lagasse@biomed.UUCP (Robert C. Lagasse) (06/25/85)
I was interested in buying a PIR detector to mount on the side of my house to detect anyone around the cars in the yard and activate a relay to turn on some floodlights for a minute or so. Has anyone used these commercially available detectors? How does the detector ignore the hot asphalt pavement on a summer evening? What about a kitty walking by? What kind of beam shape do they have? Can it see a person through the car windows? (I would think not). Any comments are appreciated. Is this the right newsgroup for this? THANKS Bobby L @ MGH
jeff@abnji.UUCP (jeff) (06/25/85)
[intruder alert! intruder alert! Ha Ha Humanoid!]
I have specs for a PIR (Passive InfraRed detector).
They are made by Raytek Inc, a member of the Hoermann Group
(whoopie-doo!). 800-227-8074.
Specifications:
mounting: ceiling (recessed or surface)
[yes I know, you don't have a ceiling over your yard so
take this for what it's worth]
range: 16 feet
pattern: 21 degrees by 43 degrees in 10 segments
input voltage: 12-24 V D.C.
Current: 10 ma
Output: Form C relay 1 A at 30 VDC
Operating Temperature: -30 deg. F to 150 deg. F
Construction: high-impact thermoplastic
Dimensions: model 410 - 2-7/8 x 5" dia.
model 430 - 2-7/8 x 6.5" dia.
Weight: 1.5 lbs
Operation and coverage:
Raytek 410 and 430 Trap Detectors operate by sensing changes
in infrared energy levels within the detection pattern. When a person
enters the protected area his body heat abruptly changes the infrared
energy level and triggers an output from the detector.
The alarm relay has a built-in alarm timer. This is used to
extend relay dropout time for special applications, such as access
control. The relay may be held in the alarm state for any length
of time between 1 and 30 seconds.
The rectangular field it covers is divided into 10 zones, 5 by 2.
You can select which ones to use to avoid areas which will cause
false triggering.
Jeff 'purr softly and carry a big stick' Skot
at the very secured ATT IS
{ihnp4 | mcnc | cbosgb} abnji ! jeffcrandell@ut-sally.UUCP (Jim Crandell) (06/27/85)
> > I was interested in buying a PIR detector to mount on the side of > my house to detect anyone around the cars in the yard and activate a relay > to turn on some floodlights for a minute or so. At least some of the newer ones work pretty well indoors, although I haven't heard of any for outdoor installation, and I suspect that most of the common ones would be problematic there. To mention a couple of items, they may not perform well in environments where temperature varies widely, and most of them don't have too much range. They easily ignore the hot asphalt, because it doesn't move (they're motion detectors, you know). However, a massive, hot object in the background can obscure the IR image of the thing you actually want to sense. A kitty walking by may or may not pose a problem, depending on the size and temperature of the kitty and the sensitivity of the sensor, which can generally be adjusted over some range (the sensor, that is; adjusting the kitty is not usually a primary recommendation, especially if it's not yours). The beam shape is determined by the optics (lenses and/or mirrors) used in conjunction with the detector, and it can be just about any shape the designer can imagine. One popular shape is the ``fingers'' configuration, which can be likened to the ribs of a fan. PIR detectors sometimes appear able to ``see'' through house windows; many glasses transmit quite a bit of IR radiation. The heat-absorbing glass used in most car windows is a different matter, however, as you might expect. In indoor installations it is becoming popular to combine PIR detectors with detectors of some other type (e.g., ultrasonic or microwave) to improve the reliability of the indication. It is not greater sensitivity that is generally being sought, though, but greater freedom from false alarms (i.e., the alarm signals are ANDed, not ORed). -- Jim Crandell, C. S. Dept., The University of Texas at Austin {ihnp4,seismo,ctvax}!ut-sally!crandell