Metal (vehicle) detector

As Bill Gates has discovered, each goose craps ~4# a day of fertilizer....

I read the website of the inductive sensor manufacturer. The sensor is a big coil of wire driving a couple of hundred feet of wire (twisted pair?).

If you use coax (like RG58), you should be able to put the sensor at one end and the control box at the other end of a 700-foot coax, with no power source or other complications at the detector end. The frequencies to be handled are very low, so loss in the coax is very low.

Next more complex is a one-FET amp at the sensor, powered by phantom power over the coax. I have driven audio signals over 1000 feet of RG59 by this method.

Joe Gwinn

is slightly

all the bad stock photos on this site is amusing

Just checked coax prices. The RG59U in my surveillance system was only 5 cents a foot. Mine is in 75 foot lengths with f type (TV) connecters. couplers are cheap, and easily waterproofed. I changed the extreme ends to BNC. Ordinary speaker wire is fine for the 12V supply, and works over long runs of wire.

Steve R.

Can I run multiple cameras thru one RG59U coax 700' long? I can live with slower refresh rates, 1/4 sec would be plenty fast.

Free men own guns - www(dot)geocities(dot)com/CapitolHill/5357/

On Sat, 20 Dec 2008 08:18:14 -0600, the infamous nick hull scrawled the following:

Sure. Just put 120v power and the video controller in a climate-controlled house at the far end and switch it to a single coax feed to your house.

Hmm, there -may- be battery-powered remote switches available, or you could design your own with RC hardware and DPDT switches.

Another alternative is to use wireless video cams, such as X-10 and other mfgrs put out.

-- It is pretty hard to tell what does bring happiness; poverty and wealth have both failed. -- Kin Hubbard

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.

On Sun, 21 Dec 2008 03:00:31 -0800, the infamous Gunner Asch scrawled the following:

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:

P.S: Happy Solstice / Joyous Saturnalia to all today!

Print some of these up and put em along the fence line

Dig a few small craters and put some clothing bits in and around them, inside the fence.

Or some of these....

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

You will need a separate cable for each cam.

Steve R.

Or a remote controlled video switcher.

I don't know how good a TV picture will emerge from 700 feet of RG58. Actually, video links are usually 75 ohms (not 50 ohms), so make that RG59 (not RG58).

I've seen writeups on the CCTV systems of casinos, and they now use fiber everywhere. So, one could run a copper power cable and a fiber signal cable together.

Joe Gwinn

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.

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="

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.

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.

Mart> >

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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.