glass break circuit help!

[legolaslee]

Can anyone show me a schematic on a glass break schematic? I need it for my project, which is building a burglar alarm system.

 

[audioguru]

A hammer can break glass. I think you want a schematic for a glass break detector.
If it detects high audio frequencies then it can detect glass breaking or children screaming or noisy birds.

 

[legolaslee]

I see. Hmm is it possible to use **broken link removed**? then connect up the application circuit shown there?

 

[audioguru]

A photo of a sensor does not talk about how to use it.
Please attach its datasheet.

 

[rahulan999]

It's a datasheet only with application notes, from muRata. He is looking for a car glass break detector I think.

 

[shokjok]

You can use a reflective infrared emitter/ detector pair or ultrasonic units for non-contact application. A thin 30 guage wire embedded in the glass ( like a defogger/ antenna wire on a car), or glued to the glass also works.

 

[JKF1000]

Was wondering if it was some kind of mercury tilt switch?

 

[Hero999]

another option is to just tape a piece of foil to the window, when the window breaks the foil will be torn which will break the circuit.

 

[JKF1000]

You used to be able to buy alarm foil tape, it was self adhesive, I used it mainly in shop front windows, due to the size of the windows, been out of the alarm business a good few years now, so am guessing its no longer used.

 

[Nigel Goodwin]

You used to be able to buy alarm foil tape, it was self adhesive, I used it mainly in shop front windows, due to the size of the windows, been out of the alarm business a good few years now, so am guessing its no longer used.

No, they use glass break sensors now, and have for a good few years - they detect the actual noise of the glass breaking.

They actually work amazingly well - our alarm at work was triggered earlier this year, and the boss went round in the middle of the night and found
nothing wrong, but it said the glass sensor had triggered.

Later on that morning someone finally noticed a glass display cabinet had one side smashed - it had just 'popped' during the night

If you remember the foil tape, you must also remember the nightmares caused by cleaning the windows?

 

[JKF1000]

Yeah I remember having to laquer or varnish over them to add a bit of protection, didn't work too well,