GB2237106A - Vehicle light management system - Google Patents

Abstract

A vehicle light management system comprises a control means which is operable in response to a signal from a light sensitive element [LDR 1] to switch a vehicle light [L] on when the intensity of the light sensed is below a first threshold value and to switch the vehicle light [L] off when the intensity of the light sensed is above a second threshold value. The second threshold value may be the same as, or different to, the first threshold value. The vehicle light may be headlights and/or sidelights. The light sensitive element may be mounted in a dashboard of the vehicle within a reflective housing, ambient light entering the housing through a diffuser. <IMAGE>

Description

Title: "Vehicle light management system" Description of Invention This invention relates to a vehicle light management system.

With vehicle light systems which are manually operated, it is a simple matter for a driver to forget to switch the lights on at night, or to leave the lights on after the vehicle has been parked. Parking lights are fitted to virtually all cars now, but must again, be manually operated.

According to one aspect of the invention I provide a vehicle light management system comprising a control means which is operable in response to a signal from, a light sensitive element to switch a vehicle light on when the intensity of the light sensed is below a first threshold value and to switch the vehicle light off when the intensity of the light sensed is above a second threshold value.

According to a second aspect of the invention we provide a vehicle having a light management system according to the first aspect of the invention.

The invention will now be described with reference to the accompanying drawings in which: FIGURE 1 is a diagram of a first electronic control circuit which controls the main headlamps of the vehicle; FIGURE 2 is a diagram of second electronic control circuit which controls the sidelights of a vehicle; FIGURE 3 is a cross-sectional view through part of a dashboard of a vehicle showing the position in which a light sensitive element of the circuits of Figures 1 and 2 is mounted; and FIGURE 4 is a plan view of a housing shown in Figure 3.

Referring to the drawings there is shown in Figure 1 an electronic control circuit for controlling the main headlamps of a vehicle. The circuit comprises a light sensitive element which in this example comprises a photo sensitive resistor LDR1 the resistance of which increases as the intensity of light falling on it increases. The resulting change in the potential difference across the resistor LDR1 in response to changing intensity of light falling on the element, is transmitted to pin no. 2 of an integrated circuit IC1 which in the present example is a 741 operational amplifier.

Pin no. 3 of IC1 is held at a constant potential by two resistors R1 and R2, and when the potential at pin no. 3 increases, i.e. when LDR 1 senses a decrease in light intensity the output from pin 6 is significantly increased. This output is fed via a resistor R4 to the base of a transistor TR1 which in the present case is a 2N3053 NPN type resistor.

Resistor R4 and a further resistor RS together ensure that the base of the transistor TR1 receives insufficient current when the output from pin no.

6 of IC1 is low, so that no current path is provided through the transistor TR1.

When transistor TR1 provides a current path through it, the coil of a relay RLA 1 is energised. In the present example, the relay RLA 1 is a 5 amp relay.

A diode D1 is provided to protect the transistor TR1 from any back EMF created as the coil of relay RLA 1 is energised or deenergised.

When the coils of the relay RLA 1 are energised, the normally open contacts RL1 of the relay RLA 1 are closed and this provides a current path from a battery B of the vehicle through the contacts RL1 to the main headlights which are indicated at L.

It will be appreciated that when the light sensitive element LDR 1 senses a light level below a first threshold, the headlamps 11 will be switched on.

When the light sensitive element LDR 1 senses a light level above a second threshold, which may be the same as the first threshold, or a different value, the headlamps L will be switched off.

It is possible to adjust the light level to which the light sensitive element LDR 1 will react, by virtue of the provision of a variable resistor VR1 which is in series with a further resistor R3, the resistors VR1 and R3, and photo sensitive resistor LDR 1 providing a potential divider to apply a voltage pin no. 2 of the integrated circuit IC1 depending on the light level sensed.

A light emitting diode LED 1 is also provided in series with a resistor R6 to provide an indication that the control circuit is operational.

To ensure that the transistor TR1 either provides a current path through it or not, in order to provide snap action switching of the relay RLA 1, a feed-back loop is provided from pin no. 6 of the integrated circuit IC1 to pin no. 3, via a feed-back resistor R7.

A smoothing capacitor C1 is provided to smooth out any voltage fluctuations which may arise. The feed-back loop including a resistor R7 has an additional benefit of making the circuit less prone to spurious switching caused by voltage transients and random background light fluctuations which are sensed by the photo sensitive resistor LDR 1.

To protect the control circuit, a 0.5 amp fuse F is inserted between a positive terminal of the battery B and a main positive line of the control circuit.

A current path to the negative terminal of the battery B is only provided once an ignition switch S1 is closed. When switch S1 is open, the control circuit is not operational.

A manual override to the circuit is provided by means of a switch S2 which permits current to pass from the positive terminal of battery B direct to the main headlamps and then to the negative terminal of the battery B without having to pass through the contact RL1 of the relay RLA 1, or the ignition switch S1 Referring now to Figure 2, a second electronic control circuit is shown for controlling the sidelights of the vehicle 10, which are indicated at L1. Similar components to those indicated in Figure 1 are indicated by the same reference numerals. It will be appreciated that in Figure 2, a relay RLA 2 with two pairs of normally open contacts RL2 and RL3 replaces the relay RLA 1 of Figure 1.

Thus when the coil of relay RLA 2 is energised, as the photo sensitive resistor LDR 1 senses a light level below a first threshold, both the pairs of contacts RL2 and RL3 of the relay RLA 2 will be closed.

When the ignition switch S1 is in an "on" condition it will be appreciated that the circuit will operate exactly as the first electronic control circuit described with reference to Figure 1. However, when the ignition switch S1 is moved to an off condition, the current path from the transistor TR1 directly to the negative terminal of the battery B is cut off, and instead an indirect current path is provided through the contacts RL3 of the relay RIzA 2, and the normally closed contacts RLA of a further relay RLA 3.Thus the sidelights will be switched on when the light sensitive element LDR1 senses a light intensity below a threshold, regardless of whether the ignition switch S1 is an "on" or "off' position However, if it is desired to garage the vehicle it will be required that the sidelights L1 are not switched on by the control circuit. Hence an override is provided in switch S3. When the switch S3 is closed with the ignition switch S1 in an off position, the coil of the relay RLA 3 will be energised, thus opening the normally closed contacts RIA of relay RLA3 to disconnect the current path to the negative terminal of the battery and hence to cause relay RLA2 to deenergise and switch the lights L1 off.Of course, when the ignition switch S1 is again switched on, the relay RLA3 is de-energised and contacts RLA close, thus resetting the circuit.

As in the first control circuit diagram of Figure 1, a manual override switch S4 is provided to enable to sidelights L1 to be switched on regardless of light level sensed by the photo sensitive resistor LVR 1.

It will be appreciated in practice that only one photo sensitive resistor LDR 1 will be required to provide a signal to both of the circuits of Figures 1 and 2, although if desired, some means of isolating the circuits from one another may be necessary.

Referring now to Figure 3, there is shown a fragmentary cross-section through a dashboard 10 of a vehicle. Sunken into the dashboard 10, is a housing 11 which comprises a reflective surface 12 which is at about 45" to the horizontal and is white.

The housing 11 comprises an opening 13 which is closed by a diffuser 14 which in this example comprises a sheet of clear perspex, the surface of which has been roughened.

The housing comprises further white reflector surfaces 15.

Light which passes through a window of the vehicle, may thus pass through the diffuser 14 into the housing as indicated by the arrow AM Extending from the housing 11 is a passageway 16 in wbich the light sensitive element LDR 1 is mounted. It will therefore be appreciated that it is not easily possible for light entering the housing 11 to fall directly on the photo sensitive resistor LDR 1. The light will however be reflected from the surfaces 15 and 12 towards the photo sensitive resistor LDR 1.

It has been found that by providing an arrangement as shown, the photo sensitive resistor LDR 1 is not prone to light transients, for example from the headlamps of oncoming vehicles, but only to the ambient light level. Thus the electronic control circuits shown in Figures 1 and 2 will not switch the sidelights L1 or headlamps L off merely because an oncoming vehicle has its headlamps on, or because the vehicle passes underneath a lamp post.

Various modifications are possible without departing from the scope of the invention. The electronic control circuits shown in Figures 1 and 2 are of course only examples of suitable control circuits which may be used. Instead of a housing 11 being sunk into a dashboard 10 of a vehicle, the housing 11 could instead be provided mounted on top of the dashboard 10, or integrally provided with the dashboard 10 but not sunken into it, or only partially sunken into it.

The photo sensitive resistor or other light sensitive element LDR 1 need not be mounted in a passageway 16 extending from the housing 11 as shown, but could otherwise be mounted in any position where it is not prone to receive other than reflected light.

Instead of the diffuser 14 comprising a sheet of clear perspex suitably roughened, any other suitable diffuser could instead be provided, and the inside surfaces 12 and 15 of the housing 11 need not be white but could be provided in other colours as appropriate.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in the terms or means for performing the desired function, or a method or process for attaining the disclosed result, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims (17)

CLAIMS:

1. A vehicle light management system comprising a control means which operable in response to a signal from a light sensitive element to switch a vehicle light on when the intensity of the light sensed is below a first threshold value and to switch the vehicle light off when the intensity of the light sensed is above a second threshold value.

2. A system according to Claim 1 wherein the control means comprises a first electronic control circuit which is sensitive to the signal from the light sensitive element to switch on or off main headlights of the vehicle, and a second electronic control circuit which is sensitive to the signal from the light sensitive element to switch on or off the sidelights of the vehicle.

3. A system according to Claim 2 wherein the second electronic control circuit is independent of an ignition switch ~of the vehicle such that whether the ignition switch is on or off, the sidelights are controlled by the second electronic control circuit.

4. A system according to Claim 2 or Claim 3 wherein the first electronic control circuit is dependent upon an ignition switch such that the main headlamps are only switched on or off by the control circuit when the ignition switch is on.

5. A system according to any one of Claims 1 to 4 wherein the light sensitive element comprises a light sensitive resistor.

6. A system according to any one of Claims 1 to 5 wherein the light sensitive element is mounted in a position such that it receives predominately diffused and/or reflected light.

7. A system according to Claim 6 which includes a housing having an opening through which in use, light, passes into the housing, and at least one reflective surface which reflects the light towards the light sensitive element.

8. A system according to Claim 7 wherein the light reflective surface is inclined at approximately 45" to the horizontal.

9. A system according to Claim 7 or Claim 8 wherein the light sensitive element is contained in a passageway which extends from the housing.

10. A system according to any one of Claims 7 to 9 wherein the opening is covered by a diffuser.

11. A system according to Claim 10 wherein a diffuser is clear perspex the surface of which has been roughened.

12. A system according to any one of Claims 7 to 11 wherein the at least one reflective surface is white.

13. A system according to any one of Claims 7 to 12 wherein the housing is mounted in or on a dashboard of the vehicle.

14. A light management system substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

15. A vehicle having a light management system according to any one of the preceding claims.

16. A vehicle substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

17. Any novel feature or novel combination of features disclosed herein and/or on the accompanying drawings.