GB2222289A

GB2222289A - Vehicle lights warning device

Info

Publication number: GB2222289A
Application number: GB8820153A
Authority: GB
Inventors: Paul Ian Phillips
Original assignee: MILANMAST Ltd
Current assignee: MILANMAST Ltd
Priority date: 1988-08-25
Filing date: 1988-08-25
Publication date: 1990-02-28
Anticipated expiration: 2008-08-25
Also published as: GB8820153D0; GB2222289B

Abstract

A vehicle lights warning device comprising a light dependent sensor 20, an alarm 25 and an electronic control circuit 12 having inputs from the sensor and from the ignition and lighting circuits of the vehicle and an output to the alarm. The control circuit is operative, when the lights are not switched on, to sound the alarm if the sensed light level remains below a predeterminated level for a predetermined period after the ignition is turned on. The alarm is disabled if the ignition remains on after the predetermined period has expired and the alarm has not been sounded. The alarm may also be sounded if the ignition is turned off when the lights are turned on and the sensed light level is above the predetermined level. <IMAGE>

Description

VEHICLE LIGHTS WARNING DEVICES This invention concerns warning devices of the type incorporated into the lighting and ignition circuits of motor vehicles and whose primary function is to sound an alarm if the vehicle's lights are unintentionally left on after the ignition has been switched off.

There is in existence various types of such warning devices giving an audible and/or visual alarm if the lights of a vehicle are left on inadvertently to prevent draining of the vehicle's battery while the vehicle is parked. Some of these devices are activated by the removal of the ignition key before the lights are switched off or upon the opening of the driver's door if the lights are still on, or by a combination of both.

There are, however, occasions when it is desirable to leave the vehicle unattended with its lights switched on. In order to do this with vehicles fitted with the known devices without activating said devices it is necessary either to leave the ignition key in place or for the driver to leave the vehicle other than by the driver's door. On other occasions, particularly at night, it may be necessary for the driver to open the driver's door of the stationary vehicle with the vehicle lights on. This causes the known warning devices to generate a nuisance alarm.

Some, if not all, of the known warning devices do not give any alarm if a driver forgets to switch on the lights of the vehicle at night which frequently happens when driving at night in areas of high visibility due to good street lighting.

An object of the present invention is to propose a warning device of the type as mentioned at the beginning hereof which in addition to giving an alarm if, in daylight, the ignition is switched off and the lights are left on also gives an alarm if, at night-time, the ignition is switched on and the lights are not switched on shortly thereafter.

With this object in view the present invention provides a vehicle light warning device comprising a light dependant sensor, an alarm and an electronic control circuit having inputs from the sensor and from the ignition and lighting circuits of the vehicle and an output to the alarm, the sensor being calibrated to provide an input signal level to the control circuit which is dependant upon a predetermined level of light, the control circuit being capable of detecting the level of the of input signal from the sensor and from the ignition and lighting circuits and sounding the alarm upon detecting those combinations of input signal levels which are indicative that the vehicle's lights should either be switched on or switched off.

The warning device of the invention has basically two modes of operation, namely a daylight mode and a night-time mode, with the light dependant sensor effectively acting as a switch between the two modes.

The calibration of the sensor is advantageously achieved by means of a calibration potentiometer forming part of the device.

In the daylight mode of the device, where the sensor detects an ambient light level at or above the predetermined or pre-set level, the alarm will be activated if also the ignition is switched off and the vehicle lights are left switched on, and will remain activated until either the ignition is switched on or the lights are switched off.

If the sensor senses that the ambient light level is or has dropped below the predetermined or pre-set level, the device will automatically be in or be effectively switched to its night-time mode.

In the nightime mode of the device the alarm will be activated if the ignition is switched on and the lights are not switched on within say a few seconds.

This short time delay is to allow for the time taken during the normal procedure of starting the vehicle in darkness so as to preclude 'nuisance' alarms.

Preferably a lighting delayed turn-on timer is provided for this purpose as part of the electronic control circuit and consists of a resistor and capacitor network connected between the ignition input and earth line of the device.

In the night-time mode of the device the alarm is only activated for a short period of time. Again this is to avoid a 'nuisance' alarm when the vehicle is being driven in daylight and passes under a bridge or enters a tunnel whereupon the sensor would sense an ambient light level below the pre-set level and therefore switch the device to night-time mode which would activate the alarm if the vehicles lights are not switched on. Apart from this being a 'nuisance', the driver may get distracted if the alarm does not switch itself off. Thus the short period of activation of the alarm in the night-time mode prevents this particular 'nuisance'. Once the alarm becomes inoperative it cannot be activated again until the ignition is switched off and switched on again.

The time limitation on the activation period of the alarm in the night-time mode is preferably provided by a time limiter forming part of the electronic control circuit and consisting of a resistor and a capacitor network connected between the ignition input and the earth line of the device.

The alarm may be either an audible alarm or a visual alarm or a combination of both.

The invention will be described further, by way of example, with reference to the accompanying drawings, it being understood that the following is illustrative and not limitative of the scope of the invention.

In the drawing: Fig. 1 is a plan view of a preferred embodiment of the vehicle light warning device of the invention; Fig. 2 is a circuit diagram of the embodiment of Fig. 1; and Fig. 3 shows the preferred embodiment in situ in the interior of a motor vehicle.

As shown in Fig. 1 of the drawings, the preferred embodiment of the warning device 10 comprises a rectangular box-like housing 11 of, for example, a strong plastics material and measuring approximately 7cms in length, 5cms in width, and 2.5 cms in depth.

The housing 11 contains an electronic control circuit 12 which is shown in Fig. 3 and will be described in more detail hereinafter.

The control circuit 12 is provided with two terminal blocks 13 and 13a, mounted on one end 13b of its circuit board which protrudes from one end of the housing, having between them six screw-type connection terminals. The terminal block 13 has two terminals 14 and 15 which serve as input terminals for respective leads of light dependant sensor 20 which also forms part of the preferred embodiment.

The light dependant sensor 20 consists of a light sensitive resistor 21 disposed in a square-shaped mounting block 22 of resilient material such as rubber or plastics.

The terminal block 13a has four terminals being respectively vehicle battery (12 volts +ve) connection terminal 16, earth terminal 17, ignition circuit input terminal 18 and lighting circuit input terminal 19.

The battery connection terminal 16 should be connected to the battery, via a fuse box (not shown), which is always live with the battery connected . The earth terminal 17 should be connected to a good chassis earth. The ignition circuit input terminal 18 should be connected to the switched live on the ignition (note: not the auxilliary if one is fitted). The lighting circuit input terminal 19 should be connected to the side lights live and not the headlights live.

Between the terminal blocks 13 and 13a is a calibration potentiometer 23, for calibrating the light dependant sensor 20, which comprises a knurled knob 24 having a slot on top for the insertion of the tip of e.g. a screwdriver. The manipulation of the calibration potentiometer 23 in calibrating the device 10 of the invention will be described hereinafter. The calibration potentiometer 23 effectively sets the level of switching between the two modes of the device, namely its daylight mode and its night-time mode.

Referring now to Fig. 2, the electronic circuit 12 forming part of the device 10 of the invention basically comprises eight integrated circuit gates, namely four NAND gates designated N1, N2, N3 and N4 respectively and four EXCLUSIVE OR gates designated El, E2, E3 and E4 respectively.

An alarm 25 which in the preferred embodiment is an an audible alarm is incorporated into the control circuit 12.

The circuit 12 also comprises a plurality of resistors designated R1 to R8. The resistor R5 is in fact the calibration potentiometer 23. There are also two capacitators designated C1 and C2. The combination of resistor R2 and capacitor C1 serves as a lighting delay turn-on timer on the ignition input terminal 18 which in the night-time mode of the device 10 delays the activation of the alarm 25 for a short time after the vehicle ignition has been switched on to allow the driver a reasonable period of time to switch on the vehicle lights. The combination of R2 and C1 forms one of the two inputs to gate N1.

If the alarm is activated in the night-time mode its period of activation is limited by a time limiter formed by the combination of resistor R3 and capacitor C2 on the ignition input terminal 18 and providing the other of the two inputs to gate N1 and one of the two inputs to gate N2. Thus, the alarm 25 will only sound for a short period after activation in night-time mode so that there is no possibility of a nuisance alarm being generated if the device is suddenly switched from its daylight mode to its night-time mode by virtue of the vehicle going under a bridge or into a dark tunnel whilst being driven in daylight.

As shown in Fig. 3, the preferred embodiment of the device 10 is located in the interior of the vehicle.

The light dependant sensor 20 should be mounted in a position where it is not likely to be obstructed, and where it can differentiate between day and night, such as on the vehicle's dashboard 26. The housing 11 of the device, which contains the alarm 25, should be mounted in an unobtrusive position such as on the lower part of or below the dashboard 26, with the wiring from the sensor 20 to the housing 11 being hidden underneath the dashboard 26.

Calibration of the sensor 20 is very important and is achieved in the following manner. Firstly, the knob 24 of the calibration potentiometer 23 is turned fully clockwise. The sensor 20 is tested by being covered with an opaque card or cloth and the vehicle ignition is turned on without starting the engine. After a few seconds the alarm 25 will sound and shortly thereafter will be de-activated. This is indicative that the unit is functioning. The ignition is then turned off. This test should not be attempted again until at least one minute has elapsed since the device takes a little time to reset.

The cover is removed from the light sensor 20 and in some suitable manner the sensor 20 is shaded from direct sunlight if calibration is being done in daylight, or is dimly illuminated if calibrated is being done at night.

The vehicle's side lights are turned on. The alarm should not sound but if it does the sensor 20 should be shaded more as there is too much light incident on the sensor 20. If the alarm does not sound, the knob 24 of the calibration potentiometer 23 should be turned anticlockwise until the alarm sounds. The side lights are then turned off.

However, for greater accuracy, calibration should be carried out at dawn or dusk since the human eye, as used in the preceding setting up precedure, is unreliable as a guage of light intensity. The procedure is basically the same as indicated above. The side lights should be switched on but with the ignition off. The knob 24 of the potentiometer 23 should then be turned to a position where the alarm is either just on or just off. It will be found that the point where the alarm sounds overlaps the point where it turns off.

This is normal and the knob 24 should be left at a point midway between the two points. The sensor 20 is now provisionally calibrated. It may be found that at dusk when the ignition is switched on the alarm prematurely sounds i.e. where the ambient light level does not necessitate side lights. The knob 24 should then be turned anti-clockwise until the alarm 25 stops. In the event that at dusk, but where there is still some daylight, the alarm is not activated with the side lights on and ignition off, the knob 24 should again be turned slightly anti-clockwise.

It should be noted that if at night the vehicle is stopped in a brightly lit area and the ignition turned off with the lights left on the alarm 25 will be activated. Conversely, if the vehicle is started in a brightly lit area at night and then driven to a dimly lit area the alarm will not activate. The reverse is true if the vehicle is started in a dimly lit area, such as an underground or multi-storey car park and the lights are not switched on.

The function of the device 10 and the operation of its control circuit will now be described with reference to truth tables.

Nomendature All positive signals are 12 volts = High = 1 All ground signals are zero volts = Low = 0 "Don't care" levels are X NAND TRUTH TABLE Input A : 0 0 1 1 Input B : 0 1 0 1 Output Y : 1 1 1 0 EXCLUSIVE OR TRUTH TABLE Input A : 0 0 1 1 Input B : 0 1 0 1 Output Y : 0 1 1 0 The function of resistor R2 and capacitor C1, resistor R3 and capacitor C2, and gates N1, N2 and E2 is to enable the alarm 10 if the ignition switch is off, and to enable the alarm 10 for a short period, after a small initial time delay, after the ignition is switched on. Thus if the ignition switch is off the device 10 is activated. If the ignition switch is turned on the device 10 is disabled, enabled and then disabled. The alarm 25 will only be activated during the enabled time if required to do so by virtue of the states of the ignition, lights and sensor 20. The outputs of gates El and E2 must both be high (Hi) for the alarm 25 to be activated by transistor TR1.

DAYLIGHT MODE TRUTH TABLE (Light sensor input = 1) a b c d e Light sensor 1 1 1 1 0 Lights O 0 1 1 0 Ignition O 1 1 0 1 Output El O 0 0 1 1 Output E2 1 X X 1 0 Alarm (25) 0 0 0 1 0 Daylight mode truth table conditions: a. lights off, ignition off b. lights off, ignition on c. lights on, ignition on d. lights on, ignition off e. lights on, ignition off, change to night-time mode Thus, as the above daylight mode truth table indicates, in the daylight mode of the device the alarm 25 only becomes active if the lights are left on when the ignition has been switched off. The change to night-time mode with the ignition on and the lights off has no effect since the output of gate E2 is low (Lo).

NIGHT-TIME MODE TRUTH TABLE (Light sensor input = 0) a b C d Light sensor 0 0 0 0 Lights 0 1 0 1

Ignition O E - O 0 Output El 0 0 - O 0 Output E2 1 X < X Alarm (25) 0 0 Night-time mode truth table conditions: a. Lights off, ignition off b. Lights on, ignition turned on c. Lights off, ignition turned on d. Lights on, ignition off Thus, as the above night-time mode truth table indicates, in the night-time mode of the device, the alarm only becomes active if in darkness the lights are not switched on within a specific time of turning on the ignition. If the alarm is activated it will be disabled by turning on the lights. If the lights are not turned on after the alarm has been activated after a further short period the alarm will automatically be deactivated until the ignition is switched off and then switched on again.

Claims

CLAIMS:

1. A vehicle light warning device comprising a light dependant sensor, an alarm and an electronic control circuit having inputs from the sensor and from the ignition and lighting circuits of the vehicle and an output to the alarm, the sensor being calibrated to provide an input signal level to the control circuit which is dependant upon a predetermined level of light, the control circuit being capable of detecting the level of the input signal from the sensor and from the ignition and lighting circuits and sounding the alarm upon detecting those combinations of input signal levels which are indicative that the vehicle's lights should either be switched on or switched off.

2. A warning device as claimed in claim 1 wherein the calibration of the sensor is achieved by means of a calibration potentiometer forming part of the device.

3. A warning device as claimed in claim 1 or 2 wherein the said device has two modes of operation, namely a daylight mode and a night-time mode, with the light dependant sensor effectively acting as a switch between the two modes.

4. A warning device as claimed in claim 3 further comprising a lighting delayed turn-on timer which in the night-time mode of the device will activate the alarm if the ignition is switched on and the lights are not switched on within a few seconds thereafter.

5. A warning device as claimed in any preceding claim further comprising a time limiter which in the night-time mode of the device ensures that the alarm is only activated for a short period of time.

6. A vehicle light warning device substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

6. A warning device as claimed in claim 4 and/or 5 wherein the lighting delayed turn-on timer and/or the time limiter forms part of the electronic control circuit and consists of a resistor and capacitor network connected between the ignition input and earth line of the device.

7. A warning device as claimed in any preceding claim wherein the alarm is an audible alarm or a visual alarm or a combination of both.

8. A vehicle light warning device substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

Amendments to the claims have been filed as follows 1. A vehicle light warning device comprising a light dependent sensor, an alarm and an electronic control circuit having inputs from the sensor and from the ignition and lighting circuits of the vehicle and an output to the alarm, the sensor being calibrated to provide an input signal level to the control circuit which is dependent upon a predetermined level of light, the control circuit being capable of detecting the level of the input signal from the sensor and from the ignition and lighting circuits and sounding the alarm upon detecting those combinations of input signal levels which are indicative that the vehicle's lights should either be switched on or switched off, characterised in that the control circuit is operative, when the lights are not switched on, to sound the alarm if the sensed light level remains below the predetermined level for a predetermined period after the ignition is turned on, and to disable the alarm if the ignition remains on after the said predetermined period and the alarm has not been sounded.

2. A warning device as claimed in Claim 1, comprising means for disabling the alarm after a predetermined delay if the alarm has been sounded with the ignition turned on.

3. A warning device according to Claim 2, wherein the disabling means comprises a NAND gate having inputs connected to respective delay circuits providing different time delays, the alarm circuit being disabled until the expiration of one time delay and after expiration of both time delays.

4. A warning device as claimed in Claim 1, 2 or 3, further comprising means for detecting when the ignition is turned off at a time when the lights remain switched on, and means for sounding the alarm if the light level sensed when the ignition is turned off is above the predetermined level.

5. A vehicle light warning device comprising a light dependent sensor, an alarm and an electronic control circuit having inputs from the sensor and from the ignition and lighting circuits of the vehicle and an output to the alarm, the sensor being calibrated to provide an input signal level to the control circuit which is dependent upon a predetermined level of light, the control circuit being capable of detecting the level of the input signal from the sensor and from the ignition and lighting circuits and sounding the alarm upon detecting those combinations of input signal levels which are indicative that the vehicle's lights should either be switched on or switched off, characterised in that the control circuit is operative, when both the lights and the ignition have been turned on, to sound the alarm if the ignition is turned off when the sensed light level is above the predetermined level.