Security devices - switches/sensors/interlocks for doors and hatches

jc55

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Hey guys, I'd like to design a real simple "fail safe" security system to deter petty theft, usually batteries and electronics. And I mean, real simple. Although there will be video surveillance aimed directly at the boat, the marina owners have no problem with me having an alarm as long as it doesn't get set off by every passing wake.

I'm thinking that magnetic switches will have too much current draw (1/4amp). I don't need a timer, remote fob, or control panel. just a 12v loop wired to a siren on a secretly located kill. (I'll give the very trust worthy marina owner the location of the kill switch). No double sided tape...they absolutely cannot send a false signal.

On a side note, a mooring in another area had a couple of boats stolen(towed) from their moorings a few years ago and set on fire. At the very least, I'd like to set off a strobe whenever a mooring line is disconnected, but not the siren.


As always I checked the iboats store first. I absolutely do not want shock sensors.
Thanks for any help in advance.
 

gm280

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Re: Security devices - switches/sensors/interlocks for doors and hatches

I hear ya! I am building such a system into my boat rebuild. And yes magnetic switches are the best because you can set them up with the proper circuitry so they have zero current drain unless something is opened or closed which ever you decide. A very simple SCR alarm circuit is your best system for that ability. If you know anything about electronics you can simply bias a NPN transistor to be off when all is ok. But the millisecond any door, hatch, or whatever is disturbed, off the circuit goes... And until you disconnect power, via a hidden switch, the SCR continues. You can't simply close the door or hatch to make it stop... It is both simple and uses zero current until its needed... Look into it...
 

jc55

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Re: Security devices - switches/sensors/interlocks for doors and hatches

Wow, that was quick GM280, thanks! Yes, you can remove the gate voltage of an SCR for it to continue, I didnt think about that. And not being able to reset it by closing the door...awesome. Any thought to the actual switches?
 

sam am I

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Re: Security devices - switches/sensors/interlocks for doors and hatches

Check into imaging security.... you said "simple" not "and cheap".......

"simply" point and click the field of interest, set up tolerances and it scans real time for changes...As in someone getting into your boat, the boat being removed etc etc,. If it detects changes above pre-set levels(a boat bobbing or slightly moving due to rope slack), it sends out alerts to your phone and you can watch real time, call cops, start strobes whatever.

Think a budget off the self system would be much easier then wiring up the boat with doors switches, wiring ropes somehow, making SCR circuits......JMO though.

Prices should be down too, with how cheap puters, memory, hardware and apps have become, might be money ahead just to look at some off the self stuff, just a thought...........
 
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gm280

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Re: Security devices - switches/sensors/interlocks for doors and hatches

Wow, that was quick GM280, thanks! Yes, you can remove the gate voltage of an SCR for it to continue, I didnt think about that. And not being able to reset it by closing the door...awesome. Any thought to the actual switches?

There are so many magnetic switches that usually have both N.C. and N.O. options. And they are available at most any electronic parts place. You would mount the reed portion on the cabinet housing, box, boat lip or whatever and mount the associated magnet on the door or hatch. That way if you move the door or hatch even a little it will either make or break your circuit. The options are all yours to setup. So easy but so undetectable and cheap too. However, you will need some type of battery to run such a circuit. But even a small NiCad or Lithium battery power source or something in that type setup would work if you don't want to use your boat batteries... The limit to this is your imagination!
 

jc55

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Re: Security devices - switches/sensors/interlocks for doors and hatches

I think I found the answer...
PCB_Bagged.JPG


For $85 I can get this board which will "time" the police siren, keep the strobe flashing constantly until reset, and allow a NC magnetic loop throughout the boat including the outboards and a line to the mooring lines.
The only other source was about $20 but was from overseas, so I didn't quite see that there were clearly labeled terminals.

Sam i am, I think you're right. Finding either a $20 car alarm black box that'll do 'er, or something already built will be much easier and cheaper in the long run than building from scratch.

Yes, I see that now gm280, the sky IS the limit. I have 3 batteries so I think I'll use onboard voltage.

Unless someone here knows car alarms, (you'd think that the trunk or hood release switch on an El Cheapo car alarm could take an NC magnetic reed switch loop?)
 

jc55

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Re: Security devices - switches/sensors/interlocks for doors and hatches

Well, talking with their tech guy, this board is designed for NO(normally open) switches only, which doesn't use any current while armed. Just can't figure out how to protect the outboards using NO switches :/
 

gm280

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Re: Security devices - switches/sensors/interlocks for doors and hatches

Well, talking with their tech guy, this board is designed for NO(normally open) switches only, which doesn't use any current while armed. Just can't figure out how to protect the outboards using NO switches :/

Well I did something very similar to a trolling motor setup without using any switch(s). Take a single wire and run it with your usual wiring harness to your O/B (trolling motor) and back into the boat (a simply loop setup). If anybody tries to remove the O/B (trolling motor) they either have to remove the wiring too, OR cut the wires and take the O/B quickly. Either way they break the wire and set off your alarm setup. You can use that loop trip wire to ground the bias voltage to an NPN transistor keeping it in the "OFF" state until the wire is opened. And once it is opened the transistor starts conducting and biases the SCR gate on...all over after that! If you select the correct current limiting resistor to the base of the NPN transistor, it would use a mere few micro-amps of current, but would never drain any battery for years. Really a very simple circuit!
 

Splat

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Re: Security devices - switches/sensors/interlocks for doors and hatches

Well I did something very similar to a trolling motor setup without using any switch(s). Take a single wire and run it with your usual wiring harness to your O/B (trolling motor) and back into the boat (a simply loop setup). If anybody tries to remove the O/B (trolling motor) they either have to remove the wiring too, OR cut the wires and take the O/B quickly. Either way they break the wire and set off your alarm setup. You can use that loop trip wire to ground the bias voltage to an NPN transistor keeping it in the "OFF" state until the wire is opened. And once it is opened the transistor starts conducting and biases the SCR gate on...all over after that! If you select the correct current limiting resistor to the base of the NPN transistor, it would use a mere few micro-amps of current, but would never drain any battery for years. Really a very simple circuit!

This^

Also you could do the same thing with a mooring line. Run a length of wire along the mooring line, through the cleat and back up. The wrote would have to be unplugged or cut for the line to be removed.

At my old dealership we used to do this with our fences, several loops of wire strung through them with connectors at the gates so they could be unplugged and the gates opened. We had our fences cut more than once. Also used to run a wire through the axle on the trailers that sat outside the locked gate at night.

We had several other tricks up our sleeves, but most would pertain to home security, such as an automation system that would randomly cycle lights, or turn them ALL on during an alarm trip. Shatter proof coatings on the windows, and CCTV system.

Oddly enough, after 2 thefts, we ended up catching the thief's when I returned after hours with the work truck and found two kids along the wood line of our fence scouting the place.

I payed no attention to them, acting like I hadn't seen them, but pulled out my phone and sent a Txt to the Sargent of the local PD, a friend of mine. About a minute later we had 2 squad cars racing in with a third on the way. That was a good day.
 

sam am I

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Re: Security devices - switches/sensors/interlocks for doors and hatches

Lil Bastards!!!!!!!

K, I'll play Devils advocate with the current loop wires that run out to PROTECT things just for fun.

If they were "smart thief's"....yes yes, I know, Oxymoron. Never the less......

My/any dock? They'd just cut the wood/plastic out from under, unscrew from the dock, hack, sludge hammer off or through the cleat and pitch the works on the boat deck...Could I suppose perhaps beef things up with steel docks, welding things on if you can, thicker Navy issue steel stuff, drilling/cut off bolt heads etc I suppose.......yeeah. So after ya get that all done........

What if I just short/jumper across the feed and return wires on the source/battery side of the current loop BEFORE I cut the outside part of the loop that goes around the O/B or cleat?...........

hmmmmmmmm, O/B, Boat GONE!!!

Hard to make anything bullet proof. With a will, there is always a way, it's true..........Kind of sucks to have to live like this but, beings this is the nature of the beast, I just remove all non-replaceable items(you know, like all those family heirlooms I always carry in my boat) , have good documentation/pictures of all the assets on the boat, save receipts of new things recently put on the boat and carry decent insurance that wouldn't try to get out of my reasonable honest claim.

I could spend thousands trying to second guess, out wit, arm, wire, camera and double step these asses for the rest of my life but, I don't. If they want it bad enough, they'll get it, somehow, some way, some day. I use common sense, simple/normal security systems that keep honest folk honest. I just reserve myself to getting new stuff If it happens. I pretty much have to have insurance anyway, moot point. Just life in the big city these days eh?

Now they come in my house with me home? Anther adage comes to mind about what they say about dead men can't talk.
 
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Splat

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Re: Security devices - switches/sensors/interlocks for doors and hatches

My grandfather used to have a saying, locks only keep honest men honest.

You'll never make anything steal proof, but you can make it less inviting than the guys stuff next to you.
 

jc55

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Re: Security devices - switches/sensors/interlocks for doors and hatches

Okay, I agree with you guys and that was my original plan, BUT!!!!!!!!!!!!!!!!!!!!!!!!!!!! That would require NC (normally closed) switches to drop the positive and bias the transistor. I was gonna do mooring lines and outboards, BUT! can't find the darn $11 circuit in the United States!

The above board is a NO(normally open) 12V loop only. I'm eyeballing the SCYTEK G20 C $29 car alarm. It uses a negative trigger and a positive trigger inputs. What are you guys using for control boards? Thanks for the discussion
 

jc55

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Re: Security devices - switches/sensors/interlocks for doors and hatches

My grandfather used to have a saying, locks only keep honest men honest.

You'll never make anything steal proof, but you can make it less inviting than the guys stuff next to you.

LOL, I'm one of the few boats among mostly pontoons. And probably the only offshore pilot house in a 50 mile radius...they're coming after me!!!
 

sam am I

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Re: Security devices - switches/sensors/interlocks for doors and hatches

My grandfather used to have a saying, locks only keep honest men honest.

You'll never make anything steal proof, but you can make it less inviting than the guys stuff next to you.

Lol, this past fall, Dad and I jumped in the boat to go out, he looked at my lectric down-riggers sat up on the gunnels with a just simple wire rope around them with a small pad-lock, laughed said, "Those would be soooo easy to take". I replied, "I know, those locks are just to keep the honest guy next to me honest and make his boat/stuff look more attractive, If a guy wanted them bad enough, he'd get them no matter how I locked them up."
 
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sam am I

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Re: Security devices - switches/sensors/interlocks for doors and hatches

Okay, I agree with you guys and that was my original plan, BUT!!!!!!!!!!!!!!!!!!!!!!!!!!!! That would require NC (normally closed) switches to drop the positive and bias the transistor. I was gonna do mooring lines and outboards, BUT! can't find the darn $11 circuit in the United States!

The above board is a NO(normally open) 12V loop only. I'm eyeballing the SCYTEK G20 C $29 car alarm. It uses a negative trigger and a positive trigger inputs. What are you guys using for control boards? Thanks for the discussion

A gun mainly, are you selling those too?
 

gm280

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Re: Security devices - switches/sensors/interlocks for doors and hatches

Okay, I agree with you guys and that was my original plan, BUT!!!!!!!!!!!!!!!!!!!!!!!!!!!! That would require NC (normally closed) switches to drop the positive and bias the transistor. I was gonna do mooring lines and outboards, BUT! can't find the darn $11 circuit in the United States!

The above board is a NO(normally open) 12V loop only. I'm eyeballing the SCYTEK G20 C $29 car alarm. It uses a negative trigger and a positive trigger inputs. What are you guys using for control boards? Thanks for the discussion
,
I am a retired Engineering Technician and therefore I design and make all my own circuits from design to actual circuit board to stuffed and soldered parts. So the circuits I explained to you, I have already built and tested. It really doesn't matter if the thief or thieves see the loop wire or not. The only way to get around setting off the alarm is to track the wires all the way back to the actual circuit and jumper it at that point. And if the loop wire is embedded into the engine wiring harness itself, that isn't much of a possibility... I mean which wire would they be looking for, what color? They would have to actually know every type engine out there and know the colored wires associated with every motor before they would even have a clue as anything different.

On my trolling motor, the loop wire is in the actual wire harness from the plug in on the boat panel up front all the way to the head of the trolling motor. My trolling motor is a 12 volt motor but I used three wires in the harness and plug. So if they simply unplug the trolling motor it sets off the alarm. If they decide to cut the harness, it set off the alarm. If they carefully take the harness apart at the head of the trolling motor (that takes too much time) then they would have to make sure they don't cut the one line that is the loop. It is mixed in with all the other wires going to the actual motor down the shaft... So I see it as safe as you can make it.
 

jc55

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Re: Security devices - switches/sensors/interlocks for doors and hatches

I do like the idea gm280. I agree, NO ONE around here would be looking at wiring harness colors in the dark, let alone anticipate these precautionary measures. It would be a couple of drunk hillbillies in a jon boat trying to jack my kicker in the dark, to sell on Craigslist for $300. They would simply cut wires and go.

I was an aviation electronics tech for 8 1/2 years in the Navy, micro miniature solder qualified, then worked 6 1/2 years for Nikon Precision in a clean room at Intel. The industry kind of leans more to "pop and swap" anymore, so I kind of lost a lot of that component level practical knowledge. Even so, with all of the projects, work, and family, going on, I just don't have the time to scratch build a circuit board. I'm gonna try the NC magnetic switches and wiring loops in series on a $29 car alarm unit. If it works, I can copy the sytem for friends or on other boats.
 

jc55

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Re: Security devices - switches/sensors/interlocks for doors and hatches

FOUND IT! Closed loop $7.99 DEI 502T

$T2eC16VHJHgFFm!6whs8BSO40K21Rg~~60_57.JPG
 

gm280

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Re: Security devices - switches/sensors/interlocks for doors and hatches

Ha, whatever works. I just like making my own...kind of like a hobby to me yet! I also built a British Siren with the two tone (hi low) sound that goes to the speakers. Very loud and attention getting. It gets its supply power from the gated SCR setup. The two circuits are actually on the very same PC board...about an 1.5" by 2.5" in size. Works nicely. Good luck!
 
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