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# Have been asked to pertake in Laser trip wire project

#### irishluck

##### New member
While you're talking about whether 1mw would last through fog/be sufficient to trip the photcell:
Have you considered the divergence? From the sound of it, you're building a triangle which covers approximately an acre of land. 1100' (is it feet?) is the distance given.
That divided by three is 366.67 feet, or 111 metres approximately.
And if you're planning to use reflectors to go the whole distance with just one laser, that's a significant increase in spot size.
Which makes me believe that using several lasers for one perimeter is a good idea (an idea which as been stated before, though for different reasons).
If you're going to be using a cheap red laser, the divergence is going to be rather poor at 1100 feet, and if it's only 1mw to start of with, energy density of the spot will really be rather low.
Infrared lasers also have rather worse characteristics in this regard, if I am right?
Anyway, my 2 cents.
Good luck!

EDIT: I did some calculations (which are probably wrong, I'm horrible at this stuff) and it puts the dot size at 5.11cm in diameter at 100 meters assuming a divergence of 1.5 mrad and an initial spot size of 2.5mm. That's what, 0.24mw per square centimetre?

EDIT NO 2: CALCULATIONS ARE ALL WRONG PLEASE DISREGARD I DON'T KNOW WHAT I WROTE
After people on here suggesting the multi laser setup, that is the way I will be going. No mirrors.

will use anywhere from a 5mw to 30mw laser. Going to run test on a few of them to see which may looks satiable for my needs.

Here is a drawling of what the acre looks like roughly that I have attached

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#### supermario680

##### New member

The answer to your "how to wire/trigger sprinklers" is TRANSISTORS AND RELAYS.

Here is a quick video I made of the setup. It involves an arduino microprocessor that was like 35\$ at radio shack, a 2n2222 NPN transistor to trigger a higher current relay coil. The relay can then be used to turn on whatever you want. The transistor was needed because the relay coil required a different voltage and more current that the microprocessor can output.

Other than that its just a cheap pointer diode I disassembled and hard wired to an output on the processor to turn it on and off etc... Bouncing it off a mirror and back into an IR sensor in this case with the analog reading on the computer screen.

Arduino DIY laser alarm IR relay out with transistor - YouTube

Sent from my iPhone

#### The Lightning Stalker

##### New member
After people on here suggesting the multi laser setup, that is the way I will be going. No mirrors.

will use anywhere from a 5mw to 30mw laser. Going to run test on a few of them to see which may looks satiable for my needs.

Here is a drawling of what the acre looks like roughly that I have attached
How are you going to do it with no mirrors? It would take a crap load of LASERs,
photodiodes, power supplies, and everything else. With mirrors, you just have everything
on one post. The beams come out of one side and return on the other. It's so much
simpler. No protection needed

The answer to your "how to wire/trigger sprinklers" is TRANSISTORS AND RELAYS.

Here is a quick video I made of the setup. It involves an arduino microprocessor that was like 35\$ at radio shack, a 2n2222 NPN transistor to trigger a higher current relay coil. The relay can then be used to turn on whatever you want. The transistor was needed because the relay coil required a different voltage and more current that the microprocessor can output.

Other than that its just a cheap pointer diode I disassembled and hard wired to an output on the processor to turn it on and off etc... Bouncing it off a mirror and back into an IR sensor in this case with the analog reading on the computer screen.

Arduino DIY laser alarm IR relay out with transistor - YouTube
You don't need an Arduino to do that.

#### supermario680

##### New member
You don't need an Arduino to do that.
I Don't recall saying it was necessary? I was just sharing what I had done.

#### Javalin

##### Active member
Irishluck, is this meant to be a test for a commercial product or is it just a general study on the effectiveness of a sprinkler system as a deterrent? If this system is a test on the viability of the laser trigger to be implemented by a consumer then you'll want to avoid mirrors. If this system will be installed by a professional company then you could look at mirrors but at almost a quarter mile the dot would be HUGE and thus power density would be dramatically reduced.

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#### irishluck

##### New member
How are you going to do it with no mirrors? It would take a crap load of LASERs,
photodiodes, power supplies, and everything else. With mirrors, you just have everything
on one post. The beams come out of one side and return on the other. It's so much
simpler. No protection needed
The problem with mirrors that Ive learned is that they are very expensive, and will need about 30 of them. The land isn't flat. So I half to deal with elevation and what not as well.

With multiple diodes, I dont need very powerful ones which someone posted something they found that was 10 diodes for \$30. Ive seen mirrors go for \$100 each.
Either way I use mirrors or multiple lasers I still have to use multiple boxes for the elevation difference.

Irishluck, is this meant to be a test for a commercial product or is it just a general study on the effectiveness of a sprinkler system as a deterrent? If this system is a test on the viability of the laser trigger to be implemented by a consumer then you'll want to avoid mirrors. If this system will be installed by a professional company then you could look at mirrors but at almost a quarter mile the dot would be HUGE and thus power density would be dramatically reduced.

Its kinda both. Ill explain. Its a general study first off to determine if its possible to use a high powered sprinkler system to scare off the animals.

If it works properly, much more study will go in affect to possibly sell the product locally for a better security system for crops being eating. Farmers put alot of time and work into those crops to earn a living and to have animals come in and eat them is just money down the hole. Thats why we are doing this.

Id be happy to post results up from my test on different diodes.

#### Slotguy

##### New member
I built something like this quite a few years ago. I pulsed the laser (Takes care of Duty cycle issues) and used a missing pulse detector for the trigger circuit. This was for a home alarm system. I seem to remember it worked pretty good, the missing pulse detector was adjustable to rule out false tripping. The limiting factor then was, being the early 90's, the available Laser diodes (680-720nm?) were in the far red band and were barely visible. I remember thinking how much a visible red beam 650-660nm would have made it so much easier. Bear in mind this was before Ebay, Amazon and most parts were sourced from the local Radio Shack, but I found that the books by Forest Mims III were very helpful in building the circuits.

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#### tsk1979

##### New member
Sprinklers... I think you are looking at a project to keep out animals. Traditional methods like "shock" or electrified fences can cause damage or injury.

Anyways, As for laser, you need a 10mW IR. Thats about it.
Good for over 100 meters.
Works in FOG too!

On the receiver type, you have to design based on what are you trying to catch. A sprinting cat, or a meandering cow.

Anyways, here is the Audrino version
Arduino Laser Tripwire

#### irishluck

##### New member
After a few months I am back with this topic.
We are actually starting to project now.

We have determined that we are going to use about 8 boxes housing 1 laser at about 12". It will use a photocell to turn the laser on at night. An arduino board will be used as well. The main power line will be 24VAC with 2 lines coming off of that. one line stepped down to 12VDC to the arduino chip and the 24VAC line going to the sprinkler valve to turn the water on and off. The arduino chip will control the main photo cell which is an arduino made board. Once tripped the arduino board will trip a relay for an average of 3 minutes of continuous water streaming and then will shut the relay off.

My main problems still I'm trying to figure out is finding a laser that will last being constantly on for an average of 10-12 hours a night. I'm also going to make this so where if a laser does burn out that it will be easily swappable. I want to use a low power red laser, not an IR beam. This is so we can make adjustments easier and can see the beam.

My 2nd issue I'm facing is how, how much, and what to power that laser with.

My last issue is what type of glass, plastic, lens I can use to attach to the weather proof box that will allow the laser to shine out of the box without messing with the beam a lot.

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#### BShanahan14rulz

##### Well-known member
Recommend keeping the power low. Less power = less heat = smaller heatsink volume or surface area required.

Aixiz modules are very common, ~12mm diameter. Even can find laser drivers that fit inside the module, so that all you'd do to replace is make the electrical connections, drop in this 12mm diameter cylinder into the heatsink block, tighten some screws, and realign.

Drivers: I don't keep up with the latest and greatest, but you may be able to find one that can take 12V and buck it, rather tahn burn off the extra voltage as heat. I'm sure someone can suggest a driver for you here.

AR coated glass window would be ideal. You'll still need to find a way to keep debris off of it, but shouldn't be that big of a deal. You can find super fancy lenses for watch dials and high end flashlights that have AR coatings, but even just a piece of flat glass would be ok.

#### Javalin

##### Active member
I have been running a diode that was like \$0.20 for 2542 hours and counting. For your purposes that's nearly a year without failing. If a 20 cent diode can make it this long I don't think you'll have too many issues as long as you stay away from DPSS lasers that are plagued by reliability issues (which you said you wanted red so that's not really an issue either).

#### IsaacT

##### New member
What if you built stakes to go into the ground, where the bottom of the hollow stake was your laser module with wiring hooked up. As the laser fires upwards, it meets a mirror to shoot the laser out of a hole in the stake that is covered by something, maybe an IR filter, and weather sealed(rubber tubeing around? Oring?). If the entirety of this is self incased in a metal stake that is wheather proofed you may get more life out of it.

If you need multiple heights, just add two more laser modules to the system and two more mirror/IR Filter holes to the top at the heights you need.

I read the first page but i am in a hurry so i didn't read pages two or three so if this has been suggested already whatevs. If not I think it would give you a good option and would be from its very nature in the form factor of a fence. Just make sure the ground is firm enough to hold it.

#### irishluck

##### New member
I have been running a diode that was like \$0.20 for 2542 hours and counting. For your purposes that's nearly a year without failing. If a 20 cent diode can make it this long I don't think you'll have too many issues as long as you stay away from DPSS lasers that are plagued by reliability issues (which you said you wanted red so that's not really an issue either).
Wow what laser are you using? that would be perfect!
Because we have calculated the laser to roughly be used for 1800 hours a year.

Where did you get this one from?

#### irishluck

##### New member
What if you built stakes to go into the ground, where the bottom of the hollow stake was your laser module with wiring hooked up. As the laser fires upwards, it meets a mirror to shoot the laser out of a hole in the stake that is covered by something, maybe an IR filter, and weather sealed(rubber tubeing around? Oring?). If the entirety of this is self incased in a metal stake that is wheather proofed you may get more life out of it.

If you need multiple heights, just add two more laser modules to the system and two more mirror/IR Filter holes to the top at the heights you need.

I read the first page but i am in a hurry so i didn't read pages two or three so if this has been suggested already whatevs. If not I think it would give you a good option and would be from its very nature in the form factor of a fence. Just make sure the ground is firm enough to hold it.
Well we have thought about mirrors except the think about them is they can get expensive for the proper ones =/

#### Javalin

##### Active member
\$1.65 5mW 650nm Red Laser Diode Module Head (5-Pack) 5-pack - 5V / parallel beam / dot light / outer diameter 6mm at FastTech - Worldwide Free Shipping

This is what I bought. They are actually \$0.33 each, but heck if it gets the job done... Like I said, if this can do it, ANYTHING can do it. As their price would suggest they aren't top-of-the-line in any category, they use a resistor as the power regulator. But they can be focused (to some extent, don't think you are going to get super precise) but you will be able to get the beam on your photocell.

I did the quick math and your 1100' perimeter broken into 8 sections gives you just over 130' per section which might be asking a lot from this diode, I haven't shined it more than 40' or so. I live on the 23rd floor and on the 10th floor there is a balcony that I can access. At 10' per floor this should be nearly exactly the distance you want. I'll see if I can get my girlfriend to help me measure the dot at this distance if you're interested.

EDIT, what are the dimensions of your photocell?

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#### irishluck

##### New member
\$1.65 5mW 650nm Red Laser Diode Module Head (5-Pack) 5-pack - 5V / parallel beam / dot light / outer diameter 6mm at FastTech - Worldwide Free Shipping

This is what I bought. They are actually \$0.33 each, but heck if it gets the job done... Like I said, if this can do it, ANYTHING can do it. As their price would suggest they aren't top-of-the-line in any category, they use a resistor as the power regulator. But they can be focused (to some extent, don't think you are going to get super precise) but you will be able to get the beam on your photocell.

I did the quick math and your 1100' perimeter broken into 8 sections gives you just over 130' per section which might be asking a lot from this diode, I haven't shined it more than 40' or so. I live on the 23rd floor and on the 10th floor there is a balcony that I can access. At 10' per floor this should be nearly exactly the distance you want. I'll see if I can get my girlfriend to help me measure the dot at this distance if you're interested.

EDIT, what are the dimensions of your photocell?
Ah yea Ive seen that one except I dont want to wait a month to get it now lol I should have ordered some of them last time I got stuff from that company. I may go ahead and grab some and see if there a few on eBay to test out as well.

This is the photocell setup I will be using!

NF-Arduino Sensor Shield Kit - PhotoCells | NightFire Electronics