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Thread: Photoelectric Detectors

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    Registered User ProLawn's Avatar
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    Default Photoelectric Detectors

    Anyone ever seen or used a infrared beam security system? They have wired and wireless systems. Here is a wireless system. http://www.optexamerica.com/productp...l1=2&l2=&id=63 I saw them around the web for about $130. But thats just 2 units that would provide one beam. So I guess if you were wanting to use it in just your front yard you would need 6 units(2 for left side-2 for right- and 2 for front roadside) Thats around $400, not too bad, but wondered if anyone has found and used one cheaper. I saw this one that was posted on PC, but dont think I would like the "motion" sensor aspect. http://www.radioshack.com/product/in...ductId=3882712 Ive got motion floodlights now, that work about 70% of the time. Any thoughts?

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    This space for rent. Al in Raleigh's Avatar
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    Default Re: Photoelectric Detectors

    My sister had a wireless detector that interfered with her cordless phones. Having multiple wireless units in the same proximity might (quite likely) cause interference with each other unless they are spread spectrum wireless which I highly doubt because spread spectrum would be too expensive. The specification for photoelectric sensors will state an effective usage distance. That distance can vary with temperature and rain. The two piece sensors are comprised of an emitter and a detector. The emitter has a infrared diode (LED) in it and the detector has a phototransistor in it. If you plan to have the sensors near to each other, such as a corner, put the emitters into the corner together. This will make sure that the emitters don't interfere with each other. Certain types of light can overwhelm a phototransistor and cause false triggering. Shielding the photodectors from car lights might be an ounce of prevention. Most newer cars have halogen bulbs and if I remember correctly halogen light interferes with IR photodectors.

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    Trying to behave here-NOT John's Avatar
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    Default Re: Photoelectric Detectors

    I use X10 IR motion detectors. False tripping was at first a real problem. Caused by sun, clouds, temperature changes, animals, birds, falling leaves, almost anything would trip a single sensor.

    My solution was to introduce logic into the system. Both my driveway and door approaches are set up the same. Using pusedo ladder logic, the driveway ( and all doors) works as follows:

    If D1 (driveway sensor 1) Turns ON, start Timer1, and

    If D2 (driveway sensor 2) Turns ON, and Timer 1 < 6 seconds,

    Then D3 = ON and trigger Enter Driveway Announcement and alarm.

    The two sensors are approx 8 ft apart, one on each side of the driveway, and about 3 feet high. When someone (foot or vehicle) enters the driveway it trips sensor D1 then if sensor 2 is also tripped within six seconds, an alarm condition is created. If D1 is tripped but D2 is not tripped, then nothing. If D2 is tripped, but before D1 trips, then nothing happens.

    In my case, the X10 signal D3 turns on an electronic RoboDog in the garage, and causes the computer controlling the whole house speaker system to announce "Someone has entered the driveway" and also turn on the driveway security cameras.

    Before this logic system, almost anything tripped the alarms, and also they tripped again on exit.

    As you mentioned with your motion sensor floodlights, they are looking for a sudden temperature increase moving ACROSS (not towards) the sensor. Which may be why you indicated they only work 70% of the time, depending on how they are approached, from the side or directly.

    Just something to consider when thinking about this type of system for outdoor use.
    John (The Mascot)
    www.tennholidays.com

    480 LOR Channels + 2 CCR + 8 Mighty Minis + 10 Rainbow Floods+ 1 vdrive and vflood, Lynx Express and over 40,000 LEDs

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