Quick and dirty bear perimeter alarm

[Dale Wambaugh]

I was looking at one of the "personal security" alarms, which make a racket and flash lights if you pull a lanyard and activate the switch. They are cheap and light, weighing 3 ounces with a 9 volt battery. I'm sure there are other lighter versions. This one came with a clip on the back like the one on a pager and I removed that, leaving the molded plastic bosses and I added a small split ring. I ground down the diameter of the switch plunger to loosen it up a bit.

My idea is to tie the black box to a tree and run a string around my camp or below my food bag, creating a trip wire to active the alarm and wake me up if I get a visitor, or better yet, the 135db noise and the flashing light will scare away the intruder.

[Luke Schmidt]

Sounds like an interesting idea. I think the trick would be a setup that is sensitive enough that a bear would trip it but not so sensitive that a breeze or a bird perching on the line would set it off. Waking up to a 135 decibal alarm would be annoying.

Edit – I doubt its water proof but there is a pretty simple solution to that. Just hang your cook pot over the alarm like an umbrella.

[Ken Thompson]

Waterproofness may be an issue in your neck of the woods.

[Delmar O’Donnell]

The manual and UL version, of course, is your bear bell tied to a monofilament line strung around your camp. BUT you'd have to do the shouting, arm-waving, and flashlight-shining manually, too.

You'd think somebody would've made a perimeter app for a smartphone, already.

[Dale Wambaugh]

A laser activated alarm with a bluetooth phone link would be cool. My version is $5 though.

[Jeff M.]

Dale, where did you get yours?

[Dale Wambaugh]

A thrift store. You can get them in big box stores, eBay, etc. They make one with a door jam switch that will go off if the door is opened. I bet that could be put under a bear can, to alert when the can is moved.

[BlackHatGuy]

http://www.guarddog.net/palarm.htm

[Dean F.]

http://www.gofastandlight.com/Portable-Motion-Sensing-Perimeter-Alarm-for-Camp-and-Tent/productinfo/E-DBL-MOTION/

http://solohunterstv.com/store/SOLO-HUNTER-Camp-Alert-Perimeter-Security-System.html

http://www.packalarm.net/

The PackAlarm with it's 330-foot perimeter line seems especially intriguing. 8oz. It actually seems like it might be a neat option in serious bear country.

A line or laser that can be set higher off the ground is probably better than a motion sensor, since I'm pretty sure a raccoon or other smaller critter would set off a motion sensor.

[Dale Wambaugh]

Clever with the pack alarm using plastic rings as line guides. That was a concern of mine. Split rings would work too. I was thinking of something like Zing-It line that would slide on tree bark, about 2' off the ground. Fishing line would work using the line guides. 6" off the ground and a hair trigger might work for raccoons.

The solution that comes to mind for weatherproofing is a ziplock sandwich bag.

[Paul Hatfield]

This one on amazon.com has good reviews and free shipping:

Mace Security 3 in 1 Sport Strobe Alarm
http://www.amazon.com/Mace-Security-Sport-Strobe-Alarm/dp/B0007VQ63M

There also seem to be many similar alarms, but in a smaller form factor alarms that are similarly activated by pulling a pin:

Vigilant 130dB Personal Emergency Panic Alarm
http://www.amazon.com/Vigilant-Personal-Emergency-Batteries-Prevention/dp/B005BCL66Y

Sports Authority carries Spectra or Dyneema fishing line. I think it is 50-pound test.

[Derek M.]

I have to admit that I don't think any of these systems would work like you all want them to in real camping situations, but just assuming that they would… I'm very curious:

What are all you guys planning to do when the alarms actually go off?

A. Hope that the hungry (and highly food motivated) wild animal(s) (that are probably not bears, by the way) will be permanently thwarted and won't find a way around the "security system" the second time around in a half an hour when you are sound asleep again?

B. Get out of your sleeping bag (10 seconds), get dressed (20 seconds), put your shoes on (10-20 seconds), get out of your shelter and, in the middle of the dark, try and locate and chase said animal away?

I'm just not seeing the end game here.

[Dale Wambaugh]

Lift up the side of my shelter, put a flashlight on the offender— if it hangs around, reset the alarm.

I'm not really worried about it, but the alarm is chaeap and adaptable if you want one. I really want an electric food bag.

[Justin Baker]

why would i need to get dressed? unzip bag, which takes way less than 10 seconds, slide on shoes, charge at bear naked with trekking poles

[Dale Wambaugh]

That should get the bear laughing hard enough to remove any threat :)

[Steve B]

I'm with Derek, I don't understand the point. Reminds me of all the car campers in Yosemite valley at night, banging their pots and pans and yelling "BEAR!". Just properly store your food and go to sleep. Let your preparations be the lesson for the animals, no reward.

Unless you are talking about needing this for grizzlies or wolves. I could see the need for those :)

Steve

[Larry Swearingen]

All I know is that I'm gonna be PISSED if some Ahole has a car alarm going off at night because a bear walked close to his food bag !

Larry

[Dale Wambaugh]

Yeah, I wouldn't use it in a campground. I'm usually solo.

[Jon Leibowitz]

Me too! I'm with Larry. Just pack your food and smellies correctly and there is no need for an alarm system.

[Pete Staehling]

…Also it will go off every time a deer walks through camp, which in some places might be multiple times per night.

[Ivan Dominguez]

Electro Bear Guard UltraLite
Portable Electric Bear Fence System For Back Packing

http://www.eaglesafety.net/Home_Personal/eagle_enterprises_safety_solutions_bearfence.html

http://www.groundtruthtrekking.org/blog/?p=1953 . Hig and Erin used it.

It's a little heavy.

Cheers

[Bob Gross]

Years ago I designed an intrusion alarm based on the idea that I got from an Army intrusion alarm that I used many years ago. The Army unit used what is called a break-wire loop. Basically, imagine an ultra-fine wire that goes around the perimeter and connects to the electronics package. When that wire is broken, the alarm goes active. In the Army unit, the actual wire was very sophisticated. They put two conductors in parallel with a transparent insulating coat, and the whole thing was the diameter of a human hair. It was so fine that a person or a bear would walk right through it (breaking it) and not notice anything. The advantage of having "both ends of the loop" in one "wire" is that you can twist on a shorting bar to one end, and then scatter it out on the path where you expect the intrusion. The other end not shorted plugs into the electronics. When I designed my own, I used an integrated circuit sensitive enough that I could have a mile or so of wire out there and it would still detect the break. In mine, I put a switch on the electronics package so that I could get a bright flashing light, or a very loud horn, or both. It scares the hell out of anybody else camping nearby.

–B.G.–

[Andy F]

"why would i need to get dressed? unzip bag, which takes way less than 10 seconds, slide on shoes, charge at bear naked with trekking poles"

This could really backfire when someone else in the group snaps a photo of these heroic efforts to chase a harmless *deer* away from camp!

:-)

[Jon Leibowitz]

….or it ends up being a Grizz and just eats you. :)

[peter vacco]

http://www.youtube.com/watch?v=KPOLYIrHGVM

this looks good, but t'is not loud enough. by a Lot it's not loud enough.
like Bob, i built my own. 18vdc x 3 sirens = way hella loud.

other than the wire-pulls-apart style, all other styles have fatal design issues. these range from needing structurally superior pole mountings, to lack of sufficient ground conductivity as allows function. nothing you can buy will work on solid rock, as there is nothing to keep the poles from falling over.
trip wires have a proven record of working, and are vastly easier to set up than other designs.

as again with Bob's, my unit has wires that separate. i incorporated mercury switches in the poles to inform me of a pole perhaps blowing over, or a connector frozen solid and a perimeter breach.

all such electronic fiddlefaddle is unnecessary paranoia for brown/black bears.

[Author]

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