As mentioned in the title, I am looking to build a simple home security system to guard my front yard from would-be vandals. By this I mean friends who enjoy spreading toilet paper in my trees, put sofas on my front lawn, etc. I am looking for a way to put a perimeter "virtual fence" if i may call it that. This is not intended at all to be a security measure against any burglars or anything, just a fun project with a good use. If you are familiar with garage doors these days, they use electric eyes to prevent the door from coming down on a person or such, and I am interested in setting up 3 pairs of eyes that will detect if an object crosses them. Here's an image to explain what I'm thinking Ok the diagram is pretty simple, the blue lines being where I want to have "eyes" surrounding the front yard. the circles at the ends of the lines indicated an area that the eyes can be attached to (objects close by, trees, wall, mailbox, etc.) Second, the control panel should be in my room, where a light would go on and stay on for 5 minutes, or a buzzer/alarm would sound. It isnt hard to run wires under the driveway/sidewalk, because when we installed the concrete, we put hollow pipes to run things through if we needed to. Any suggestions would be appreciated.
Try using laser pointers modulated at some rate so the sensors can tell the difference between a laser beam and sunlight.
could you go into more detail? so i use laser pointers with some kind of AC adapter to let them stay on constantly, and then what do i use for the other end to decide if the circuit was broken?
You could use a LDR, in a box so that only light shining directly (from the laser pointer) will hit the LDR, and avoid the sunlight / other light. Heres a stupid diagram of my idea: P.S. There is most certainly a better way… just wait and see what gets posted.
Have you seen this: http://www.thesentrygun.com/ Even if you don't want the gun you could probably do it with a simple webcam and some motion sensing software. At night you could use some big infra red lamps to 'iluminate' the area Rod
3141592 - I like your idea to keep the sun from the light dependent resistor (LDR, but I'm not qualified enough to design an electronics setup that would do this. Say I want to have 2 wires out to every single component (example running like low voltage through speaker wire) such as electric for the laser pointers, sensing wire for the LDR, and whatever else, and then have them all come together in a small box in my room (or on the outside of the house). Obviously I would need some sort of power source for the 3 laser pointers, and also wires coming from the LDR to the main box, where some mechanism would trip a light or a buzzer assembly. could I make runs of 100ft or 90ft and still be able to detect when the laser beam is broken? Thanks
I also like the idea of Infra red lights to illuminate the front yard, so I can have a camera with nightshot enabled that i can see too. That would be way down the road, but a good idea.
I have been led to beleive that comercial laser pointer modules will not have long lifespans if used continously. YMMV but it would be something to investigate before setting up the system. Have you considered getting a dog
I've a suspicion somebody could sue you if you have laser beams criss-crossing your unfenced property...especially in your part of the world.
in the US? why would they want to sue me? all they would be is like the ones you buy for pointing use at some electronics store-not highpowered lasers. I do understand though, that some people could get mad. However, I am looking to pursue this project. Does anyone know what I could use to keep the lasers continuously supplied with power? Would a computer power supply modded a little take care of it? Waaaay too much power i think, but a little resistance might do it.
You could use IR lasers which are invisible. Or depending on the distances, even an IR LED and a lens may work. Then use 40kHz modulation on the transmitters and use IR receiver modules in the receivers. As for power, a wall wart should be enough.
just put lots of fishing wire around ur front yard, like criscrosing and stuff, and when they trip over and scream run out with a rife ( or a shovel) and say "your mine NOW!" and do an evil laugh!
yeah...but that takes all the fun out of the ELECTRONICS part of it. Sure, Ener, your idea would work, and it would work well, but too many innocent victims and i dont have a rifle - im only 17. star882-would a power pack-aka wall wart be enough to power 3 small lasers? also, anyone have a schematic on how I could use the LDR and have it trip a buzzer or light for more than a split second that the circuit is broken?
The photoEyes as they are called work in pairs and are to the best of my knowlage allready laser. As to the legality of using them like this their shouldn't be an issure as long as they cause no HARM to people since PhotoEyes have to met the reg anyway your cool. If you were to use laser pointers instead you may get issues becouse of the "possible Blindness" thing. This is all just off the top of my head. Note: about the photoeyes they are a pain in the *** to aline and they are Always getting knocked out by the littleist of things
I would recommend using only a single laser pointer and using mirrors to bounce the light to its final destination at the LDR detecting circuit. It would require a lot less wires.
yes, I really like the mirror idea, but would a laser actually work with them? This is now a distance of almost 150 feet, with it bouncing off of 2 mirrors.
If you did that, you wouldn't be able to tell what side of the yard the person was coming from, just that someone broke the beam.
no it doesnt really matter, my house isnt that big. Can anyone confirm that a laser will indeed travel at least 150 feet after being reflected off 2 mirrors? If it does, my job just got much easier - just one laser that is always on, and a LDR with a signal device at the end
