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
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
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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