David, thanks, that is simple enough. I appreciate it. Funny that I
just got a phone call from a co-worker telling me my parking lights
were on!
Thanks again.............
Miguel

I have not failed. I've just found 10,000 ways that won't work.
  - Thomas A. Edison

On Mon, May 24, 2010 at 10:01 PM, David Beierl <dbeierl@attglobal.net> wrote:
> At 11:48 PM 5/24/2010, miguel pacheco wrote:
>>
>> How about a more detailed explanation of george jannini's dummy alarm?
>> Miguel
>
> Hi Miguel,
>
> What you need for a headlight alarm is a buzzer and a diode, to allow
> current to flow only one way through the buzzer.  Piezo buzzers are that way
> by nature, and the Radio Shack buzzer that I called out apparently has an
> internal diode.
>
> Now you must locate two wires:  one of them goes on and off with the
> ignition and the other goes on and off with the parking lights.  Hook the
> negative lead of your buzzer to the first wire, and the positive wire to the
> second.  That's it, you're done.
>
> If both ignition and lights are on, no current flows because the voltages
> are equal.
>
> If ignition is on but lights are not, no current flows because the diode
> prevents it.
>
> But if lights are on and ignition is not, current will flow through the
> buzzer and ground itself through the various devices that are powered by the
> ignition wire you chose.  Bzzzzzzzzzzzt.....
>
> Yours,
> DAvid
>