Automatic headlight control circuit

• US 3,963,940 A
• Filed: 02/04/1975
• Issued: 06/15/1976
• Est. Priority Date: 02/04/1975
• Status: Expired due to Term

• Current Assignee: Michael R. Adamian
• Original Assignee: Michael R. Adamian
• Inventors: Adamian, Michael R.
• Primary Examiner(s): Hohauser, Herman J.
• Application Number:
  US05/547,002
• Time in Patent Office: 497 Days
• Field of Search: 307/10 LS, 307/10 BP, 307/10 R, 315/83, 315/82, 315/77, 315/76, 340/56, 340/76
• US Class Current: 307/10.8
• CPC Class Codes: B60Q 9/001 Alarm devices when the motor is stopped and the lights are on

Abstract

An automatic headlight control circuit is disclosed which will serve to turn-on automobile lights in response to pulsed external signals such as ignition pulses. A delay circuit is provided which will cause the lights to be turned-off a predetermined period of time after the external signals to the control circuit have ceased. A delay of several minutes is accomplished using an emitter follower circuit.

Claims

1. Automatic control apparatus for use in an automotive vehicle having one or more lamps, an electrical power source, and a source of engine ignition pulses, said control apparatus comprising:

circuit means connected to said source of ignition pulses for generating a first series of output signals corresponding to said ignition pulses at least in duration;

light sensitive means responsive to changes in ambient illumination for indicating level of ambient illumination;

gate circuit means responsive to said light sensitive means and said first series of signals for generating a second series of output signals corresponding to said ignition pulses, at least in duration, when ambient illumination is below a selected level;

a gate controlled bi-stable semi-conductor device having a control terminal, a current input terminal, and a current output terminal, and connected at its current input and output terminals in series in a current path from said power source to said lamps and responsive to one of said second series of signals from said gate circuit means corresponding to said ignition pulses at least in duration, applied to said control terminal, to switch from a non-conducting state to a conducting state; and

circuit means for selectively switching said semi-conductor device from the conducting state to the non-conducting state comprising a transistor connected between said input terminal and said output terminal for shunting current there-between external to said semi-conductor device, and a capacitor connected to said transistor for temporarily placing said transistor in a conducting mode for shunting current external to said semi-conductor device when said lamps are to be extinguished.

2. Automatic light control apparatus for use in a automotive vehicle having one or more lamps, an electrical power source, and means for producing a first signal indicative of operation of said vehicle, said apparatus comprising:

light sensitive means responsive to changes in ambient illumination for indicating level of illumination;

a gate circuit responsive to said light sensitive means and said first signal for generating a second signal when ambient illumination is below a selected level;

a capacitor;

a current flow control switch connected serially in a current path from said power source to said lamps and operative to close said current path in the presence of a control signal;

circuit means responsive to said second signal to selectively allow and prevent the flow of charging current to said capacitor;

a capacitor discharge control circuit comprising a resistor and a first transistor operative to provide a capacitor discharge path and to generate said control signal and having an input terminal connected to said capacitor, a first output terminal connected to said resistor whereby the effective impedance in the capacitor discharge path includes the impedance of said resistor multiplied by the amplification factor of said first transistor, and a second output terminal connected to said current flow control switch.

3. Automatic light control apparatus in accordance with claim 2, and further comprising circuit means for cutting off electrical power to said discharge control circuit after the potential across said capacitor has dropped below a predetermined level.

4. Automatic light control apparatus in accordance with claim 2, wherein said capacitor discharge control circuit further comprises a second transistor and wherein said first and said second transistor form a comparator circuit controlled by a reference potential and a potential across said capacitor, said comparator circuit being operative to complete a capacitor discharge path only when said potential across said capacitor exceeds said reference potential.

5. Apparatus for controlling automotive headlights comprising:

a capacitor;

circuit means responsive to a headlight turn-on signal for allowing flow of charge to said capacitor and responsive to a headlight turn-off signal for preventing flow of charge to said capacitor;

a bi-stable comparator circuit connected to said capacitor and a reference potential, said comparator assuming a first state when the potential across said capacitor exceeds said reference potential and second state when said reference potential exceeds the potential across said capacitor;

circuit means connected to said comparator for establishing a path from a vehicle power source to said headlights when said comparator is in said first stable state and opening said path when said comparator is in said second stable state.

6. Apparatus in accordance with claim 5 wherein said comparator circuit comprises at least two transistors and said capacitor has a discharge path through one of said transistors.