DIY: home made anti-theft bike alarm system (soldering skills needed)

Scared of losing your precious beloved to thieves but cannot afford or don`t want to pay huge money for an anti theft system? Well, by following these steps you can make one yourself!

The backbone, heart and sould of the whole unit, and any other commercial unit is actually just one very simple component that has many different names, probably the most common ones being a tilt sensor or a mercury switch. It can look like something like this:




here are a few different versions I found from an electric component shop:



Essentially it is a small glass tube with two electrodes and a small drop of liquid mercury (or a steel ball on units manufactured after 2006 like in the black box) When fixed in a right position on a motorbike the mercury drop stays on the far end of the tube when leaning on the side stand and slides to the other connecting the two electrodes when the bike is lifted upright. Can`t get any simpler than that.

Here is the first schematic that acts as the backbone of the whole device, some component values are still to be tweaked slightly, for example the blinker LED preload resistor has to be dialed in with the LED, ask your components dealer what cill be the best, but I`d guess something like 470 ohm should suffice, I`m using LED:s that have slightly higher operating voltage than usual, of course if you can find 12v blinker LEDs you won`t need the preload resistor at all.





The circuit board. If you want to make your own scale it so that the printout version is 58mm wide and 36mm high.



Parts layout. The reed relay is a HF41F type 12v 6A.


Stay tuned for more!

 

It`s not that hard if you have a good soldering iron and good instructions. That version is still a little "brute force" cause the delay is done with a massive capacitor, I`m currently studying LM555 and LM556 IC circuits if I could make the startup and alarm delays a bit more sophisticated. I`m trying hard to keep it simple enough for any common joe to be able to make. Basically the hardest part is making the actual circuit board if you can`t get anyone to make it for you.

 

Yes, it is also possible to run the starter switch ground wire through the high beam switch so that the high beam has to be on for the bike to start, after it has started the high beam can be turned off. But this isn`t an immobiliser, it`s an alarm that arms itself every time the ignition is turned off and disarms when on.

The circuit you described can also be done with a magnetic reed relay so that a magnet has to be in a secret place x ( for example on the dash, on the door, or wherever) for the device to run, and when it is off the relay is open so naturally nothing happens.

 

Well, this was actually done by demand to some friends at another bike forum cause their bikes spend their nights at their own yards so they hear the siren go off themselves, basically it`s a brain stretch for me to hone the little skills I have at circuit designing, if you don`t need one then fine by me, I gain no profit of this, quit the opposite... But as said this is an ever-evolving process, who knows I might even add an immobilizer to it some day

 

Well, pretty much ANY device, including this, is hackable. It doesn`t even try to be hack-proof in any way, the point is the element of surprise if some sorry fu*ker tries to steal your bike to joyride it, gets spooked by the siren and runs off, wouldn`t it be a great feeling to know the thing that stopped the theft is your own build? If some "professional" thieves are gonna take your bike they do it even if it has disc locks, sirens and a big chain which bolts it to the ground...

I`m planning to make a more sophisticated version of this at some point in the future when I get the time and motivation but quite frankly, am not sure am I going to post it here...