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Bike Shed Alarm idea

(20 posts)
  • Started 8 years ago by Greenroofer
  • Latest reply from chdot

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  1. Greenroofer
    Member

    I've had an idea for a bike alarm. I expect it's been had before. Do you know where to buy one? If not (and you are an [electronic] engineer), can you provide a parts list and circuit diagram so that I can build one myself.

    It works like this...
    On the wall in the house I have a box with a key-switch on it and an indicator light. Inside the box is a shrieker and a power source. Leading from the box are two wires that go into my bike shed. In the bike shed they terminate in a socket each. In the bike shed I have a long wire with a plug on each end.

    When I want to secure my bikes, I lock them with my choice of lock (although this is optional). I then thread the long wire through the bikes and plug the ends into the sockets I mentioned earlier. This completes a circuit to the box in the house. I then go into the house and switch the box 'on'. The light on it comes on. If someone cuts the wires (or just unplugs them) the box will start shrieking.

    So basically the box monitors the circuit and shrieks as soon as it's broken. It doesn't matter where the wires are cut (even between the bike shed and the house) it will still start shrieking. So there's no way to remove the bikes without the alarm going off, and because the alarm's in the house, there's nothing a thief can do to disarm it before they nick the bikes.

    Does it exist already? Can you help me build one?

    Posted 8 years ago #

  2. Ed1
    Member

    Sounds good and any security measure may be an improvement over none but I suppose in theory the thief could slice the wire and create a bia pass then steal the bikes without sounding the alarm.

    Posted 8 years ago #

  3. I were right about that saddle
    Member

    @Greenroofer

    What has brought you to this pass? Lurkers in the garden?
    Remember that if a thief really wants your bike they'll wait until you unlock it and then take it from you.

    Posted 8 years ago #

  4. neddie
    Member

    The best alarms & immobilisers are ones where the thief doesn't know what you've done i.e home made ones.

    Posted 8 years ago #

  5. Greenroofer
    Member

    @IWRATS - well the number of bikes in the shed has increased (due to ill-advised procurement on my part), and Kamal up the street has had his bike shed broken into again* and (mainly) because it seems like an interesting idea to develop.

    *although I kind of hope (sorry Kamal!) that this is on the running away from a tiger principle. My shed now has one-way screws on the hinges and a high-security hasp and padlock, so it may be diverting casual ne'er-do-wells to his.

    @edd1e_h Exactly. I hope that a thin black wire will go unnoticed until it's too late. While I take @Ed1's point about it being possible to divert around it, I'm hoping that anyone who saw and realised what it was would decide to abandon my shed and go to Kamal's, rather than go to the trouble of avoiding it. Our bikes aren't that valuable, it's just that they are ours and we like them.

    Posted 8 years ago #

  6. I were right about that saddle
    Member

    Ah, candidates for the stakes and ravens are at hand? Not so good. Hope your steeds stay where they should be.

    I must have missed your procurement. My current employer forbids access to CCE (on the genius grounds that it concerns 'vehicles') so my lunchtimes are spent elsewhere. What did you get?

    Posted 8 years ago #

  7. Morningsider
    Member

    Yikes! This is worrying news - although I did fortify my shed a few years ago after it was broken into (but nothing taken - despite have a £1k road bike in there, they nicked my neighbour's beater instead). Non-return screws fitted and an extra couple of padlocks added. All for show really, probably slow determined types by about 30 seconds.

    Now - trying to extract my road bike from the shed is another matter. It would probably take about 15 minutes (in the dark) and hopefully involve the would be thieves getting a comedy rake handle in the face. Really should get round to clearing it out one day.

    Posted 8 years ago #

  8. Greenroofer
    Member

    @Morningsider - maybe poor Kamal keeps being the unfortunate victim of our (obviously successful) attempts at deterrence and diversion of miscreants elsewhere....

    Posted 8 years ago #

  9. acsimpson
    Member

    It sounds like a simple circuit with a logical not gate on the wire so that if it's connected then the not gates output is off and so is the buzzer. From my memory of doing this as a kid the not gate would be an IC (chip) so complicates things a little). I have a niggly feeling that there is a limit to circuit length for battery powered circuits so you would have to make sure enough power is getting round the security circuit or make sure that the power for the sounder isn't going round the whole circuit.

    The master switch could either be connected as a master switch for the whole system or via a logical and for the sounder.

    You could further thief proof the system by measuring the resistance of the circuit and possibly putting a microswitch on the door so that when it opens the alarm will go off if activated too but either would complicate circuit design.

    Posted 8 years ago #

  10. Snowy
    Member

    I think it's a NAND gate but, more usefully, you're not the first to want to do this :-) Have a look at the suggestions posted here, the first one especially.

    Posted 8 years ago #

  11. urchaidh
    Member

    A simple microcontroller might be you're best bet. Something like an Arduino might be overkill but the advantage is all the support out that is already there. Would need a wee bit of coding, nothing too hairy.

    It would give you lots of options in terms of sensors and control. You could have your basic wire, wire with resistance measuring, a wire pair such that one should be open circuit and one closed, light, sound, motion. That would give even Tom Cruise or Catherine Zeta Jones* a run for their money.

    * other high-tech burglars are available.

    Posted 8 years ago #

  12. Snowy
    Member

    Perhaps a portable IR alarm would be less hassle (although probably less fun, too...).

    Posted 8 years ago #

  13. kaputnik
    Moderator

    How about an induction loop in the door that is triggered when a metal object is removed from the shed without first disabling the alarm. Also covers garden power tools perhaps.

    Or a simple light gate that activates when someone enters the shed without disabling the alarm?

    Google also "smokecloak". Those keen on electronics could probably build their own using mobile disco components.

    Posted 8 years ago #

  14. acsimpson
    Member

    @Snowy, I don't think NAND logic is correct. You want the alarm to go off if the master switch is on and the circuit is broken. A NAND would sound the sounder whenever the master was off and the circuit intact too.

    Regardless of the logic if opting for simple electronics you would also need to produce a circuit which leaves the sounder on until the master switch is reset as otherwise a theif might be able to operate quickly enough not to rouse sleeping occupants by replugging the wire.

    Posted 8 years ago #

  15. Snowy
    Member

    @acsimpson You're quite correct, I hadn't thought that through.

    A microswitch on the shed door was a good idea; sounds like a less fiddly option than having to manually wire up the bikes.

    I wonder if you could build this sort of circuit into a bike lock such that if the cable got snipped, a speaker would scream. Might surprise a thief enough that they'd scarper, or grant a few vital seconds to react and intercept.

    Posted 8 years ago #

  16. acsimpson
    Member

    Something like this:

    http://lockalarm.com/

    Posted 8 years ago #

  17. wingpig
    Member

    "a speaker would scream"

    I'd prefer a foghorny noise, or a big bassy tigery growl from immediately behind. Perhaps some frenetic music to get the perpetrator's heart rate up and make them nervous and twitchy, like our former under-neighbour's ill-chosen night-time music would.

    Posted 8 years ago #

  18. kaputnik
    Moderator

    Or there's the "record your own" option of the Invader 2000 as heard in Phoenix Nights.

    HONK! "Get back you (insert expletive here), or I'll break your legs!" HONK!

    Posted 8 years ago #

  19. acsimpson
    Member

    The sound of a door slowly closing followed by steel bars being slid quickly into place should get their heart rate going.

    Posted 8 years ago #

  20. chdot
    Admin

    "

    Edinburgh Police (@EdinburghPolice)
    15/04/2016, 12:06 pm
    Crime Prevention stall at Cameron Toll 2-4pm, 2moro. Break in to those piggy banks - there's shed alarms for sale!

    http://pic.twitter.com/p5Ybh1oUcg

    "

    Posted 8 years ago #

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