Metal (vehicle) detector

Joseph Gwinn wrote:


It will still be worthless. You want RG-6 or larger, or modulate the video and send it as RF. The baseband signal will lose most of the higher frequencies (lose resolution) at that distance. Look at the data on the cable you are looking at and see how steep the rolloff is from DC to 5 MHz.

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What if somebody WALKS in? We have been using a Dakota Alert IR unit for the last 15 years to signal us by rf from 600 feet away. We added a box from them that gives us a 20 amp set of relay contacts with an on-timer. I bought one of those half-million candlepower 12 volt hand lanterns, got an 8 amp transformer from Surplus center and hooked it all up. I don't have a hill in the way, so the recieving equipment is in a spare bedroom. If I go down to get the mail after dark, I can read it at the mail box. The light, aimed at the very end of the driveway where the mailbox sits, almost blinds you at night. Yes, we get a few false alarms, but they are almost always deer or the stray cat who seems to "come to work" here in the late morning and then go back to wherever at night. The transmitter uses a 9v battery which lasts about 8 months.
Just a note on the lamp: I am amazed at the life of the bulbs. I have only replaced 3 or 4 in 15 years! The thing gets activated several times EVERY day.
I have thought about the camera idea from time to time, but haven't acted on it. I think that I'd put the camera in or on the house and use a long lens. That way there's less stuff for vandals to ruin. Then there's the issue of what to do with the camera images. Do you store them? PC? How long? How much of your life do you want to devote to watching the UPS guy turn around in your driveway? Does it "film" constantly or does it simply "wake up" when called upon by an alarm? Is it IR or does it have to turn on a strobe or something to "see" in the dark? If it does "flash" at night, won't the intruder just yank the thing out and take it away? I have also thought about getting one of those hunters' cameras, that take pix when the deer walks by. A friend has one and it works well, but it is a film camera. They must have digital ones by now.
Pete Stanaitis -------------------
nick hull wrote:

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Walking in is less of a problem and when they do there is no way I can monitor thousands of feet of line fence. OTOH if they park outside my gate I want to know about it wether or not they walk in. I live on a dead end road, the nearest neighbor is 1/2 mile away.
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nick hull wrote:

Actually, it's relatively easy to monitor the fence line if you do it appropriately.
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If the fence is cleared and sturdy it's not bad. Mine is old, grown up, difficult to clear, hilly, wooded etc. No convienent perimeter road ;(
Free men own guns - www(dot)geocities(dot)com/CapitolHill/5357/
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nick hull wrote:

Think a few IR laser beams shooting down the length of the fence line at suitable positions. Might not catch folks using night vision gear, but I suspect they aren't the issue.
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It would take many, my property has 12 sides and many are hilly and would require multiple lasers per side. Just getting power to that many remote points would be a challenge.
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nick hull wrote:

Good sized flock of geese to guard, some remote microphones and a bit of processing to trigger your alarm when the level of cackling gets too loud? Or guard dogs with anti-bark collars hacked to transmit to the alarm rather than shock the dog. Can't beat bio-sensors :-)
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As Bill Gates has discovered, each goose craps ~4# a day of fertilizer....
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http://www.meco.org/catalog/product_info.php?cPathA_42&products_id 0 "They couldn't hit an elephant at this dist..." Maj. Gen. John Sedgewick, killed by a sniper in 1864 at the battle of Spotsylvania
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On Sun, 21 Dec 2008 03:00:31 -0800, the infamous Gunner Asch

The 3rd time I tried this link this morning, I waited for about 5 minutes and it never did fully load.
Here's a cartoon I'm sur you'll love: http://www.daybydaycartoon.com/ for today, Sunday, 12/21/08
P.S: Happy Solstice / Joyous Saturnalia to all today! http://www.candlegrove.com/solstice.html
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On Wed, 17 Dec 2008 11:40:46 -0600, spaco
<snip>

Yup! lots of digital trail cameras around now. Poke around at Cabela's website for some examples.
It you happen to have an older digital camera collecting dust that still works, take a look at this sites stuff:
http://www.pixcontroller.com /
Complete packages and do-it yourself stuff. No experience with them, just found the site a while back and thought they had some interesting items for sale.
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Leon Fisk
Grand Rapids MI/Zone 5b
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nick hull wrote:

Don't forget the remote controlled klaxons. ;-)

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The detectors routinely used in conjunction with traffic control are inductive. They use buried wire loops as sensors. They're able to sense automobiles and motorcycles. They're not expensive but I don't know where you'd get just one. Might try to talk to a city, county or state traffic engineer in your locale. Most significant signallized intersections outside of inner city grids use a bunch of such sensors. http://www.humantransport.org/bicycledriving/library/signals/detection.htm
http://www.globalspec.com/FeaturedProducts/Detail/EMXIndustries/Miniature_Vehicle_Loop_Detector_for_Gate_Doors/37834/0 Wireless live camera coverage requires significantly more bandwidth than annunciation of alarms. Very inexpensive 432 MHz radios (like $5 at Mouser and DigiKey) can handle annunciation or "alert" over 700 feet with an intervening hill, but not live video. But then, PLC (power line carrier) could also do that. X-10 is PLC.
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What you need is a tall pole next to your entry gate. Go down to the local medical supply house and get a realistic looking plastic skull. Place it atop the pole. Hand a 'No Trespassing' sign beneath it.
Most people will get the hint.
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On Sat, 20 Dec 2008 20:04:46 -0800, "Paul Hovnanian P.E."

Print some of these up and put em along the fence line
www.glasgowaccies.cc/img/minefield.jpg
Dig a few small craters and put some clothing bits in and around them, inside the fence.
Or some of these....
http://flickr.com/photos/pincharrata/416718486
Gunner
"They couldn't hit an elephant at this dist..." Maj. Gen. John Sedgewick, killed by a sniper in 1864 at the battle of Spotsylvania
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I picked up a GE GE5806DWM "Driveway Monitor Alert Unit" at Lowe's several years ago. It appears to be a fluxgate magnetometer.
The sensor is about 2x3x6" and eats a pair of "C" cells every month. I set a 4' piece of 4" plastic DWV pipe with about 12" buried; the exposed part was painted with plastic furniture paint. The top cap was left loose so I can change batteries. Sensor has a detection range of about 30'. The thing runs on 433.92MHz. The receiver only "beeps", no contacts for external alarms; also alerts on low transmitter battery. My receiver is in the den and the sensor is mounted about 300' up the driveway with a clear line of sight. I didn't try it at longer range as the upper end of the driveway is shared with a neighbor. If you put an external yaggi antenna on an appropriate pole on the receiver end you could probably make the 700'.
The box worked without a single false alarm for a couple of years, but for the last two or three years I have gotten multiple false alarms when strong weather fronts come through. A friend of mine about 20 miles away also has one of the things and the couple of times I have asked him he has also had false alarms about the same time. Guess there are some earth field glitches associated with strong weather fronts. Also had a couple of false alarms during thunderstorms. I have considered adding a second unit with some processing to ignore simultaneous alarms.
Looks like this is the current incarnation: href="http://www.lowes.com/lowes/lkn?action=productDetail&productId4405-60740-FM131&lpage=none" A high antenna at the house should be able to stretch the range. Powering the transmitter from the AC line should not be a major problem, just add a REALLY GOOD surge supressor to the power line as 700' of (I presume) buried power cable is really good at picking up lightning strikes.
As to perimeter sensing, anything optical has to be able to handle flapping brush, geese, swans, rain, fog, and bambi 8o) So far it looks like sticking to vehicles and the inside of structures.
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I need one of those - was thinking of optical. Mag is better. Since we have hogs, and other vermin like deer that walk the driveways.
Remember lightening is a high current that discharges into the ground. Magnetic and electromagnetic flux is generated and it far exceeds that of a power line.
I'd rather have a random false once in a while than no notice at all.
Martin
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href="http://www.lowes.com/lowes/lkn?action=productDetail&productId4405-60740-FM131&lpage=none"
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On Fri, 26 Dec 2008 20:31:46 -0800, Gunner Asch

My thought was to mount the second sensor about 100' up/down the road from the first so a vehicle would only trigger one at a time. Of course I wouldn't get an alarm if a column of tanks came after me 8o) Another option would be to put the second sensor just past the break in the circle drive so I could determine if they were heading for the front door or the shop/back door.
As to thunderstorms, the falses are rare. OTOH weather fronts can generate falses every few seconds for >15 min. I don't know how long they last because that's when I unplug the receiver.
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