Last night I accidentally left my car unlocked. Stupid, yeah I know. But anyway, even if it was locked, it doesn‘t have a car alarm. I was wondering if there was anyway that I could make a homemade car alarm to catch this thief that has been stealing stuff from people‘s cars lately in my neighborhood? Any ideas? It‘s becoming quite bothersomeEspecially since he stole over 100 bucks from my dad and 40 bucks from me -.-; Basically I want something to where if you open the door, something loud and scary goes off.like a blowhorn gt;:D!
You need RF receivers to detect the signals. Now you need to know what frequency as well, then your going to have distance issues. there are even transceivers on the market that can tell you if the alarm was tripped. Page you or call your cell phone. And you could start with the fob that comes with a new car most of them come with a panic button that's starts the alarm to warn off predators.
I've got an idea. Place a small switch inside your gas door (somewhat hidden, easy to access and away from the elements of mother-nature), this will be the power switch. Run one side of the switch to your dome light(s), or at least to the circuit for the dome light. The second side of the switch will go to a small relay (that you could pick up from any auto parts store). Get power to the relay from a non-keyed power source (so it is always energized). From the relay tie it to your car horn. When you leave your car for the night, step back and open the fuel door, flip the switch then shut the fuel door. Now, if a car door gets opened, the dome light comes on, energizing the relay, and causing your car horn to honk (it will be continuous as if you held in the horn button), and will continue to honk till the door(s) are closed (unless your dome lights have a 15sec delay before they go off, then the horn will honk till the lights go out). When you want to get in the car, step to the fuel door, turn the switch off, then get in your car as normal. Total cost about $15. Remember you will need some understanding of electrical circuits and understand operation of a relay. You asked for a cheap way, you got it.
well i wish i could show you what a friend of mine made . ill try to explain it you need a small battery 12v,horn, wire ,relay and a switch like a spring loaded switch .then you can put it all together .the switch can be put on anything the relay is powered with the battery .when the relay is tripped the only way for the noise to stop is to remove the battery .so if you put it on a door and the person closes the door the thing keeps on going off really loud. hope this helps
