wstef@lowrider.eng.clemson.edu (W. Gregg Stefancik) (09/24/90)
I am looking for some good fairly inexpensive motion detectors. I wish to use them in and outdoor area as part of an intrusion detection system. W. Gregg Stefancik < wstef@eng.clemson.edu >
ee5391aa@hydra.unm.edu (Duke McMullan n5gax) (09/25/90)
In article <10572@hubcap.clemson.edu> wstef@lowrider.eng.clemson.edu (W. Gregg Stefancik) writes: >I am looking for some good fairly inexpensive motion detectors. I wish >to use them in and outdoor area as part of an intrusion detection system. Sitting across from me are three (3 - count 'em) infrared motion detectors from the in/outdoor "motion sensing" type of floodlight. This particular type is the Intelectron (TM) model BC 863K. The whole unit (including mounting plate, waterproof sockets, hardware, soft- ware (rubber washers, of course ;^), plastic bags and cardboard box) comes from the local Price Club for $15.99 plus state and municipal cumshaw. If you hook one up and snoop through the electronics with a voltmeter, you find that 16VDC seems to be what runs things. If you remove the rectifiers, filter cap and triac, then hook it up to 12VDC, you'll find that the sensing circuitry works just fine at that voltage. Pulling the optoisolater, you can feed the signal into the base of a switch- ing transistor, put a relay in the collector circuit, and switch whatever you bloody well please. I've got three of 'em over there on account of because of the reason is that I'm building three little motion-sensing space alarms for a local engineering firm. They'll switch a little security siren from Radio Schlock, the stock number 49-489A. Those little buggers run on 6-12VDC, and at 12V, they'll pin your eardrums together. I've seen naked motion sensors offered for about forty dollars -- not only is this cheaper, you get some rectifier diodes, capacitors, optoisolators and triacs to boot. You may not be able to get a price that friendly on a regular basis, but if you'll look for sales, you should be able to get 'em below twenty dollars with little difficulty. You'll want to do some experimenting. The things are given to falsing when outdoors, due to waving branches and wandering animals. They usually have a sensitivity setting, and location can be critical. The blurb in the box will give you a good idea of the kind of coverage you'll get. I've observed that they become noticably less sensitive in very hot weather, but you'd expect that. They will do better at night. Many of them have a luminance sensor that cuts them OFF in the daytime...watch out for this. The units I'm using have three time settings, and a TEST setting. In the TEST setting, they're on even in daylight, so that's the one I use. Your applica- tions may vary; likewise your mileage. Some of you will say: "Haven't you posted stuff about this before?" Sure. Other people have asked similar questions, too. Obviously, this isn't the only type of motion sensor around. It's one of the very best bargains I've seen, however. Additionally, it's damn hard to sneak up on these things. From the rear, sure, but I mean through the field. If you have that critical an application, several sensor heads can be combined for VERY wide-field detection. Let me know how it works out...I've only worked with this one brand of sensor (although I've examined another type with a meter), and I'd be interested in any new information you get. Alsoditionally, I'd like to know if anyone comes up with a RELIABLE way of sneaking through the field. Everything I've tried failed, but if there's a way, I WANNA KNOW ABOUT IT. After all, it's MY sec- urity system, too. I want to know about the holes.... G'luck, d -- "...he tore into them like a berserk Cuisinart, dicing and shredding and pureeing, scattering the ground with chunks of bodies, sending gouts of V-8 juice splashing through the air." -- Mark E. Rogers Duke McMullan n5gax nss13429r phon505-255-4642 ee5391aa@hydra.unm.edu
paul@hpldola.HP.COM (Paul Bame) (10/20/90)
> Alsoditionally, I'd like to know if anyone comes > up with a RELIABLE way of sneaking through the field. Everything I've tried > failed, but if there's a way, I WANNA KNOW ABOUT IT. After all, it's MY sec- > urity system, too. I want to know about the holes.... Most of the units seem to trigger due to changing light levels on the IR sensor. They use this funny plastic sheet to focus the IR in such a way that the visual field is essentially broken up into zones - each optical "zone" is separately focused upon the detector. When something moves across "zones", the detector sees a pulse. Some units may require only one pulse, some count 2 or more pulses (within some time limit) before triggering to prevent false alarms (like a lamp coming on within their field of view). So, either never move between optical zones or do so very slowly. I've had some success approaching a sensor slowly from afar without moving laterally across the field of view. This is risky since most of them seem to also divide the vertical view into fields as well - though not as many. I've also had luck moving VERY slowly laterally. In units which require more than one pulse to trigger, you should be able to move slowly enough that they think they're just seeing lots of false triggers. I've made up some of this but it's probably close - try it. Blinding the sensor with an intense IR source might work - or at least the de-sensitization might help the other schemes. -Paul "Spice is the Variety of Life" Bame paul@hpldola.hp.com N0KCL