GB2308653A

GB2308653A - Automatic vehicle light activation system

Info

Publication number: GB2308653A
Application number: GB9624735A
Authority: GB
Inventors: Robert Renton
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-12-22
Filing date: 1996-11-28
Publication date: 1997-07-02
Also published as: GB9624735D0

Description

VEHICLE LIGHT SYSTEM This invention relates to a light system particularly, but not exclusively, for use with private and/or commercial road vehicles.

According to a first aspect, the present invention provides a vehicle light system adapted to activate a light of a vehicle upon detection at a light responsive sensor of an ambient light level below a preset threshold.

Activation of the light may cause it to be turned on.

The system may be adapted to deactivate the light upon detection at the or a light responsive sensor of an ambient light level above a preset threshold. The threshold for deactivation of the light may be higher than the threshold for activation of the light.

The sensor may be a light sensitive resistor and may be positioned within the vehicle. The preset threshold or thresholds of the sensor may be adjustable.

A plurality of sensors may be provided for activation and/or deactivation of the light. Separate sensors may be provided for activation and deactivation.

The system may comprise a plurality of lights; one light, a plurality of lights or all of the lights of the system may be activated and/or deactivated in response to detection at the sensor.

The'light system may incorporate a timing device; this may be arranged to prevent the light flashing on or off momentarily.

The timer may provide a delay during which time the lights are kept on despite ambient light above the preset threshold being detected at the sensor. At the end of the delay period, the lights may be turned off by the system provided that the ambient light conditions at the sensor are still above the preset threshold.

The timer may be arranged to provide a delay to the lights being switched on.

The vehicle may be a road vehicle; it may be motorised.

The vehicle may be a car and the system may be arranged to activate and/or deactivate the car's side lights and/or driving light and/or headlights and/or day running lights.

The system may be arranged to operate only when activated; the system may be activated, for example, by a manual switch and/or when an ignition system of the vehicle is turned on. The system may have an over-ride to over-ride its operation.

The system may be fitted as original equipment to the vehicle or it may be retrofitted.

According to a second aspect, the present invention provides a method of activating at least one light in a vehicle light system in which an ambient light level is detected at a light responsive sensor and detection of an ambient light level at the sensor below a preset threshold causes activation of the at least one light.

Detection of an ambient light level at the sensor above a preset threshold may cause deactivation of the at least one light.

According to a third aspect, the present invention provides a vehicle incorporating a vehicle light system in accordance with the first aspect of the invention.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings of which: Fig 1 is a circuit diagram of electronic components of a vehicle light system; Fig 2 is a circuit diagram of an alternative vehicle light system; Fig 3 is a perspective view of a light sensor; and Fig 4 is a circuit diagram of a further vehicle light system.

The light system of Fig 1 is intended for incorporation in a car and is activated when the car ignition switch 101 is closed. The system is powered by the car battery 102.

Ambient light levels are detected by a light dependent resistor (LDR) 103. The LDR has a higher electrical resistance at low ambient light levels than it has at high ambient light conditions.

A transistor 104 activated by an electrical output from the LDR connected to its base acts as a switch to turn the vehicle lights 105 on and off via a relay 106. The threshold below which the ambient light conditions cause the lights 105 to be turned on and above which cause the lights 105 to be turned off is set by a variable resistor 107 in parallel with the LDR 103.

Fuses 108 and resistors 109 are provided as appropriate.

The light system of Fig 2 is also intended for incorporation into a car. It has three main sections to its circuit: a. a voltage regulator, current limiter and thermal overload protection circuit; b. a light sensor and amplifier; and c. a timer which provides a delay function.

As before, the system causes the output of a light dependent resistor (LDR) 201 to switch the vehicle lights on and off via a relay 202 depending on ambient lighting conditions.

The voltage regulator is intended to allow the system to be used with one of a number of vehicles having different voltage supplies, eg cars, motorbikes and commercial vehicles. This part of the system comprises an LM117 203, an input filter capacitor C1, a current controlling resistor R1, a voltage controlling resistor R2 and an output capacitor C2. The capacitors C1,C2 are intended to improve transient response. The voltage regulator drops the voltage to 9.5 volts and stabilises the unit on vehicle start or heavy load. It also allows the system to be used with 12 volt or 24 volt supplies.

The LDR 201 incorporated in the system is shown in Fig 3. The LDR 201 is arranged within a substantially transparent housing provided in this case by a length of perspex tube 302 having a substantially opaque portion 303 spaced from the LDR. The opaque portion 303 is provided by a black plastics cap which, in this case, overhangs the tube 302. The tube 302 may act as a diffuser. The arrangement helps prevent unintentional firing of the system. A shrink wrap sleeve 304 is arranged around the wires of the sensor at the point where they cooperate with the housing.

The LDR is preferably positioned within the vehicle such that it can receive natural light.

The amplifier consists of four resistors, R3,R5,RX,R7, a variable resistor R4, a transistor 204 and a 741 operational amplifier integrated circuit 205. The circuit works like a set of scales with resistor R3 and LDR 201 as one half and variable resistor R4 as the other half. As the ambient light level falls (ie it becomes darker) the resistance of the LDR 201 increases; this tips the balance towards terminal 3 of the op amp 205 which switches terminal 6 on op amp 205 from positive to negative and goes through resistor R4 to switch transistor 204 on and in turn feed relay 202 and switches the lights (not shown) on.

Resistor R5 between terminals 6 and 3 of the op amp provides hysteresis between the on and off conditions of the op amp as activated by the LDR.

The level of ambient light at which the system is activated/deactivated is adjustable by means of variable resistor R4.

The timer incorporated in the system is intended to stop the vehicle lights coming on momentarily and appearing like flashing lights to other road users.

The timer circuit consists of three resistors R8,R9,RlO, three capacitors C3,C4,C5, a diode D1, a switch S1 and a 555 timer integrated circuit 206. The timer circuit is connected to the switch side of relay 202 from terminal 3 (output) of the 555 timer ic 206 through diode D1 and switch S1. The switch S1 allows variable resistor R4 to be adjusted to adjust the light sensitivity of the system without activating the timer.

The trigger for the timer 206 is terminal 2 which will switch on upon a negative impulse. This will happen as the relay switches off and will discharge through capacitor C3 to give a short negative impulse. It will then return to positive by going through resistors R8 and R9 to above one third of supply. This will allow it to go through the timing sequence; it will then switch off until the LDR 201 senses a change in light to the preset value to activate the system.

Possible values for the components of the system are: R1 240 Q R2 1.5 kQ R3 8 kQ R4 variable resistor R5 5 kfl R6 2 kQ R7 1 kQ R8 1 k# R9 47 kS2 R10 100 k# C1 0.1 ssF C2 1 F C3 2 F C4 2 F C5 100 ssF The timing device may ensure that, under dark conditions when the vehicle lights are illuminated, there is no temporary deactivation/reactivation of the vehicle lights for example when the vehicle temporarily passes below a street light which causes a high temporary light level to be sensed by the sensor.The timing device may also ensure that under light conditions when the vehicle lights are not illuminated and the light sensor detects a temporary deterioration in the light level, that the vehicle lights are illuminated for at least the time set by the timer device so as to prevent a flashing of the vehicle lights.

Fig 4 is a circuit diagram of a further vehicle light system similar in many ways to that of Fig 3.

This arrangement has additional components inductor H1 to help smooth the signal from the voltage regulator and resistor R11. Possible values for the components in this system are: R1 240 Q R2 1.5 KQ R3 8 Ka R4 variable R5 10 K# R6 2 K# R7 1 K# R8 1 K# R9 47 K# R10 100 K# R11 8 K# C1 0.1 F C2 22 F C3 2 F C4 2 ssF C5 100 F H1 4.7 Hz

Claims

CLAIMS 1. A vehicle light system adapted to activate a light of a vehicle upon detection at a light responsive sensor of an ambient light level below a preset threshold.
2. A vehicle light system in accordance with Claim 1 in which activation of the light causes the at least one light to be illuminated.
3. A vehicle light system in accordance with Claim 1 or Claim 2 in which detection of an ambient light level above a preset threshold causes deactivation of the at least one light.
4. A vehicle light system in accordance with Claim 3 in which the threshold for deactivation of the at least one light is higher than the threshold for activation of the at least one light.
5. A vehicle light system in accordance with any preceding Claim in which the light responsive sensor is a light sensitive resistor.
6. A vehicle light system in accordance with any preceding Claim in which the light responsive sensor is positioned within the vehicle.
7. A vehicle light system in accordance with any preceding Claim in which the preset threshold of the sensor is adjustable.
8. A vehicle light system in accordance with any preceding Claim in which the system is adapted to activate the headlights of a vehicle.
9. A vehicle light system in accordance with any preceding Claim in which the system is adapted to activate the rear safety lights of a vehicle.
10. A vehicle light system in accordance with any preceding Claim in which the system comprises a timing device.
11. A vehicle light system in accordance with Claim 10 in which the timing device is arranged to provide a delay between an ambient light level above a preset threshold being detected at the sensor and the system turning off the at least one light.
12. A vehicle light system in accordance with Claim 10 or Claim 11 in which the timing device is arranged to provide a delay between an ambient light level below a preset threshold being detected at the sensor and the system turning on the at least one light.
13. A vehicle light system in accordance with any one.

of Claims 10 to 12 in which the timing device is activated via a relay.
14. A vehicle light system in accordance with any preceding Claim in which there are a plurality of sensors.
15. A vehicle light system in accordance with any preceding Claim in which the vehicle is a motorised road vehicle.
16. A vehicle light system in accordance with any preceding Claim in which the light system is arranged to be activated when an ignition system of the vehicle is turned on.
17. A vehicle light system in accordance with Claim 16 in which the light system has a manual over-ride to over-ride its operation.
18. A method of activating at least one light in a vehicle light system in which an ambient light level is monitored using a light responsive sensor and detection of an ambient light level at the sensor below a preset threshold causes activation of the at least one light.
19. A method of deactivating at least one light in a vehicle light system in which an ambient light level is monitored using a light responsive sensor and detection of an ambient light level at the sensor above a preset threshold causes deactivation of the at least one light.
20. A vehicle incorporating a vehicle light system in accordance with any one of Claims 1 to 17.
21. A vehicle light system substantially as described herein with reference to one or more of the accompanying drawings.