Electronics 2000

Hi all
I am new to this sort of thing but I need a simple (i think) circuit for an alarm system.

I am after having a kind off wire circuit that activates an alarm if the wire is cut, this wire would have a long length of around 100 metres or more. I need to cover a very large area and be flexible, I have seen conductive thread and thought this may be a possibility.

Could anyone shed light on what I should be looking at or point me in the right direction.

Many thanks in advance and hope you can help me.

VoodooJai

You could consider a fibre optics?

A fibre optic cable would be very hard to reconnect after a breakage,without a proper kit, that takes time and your intruder's enemy is time.
.. and you certainly could not bridge the break with wire & clips (as seen in movies) by an intruder.
The other advantage is that a 100metres is absolutely nothing in resistance terms in a fibre optic cable.

In its simplest form you would need a photo cell at one end and a light at the other. Obviously when the light went out due to a break in the cable it would change the resistance on the photocell
and you could use that to operate a relay with a 555 chip or something.
You would need a long life life,low consumption, reliable light like an LED for example.

A more complicated design would have a data stream travelling down the cable.Which could be anything (even Frank Sinatra) but when anything diffrent occured alarm bells would ring so to speak.

Biffo wrote:You could consider a fibre optics?

A fibre optic cable would be very hard to reconnect after a breakage,without a proper kit, that takes time and your intruder's enemy is time.
.. ............
...............

A more complicated design would have a data stream travelling down the cable.Which could be anything (even Frank Sinatra) but when anything diffrent occured alarm bells would ring so to speak.

I did wonder if fibre optics was a possibility, but need the thread or fibre to be very flexible so it can be bent into a tight wave like pattern.

Where would I get a circuit diagram for the fibre optic option.

Many thanks again.

VoodooJai

Just came across this post and wondered if you ever managed to resolve your query about using optical cables for this project? Fibre Optics would be an excellent choice from a security perspective with the only disadvantage being that it would probably cost a little more than a conventional copper circuit. There are many suppliers of outdoor CST (Ruggedised) pre-terminated fibre optic cables such as http://www.completeconnect.co.uk and there are even speciality manufacturers of optical based perimeter intruder systems now as well. I have a lot of knowledge on the optical connectivity side of things so if I can help then please let me know.

Electrical glue or paint ... conducting paint ... ebay.

Tar&stuff.