GB2095450A

GB2095450A - Warning device

Info

Publication number: GB2095450A
Application number: GB8208694A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-03-24
Filing date: 1982-03-24
Publication date: 1982-09-29

Abstract

A device warns that a first electric circuit is energised after a second electric circuit has been de-energised e.g. that vehicle lights have been left on after the ignition has been switched off. The ignition and lighting circuits include respective ignition and ON-OFF switches S1 and S2 with both switches closed relays, 1,2,4 operate to move their contacts from the position shown. On operating the ignition switch S1 to switch off the ignition, the relay 1 is de-energised and relay 7 is energised to energise after a delay provided by a device 10, warning means 9, 12 to indicate that the lights are switched on. If it is desired to leave the lights on the switch 52 is opened to de-energise relay 2 then closed again. An alternative circuit using transition and NAND gates is described. <IMAGE>

Description

SPECIFICATION Warning device The invention relates to a device for warning that an electric circuit is energised after another electric circuit has been de-energised and is particularly but not exclusively, concerned with a device for warning a driver of a vehicle, before leaving the vehicle, that the lighting circuit is still energised.

It is now quite common practice to use side lamps and headlamps in bad visibilty during daylight hours and this has led to an increased risk of leaving the lamps switched on when leaving the vehicle. Varous devices have been proposed hitherto warning that the lamps are still switched on, the devices usually causing some kind of alarm to sound as soon as the engine is switched off or when opening a door. One particular problem which arises with certain systems is that a switch in addition to the existing ignition and light switches is necessary to switch off the alarm if the driver wishes to leave the lights switched on for parking when leaving the vehicle. Moreover, if the driver forgets to re-set the additional switch on his return to the vehicle, the warning device will not operate next time.It has been proposed to arrange the device so that, on re-starting the engine after the lights have been left on for parking, the alarm will sound again until the additional switch is thrown to re-setthe system. However, the provision of the extra switch complicates installation of the device in the vehicle and increases the overall cost.

According to one aspect of the invention there is provided a device for warning that a first electric circuit is energised after a second electric circuit has been de-energised, said circuits including respective first and second switches operable to energise and de-energise the circuits, the device comprising means responsive to operation of said second switch to energise the second circuit, said means being associated with said first switch so that on operating the first switch to energise the first circuit and on operating the second switch to de-energise the second circuit said means enables electric current from the first circuit to energise warning means.

If it is desired to leave the first circuit energised and de-energise the warning means, said means may be so arranged that after the warning means has been energised, the warning means can be de-energised by operating the first switch to deenergise the first circuit and the first switch can be operated subsequently to re-energise the first circuit without operating the warning means.

A time delay device may be provided so that on de-energising the second circuit with the first circuit energised there will be a time delay before the warning means is energised.

Preferably, said means is energised in one condition by operation of said second switch to energise the second circuit, is energised in a second mode when, in addition, the first switch is operated to energise the first circuit, and is energised in a third mode when the second switch is subsequently operated to de-energise the second circuit, the warning means being electrically connected in circuit with said means so that current will flow to the warning means from the first circuit when said means is energised in said third mode.

In one embodiment said means includes a first relay which is open when the second circuit is energised and closed when the second circuit is de-energised and a second relay which receives current from the energised second circuit and the energised first circuit to hold it closed so that when the second circuit is de-energised the first relay closes whilst the second relay is held closed by current from the energised first circuit, contacts of the two relays being interconnected to enable current from the first circuit to flow through the closed contacts of the relays to operate the warning device.

In such a case, current from the closed contacts of the first relay may close the contacts of a third relay, the closing of the contacts of the third relay allowing current from the first circuit to energise the warning means. Preferably a fourth relay is connected to the first circuit so that is contacts will be closed when the first circuit is energised, the closed contacts allowing current from the first circuit to flow through the second relay when the second circuit is deenergised.

In another embodiment said means includes a logic circuit arranged so that in the first and second modes of operation current passes through the logic circuit in such a manner that a transistor is held in an OFF condition to prevent current from the first circuit energising the warning means, and so that in the third mode of operation the current passes through the logic circuit and switches the transistor ON to allow current from the first circuit to energise the warning means.

According to another aspect of the invention there is provided a device for warning that a lighting circuit of a motor vehicle is energised after an ignition circuit of the motor vehicle has been deenergised, said circuits including respectively an ON-OFF switch and an ignition switch operable to energise and de-energise the circuits, the device comprising means responsive to operation of the ignition switch to energise the ignition circuit, said means being associated with the ON-OFF switch so that on operating the ON-OFF switch to energise the lighting circuit and on operating the ignition switch to de-energise the ignition circuit said means enables electric current from the lighting circuit to energise warning means. In such a manner, no manually operable switch in addition to the existing ON-OFF switch and ignition switch is necessary to operate the device.A time delay device as aforesaid in such a circuit is particularly useful because with some vehicles it is necessary to turn the iginition switch to the OFF position before it can be turned to the START position if the engine stalls. Provided that the driver switches the ignition off and then on again within the set limit of the time delay, the warning means will not be energised.

Device in accordance with the invention will now be described by way of example with reference to the accompanying drawing in which: Figure 1 is a circuit diagram for a relay version of a device in accordance with the invention in a de energised condition, and Figure 2 is a circuit diagram for a logic circuit version of a device in accordance with the invention.

Afirst relay 1 (normally closed) is connected to a vehicle ignition switch 51. A second relay 2 (normally ly open) is also connected to the ignition switch through a diode 3. A third relay 4 (normally open) is connected to a lighting circuit 5 of the vehicle which includes an ON-OFF switch S2. Afourth relay 7 (normally open) is connected to contact 1b of relay 1.

The relay 1 has a contact 1a connected to a contact 2a of relay 2 and contact 4a of relay 4.

The relay 2 has a contact 26 connected to the lighting circuit 5 at a contact 7a of relay 7.

The relay 4 has a contact 4b connected to the relay 2via a diode 8.

The relay 7 has a contact 7b connected to an alarm such as a buzzer 9 via an adjustable delay device 10 and a diode 11. A warning lamp 12 is connected between the delay device 10 and diode 11.

A lead 13 may be provided for connection to the directional indicator circuit of the vehicle. The lead 13 includes a diode 14.

The operation of the device will now be described.

With the switches S1 and S2 open the ignition and lights are off and the device is de-energised.

If the switch S1 is closed to turn on the ignition only, the contacts la, 1b open and contacts 2a, 2b close but the circuit remains otherwise de-energised.

If the switch S2 is closed to turn on the lights contacts 4a, 4b close but the circuit remains otherwise de-energised.

If both switches S1 and S2 are closed so as to turn on the ignition and the lights, current from the ignition circuit opens contacts la, 1b and closes contacts 2a, 2b. At the same time current from the lighting circuit closes contacts4a, 4b and current flows from contact 7a through contacts 2a, 2b; la; 4a, 4b; diode 8 and finally through relay 2 to earth.

The buzzer 9 is not energised with the circuit in that condition.

If the switch S2 is then opened, the contacts 4a, 4b also opens and the current can no longer flow to the diode 8 from the lighting circuit.

However, if with S2 closed switch S1 is opened to turn off the ignition, contacts la, 1b close and current from the lighting circuit passing through relay 2 via closed contacts 4a, 4b and diode 8 holds contacts 2a, 2b closed and current flows from contacts la, ib, through the relay 7 to close contact 7a, 7b. On so doing current from the lighting circuit flows via the time delay device 10 and diode 11 to the buzzer 9.

If the driver then opens switch S2 to turn offthe lights, the contacts 2a, 2b will open along with contacts 7a, 7b to switch off the buzzer.

However, if the driver wishes to leave on the lights for parking purposes he simply opens switch S2 to switch off the buzzer (the circuit then returning to the de-energised state as in the drawing) and then closes the switch S2 to turn on the lights.

lf the driver stalls the engine with the lights on and needs to turn the ignition switch through the 'OFF' position to the 'START' position, the time delay will normally be set to give two or three second before the buzzer sounds.

If the lead 13 is connected to the directional indicator circuit the latter will operate the buzzer in time with the usual flasher but the diode 14 prevents the indicator circuit operating the delay device 10 and the lamp 12.

The device may be instailed in a convenient point in the vehicle but no drilling of the dashboard is necessaryforfixing an additional switch as is required by the prior art devices. The lamp 13 can be installed at some convenient point where it can be seen by the driver, but, if desired, the lamp may be omitted.

Although the circuit illustrated in Figure 1 utilises relays, the device can be constructed by using logic components as shown in Figure 2.

In Figure 2 switches S1,S2 correspond to the switches S1,S2 in Figure 1 and the buzzer and warning lamps are indicated at9 and 12 respectively.

With switches S1 and 52 open, the ignition and lights are off and the device is not energised.

With the ignition switch S1 turned on and with the vehicle running normally, current flows through switch S1 to the emitter of a transistor 20 via a diode 22. A resistor 23 reduces the voltage e.g. 12 volts to a suitable value, e.g. 5 volts, which is used to power the logic circuitry as described below. A resistor 24 is in series with a capacitor 25 to provide a combination which applies an input pulse to a bistable indicated generally at 26 and comprising two NAND gates 27,28. An output from gate 28 goes negative and is inverted by gate 27 to provide a latching positive input to gate 28. The negative output from gate 28 constitutes one input to a further NAND gate 29, the other input being held negative via a resistor 30 (the vehicle being negative earth) in the absence of an electrical input via open lighting circuit switch S2.The NAND gate 29 provides a positive output which is inverted by another NAND gate 32 to become a negative input to a further NAND gate 33.

Current from switch S1 also provides a positive input to a NAND gate 34, the input being inverted to provide a negative further input to gate 33. Another input (12 volt positive) to gate 33 is derived from the switch S1 (or via a diode 21 from switch S2 when the latter is closed). The negative and positive inputs to gate 33 effectively cut off transistor 20 so that no current can flow through the transistor. The collector is in circuit with the lamp 12 and, via a diode 35, with the buzzer 9. However, with the transistor 20 switched off, the lamp and buzzer are not energized.

If the switch S2 is now switched on, current in the lighting circuit applies an input pulse via a capacitor 36 and a resistor 37 to gate 27 of the bistable. That sets the bistable to the state which provides a positive input to gate 29 which is NANDed to the positive input from switch S2. That state does not change the conditional states of gates 32 and 33.

Therefore transistor 20 remains cut off and no warning is initiated. However, the system is now prepared for subsequent opening of switches S1 or S2 to switch off the ignition or lights.

The NAND gates are formed by intergrated circuits with the following characteristics: On any one gate with either or both inputs low the output will be high, or with both inputs high the output will below.

If the switch S1 is opened to switch off the ignition but to have the lights on, a negative pulse via capacitor 25 is applied to change the state of the sistable 26. The result appears via gates 29 and 32 as the positive input to gate 33 which switches on the transistor, all inputs to gate 33 now being positive.

Current will then flow through the transistor 20 to operate the lamp and buzzer. Alternatively, the current flowing through the transistor may be arranged to switch on NAND gates 37,38 which are connected as an audio frequency oscillator driving a piezo-electric transducer 31. The transducer 31 then provides the audible warning that the lights are switched on. The alarm can be cancelled by switching off the lights.

It should be noted that the double positive input condition at gate 33 will apply only so long as a capacitor 39 remains charged positively. The warning will continue until capacitor 39 is discharged via a resistor 40.

Where the vehicle lights are to be left on afterthe ignition is switched off for parking purposes, the switch S2 is opened to cancel the warning and switch off the lights and is then closed once more to switch the lights on again. However, such action does not re-actuate the alarm as only two inputs to gate 33 are positive. The warning system is reinstated for operation when both lights and ignition are switched on again, the system being energized via diode 21. The logic state is such that transistor 20 does not conduct and there are no visual or audible warnings. Capacitor 39 remains discharged until the ignition switch is reselected.

As with the system of Figure 1, the audible warning may be energised independently by the directional indicator of the vehicle. To operate the audible warning, the directional indicator circuit may provide a negative input to a terminal T1 to switch on a transistor 41 and allow current to flow to the buzzer 9 or transducer 31 via a diode 42. Alternatively the buzzer can be energized by applying a positive input from the indicator circuit to a terminal T2.

Diode 35 acts as a blocking diode to prevent operation of the warning lamp 12 by the indicator circuit.

If the ignition switch S1 need to be opened when re-starting the engine after stalling, the capacitor 39 will provide a short time delay before the onset of alarm to provide time to re-start the engine without actuating the alarm.

Conveniently, the components of the circuit in Figure 2 can be mounted on a printed circuit board.

The device could be used in other applications to provide an indication that a circuit is switched on when another is switched off.

Claims

1. A device for warning that a first electric circuit is energised after a second electric circuit has been de-energised, said circuits including respective first and second switches operable to energise and de-energise the circuits, the device comprising means responsive to operation of said second switch to energise the second circuit, said means being associated with said first switch so that on operating the first switch to energise the first circuit and on operating the second switch to de-energise the second circuit said means enables electric current from the first circuit to energise warning means.

2. A device according to claim 1 in which said means is so arranged that after the warning means has been energised, the warning means can be de-energised by operating the first switch to deenergise the first circuit and the first switch can be operated subsequently to re-energise the first cirucit without operating the warning means.

3. A device according to claim 1 or 2 in which a time delay device is provided so that on deenergising the second circuit with the first circuit energised there will be a time delay before the warning means is energised.

4. A device according to claim 1,2 or 3 in which said means is energised in one mode by operation of said second switch to energise the second circuit, is energised in a second mode when in addition, the first switch is operated to energise the first circuit, and is energised in a third mode when the second switch is subsequently operated to de-energise the second circuit, the warning means being electircally connected in circuit with said means so that current will fow to the warning means from the first current when said means is energised in said third mode.

5. A device according to claim 4 in which said means includes a first relay which is open when the second circuit is energised and closed when the second circuit is de-energised and a second relay which receives current from the energised second circuit and the energised first circuit to hold it closed so that when the second circuit is de-energised the first relay closes whilst the second relay is held closed by current from the energised first circuit, contacts of the two relays being interconnected to enable current from the first circuit to flow through the closed contact of the relays to operate the warning device.

6. A device according to claim 5 in which current from the closed contacts of the first relay closes contacts of a third relay, the closing of the contacts of the third relay allowing current from the first circuit to energise the warning means.

7. A device according to claim 6 in which a fourth relay is connected to the first circuit so that its contacts will be closed when the first circuit is energised, the closed contacts allowing current from the first circuit to flow through the second relay when the second circuit is de-energised.

8. A device according to claim 4 in which said means includes a logic circuit arranged so that in the first and second modes of operation current passes through the logic circuit in such a manner that a transistor is held in an OFF condition to prevent current from the first circuit energising the warning means, and so that in the third mode of operation the current passes through the logic circuit and switches the transistor ON to allow current from the firstcircuitto energise the warning means.

9. A device according to any preceding claim in which the warning means provides an audible and/or visual warning.

10. A device, according to claim 9 and in the case where an audible warning is provided, in which the warning device is connected to a third circuit independent of the first and second circuits to enable the warning device to warn that the third circuit is energised.

11. A device according to claim 9 or 10 and in the case where an audible warning is provided, in which the audible warning is provided by a piezo-electric transducer.

12. A device for warning that a first electric circuit is energised after a second electric circuit has been de-energised, said circuits including respective switches operable to energise or de-energise the circuits, the device being constructed and arranged substantially as herein described with reference to Figure 1 or Figure 2 of the accompanying drawings.

13. A device for warning that a lighting circuit of a motorvehicle is energised after an ignition circuit of the motor vehicle has been de-energised said circuits including respectively an ON-OFF switch and an ignition switch operable to energise and deenergise the circuits, the device comprising means responsive to operation of the ignition switch to energisethe lighting circuit and on operating the ignition circuit said means enables electric current from the lighting circuit to energise warning means.