GB2065344A - Warning circuit - Google Patents

Abstract

A warning circuit for an automotive vehicle provides a visual indication of the need to fasten a safety belt, and an audible indication that the safety belt has not been fastened when starting the vehicle, that the ignition key is still inserted in the ignition lock switch when a door is opened, that the door is open whilst driving, and that the vehicle lights have been left switched on after the ignition key has been removed from the ignition lock switch. The warning circuit (5) includes an audio generator and a pilot light, the audio generator having two associated circuits, one (19) for determining the repeat frequency, and the other (53) for determining the audio frequency of the warning signal which has the form of a melodic chime. <IMAGE>

Description

SPECIFICATION Warning circuit for automotive vehicles for monitoring the fastening of a safety belt and the vehicle lights The present invention relates to a warning circuit for automotive vehicles for monitoring the fastening of the safety belt and the vehicle lights upon closing the door.

Automotive vehicles are frequently parked accidentally with the lights left on, whereby if left for a long parking period the battery is discharged and the engine of the automotive vehicle cannot be started. The danger of forgetting to switch off the lights is particularly great when the lights of the automotive vehicle have been switched on due to bad visibility during adverse weather conditions. The reason for this resides in that the control indications provided in the interior for the vehicle lighting being switched on during daylight are almost unnoticeable. To remove this adverse feature German Gebrauchssmuster 7 712 096 already discloses an acoustic warning device to warn of the headlight operation with the ignition switched off, which is indicated to the driver before leaving the vehicle by means of a buzzing sound that the headlights are still on.For this purpose in a boxshaped housing two transistor-controlled and alternately excitable coils with opposing windings are mutually located on a rod-shaped coil core passed through central apertures in the coils and diaphragm adapted to be oscillated in the movement path thereof. By a suitable connection with the door contact switch the buzzer tone does not occur until the vehicle door is opened. Apart from the fact that a buzzing sounds relatively monotonous, this known warning circuit does not produce a signal when the safety belt is put on which, with present day traffic conditions, has to be regarded as extremely disadvantageous.

The invention therefore has as its object to provide a warning circuit for automotive vehicles which informs the driver, firstiy when he has not put the safety belt on when starting the vehicle, secondly warning that the key is still inserted in the ignition lock when the door is opened, thirdly that the lights are still switched on although the key has been removed from the ignition lock and the door is opened, and fourthly during driving with the door open.Hence the object underlying the invention resides in realising a warning circuit of the aforesaid type as simple as possible, whereby the warning occurs by melodic chime and a flickerfree lighting of a pilot lamp occurs, and moreover, a high degree of insensitivity to interference from the internal power supply of the automotive vehicle is ensured or the circuit fulfils the requirements of the electromagnetic compatability.

According to the present invention there is provided a warning circuit for automotive vehicles for monitoring the fastening of safety belts and the vehicle lights upon closing the vehicle door, in use, comprising an audio generator and a pilot light, and an input for an ignition lock switch, an input and an output for a belt switch, and wherein the output for the belt switch is connected with a door contact switch, an input and an output for the pilot light, and an input for the light switch of the vehicle and an earth connection are provided, the audio generator having two combined timing generator circuits, one of which produces the repeat frequency and the other the audio frequency of a chime or alarm and having a circuit arrangement connected at its output for producing the melodic chime or alarm associated therewith and the pilot light is connected to a monostable circuit for flickerfree lighting.

Preferably, the circuit arrangement includes a Darlington transistor connected at its emitter to the audio generator and at its collector with inputs of the light switch and the ignition lock switch, the base of the transistor on the one hand being connected via a resistor and a diode to the audio frequency generator and on the other hand, via this resistor, a further resistor and a further diode, to the timing generator for the repeat frequency, whereby between the further resistor and the further diode a capacitor, connected to the earth lead, is connected, by means of which the characteristic chime is produced.

The monostable circuit preferably contains a second transistor connected with its emitter at the input of the positive supply voltage and with its collector is connected via two seriesconnected resistors to earth, the base of the second transistor being connected via a resistor to a positive lead and furthermore to an RC-circuit which, at its other end, is connected via a diode to the output of the pilot light. A capacitor is also preferably connected between the collector and the base of the second transistor. Said other end of the RCcircuit moreover is preferably also connected via a diode to an output of the safety belt switch and to the collector of a third transistor, the base of which is connected to a connection between the two series-connected resistors and via these resistors to the emitter of the second transistor and to the earth lead.

The basic advantage obtained with the invention resides in the reliable warning of the driver of the vehicle by melodic chimes firstly, when the safety belt switch is closed, i.e, the safety belt has not been put on when starting, secondly when the key is left in the ignition lock when the door is opened, thirdly that the lights are still switched on even though the key had been removed from the ignition lock and the door is open, and fourthly when driving with the door open. On the other hand, during starting the flickerfree control lamp lights up for a certain time so that the passenger is always requested to fasten his safety belt.

The present invention will be described further by way of example, with reference to the accompanying drawings, in which: Figure 1 shows the connection diagram of the warning circuit according to the invention; Figure 2 shows the wiring diagram of the warning circuit of Fig. 1; and Figure 3 shows the voltage cycle, with respect to time, for producing ringing sounds.

An ignition lock switch 1 of a vehicle is connected to an input 2 of a warning circuit 5 and a light switch 3 is connected to the input 4 of the warning circuit 5. Furthermore, the warning circuit 5 is connected to a control lamp 6, which has the function of illuminating a reminder "please fasten safety belt", via an input 7 and an output 8. Furthermore, the warning circuit 5 is connected to a switch 9 in the buckle of the safety belt of the driver of the vehicle via an output 10 and an input 11, the input 11 is also connected to a door contact switch 1 3 via a connection 1 2. Finally, the warning circuit 5 is connected to earth via the connection 14.

From Fig. 2 it can be seen that the input 2 of the ignition lock switch 1 leads via a lead 1 5, incorporating a diode 1 6 and a resistor 17, to the emitter of a transistor 18, the collector of which is connected to a timing generator 1 9. The base of the transistor 1 8 is connected via a connection 20 to the earth connection 14, via a capacitor 21, and via a resistor 22, a connection 23, a resistor 24 and a diode 25, to the input 4 of the light switch 3, and also to the input 11 of the safety belt switch 9 via a diode 26. The collector of the transistor 1 8 is connected, via a resistor 27 and a connection 28, to the input of a NAND gate 29. From the connection 28 a lead 30 incorporating a resistor 31 leads to the output 32 of the timing generator 19.The output of the NAND gate 29 leads via three connections 33, 34, 35 to a further NAND gate 36, the output of which is connected, via connections 37 and 38, to the output of the timing generator 19, and also via connection 37 to a capacitor 39. The capacitor 39 is connected via a lead 40 including connections 41 and 42 with another input of the NAND gate 29. The connection 41 leads via a resistor 43 to the connection 34, and the connection 42 leads via a resistor 44 and a diode 45 to the connection 33.

Following the resistor 1 7 incorporated in the lead 15, there are in sequence a connection 48 for a Zener diode 49, a connection 50 for a capacitor 51, and a connection 52 for the sound generator 53. The connection 52 leads via a lead 54 to the input of a NAND gate 55. In front of this input of the NAND gate 55 there is a connection 56 which is connected via a resistor 57 to the earth lead 58. The output of the NAND gate 55 leads via a lead 59, with two connections 60, 61, to the inputs of a further NAND gate 62, the output of which, via a connection 63, extends to the output 64 of the sound generator 53 and, via a capacitor 65 and a connection 66 to the other input of the NAND gate 55.

Between the connections 66 and 60 there is connected a resistor 67.

The output 32 of the timing generator 1 9 is connected via a diode 68, a connection 69, a resistor 70, a connection 71 and a further resistor 72 to the base of a Darlington transistor 73, the emitter of which is connected via a sound generator 74 to the earth lead 58. The collector of the Darlington transistor 73 is connected via respective connections 75, 76 to the inputs 4, 2 of the light switch 3 and the ignition lock switch 1. The connection 71, located between the resistors 70 and 72, is connected via a diode 77 to the output 64 of the sound generator 53. The connection 69, located between the diode 68 and the resistor 70, is connected via a capacitor 78 to the lead 58. Between the connection 75 and the collector of the Darlington transistor 73 a capacitor 47 is connected via a connection 79, the capacitor 47 being connected to the earth lead 58.

The input 7 of the control lamp 6 is connected via a lead 80 to the emitter of a transistor 81 the collector of which is connected, via a connection 82, a resistor 83, a connection 84 and a resistor 85, to the earth lead 58. The base of this transistor 81 extends, via a connection 101, a connection 86, a capacitor 87 and a resistor 88, to a connection 89, which is connected to the output 8 of the control lamp 6 via a diode 102, and via a diode 90 to the output 10 of the safety belt switch 9 and also to the collector of a further transistor 91. Between the connections 101 and 103 a resistor 104 is connected. The emitter of transistor 91 is connected to the earth lead 58 and its base is connected to the connection 84 between the two resistors 83 and 85. Parallel to the transistor 81, between the connections 86 and 82 a capacitor 92 is located, which acts as protective capacitor against undefined switching-on during voltage peaks.

The combination of capacitor 51, Zener diode 49 and resistor 1 7 stabilises the voltage for sound and time frequency. The voltage is supplied from the internal supply of the automotive vehicle at the inputs 4 and/or 2 of the warning circuit 5. The current first passes through the diode 25 and/or the diode 1 6 and then through the resistor 17, whereupon it is divided and thus producing a relatively small current for the sound and time frequency and relatively large current flows via the transistor 73 and the sound generator 74.

The capacitors 51 and 47 protect the warning circuit from possible voltage peaks in the internal supply of the automotive vehicle.

By means of the sound generator 74 melodic chiming sounds may be heard. The output amplification of the chime occurs by means of the Darlington transistor 73. The repeat frequency of the chime is determined by the timing generator circuit 1 9 and the audio frequency of the chime is determined by the sound generator circuit 53. The chime is produced in that the amplitude continuing sound is allowed to diminish substantially exponentially (curve envelope of a chime). If the capacitor 78 is charged, then the voltage V, approximates to supply voltage of the timing generator 1 9 and the Darlington transistor 73 is conducting. Since the current gain of the Darlington transistor 73 is very high, a small base current flows in the Darlington transistor 73, so that a slight voltage drop is present across the resistors 70 and 72.The base voltage V2 is periodically switched via the diode 77 towards zero synchronous with the audio frequency. Momentarily, the capacitor 78 is slightly discharged via the resistor 70, and V2 is equal to V3 and is equal to zero, whereby the Darlington transistor 73 is nonconducting. A half cycle later V, is again equal to V2 and the Darlington transistor is again energised. However, V3 is now somewhat lower. This process continues until the capacitor 78 is completely discharged and the Darlington transistor 73 can no longer become energised. This switches off the chime.

From this circuit principle a melodically ending chime results.

The chime will not restart until the capacitor 78 is again charged. If, at the output 32 of the timing generator circuit 19, the voltage V4 rises, then the capacitor 78 is charged via the diode 68. By the provision of the resistor 44 and the diode 45 the charging pulse for the capacitor 78 does not last as long, whereby the sound produced is like a gently terminating chime (see Fig. 3).

By means of the transistor 1 8 the timing generator circuit 1 9 is switched on and off. As long as the voltage V5 is connected, thus as long as the transistor 1 8 is conducting, the timing generator circuit 1 9 is switched on.

The resistor 31 prevents the chime ending abruptly during switching off, because the capacitor 78 is not charged completely when it is switched off during the pulse period. If the transistor 1 7 switches off, the chime ends completely since the voltage V, is high.

Capacitor 39 and resistor 43 determine the frequency of the timing generator circuit 19.

The resistor 27 serves to limit the current. The capacitor 21 serves as protective capacitor should voltage peaks reach the base of the transistor 1 8 via the inputs 2, 4 and 11. The resistor 22 is the base resistor to limit the control current.

If positive voltage is connected to the input 7, then the capacitor 87 is charged via the resistor 104. As long as a negative potential is supplied to the base via the connection 101 at the transistor 81, the latter is conducting and a positive voltage is supplied to the base of the transistor 91. The transistor 91 switches the negative voltage via the emitter to the collector at the connection 89. This state is maintained as long as the transistor 91 is energised. If the capacitor 87 reaches substantially the potential of the positive voltage, then it blocks this and the transistor 91 is supplied with negative voltage via the resistor 85 at its base and also becomes nonconducting. Hence, a time constant determined by the capacitor 87 and resistor 88 is attained.If a negative potential is connected to the connection 89, then at the output 8 there is also a negative potential and the control lamp 6 lights up. Via a diode 90 at the output 10, a negative potential is also supplied which, with the safety belt switch 9 closed, is also connected at the input 11 and the chime is sounded. If the safety belt switch 9 is open, the chime ceases, but the control lamp continues to light up until the monosta ble multivibrator at the connection 89 no longer has any potential. If after this the safety belt switch 9 is again closed, then a negative potential reaches the input 11 and the chime is emitted until the door is again closed and no further positive voltage is connected to the input 2 or 4. The control lamp 6 is unable to light up due to this, because the negative potential does not flow via the diode 90. The rapid repetition of the monostable multivibrator is attained in that externally, lowrated consumers are connected at the input 7.

Via the resistor 104 in the lead 80 and via externally located low-rated consumers, the previously connected positive potential of the capacitor 87 is immediately discharged.

The resistor 24 renders the input 11 of lowimpedance, whereby the chime does not come into operation until there is a correct current passage through the input 11. The diode 1 6 acts as logic link for the external circuitry.

The warning circuit permits an overall structure of very small dimensions as known for relay housings. Herewith the connecting plugs may be so arranged that they may be plugged into the known screen system of the relays.

Claims (11)

1. A warning circuit for automotive vehicles for monitoring the fastening of safety belts and the vehicle lights upon closing the vehicle door, in use, comprising an audio generator and a pilot light, and an input for an ignition lock switch, an input and an output for a belt switch, and wherein the output for the belt switch is connected with a door contact switch, an input and an output for the pilot light, and an input for the light switch of the vehicle and an earth connection are provided, the audio generator having two combined timing generator circuits, one of which produces the repeat frequency and the other the adio frequency of a chime or alarm and having a circuit arrangement connected at its output for producing the melodic chime or alarm associated therewith and the pilot light is connected to a monostable circuit for flickerfree lighting.

2. A warning circuit according to claim 1, in which the said circuit arrangement includes a Darlington transistor connected at its emitter to the sound generator and at its collector with the inputs for the light switch and the ignition lock switch. the base of the Darlington transistor being connected via a first resistor and a first diode to the audio frequency generator, and via said first resistor, a second resistor and a second diode to the timing generator for the repeat frequency, and between the second resistor and the second diode a capacitor is connected, which is connected to the earth lead.

3. A warning circuit according to the claims 1 and 2, in which the input for the light switch and the input for the ignition lock switch are linked via diodes.

4. A warning circuit according to claims 1 to 3, in which to provide voltage stabilisation, the diodes connected at the inputs of the light switch and the ignition lock switch are connected via a further resistor with a Zener diode and a capacitor.

5. A warning circuit according to claims 1 to 4, in which the monostable circuit contains a second transistor connected with its emitter to the input of the positive supply voltage and with its collector connected via two series resistors to earth, the base of the second transistor being connected via a resistor to the positive supply voltage and furthermore to an RC-circuit having an end connection which leads via a diode to the output of the pilot light and a capacitor is provided between the base of the second transistor and the collector of the second transistor.

6. A warning circuit according to claim 5, in which the said end-connection of the RCcircuit furthermore is connected via another diode to the output for the safety belt switch and to the collector of a third transistor, the base of the third transistor being connected to a connection between two resistors and via these to the emitter of the second transistor and to the earth lead.

7. A warning circuit according to any of claims 1 to 6, in which the timing generator circuit for the repeat frequency of the chime or alarm is adapted to be switched on and off via a third transistor, the emitter of which is connected to the inputs of the ignition lock switch and the light switch, the collector of which is connected to the timing generator circuit, and its base is connected via a capacitor to the earth lead via two resistors to the inputs of the light switch and the ignition lock switch and via one of said resistors and a diode to the input of the belt switch.

8. A warning circuit according to any of claims 1 to 7, in which the repeat frequency of the chime or alarm is dependent upon the values of the RC-circuit of the timing generator circuit and the audio frequency of the chime or alarm upon the values of the RCcircuit of the audio generator.

9. A warning circuit according to any of claims 1 to 8, in which it is adapted to be incorporated entirely in a very small housing having the dimensions of a conventional relay housing.

10. A warning circuit according to claim 9, in which the connecting plugs are adapted to be plugged on the housing in the known grid system for relays.

11. A warning circuit for automotive vehicles, substantially as herein described with reference to and as illustrated in the accompanying drawings.