XPost: alt.autos.toyota, rec.autos.tech, alt.autos.honda   
   From: Skenny@highstream.invalid   
      
   John S. wrote:   
   > On Aug 17, 9:36 pm, Hachiroku       wrote:   
   >   
   >>And come up with a Cheap-Ass alarm.   
   >>   
   >>On the Mazda, I don't want to go to the trouble or expense of installing a   
   >>real alarm, but I want something.   
   >>   
   >>Honking the horn and flashing the flashers would be good enough. I want   
   >>the horn to 'beep', so a flasher unit and a relay or two would be good.   
   >>   
   >>There's two ways to set the thing up:   
   >>   
   >>Put something like a key switch under the fender, turn on when leaving,   
   >>turn off when using the car.   
   >>   
   >>Or, a little more sophisticaed: put a switch inside the car. Now, this   
   >>would mean triggering the 'alarm' when getting into the car, something I   
   >>don't want to do at 1 AM when I'm leaving on my 'paper route'. So, some   
   >>kind of delay would be good. I was thinking a capacitor between the hot   
   >>line and the 1st relay, so the cap charges and when it reaches charged it   
   >>triggers the relay and starts the flasher.   
   >   
   >   
   >   
   > All I've read so far are questions about how the car owner would   
   > switch an unidentified alarm system off and on.  Since you are not   
   > buying an off-the-shelf alarm what kind of alarm system are you   
   > proposing.  And more importantly how will the alarm be triggered by a   
   > potential intruder.   
   >   
   >   
   >   
   >>But, I need a hint what size cap to use, and how to wire it into the relay   
   >>so that it charges before setting off the horn, maybe 20 seconds is good.   
   >>   
   >>Of course, we could get REAL sophisticated and use the ol' venerable 555   
   >>timer, but that's more involved than I want to make it.   
   >>   
   >>Any ideas?   
   >   
   >   
   >   
   Why not just have a scr trigger from the interior light?   
   The scr will switch the horn relay to ground.   
   Door opens, light switch fires SCR, horn blows until someone turns off   
   the hidden (under dashboard or seat) switch, which breaks the circuit to   
   SCR. You could use a capacitor to give you a few seconds to leave or   
   enter the car.   
   After thinking about it, you may have to use a transistor to invert the   
   signal from the door switch. You could set up your delay with the   
   capacitor, resistor, to wait 10 or so seconds before firing the   
   transistor, which would then set the scr.   
   Back in the 70's when the price of gas was rocketing, people stealing   
   gas from your car at night became a common occurance.   
   I thought about attaching a small magnetic reed switch to the gas cap   
   cover that would do the same thing. Just never got around to doing it.   
   One guy I know wired a 120 volt hot wire to the frame of his car. I   
   wouldnt recommend doing this though, it could kill someone and give you   
   a manslaughter charge.   
   (I know, it shouldnt be against the law to kill a thief, but it is.)   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)