I'm trying to build my own cable lock alarm (for science!) and am having trouble figuring out a way to detect that a wire has been cut.
The circuit has to
- Use no power at idle (or at least, very very little so that the batteries don't have to be changed every hour)
- Sound a speaker when a specific wire is cut
My knowledge of electronics is minimal.. I know what capacitors, diodes, resistors and other basic stuff are and do, but I don't have a good grasp on how electricity flows in anything other than a single loop.
I seem to remember once making a circuit that was something like this.. (and oh geez, I don't even know how to do a proper diagram so forgive me folks)
/----------[battery]-------\ | | |--------[light bulb]------| | | \-----[wire to be cut]-----/
And the bulb would only light up if the wire below was cut, because electricity always takes the path of least resistance.
Anyway, this is going to be a battery operated circuit and I'm pretty sure that diagram up there is a short. I think there was a resistor involved but I don't remember where it went.
If anyone can give me some pointers that'd be great!