jgd@rsiatl.UUCP (John G. DeArmond) (10/09/90)
hbg6@citek.mcdphx.mot.com writes: >>Since my concern was from leaving my lights on and not cold weather, I >>am now considering building a device I saw in a popular electronics >>magazine that buzzes if you leave your lights on. (I don't have the >>magazine with me but can give details to anyone who wants more >In my wifes car, I installed a relay in series with the headlight relay >that insures that if the key is off, the headlights are off. >Interestingly, our '75 Volkswagen van has this feature built in but it >only turns off the headlights, not the running lights. My wife's Camrey has its own little computer to figure out when to turn the lights off. What'll they think of next to put some silicon in? :-) Making a is trivial. All one needs is a Sonalert or similiar device and a 1 amp diode (1n4002 works well). connect the diode in series with the sonalert with the cathode connected to the (+) lead of the sonalert and the anode lead ready to connect to wire. Locate a point where where there is swiched 12 volts from the ACCessory switch position. This is usually marked on the fuse block. Next find a place where there is switched power to the headlights. The dimmer switch and/or the headlight switch are obvious places. Connect the Sonalert assembly such that the (-) side of the sonalert is on the ACC switched 12 volt lead and anode of the diode is on the switched headlight circuit. The circuit works as follows. When both the ignition and the lights are on, there is 12 volts on both sides of the sonalert and thus no current flow through it. When the lights are off and the ignition is on, there is voltage on the (-) side of the Sonalert and there is an effective ground through the headlight filaments. The diode is reverse biased, however and the sonalert remains quiet. With the lights on and the ignition off, the anode of the diode and therefore the (+) side of the Sonalert is at 12 volts while the (-) side of the sonalert is at an effective ground through the de-energized load on the ACC terminal. Since the diode is forward biased, the Sonalert sounds, alerting you to turn the lights off. Simple, reliable and only 2 components involved. John -- John De Armond, WD4OQC | We can no more blame our loss of freedom on congress Radiation Systems, Inc. | than we can prostitution on pimps. Both simply Atlanta, Ga | provide broker services for their customers. {emory,uunet}!rsiatl!jgd| - Dr. W Williams | **I am the NRA**
tell@oscar.cs.unc.edu (Stephen Tell) (10/10/90)
In article <4233@rsiatl.UUCP> jgd@rsiatl.UUCP (John G. DeArmond) writes: >hbg6@citek.mcdphx.mot.com writes: > >>>Since my concern was from leaving my lights on and not cold weather, I >>>am now considering building a device I saw in a popular electronics >>>magazine that buzzes if you leave your lights on. (I don't have the >>>magazine with me but can give details to anyone who wants more Radio Shack sells a ready-made module for this purpose, and a few sonalert-equivilent buzzers if you want to make your own. >Making a is trivial. All one needs is a Sonalert or similiar device >and a 1 amp diode (1n4002 works well). [text replacd with picture] Diode Buzzer Headlights -------------->|-----------------------()---------- ACCessory + - >The circuit works as follows. When both the ignition and the lights are >on, there is 12 volts on both sides of the sonalert and thus no current >flow through it. When the lights are off and the ignition is on, there >is voltage on the (-) side of the Sonalert and there is an effective >ground through the headlight filaments. The diode is reverse biased, >however and the sonalert remains quiet. With the lights on and the >ignition off, the anode of the diode and therefore the (+) side of the >Sonalert is at 12 volts while the (-) side of the sonalert is at an >effective ground through the de-energized load on the ACC terminal. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ >Since the diode is forward biased, the Sonalert sounds, alerting you to >turn the lights off. Ah, but what if there is no de-energized load on the ACC terminal? I installed a circuit like this (Actually the radio shack module, I was lazy) in my 1983 Toyota Tercel. The instructions said find an "Ignition" wire (not accessory). I couldn't locate one of those easily, and so used the easily-available accessory power wire for the radio. The result is that the circuit works fine only if the radio is left on when you turn off the car and not the headlights! If the radio isn't on, it might beep a few times, I think as capacitor charges someplace, probably in the digital clock I installed at the the same time. So, unless you're in the habit of leaving other stuff on all the time too, best find a wire that is only live when the engine is running. >John De Armond, WD4OQC | We can no more blame our loss of freedom on congress >Radiation Systems, Inc. | than we can prostitution on pimps. Both simply >Atlanta, Ga | provide broker services for their customers. >{emory,uunet}!rsiatl!jgd| - Dr. W Williams | **I am the NRA** -------------------------------------------------------------------- Steve Tell e-mail: tell@wsmail.cs.unc.edu usmail: #5L Estes Park apts CS Grad Student, UNC Chapel Hill. Carrboro NC 27510