll be easy to get it to work.

Cheerful regards,

Bob


2007\07\17@122051 by Walter Banks

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www.bytecraft.com/Touch_Sensitive_Switch

This is a starting point.
I would want to isolate the port pin from the roof.
A local cat could easily destroy a PIC.

w..


Andre Abelian wrote:

{Quote hidden}

> -

2007\07\17@132115 by David VanHorn

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I'd suggest a simpler sensor, like loss of video or breaking a loop
(with known resistor inside the camera housing)

2007\07\17@134106 by Timothy J. Weber

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David VanHorn wrote:
> I'd suggest a simpler sensor, like loss of video or breaking a loop
> (with known resistor inside the camera housing)

And: put that inside a cheap "dummy," obvious-looking security camera;
use a small, hidden camera trained on the decoy.  That way you may get a
better shot of the person removing the dummy one!
--
Timothy J. Weber
http://timothyweber.org

2007\07\17@140415 by Bob Blick

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--- Andre Abelian <aabelianspamKILLspammason-electric.com> wrote:

> if any
> one wants to
> go on the roof it will trigger the alarm or any kind
> of sound.

A friend of mine had problems with people jumping over
his fence. He solved it by putting two strips of
carpet tackstrip on the top of his fence. Not only was
it a repellant, he also got a loud audible signal each
time it got used :)

Cheerful regards,

Bob

2007\07\17@145539 by Recon

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Bob Blick wrote:

> A friend of mine had problems with people jumping overhis fence. He
> solved it by putting two strips ofcarpet tackstrip on the top of his
> fence. Not only wasit a repellant, he also got a loud audible signal each
>
>time it got used :)
>
>Cheerful regards,
>
>Bob
>  
>
Unfortunately You can get sued for damages in alot of states for doing
that.  You have to get the crook after he has done the dirty deed and is
trying to get away.

Recon

2007\07\17@165419 by Andre Abelian

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Hi Bob, every body

I like to thank all of you for giving ideas, suggestions
I will let you know the update later.

once again thanks

Andre






{Original Message removed}

2007\07\17@174806 by Walter Banks

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Theives have been known to take the replacements
in a week or so.

w..


Andre Abelian wrote:

{Quote hidden}

> -

2007\07\17@184821 by Robert Rolf

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Just use a pair of PIR (passive infra red) motions sensors on the ends of the
roof. The only way they'll see any 'motion' in the roof plane is if someone
is trying to steal the cameras.

As for capacitance sensing, just drive the roof with a high frequency (400kHz)
AC signal though a high value (1k) resistor (and coax). Any loading by a human will
cause the amplitude to drop. There will also be a phase shift so you could
use the PIC PWM to generate the AC drive, and the CCP to measure the delay across
the series resistor. Any load change will change the delay by enough uSec that
you can detect it. And with long term averaging for the threshold,
you can account for changes caused by rain, drying or temperature.

Just be sure to put clamp diodes/MOV on the cable sufficient to handle a lightening
strike <G>.

Robert

Walter Banks wrote:

{Quote hidden}

>>-

2007\07\17@190535 by David VanHorn

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On 7/17/07, Robert Rolf <.....Robert.RolfKILLspamspam.....ualberta.ca> wrote:
> Just use a pair of PIR (passive infra red) motions sensors on the ends of the
> roof. The only way they'll see any 'motion' in the roof plane is if someone
> is trying to steal the cameras.

Or birds, or bugs, or sunrise/sunset, or heating/cooling of machinery
and vents..


> As for capacitance sensing, just drive the roof with a high frequency (400kHz)
> AC signal though a high value (1k) resistor (and coax).

And apply for that international broadcasting permit!  :)
What happens when it rains?

2007\07\17@202017 by Russell McMahon

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> around the roof there is 24 square feet metal that is isolated

100 or 230 VAC on the isolated metal ? :-)


       Russell


2007\07\17@214754 by Richard Prosser

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Or, if it really is isolated, then it could build up a significant
static charge - even more so "with a bit of help" - say from an
ignition coil  or TV tripler. Current linited of coarse. Might help
any stray cat problem also,

RP



On 18/07/07, Russell McMahon <EraseMEapptechspam_OUTspamTakeThisOuTparadise.net.nz> wrote:
> > around the roof there is 24 square feet metal that is isolated
>
> 100 or 230 VAC on the isolated metal ? :-)
>
>
>        Russell
>
>
> -

2007\07\17@220937 by Roger, in Bangkok

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Souped up fence charger that can "jump" through the gloves, etc.

Augment that with a couple of flat runs of razor wire around the
eaves/gutters and you may well be able to collect some DNA samples :-)

Regards/Roger, in Bangkok

On 7/17/07, Russell McMahon <apptechspamspam_OUTparadise.net.nz> wrote:
>
> > around the roof there is 24 square feet metal that is isolated
>
> 100 or 230 VAC on the isolated metal ? :-)
>
>
>         Russell
>
>

2007\07\18@015244 by Yigit Turgut

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     Hi all,

     Assuming you do not have detailed knowledge about capacitors,
their nature consists of (plate-plate capacitors) by fixed distances
of any 90 degree linear line (lets say X) from a plate to the
other.Guy walking on your roof might or not trigger your capsense
alarm but not the way you think.When he stepped on the roof he will
break the length ratios of X's resulting your capsense application to
malfunction.And depending on your capacitance, it's possible for him
to end up dead.Also I haven't mentioned about rainy days, variable air
moisture and density.Meantime covering your roof with a metal plate is
not a good idea at all,  trust me.On the other hand (if you don't want
to kill the man) this technique makes no sense.Say everything written
above is handled somehow, you noticed there is a guy up, it's not wise
to get out and while your children and wife are at home.

What you need is a precisely calibrated action sensor triggering an
alarm or a siren.You can use PSoC for designing a module for
automatically calling the local cops, easy as making a cup of tea.

Cheers

Yigit

2007\07\18@080650 by Master Yager

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*Motion Detectors* – Use these awesome Motion Detectors inside your house to
be alerted of any movement. When someone walks by, your alarm will sound!
Wireless, cheap and will not hurt anyone.
http://www.x10.com



On 7/18/07, Yigit Turgut <@spam@y.turgutKILLspamspamgmail.com> wrote:
{Quote hidden}

>

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