Why aren't cheap lasers being used as electric eye perimeter sensors?

NeverDie

NeverDie

Senior Member
Or, maybe they are, and I just haven't seen product?
 
I picked up a red laser pointer at the store the other day for $1, with batteries included.  It looks exactly like this:
pointer.jpg

 
The build quality is awful, but it works!  Yet, I haven't seen cheap electric eyes using lasers...  Why not?  Wouldn't it deliver longer range?  With a few mirrors you could cheaply zig-zag all over the place.  Handy for perimeter coverage?  Or is it too much of an installation hassle?  Or does it have to do with the "Danger" sticker that's on it?  If so, at what power setting would it no longer be a danger?
 
For comparison, I notice these Seco-Larm retroreflector electric eyes are fairly inexpensive ($41.50) and seem to have a decent range (35 feet):
41ppFnaNIqL.jpg

http://www.discounthomeautomation.com/Seco-Larm-Enforcer-Reflective-Beam-Sensor-SEE931S35RRQ?catargetid=120154320000144283&cadevice=c&gclid=CjwKEAjwwN-rBRD-oMzT6aO_wGwSJABwEIkJyv5HmOEhIXV2qsc4_em3q1UG9J0LydQxTpFs-izFehoCUOnw_wcB
The Amazon reviews are generally positive about it.  However, I presume having more than one in the same vicinity would interfere with one another.  Is that correct?
 
Which situations call for the use of an electric eye, instead of PIR or something else?
 
 I imagine those cheap lasers burn out quickly running them for a long period of time, if you blind someone with your laser I doubt it would end well for you in court.
 
The reason is lasers really aren't used for home parameter security applications is because the laser beam is too narrow and pretty hard to aim for this application. For the most part, these beams are IR, so a beam like a laser would be very hard to aim correctly over anything but the shortest distances. An IR LED with a lens produces a much more manageable beam in terms of installation. Plus a very thin laser beam would be susceptible to being blocked by very small objects, whereas a wider beam is more resistant to this while still detecting people. 
 
Lasers are used for more high-end applications, but they are very limited for residential at least currently.
 
I write a blog on laser uses in Laser Focus World. You can read my latest one on laser pico projectors here...
http://www.laserfocusworld.com/articles/2015/06/first-laser-picoprojector-in-a-smartphone.html
 
I like to use these:  http://www.amazon.com/Seco-Larm-Enforcer-Curtain-Sensors-E-9680-10B25/dp/B007I90UMY/ref=sr_1_4
It produces a wall of beams and works well. For example, I have one across my garage door to detect for obstructions, like my hatch being open. The beams don't interfere with each other because each is a different frequency. 
 
Beam sensors like this are best if you want to detect something blocking the beam. PIR sensors detect motion of warm bodies. IR beams detect one specific area where motion detectors detect large areas.
 
The place I once worked, we had a laser beam that ran across the basement parking garage from one entrance to the opposite entrance connected to the alarm.
One day a goose tailgated a car entering the door.   Later that night when the alarm was set, the goose went wandering and tripped it.  
 
The laser worked well when there was no water foul.   Same with in the office space with motion detectors until a bat or bird got in and set it off one night.  
 
What about pets.   Who has pets setting off motion detectors?
 
I have had rabbits triggering motion sensors in the back yard.  Today while it was raining I saw a small rabbit peering inside the kitchen via the deck door.  No motion sensors were triggered.
 
The deck is elevated a few steps from the ground and while we do have a few rabbits around I have never seen one climb on to the deck and hang around the door to the kitchen nook.
 
Ummm, how about the safety and liability issue of lasers in general, especially in locations that people could look directly into the beam?
 
Yeah; here a few years back over did it a bit with some Christmas laser display which I upgraded a bit cause it wasn't bright enough. 
 
It was very low on the WAF such that I retired the display that year.
 
DELInstallations said:
Ummm, how about the safety and liability issue of lasers in general, especially in locations that people could look directly into the beam?
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Laser with wavelegths greater than about 1.4 μm (micron) are what are considered "eye-safe."  What this means is that this wavelength range is strongly absorbed in the eye's cornea and lens and therefore cannot reach the sensitive retina. Being eyesafe is a requirement for lasers where people could inadvertently be exposed to them.  These lasers are higher IR meaning they aren't visible, but its easy to add another visible laser to be used just for aiming purposes.
 
I used an optical sensor on my old driveway in the late 80's in to the 90's.  It did work most of the time.  Yesterday we went grocery shopping and left in the middle of a rainstorm with a bit of wind.  I couldn't shut the garage door as the rain was triggering the IR sensor.
 
Dumb analogy but I always mention RF is RF and can be magical; similiar light is light (laser) and can be magical sometimes.  Like the use of mirrors to carry a beam endlessly across an expanse.  Like knowing a bit of electricity (knowledgbase) same holds true for the use of a laser when wanting to implement its use for automation.  (many folks unknowingly disregard those cautions printed on the device or want to experiment).  Personally one of my favorite tools today is that laser level when trying to draw a straight line on a wall. 
 
I like the idea of the car hatch open check.  Think too they do work better inside (well a garage) than outside. 
 
The price of low-cost LIDAR units will really be a boon to the home automation world.  This should open up many types of new lowcost sensors. LIDAR uses a laser to measure the distance to an object.  I have a LIDAR tape measure that i think i paid about $800 for 10 years ago. It can measure out to 300' with 1/32 accuracy. I have used it for years, but now the technology is getting much cheaper. You can buy LIDAR sensors that go about 30 ft for under $100 now. 
 
Why would you need one?  For years i have been attempting to make a reliable bed sensor, to detect when a person/people are in bed.  I had a reliable one for a few years that used a spring sensor under one foot of the bed and it worked, but it was a pain to adjust.  So my new idea is to use a LIDAR unit attached to a bed post to measure the distance to the blanket.  I thought about using ultrasonic but there is some evidence that long-term exposure is not good. A LIDAR bed sensor may work nicely. 
 
ano said:
For years i have been attempting to make a reliable bed sensor, to detect when a person/people are in bed.  
Click to expand...
Hmm... You just gave me an idea!  I have a sleep number bed.  The remote for adjusting the bed gives you a readout of the firmness - not sure if the scale is PSI pressure or not as they don't state, however, it is related to the pressure of the internal mattress chamber.  My normal setting when I'm on the bed is about 60, but when I'm not on it, it only reads about 10.
 
I could easily put a pressure transducer on the mattress feed hose to determine in bed vs out of bed based on the pressure feedback.  Cool thing is that you have separate readings for each side of the bed.  No more stumbling in the dark for that 2 AM trip to the urinal!
 
I have tried pressure mats without much luck.  Problem is it has to be very large and when laying your weight is distributed. You don't want normal movement to trigger it.  There are pads to monitor hospital patents, but they can be pretty pricey.
 
The whole bed is already a pressure mat.  There is an inflatable mattress inside the main mattress.  The sleep number adjusts the pressure of the internal air mattress.  I just have to put a pressure switch on the air feed line to the bed and I can tell if someone is laying in it or not.  I just need an adjustable pressure switch so I can set the cut out pressure.
 
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