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 |
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