Security System

Let's Make Robots
1

Hi all,

To start with, this has nothing to do with robots. I'm seeking advice on a security system.

I've been tasked with securing a length of fencing, to prevent a reoccurring intruder. This is to help a friend, who is feeling threatened by someone creeping around at night and any advice, you can offer will be received most graciously.

As neither myself, or friend has stacks of money to plough into this project, I thought a simple Arduino system may be in order. Due to me being outraged by this intruder, I'm struggling to think straight, not to mention working out a system in my own head, so thought I could rely on some advice from all you LMRers.

The fence in question, is approximately 200 yards long, 4 foot high and of wooden construction. The interior of the fence houses animals, while to the exterior is a bridleway (dirt track). The intruder is known to be climbing over this fence. Due to local regulations, the fence can't be made higher, or barbed wire, etc installed. One end of the fence houses an out building, with power and to the other end, is hedge row.

I'd like something, that would trigger an alarm, or light, even a camera, however, due to the length of this fence, I'm unable to fully work out the triggering mechanism. Animals in the field also need to be considered, as these could easily set off the device, when scratching at a fence post, or similar.

As I say, any advice will be gratefully received, but please remember to keep costs down.

Thanks guys

2

Security of security

Even with lots of PIR sensors and photocells, the thief may as well cut the wire off and disarm the sensors.

You could use some kind of robot sentries or solar led lamps triggered by movement.

3

Crazy thought

Add a couple of hoses that run the length of the fence. Figure out a way to test the pressure in the hoses. Also, add a sensor to let you know if water is gone. A bird won’t weigh enough to cause a pressure increase, but, someone lifting themselves over the fence will cause an increase.

I wonder if a gravity fed reservoir with a flow meter might alert you to both pressure and a leak.

</brainstorm>

4

Same can be do electrically

Pressure switches do exactly that, but it may get expensive. Or lever switches on the upper bar of the fence; when climbing it will push down the lever switch, so you know exactly where, if these are wired it parallel or many tiny I2C controllers.

Anyway powering the fence is going to cost much power and work, i’d prefer to have some kind of guardian watching the fence. Guard dogs may be an effective choice.

5

Maybe this image will be worth a couple words.

6

Thanks guys,I knew I’d find

Thanks guys,

I knew I’d find inspiration on LMR.

I had a few thoughts myself now too. Perhaps I could have some input back, as these work in my mind, however someone else may spot a flaw.

A tight cable on the outer of the fence, so when pulled, or moved, causes a trigger at one end. If positioned correctly it should be out of reach of the animals. I had thought of fibre optic cable loosely connected in sections, so if a connection is broken, then that’s the trigger. This type of cable makes it prohibitively expensive, however.

Is there a way of running a single wire along the fence, so when touched, it goes to ground? Like an electric fence, but with less voltage, so there’s no shock?

Thanks for the help guys.

 

7

Thanks Silux,Guard dogs are

Thanks Silux,

Guard dogs are by far the best option, however there are a number onsite, which haven’t so much as growled, suggesting the dogs know the intruder.

8

Thanks Birdmun,Your idea,

Thanks Birdmun,

Your idea, may be worth exploring.

 

9

I had considered attempting a circuit to ground as well.

Realizing that the invader is likely wearing gloves and shoes, I imagined the path to ground would be all but impossible to create. That is what caused me to consider the hose/flow meter approach.

A cable pulled taught will give you a heads up when extra tension is added, but, you also need to know if/when the cable is cut. I suppose a system with a pair of switches, one to sense extra tension and the other to notify you if/when the cable is broken. I am envisioning a triplet of plates. The two outside plates are for over/under tension. The center plate has a couple of linear bearings/bushings that allow the other two plates to slide side to side and a couple of springs to keep the proper spacing for when the cable is tight but not too tight/loose.

10

Thanks Birdnum,I really like

Thanks Birdnum,

I really like the hose idea, the more I think about it, the better it becomes. It may become a reality soon. Due to the British weather, it is probably going to need an element of antifreeze in it.

You’re right about the gloves too.