window screen proximity alarm

[nederlander]

Is there a simple circuit that would allow me to activate an alarm should someone touch any of the window screens on my house? I have some basic electrical experience.

thanks
Nederlander

 

[MikeMl]

Metallic screens?

 

[nederlander]

Yes, they are metal screens in aluminum frames.

 

[Birdman Adam]

This is a great idea for home-security. They don't even get to touch the window before the alarm goes off! Or maybe people are stealing your screens? I think you could have a circuit sense the change in capacitance when someone touches the screen. Since it's metal it should be easy to 'interface' with!

 

[magnatro]

the windows may be painted, so the idea of bird man may help.

try this: take a transistor wire it in switching mode and take another transistor couple it with the first and get a 2 stage amp. then the output can be fed to a 555's(wired in astable mode with speaker at pin 3) reset pin (4) and there you have it!

 

[magnatro]

a voltage divider network must be used at the first transistors's base and wire it as the sensor( to the frame)

 

[mneary]

More questions, first. For basic circuits to be useful, the screens and their metal frames need to be isolated from earth. In my house the wire mesh that supports the stucco is also touching other things like gas and water pipes, and electrical conduits.

You probably don't have this, but it's good to know before you build something.

 

[bychon]

My first thought is that there is so much electrical noise around that you'd have to drive a frequency into the screens and sense the changes from people affecting the frequency or loading down the amplitude..

 

[nederlander]

Lacking the need for an advanced project here is there someway to just electrify the screens to "wake up" anyone attempting to enter?

 

[danrogers]

Lacking the need for an advanced project here is there someway to just electrify the screens to "wake up" anyone attempting to enter?

yes, connect them to the mains supply

 

[nederlander]

ROFLMAO! Don't tempt me.......

 

[nederlander]

Having given this some thought overnight it appears it might be cheaper and simpler to but a cattle fence transformer and just connect all the screens, frames and doorknobs!

 

[bychon]

True. There are often cheaper ways than working for a week to make something elegant and safe. I hope the bad guys don't wake you up with their screaming and falling down noises.

 

[nederlander]

The goal is not to terminate anyone; just to keep them out. If you lived where we do how close do the murders have to come to your house before you wake up? Is a block close enough? My wife and I did not vote for this "new world order", we just have to survive it.

 

[bychon]

Cattle fence pulsers usually don't kill people. They just make 'em scream and fall down ;-)

 

[nederlander]

Cattle fence pulsers usually don't kill people. They just make 'em scream and fall down ;-)

If they scream and fall down it means they have penetrated my primary lines of defense and are now in the no mans zone. Maybe they will land on my punji stakes or nail boards. Then I will have a dna sample for the police. Seriously, a couple of years ago I found a boot knife with a skull handle outside my wifes sideyard bedroom window! Now how did that get there? I only use sabres. Rhodesian ridgebacks on order. Will start wiring the windows today.

 

[shortbus=]

Don't forget that the "hot" wire still needs to be insulated from any "ground". The fence wire is supported by plastic hold-offs in a field.

 

[Sceadwian]

The cattel fence electrifier idea would work fantastically... Until it rained, and the wood it was attached to effectively dead shorted the fencer electrifier to ground, or worse, the houses electrical system.

 

[AlarmTech]

Hello,

Are you aware that you can buy alarm screens? They have a wire woven into the fabric every few inches and connect to a plug and use your frames. There is a reed contact install in the frame opposite the take off point.

I have been out of the installation/purchasing field for over 3 years now but if you google alarm screens or contact local alarm companies in your area you might find what you are looking for. I remember the alarm contractor would mark and collect the screens then deliver them to the screen maker and get them back in about two weeks. Some screen companies would sell "kits" that allowed the dealer to make his own screens.

Look into this. It's got to be alot less safer than putting the mains on the screens.

HTH,

AlarmTech

 

[keny]

why not just square your whole house off with laser triggers?