| Author | Message | ||
| Jim in California Rating: N/A |
Guys: Picture half a dozen Harleys or whatever parked outside your rig at a campsite somewhere, people inside asleep, you don't want the bikes stolen. So you run a single piece of electrical cable on a 100ft reel out from one of your cargo bays, through all the bikes plus your trailer, ATVs, genset, whatever, and then back to the bus on a screw-in connection. And once done, you trip a key-switch inside that arms the alarm. There's no serious voltage through the cable, but stripping it and shorting it out near the bus will NOT work because it's not a continuity based circuit. The same concept could work for construction equipment at night, bicycles outside a bike shop, even guns at a gun show table...anywhere you need an alarm of that sort. RVs are just one use. Does this seem useful? Anybody with circuit design experience wanna go in on some prototypes?  Jim | ||
| James Maxwell (Jmaxwell)
Rating: N/A |
You seem to be mixing the concepts of security alarm with "booby trapping". If ure talking about a security "alarm" ok, if ure talking about delivering an electrical shock impulse via an "electric cable" that is booby trapping, not ok, and against Federal and State law. Very low voltages are on record as having been lethal to some individuals and if you will, imagine some totally innocent person just coming by to admire your toys and wearing a pace maker. I think perhaps a taser armed and fired by motion sensors would be more fun to watch. Or maybe a Remington 1100 Street Sweeper or 2 triggered by motion and pressure sensitive switches. Hang out with good people and you don't need all that crap, including the illegal booby trap. | ||
| Johnny Rating: N/A |
From the description, it sounds like the current would be no more than, say, a 12V battery. It seems to be a simple alarm. And a pretty good one. | ||
| Jim in California Rating: N/A |
Yes, it's a simple alarm, NOT a booby trap. Zero shock value. The REAL trick is that instead of using continuous current to check the cable's state with a continuity check (beatable via short-circuit), you use coax cable (50 or 75ohm) which is tough stuff (cable TV stuff basically), and you hook one end up inside the coach to a Time Domain Reflectometer and the other to a resistor plug. OK, what the hell is a Time Domain Reflectometer? I used to be a computer network tech. Say you've a 500ft cable run that doesn't work...something is screwed up. Question is, where? You plug the TDR into one end and it bounces something akin to a "radar signal" down the line, reading out digitally how long the cable really is by the "reflexion's" "time delay". Follow? So instead of a readout, just set it up so that it measures the length of whatever cable you use at the time of each "system startup" and then yells a 90db or more "screamer" alarm if the cable changes in any way while armed. Need to protect a whole parking lot full of Harleys? No problem - just score a longer piece of standard cable TV coax cable and loop it all around, connecting it to the two screw-in plugs external to the coach. Go inside, flip the key, it's armed. *Any* messing with that cable, it alarms. Voltages through the cable are less than the output of a hearing aid battery so it's damned sure not a booby trap. | ||
| CoryDane RTSII Rating: N/A |
Wouldn't it be easier to just have a motion sensor (theymake them for outdoors use) and it can be mounted on the bus permanent or temp and it can just turn on lights or sound an alarm.... Sounds good to me cd | ||
| Jim in California Rating: N/A |
Motion alert? At a fairly crowded campground? Or even an empty one - what happens when a 60lb coon, or a deer, or a bear walk by? Or you're at a rest stop or similar and have the line run around the trailer? I don't want to alert on anybody walking by! I want to alert on people trying to actually tamper with my stuff. | ||
| John that newguy Rating: N/A |
Just take any automotive ignition coil and connect the high side to your bus shell. Once energized, you'll know if anyone's tampering by the pitch of their scream. Hey man.... if you're gonna' screw with a bunch of biker's hogs, you don't need an alarm system, you need your head examined. | ||
| Jim in California Rating: N/A |
Sigh. In reality, Harleys are a MAJOR theft target. See...a whole "big twin" is worth basically a minimum of $12k used and prices go WAY up from there. But the only serial numbers are on the frame and engine case. Aftermarket frames are about $800 - $1,000. Sputh or S&S engine cases, $500 - $800. Time needed for a full switchover: two guys, a weekend and a case of beer...and register it "Special Construction Harley Davidson" at DMV the following Monday AM. HUGE problem. | ||
| BrianMCI Rating: N/A |
Jim is right Harley theft is a huge problem and even a "special Construction" bike can be worth huge money... Sounds to me like his alarm cable might be a viable anti-theft device... A list of the components needed might be handy, Jim. Brian | ||
| Ian Giffin (Admin)
Rating: N/A |
I had a Rollscan Harley once and had no theft/security issues with it. Ian www.busnut.com | ||
| ChuckMC9 (Chucks)
Rating: N/A |
Jim I have a computer laptop antitheft device that works in exactly the same way, (without the additional sophistication of the time-delay notion) I know exactly what you're talking about and it works great. You're just doing it on a massively larger scale. Targus DEFCON™ 1 Ultra Notebook Computer Security System http://www.targus.com/us/accessories_security.asp | ||
| Sean Welsh (Sean)
Rating: N/A |
A TDR is an expensive piece of equipment, and unnecessary for this purpose. Much simpler to measure the resistance of the loop of wire, and trigger the alarm on any significant change. There are many such systems on the market (some of which use a loop of fiber optic rather than wire -- harder still to defeat), but they are usually pretty pricey. They are made for public computer clusters and retail displays (surely you've heard such a system triggered in a retail store when some doofus pulled the cable out of a high-end electronic goodie, or maybe a leather jacket). OTOH, making a simple trigger from a quad voltage comparator such as the LM139 would be straightforward and cost only around $5 or so. -Sean | ||
| Brian (Bigbusguy)
Rating: N/A |
If you use phone wire 2 pair and a NO and NC relay some one would have to take a good guess to cut and splice it to conect the right wires up or have a meter to check the wire and most will pass . Bikes and ATC's are high theft items in the sand dunes also. I used that system hooked it up to my truck horn and simple phone jacks for the plug in. I just used 1 relay and hide the line in the sand so no one saw it. Brian 4905 Klamath Falls Oregon | ||
| Jim in California Rating: N/A |
Hmmmmmmm. You know...Sean, that ain't a half bad idea, in that if we use coax and a terminating resistor of a known value, we could probe pretty sensitively for changes. A TDR circuit custom-built for this purpose wouldn't be THAT expensive though, as it needs no calibration (we don't care WHAT the values are, only that they changed!) and it'll only be good for a specific cable type and endcap resistance value. I like coax over twisted pair simply because it's much tougher and the screw-connections much more reliable. Last thing I want is "false positives" because one end came unglued. Cable TV companies use coax outdoors for good reason: it holds up. | ||
| Abajaba Rating: N/A |
Hey guys: Another idea. TDR on Cat 5 cable with RJ45 connectors on both ends. We know that the cable will be a given length. It will confuse the heck out of someone if they try to strip it and make it work. The voltage on the wires is enough to confuse someone but not enough to hurt them and there are no false positives. Negative side is that every once in a while the cable will need to be replaced as most of the Cat 5 is not meant for outdoors. On the plus side, the cost of the cable is low and they are easy to come by in many different lengths. And there are splice blocks that can be used to tie the cables together. That could cause problems someplace where it is wet but it should be able to be kept dry by keeping it covered up off the ground. | ||
| gillig-dan Rating: N/A |
Alarm loops I've seen work on monitoring a resistance value at the end of a loop like Sean pointed out. It's a fairly simple circuit to check whether the resistance value increased (cut wire) or decreases (someone shorts it out to try do defeat it). I'm sure a web search for a schematic would show something. It should only cost a couple bucks for part to make a circuit for it. Another type I've worked with in the past used a special coax cable coupled to a high gain amplifier. The coax acted like a microphone when it was touched or moved anywhere along the length of the cable. The input circuit would trigger an alarm if more than a couple bumps/minute were detected. High winds would trigger false alarms if anything near the wire would move in the blowing conditions. The nice part about this circuit is that if someone is stealing your expensive accessories or valdalizing your bike, it will alarm. Gillig-Dan | ||
| Gary Stadler (Boogiethecat)
Rating: N/A |
Or just use coax and measure the capacitance of it. if it gets cut, shorted, or shortened it will be very easy to detect changes in capacitance. My favorite alarm for entry detection is to pressurize a room (or the bus) with a small squirrel cage blower, and use a photohelic gauge to detect the tiny amount of air pressure that it creates. On the order of 1/2 to 1 inch of water. Open any door, window, or create any kind of hole in the protected space, the pressure drops and the alarm goes off... BTW Photohelics are cheap as can be on ebay... | ||
| simple mind Rating: N/A |
Why couldn't you just wire one side of the coax cable into the coil of a spdt relay. The other side wired through one side of a dpst switch to 12v. Your alarm is wired from 12v, through the other side of the dpst switch, through the NC side of the relay, through the alarm, to ground. When the switch is activated, both the coax and alarm circuit is energized. The energized coax energizes the relay coil, which opens the relay contacts. As long as the relay is energized, the contacts stay open and the alarm is silent. If the coax is cut, the relay deenergizes, closing the relay contacts, and activating the alarm. Requires one relay, one switch, some cable and connectors, and no fancy resistance or capacitance detection equipment. | ||
| Sean Welsh (Sean)
Rating: N/A |
Dear Mr. Mind, Yes, the solution you're suggesting is simple. However, the above discussion deals with preventing the system from being easily circumvented. The problem with your suggestion is that it is trivial to defeat -- a circuit based on simple continuity is easily defeated merely by shorting the two conductors together. The remaining wire can then be cut at will. Using coax rather than plain wire adds only a minimal degree of difficulty -- shorting the center conductor to the braid without cutting either is quick and easy. -Sean | ||
| niles steckbauer (Niles500)
Rating: N/A |
Jeez - I never want to park near you all - You know WAY TOO MUCH about this stuff - LOL - Niles | ||
| simple mind Rating: N/A |
Sean, In my above scenario, only the center conductor is used to control the relay. The braid is grounded. Shorting the center conductor to the braid would short the power to the relay, which would cut power to the coil, and thereby activate the alarm. Granted, if one had knowledge of how the system were constructed, he could conceivably whittle down the insulation to the center conductor and attach a jumper around the stuff being protected which would allow a cut in the cable. That would require prior knowledge and considerably more time than your average thief will spend. If someone was really bent on stealing your stuff, a little noise for a few seconds isn't going to deter him anyway so they would simply cut through the cable, activating the alarm, and away they would go. If it's your precious bike being stolen, it would already be running, and within 2 seconds of cutting the cable, it would be gone. Even before you hear the first wail of the alarm. Years ago, I lived in Phoenix. Car alarms were common due the massive influx of illegals. A cordless drill with a long bit became their first tool of choice because they figured out they could drill through the fender of an automobile into the battery. The acid drained out, and the alarm was effectively disabled. All systems can be circumvented, give enough time and knowledge. |