WO1998052788A2

WO1998052788A2 - Vehicle headlamp controller

Info

Publication number: WO1998052788A2
Application number: PCT/SG1998/000037
Authority: WO
Inventors: Mun Chor Chow
Original assignee: Mun Chor Chow
Priority date: 1997-05-22
Filing date: 1998-05-22
Publication date: 1998-11-26
Also published as: WO1998052788A3; WO1998052788A9; AU7562398A

Abstract

This invention is an automatic controller for switching on and off the headlamps of a vehicle according to the ambient lighting conditions. With just one optical sensor and a controller, the present invention when connected to the relay of the headlamps controls the headlamps accurately and intelligently under all conditions. The controller incorporates a filter (R3C2) and a voltage divider (VR1, VR2, R4) which in turn are connected to a comparator (IC1). The filter (R3C2) removes the alternating component of the output from the optical sensor caused by artificial lighting, while the voltage divider (VR1, VR2, R4) sets a preset threshold intelligently for the activation and deactivation of the headlamps in response to a variety of ambient conditions. The invention also switches off the car lamps when the engine is turned off. This will increase the life of the battery without the drivers having to remember to switch off and on the headlamps.

Description

VEHICLE HEADLAMP CONTROLLER

FIELD OF THE INVENTION

This invention is a method and apparatus for controlling a vehicle's headlamps in respond to the ambient light levels.

BACKGROUND OF THE INVENTION

Some drivers may turn off the 'parking' lamps during dusk and may forget to switch on the headlamps when the sky gets darker due to high artificial lighting levels in cities, covered carparks and tunnels. Alternatively, they may not even switch on the headlamps while driving in covered carparks and tunnels during the day. These conditions are extremely dangerous for the pedestrians and the riders together with the occupants as the vehicles will be less visible under these conditions.

Another problem associated with the forgetfulness of the drivers is that the headlamps were left on after parking their cars. This is especially true if the driver had switched on his headlamps while driving in covered carparks or tunnels and forgot to switch them off as the sky was too bright in the day. This will lead to a high drain in the battery and eventually a dead battery the next day. Many new cars are fitted with an alarm that warns the driver when the car lamps are left on while the engine is turned off; this may address the issue of having a flat battery, but no the issue of safety.

Automatic switching of headlamp in vehicles is known, however most of the prior art switch on the headlamps as soon as the light level falls below a preset threshold level and switch off above the preset threshold level. Examples are US Pat. No. 4, 613,791 issued to Kurihara et al and US Pat No. 4,956,580 issued to Wang Yun-Shang. These prior art have instability problems in certain operational conditions such as driving through ambient light level near that of the preset threshold level such as shadows cast by trees or buildings. At this critical light level, the prior art headlamp controllers often change state, causing them to switch the headlamps on and off unpredictably. Such "chattering" create road hazards and irritates other road users.

US Pat. No. 4,665,321 issued to Chang at al uses a mechanical relay's latching and dropping off voltage properties to provide a "hystersis" to make his invention work. This method has the major disadvantage in that the latching on and dropping off voltages cannot be accurately defined and controlled , and is likewise unstable. Since deactivation of the headlamps depends on the dropping off voltage of the relay, the switching off light level cannot be defined and thus is not repeatable in operation for the same unit or when compared with other units. Chang also uses a pick-up coil to detect whether the engine has started. This method had serious drawbacks as it cannot detect diesel engine powered vehicles.

OBJECT OF THE INVENTION

An objective of this invention is to activate automatically the headlamps, taillamps and license plates and other associated lamps as soon as the ambient light level falls below a preset threshold level to make the vehicle more visible to other road users.

Another objective of the present invention is to switch on or off the headlamps automatically according to the ambient lighting condition such as dawn or dusk.

An additional objective of the present invention is to control with one optical sensor various lamps and lights of a vehicle in response to a variety of ambient conditions.

Yet another object of this invention is describe a vehicle headlamp controller that can be manufactured economically, robustly and reliably and installed easily in a vehicle.

SUMMARY OF THE INVENTION This invention is an automatic controller for switching on and off the headlamps of a vehicle according to the ambient lighting conditions. With just one optical sensor and a control unit, the present invention when connected to the relay of the headlamps controls the headlamps accurately and intelligently under all conditions. The controller incorporates a filter and a voltage divider which in turn are connected to a comparator. The filter removes the alternating component of the output from the optical sensor caused by artificial lighting, while the voltage divider sets a preset threshold intelligently for the activation and deactivation of the headlamps in response to a variety of ambient conditions. The invention also switches off the car lamps when the engine is turned off. This will increase the life of the battery without the drivers having to remember to switch off and on the headlamps.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of the vehicle headlamp controller of the present invention being connected to the relay of a vehicle's headlamps.

DETAILED DESCRIPTION OF THE INVENTION

This invention addresses the safety issues caused the carelessness and forgetfulness of some drivers who fail to turn on their car headlamps while driving in brightly lighted cities, during the dawn and dusk hours, covered carparks and tunnels where artificial lighting levels are high. This condition makes the vehicle less visible to other road users and pedestrian thus is highly dangerous for the drivers and their passengers as well as others, causing higher chances of accidents. This invention also prevents flat batteries caused by drivers who forget to switch off their headlamps after parking their vehicles, especially if they had switched on their headlamps while driving in a covered carpark or tunnel in the day. When the vehicle engine is switched off, this invention will automatically switches off the lights in which this invention is controlling.

In FIG. 1 the vehicle headlamp controller of the present invention comprises a optical sensing means, a filter means, a hystersis means, a presetting means, and a switching means. The components of the present invention are coupled in parallel to the headlamp via a headlamp relay (not shown in figure). The optical sensing means comprises a sensor for sensing the ambient light level of the vehicle. The optical sensor is coupled to the comparator IC1 via the filter means. When the voltage of the sensor output reaches a preset threshold of the comparator, the output of the comparator turns on the transistor T2 via the resistor R5. The sensor detects when a preset threshold voltage is reached or the slightest change in voltage across the controller of the present invention in order to produce an output voltage to the comparator via the filter means. R3 and C2 forms the filter means of the present invention. The output from the light sensing means is provided as input the filter means and it filters the alternating voltage components of signals detected by the sensor under artificial lighting conditions. The filter means enables this invention to work reliably and with stability while the vehicle is driven in brightly artificial lighted areas such as tunnels and some covered carparks or driving under sudden changes in light intensity such as shadows from trees and building. Together the filter means and the hystersis means comprises the control unit referred to throughout the description of the present invention.

Referring again to FIG. 1 , the filer means is coupled to the presetting means of the present invention. The presetting means comprises the comparator IC1 and a voltage divider VR2 and R4 coupled to one of the two inputs of the comparator. Together with the hystersis means, the presetting means of the present invention prevents the user to preset the "turn on" voltage threshold lower than that of the "turn off" voltage threshold at junction J1. The presetting means thus prevents erroneous operation of this invention. It also facilitates the calibration of the controller of the present invention. Again in FIG. 1, the hystersis means of the present invention comprises a variable resistor VR1. This means is coupled to a relay contact S1 or any switching means. The hystersis means allows the user to adjust accurately the preset threshold level and is one of the novel features of the present invention. The interaction of the hystersis means will be elaborated below in connection with the detailed operation of the controller. Finally, the switching means of the present invention is coupled at its input to the hystersis means and the presetting means and at its output to the headlamp. The switching means comprises the relay (D2, S1 and S2), a transistor T2 and a resistor R5 respectively. Again, the function of the switching means will be explained in detail below together with the description of the operation of the controller. In FIG. 1, the junction J1 of the voltage divider VR2 and R4 provides a reference voltage for the comparator IC1. Since the hystersis means resistor VR1 is shorted by the relay contact S1 , this resistor is out of the circuit while the relay is de-energized. When the ambient light level is high, the voltage output of the sensor has a lower voltage. As the ambient light decreases, the voltage output of the sensor increases. When the sensor's output voltage exceeds the voltage at J1 , IC1 will have a high output to the switching means causing transistor T2 to conduct. The output of T2 energizes the relay, causing contacts S1 to open and S2 to switch on the car headlamp relay. With S1 in a open-circuit position, the hystersis means resistor VR1 is no longer shorted but is now in series with VR2. In this condition, the reference voltage at J1 is now lowered to the preset threshold value. This in turn requires a higher ambient light level to reaching the sensor before the output voltage of the sensor can be lowered than that of the voltage at J1. When the output voltage of the sensor is lower than the voltage at J1 , the comparator IC1 provides a low output and switches off the transistor T2. This de- energizes the relay causing contact S1 to short circuit and S2 to switch off the car's headlamp. The contact S1 will now short-circuit the resistor VR1 again, raising the voltage at junction J1. This condition necessitates the sensor to detect a lower light level before the comparator IC1 can have a high output again. This change of reference points forms an electronic ' Hystersis Means' which is accurately adjustable and repeatable by changing the resistance values VR1 and VR2.

With this method of connection, this invention can "turn on" the car headlamps at low ambient light levels but can only turn it off at higher ambient light levels than the "turn on" ambient light level. This allows a stable operation of this invention especially when the vehicle is driven under shadows at dusk as well as to prevent 'chattering' especially when the ambient light level approaches that of the preset value.

The present invention uses a simple filter to remove the alternating voltage component from the output of the optical sensor to operate reliably under bright artificial lighting, and a method of using one comparator to detect two levels of ambient light accurately, fully presetable and with repeatability and reliability.

While the present invention has been described particularly with reference to FIG.1 with emphasis on an apparatus for controlling vehicle headlamps, it should be understood that the figure is for illustration only and should not be taken a limitation on the invention. In addition, it is clear that the method and apparatus of the present invention have utility in many applications where detection and control of ambient light is required. While the optical sensor in FIG. 1 is shown to be a three wire device, it should be understood by one skilled in the art that the optical sensor can be a two wire device or a hybrid device etc. Furthermore, the output of the optical sensor need not be calibrated or linear as only two operation points on the voltage output curve are required and can be calibrated from the comparator. It is contemplated that many changes and modifications may be made by one of ordinary skill in the art without departing from the spirit and the scope of the invention as described.

This invention can be used to control the high or low beams of a vehicle's headlamps by changing the calibration of the voltage divider to allow the present invention to detect changing ambient lighting conditions such as that of emerging from a dark road to a lighted area or visa versa. For instance, this invention can also be used to switch on garden lights automatically when the light levels drops to a certain value at dusk and switches it off again in the morning. The normal timers used to switch these lights are not ideal as the light levels at a certain time is very different between summer and winter. Ordinary light sensors will not work properly as shadows from trees or other plants may cast shadows on the sensors causing these devices to operate erratically. Chattering or flickering of the lamps will also occur as the light levels approaches the threshold level and can be damaging to the equipment and itself.

Claims

1. A vehicle headlamp controller comprising: a sensor for detecting ambient light; a filter means coupled to said sensor for receiving output signals therefrom, said signal further comprising alternating and non-alternating components, said filter means removing alternating components from said signals; a presetting means coupled at its input to said filter means for allowing users to set a predetermined threshold corresponding to a preset ambient light level accurately and reliably; a switching means coupled at its input to said presetting means for tuming on and off at least a headlamp coupled to the output of said switching means; and a hystersis means coupled to the input of said presetting means and said switching means for adjusting said predetermined threshold accurately; whereby said controller turns on and off headlamps automatically and safely while discriminating reliably artificial lighting conditions from those that necessitate activation and deactivation of headlamps.

2. The controller as in claim 1 wherein said sensor is a three wire device.

3. The controller as in claim 1 wherein said filer means comprises a resistor and a capacitor.

4. The controller as in claim 1 wherein said presetting means comprises a voltage divider and a comparator.

5. The controller as in claim 1 wherein said switching means comprises a relay and a transistor.

6. The controller as in claim 1 wherein said hystersis means comprises a variable resistor.

7. The controller as in claim 1 wherein said hystersis means comprises a calibrated resistor.

8. A method of controlling vehicle headlamp comprising the steps of: detecting ambient light with a sensor; receiving output signals from said sensor and removing alternating components thereof with a filter means coupled to said sensor; setting a predetermined threshold corresponding to a preset ambient light level accurately and reliably with a presetting means coupled at its input to said filter means; tuming on and off at least a headlamp with a switching means coupled at its input to said presetting means and at its output to said switching means; and adjusting said predetermined threshold accurately with a hystersis means coupled to the input of said presetting means, whereby said controller turns on and off headlamps automatically and safely while discriminating reliably artificial lighting conditions from those that necessitate activation and deactivation of headlamps.

9. The method as in claim 8 wherein said sensor is a three wire device.

10. The method as in claim 8 wherein said filer means comprises a resistor and a capacitor.

11. The method as in claim 8 wherein said presetting means comprises a voltage divider and a comparator.

12. The method as in claim 8 wherein said switching means comprises a relay and a transistor.

13. The method as in claim 8 wherein said hystersis means comprises a variable resistor.

14. The method as in claim 8 said hystersis means comprises a calibrated resistor.