Electronic Trip Wire

[Paul Kane]

Help please!
I am seeking to make an electronic trip wire, using a laser beam of light that sounds an alarm when an intruder breaks the light beam.

If any one has this knowledge to document in schematic format It will be very appreciaive and possible benifits.

The beam of light would be a distance of 165 ft. square and installed would work in both daylight and night time.

Phone: 714-225-1930
Thank you,
Paul Kane

 

[The Mad Professor]

There are plenty of circuits around for photo-electric break beam applications, most use infra red light rather than a laser but the principal is the same.

A lot of people are going to point out the obvious flaw with using a laser beam that can be seen as 'trip-wire' alarm, if the would be intruder can see it , what stops them from just stepping over it?

https://www.nlectc.org/perimetr/Full2.htm
All is not lost however, have a read of the above link and see if this gives any further ideas...

Must admit, though it's fiddly to set up, a Laser Fence is a damm good visible deterrent.
Add a couple of loudspeakers to provide that low hum to suggest in the mind the hidden slicing power of the lasers for added effect

 

[Torben]

A lot of people are going to point out the obvious flaw with using a laser beam that can be seen as 'trip-wire' alarm, if the would be intruder can see it , what stops them from just stepping over it?

Lasers (at least, of the type that would be used in an alarm system) are invisible in air unless the air contains enough particulate matter to reflect or refract the beam. A well-designed alarm system may be triggered if enough particulate is introduced into the beam path for the beam to be easily seen.

Even if that were not the case, it would be simple to use IR lasers, where even the reflections would be invisible.


Torben

 

[Torben]

Help please!
I am seeking to make an electronic trip wire, using a laser beam of light that sounds an alarm when an intruder breaks the light beam.

If any one has this knowledge to document in schematic format It will be very appreciaive and possible benifits.

The beam of light would be a distance of 165 ft. square and installed would work in both daylight and night time.

Phone: 714-225-1930
Thank you,
Paul Kane

Hi Paul,

Welcome to the forum. Search the site for 'beam break' and 'dark alarm'. This topic has been covered a few times before. Also, googling for the above terms should also turn up some interesting hints.

It would help if you could clarify the conditions. e.g. what are the distances you need to cover, what are the environmental conditions, what kinds of traffic might there be. . .?


Torben

 

[ericgibbs]

Hi Paul,

Welcome to the forum. Search the site for 'beam break' and 'dark alarm'. This topic has been covered a few times before. Also, googling for the above terms should also turn up some interesting hints.

It would help if you could clarify the conditions. e.g. what are the distances you need to cover, what are the environmental conditions, what kinds of traffic might there be. . .?


Torben

hi Torben
My long range lasers would work in moderate rain, not so good in a fog and poor in falling snow.

There are 'windows' in the absorbtion 'air' path, the gap at 904nM is reasonable

 

[Torben]

hi Torben
My long range lasers would work in moderate rain, not so good in a fog and poor in falling snow.

Hi Eric,

Would the lasers be easily visible in moderate rain? What if they were IR?


Torben

 

[ericgibbs]

Hi Eric,

Would the lasers be easily visible in moderate rain? What if they were IR?


Torben

hi,
The 904nM is of course IR and not visible to the eye.

The point I am trying to cover is that outside laser perimeter fences are subject to the weather conditions.

In heavy rain or snow the OP would have to turn it off.!

One of the problems is speed of response, as the beam is very narrow, it has to detect the 'leg' of someone walking thru it.

If someone walked thru it at say 5mph, thats about 7ft/sec and say the width of the lower leg is 6inches.
I make that about 70mSec blocking time.

Rain, snow and birds can give that block, causing the alarm to trigger.
He really needs two beams, about 1mtr vertical separtation, the lower one at least 0.5mtr above the ground. [animals]

We would make an exception for your cat.

EDIT: taking your earlier point about particulates, Myth Busters showed that if you put enough dust in the visible laser beam path to see it, the beam was bloacked.

 

[jpanhalt]

Here is an interesting report on large animal detectors for highway safety. They apparently use IR and low-power microwave(p. 106).

False positives are a problem. Dual beams is one way to reduce that number. That is, both beams must be broken for a positive. That avoids interference from, for example, birds. I have driven that stretch in Indiana many times, and the system certainly contributes to peace of mind at night.

The document doesn't have schematics, but does discuss reliability issues. Is interference from snow a problem in your part of SoCal?

John

 

[ericgibbs]

Here is an interesting report on large animal detectors for highway safety. They apparently use IR and low-power microwave(p. 106).

False positives are a problem. Dual beams is one way to reduce that number. That is, both beams must be broken for a positive. That avoids interference from, for example, birds. I have driven that stretch in Indiana many times, and the system certainly contributes to peace of mind at night.

The document doesn't have schematics, but does discuss reliability issues. Is interference from snow a problem in your part of SoCal?

John

hi John,
Slightly off topic.
There are domestic/outdoor PIR's and uWave Combo security lights, which need both sensors to be activated to sound an alarm.
I understand they are very effective and cause minimal false alarms.

 

[jpanhalt]

Sorry for the earlier cross-post. The relevance, as I saw it, was the data on field reliability and use of microwave vs. light. It is great to have a theoretical device (beam break or reflective), but actual data are often lacking with respect to false triggers.

John

 

[ericgibbs]

Sorry for the earlier cross-post. The relevance, as I saw it, was the data on field reliability and use of microwave vs. light. It is great to have a theoretical device (beam break or reflective), but actual data are often lacking with respect to false triggers.

John

John,
The ref to off topic was aimed at myself.! not you.

 

[Hero999]

PIR seems like a better alternative as there's no way somone could duck underneath the beam but you might need several sensors for such a large area.

 

[Paul Kane]

Trip wire project

I am not electronic savvy in the art. I want build the best and cheapest security fence using LED, Infrared or Laser that would detect an intruder from entering the perimeter of my property. It would give off alarm or sound or send a signal to my cell phone. Please direct to me to a simple means of accomplishing this task.
Thanks again,
Paul

There are plenty of circuits around for photo-electric break beam applications, most use infra red light rather than a laser but the principal is the same.

A lot of people are going to point out the obvious flaw with using a laser beam that can be seen as 'trip-wire' alarm, if the would be intruder can see it , what stops them from just stepping over it?

https://www.nlectc.org/perimetr/Full2.htm
All is not lost however, have a read of the above link and see if this gives any further ideas...

Must admit, though it's fiddly to set up, a Laser Fence is a damm good visible deterrent.
Add a couple of loudspeakers to provide that low hum to suggest in the mind the hidden slicing power of the lasers for added effect

 

[Paul Kane]

IR Laser security fence

Hi Torben,
It would be low density traffic, environment high and low desert conditions, distances of 100-660 in feet. I agree with you about the type of laser you mention a IR laser is best and probably the cheapest to make. I have desert property where I am vulnerable to intruders tresspassing and steeling my belongings from my property. I have been asked to put up a fences that would cost me $8,000.00 to surround my 1/2 acre peice of land. I don't want to spend the money when I can develop a security fence using electonic light beam to do the job for a lot less. I am also doing this project so that there may be some commercial value to sell it as a product to ADT and others who do not have this yet.
I have seen other devices on the internet but they are limited and unreliable only for swimming pool and cover just small areas. My idea will be to cover for large area of land a keep it bullet proof from intruder entering.
If you have knowledge in this area and can help me develop it. I would be very appreciative. Please keep this email confidentail.

 

[Paul Kane]

IR Laser

I am including this .pdf diagram that will explain to you what I am trying to accomplish.
Please let me know that you received this attachment.
Thanks.

Hi Torben,
It would be low density traffic, environment high and low desert conditions, distances of 100-660 in feet. I agree with you about the type of laser you mention a IR laser is best and probably the cheapest to make. I have desert property where I am vulnerable to intruders tresspassing and steeling my belongings from my property. I have been asked to put up a fences that would cost me $8,000.00 to surround my 1/2 acre peice of land. I don't want to spend the money when I can develop a security fence using electonic light beam to do the job for a lot less. I am also doing this project so that there may be some commercial value to sell it as a product to ADT and others who do not have this yet.
I have seen other devices on the internet but they are limited and unreliable only for swimming pool and cover just small areas. My idea will be to cover for large area of land a keep it bullet proof from intruder entering.
If you have knowledge in this area and can help me develop it. I would be very appreciative. Please keep this email confidentail.

 

[Paul Kane]

IR Laser security fence

This message is directed to Torben. I don't know if you got the first message so here goes a second message with an attachment for your eyes only.
Thanks,
Paul

 

[ericgibbs]

This message is directed to Torben. I don't know if you got the first message so here goes a second message with an attachment for your eyes only.
Thanks,
Paul

Hi Paul,
If you need to send Torben a private message, left click on his name box on one of his posts and send a pM or email..OK.

 

[Torben]

hi,
The 904nM is of course IR and not visible to the eye.

*smack*

That was the sound of me slapping myself for not reading properly.


Torben

 

[Paul Kane]

My IR Laser Project

Hi Eric,
I am sorry that I am making things worse for you but I don't know how else to communicate using the tools on this Forum.
Mainly I just need your professional advice about my desire to make a low cost electronic beam of light surrounding all four corners of my high-desert property like called a security fence using IR, laser diodes or anything else that would do the job. Please let me know you got this emal
My email address is kanetechnical@gmail.com.
Thanks,
Paul

Hi Paul,

Welcome to the forum. Search the site for 'beam break' and 'dark alarm'. This topic has been covered a few times before. Also, googling for the above terms should also turn up some interesting hints.

It would help if you could clarify the conditions. e.g. what are the distances you need to cover, what are the environmental conditions, what kinds of traffic might there be. . .?


Torben

 

[Torben]

Hi Eric,
I am sorry that I am making things worse for you but I don't know how else to communicate using the tools on this Forum.
Mainly I just need your professional advice about my desire to make a low cost electronic beam of light surrounding all four corners of my high-desert property like called a security fence using IR, laser diodes or anything else that would do the job. Please let me know you got this emal
My email address is kanetechnical@gmail.com.
Thanks,
Paul

Hi Paul,

You're not making anything worse for anybody else, but if you were hoping to keep the diagram secret I'm afraid the cat is now out of the bag as it's now been posted three times on a public forum (i.e., this thread).

I should point out that I'm just a hobbyist. The beam-break sensors I have made were for use in a foosball scoreboard, so the conditions were very favourable: the laser diodes and phototransistors are buried inside the black plastic goal cups. So only about 6" of space needed to be crossed, no weather or ambient light concerns, and no animals wandering through the beam--hopefully. There are many others here who would be able to help you more.

For your use I'd think you need what others such as Eric have already mentioned as far as dual beams, plus ambient light rejection. I believe that usually shielding and beam modulation are used to handle that.

Personally if it were my place, I'd prefer to trust the real fence option. Real fences don't need to be monitored, plus they offer a nice visual cue that says "keep out". If someone doesn't see the laser line they'll just walk through. If you're home you'll hear the alarm. If you're not, they get your stuff.


Torben