GB2226671A

GB2226671A - Vehicle intruder detecting apparatus

Info

Publication number: GB2226671A
Application number: GB8923172A
Authority: GB
Inventors: Paul Andrew Cunnane; Patrick John Lyons; William Francis Clancy; Joseph Oliver Mcbreen
Original assignee: Hi Key Ltd
Current assignee: Hi Key Ltd
Priority date: 1988-10-19
Filing date: 1989-10-13
Publication date: 1990-07-04
Also published as: IE71522B1; ZA888369B; GB8923172D0

Abstract

The apparatus comprises a circuit controlled by a microcontroller (16 Fig. 1, not shown). The circuit comprises a voltage drop detector circuit 18 for detecting a voltage drop in the battery of the vehicle. The circuit 18 comprises an AC amplifier 40 coupled to the positive terminal of the battery through a coupling capacitor C10 and a resistor R9 and a terminal 3. The output from the amplifier is fed into one input 43 of a voltage comparator 44. A reference voltage derived across a potential divider R16 and 17 is delivered to the other terminal 45 of the comparator. On the voltage on the pin 43 increasing above the reference voltage, the output pin 46 of the comparator goes from a logic low to a logic high, thereby indicating a voltage drop across the vehicle battery. This puts a high on pin (19) of the microcontroller (16) which activates an alarm means. Also disclosed are means for arming and disarming the apparatus, eg by radio, and other means, eg ultrasonic transmitter and receiver, for detecting intrusion into the vehicle. <IMAGE>

Description

VEHICLE INTRUDER DETECTING APPARATUS The present invention relates to a vehicle intruder detecting apparatus, and in particular though not limited to apparatus for detecting an attempt to enter a vehicle, such as, for example, a car, van or the like.

According to the invention, there is provided vehicle intruder detecting apparatus comprising a control means, detector means for detecting power being drawn from the vehicle battery, the detector means being connected to the control means, means for activating an alarm means controlled by the control means and means to arm and disarm the apparatus, wherein the detector means is provided by a voltage detector circuit, the voltage detector circuit comprising an AC coupling means for AC coupling the detector circuit to the vehicle battery, and a voltage comparator connected to the AC coupling means and a reference voltage for comparing the AC coupled voltage with the reference voltage, the output of the voltage comparator being connected to the control means, so that on the AC coupled voltage passing across the reference voltage the alarm activating means is activated by the control means.

In one embodiment of the invention, the detector circuit comprises an amplifier for amplifying the voltage output from the AC coupling means for delivery to the comparator. Preferably, the AC coupling means comprises a capacitor and resistor in series.

Advantageously, a power supply is provided to deliver the reference voltage to the voltage comparator.

Preferably, the reference voltage for the voltage comparator is derived across a potential divider.

In one embodiment of the invention, the control means is provided by a microcontroller. Preferably, the alarm activating means is provided a driver controlled by the control means. Advantageously, the driver is adapted to activate the vehicle siren and lights and to isolate the ignition circuit.

In another embodiment of the invention, the means to arm and disarm the apparatus comprises a radio wave receiving circuit to receive a remotely transmitted signal, the radio receiving circuit being connected to the control means. In a further embodiment of the invention a transmitter/receiver circuit is provided for connection to an intruder detector transducer, the transmitter/receiver circuit being connected to the control means.

Additionally, the invention provides a method for detecting an attempt to enter a vehicle comprising the steps of monitoring the voltage across the vehicle battery by AC coupling the vehicle battery to a comparator, and comparing the AC coupled voltage with a reference voltage, and activating alarm means in the event of the AC coupled voltage exceeding a predetermined level.

The invention will be more clearly understood from the following description of a preferred embodiment thereof, given by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a block diagram of vehicle intruder detecting apparatus according to the invention, and Fig. 2 is a circuit diagram of a detail of the apparatus of Fig. 1.

Referring to the drawings, there is illustrated a block diagram of a circuit indicated generally by the reference numeral 1 of a vehicle intruder detecting apparatus according to the invention. The apparatus is suitable for mounting in a car, van or the like for detecting an attempt to enter the vehicle by detecting a voltage drop in the battery 10 of the vehicle. Such voltage drop would normally be caused by current drawn from the battery by the courtesy light being switched on as a result of a door, boot or bonnet lid of the vehicle being opened.

The components of the circuit 1 provided within the box indicated by the chain dotted lines 2 are all mounted within a housing (not shown) of plastics material. This thus provides apparatus which is easily and conveniently mounted in a vehicle. The housing (not shown) is provided with terminal sockets 3 to 9 and 51 to 53 which are connected to the circuit 1. The terminal socket 3 is provided for connecting the circuit 1 to the positive terminal of the vehicle battery 10. The terminal sockets 4 and 5 respectively connect the circuit 1 to the vehicle lights 11 and vehicle siren 12 for activation of the lights 11 and the siren 12 in the event of the circuit 1 detecting a voltage drop in the battery 10.The terminals 6 and 7 connect a relay RL1 described below in series with the ignition circuit (not shown) of the vehicle for isolating the ignition circuit, on the circuit 1 being armed as described below. The terminal sockets 8 and 9 respectively connect the circuit 1 to intruder detector transducers, namely an ultrasonic transmitter 14 and receiver 15. The ultrasonic transmitter and receiver 14 and 15 are mounted in the vehicle for detecting movement within the vehicle. The terminals 51 and 52 are provided for connecting the circuit 1 to other components of the vehicle, such as, the flashers, brake lights and the like, should it be desired to activate these on the circuit 1 detecting a voltage drop in the battery. The socket 53 connects an aerial 54 into the circuit 1. The aerial receives and delivers an arm and disarm signal into the circuit for arming and disarming the circuit 1.This is described below.

The circuit 1 is controlled by a control means, namely, a microcontroller 16 under the control of suitable software which will be known to those skilled in the art. A power supply circuit 17 is connected to the terminal 3 and is powered by the battery 10. The power supply circuit 17 delivers a regulated voltage VCC, in this case 5.0 volts for powering the circuit 1. A detector means for detecting power being drawn from the battery 10 is provided by a voltage detector circuit 18 connected to the terminal socket 3 which detects a voltage drop in the battery 10. The detector circuit 18 is described in detail below. On the voltage detector circuit 18 detecting a voltage drop a logic high signal is placed on pin 19 of the microcontroller 16.The microcontroller 16 drives a driver 20 which activates the lights 11 and siren 12 connected to the terminal sockets 4 and 5 on the pin 19 going high. A signal generator 22 under the control of the microcontroller 16 delivers pulse signals through the terminal socket 8 to the ultrasonic transmitter 14. The transmitted signals are received by the ultrasonic receiver 15 which are fed through the terminal socket 9 into an amplifier 24. The amplified received signal is fed to an analyser circuit 25 which anaylses any variation in the received signal which would be caused by movement in the vehicle. On movement being detected by the analyser 25, an output pin 26 of the analyser 25 goes high, thereby putting a high on pin 19 of the microcontroller 16. This causes the microcontroller 16 to activate the lights 11 and the siren 12.

An arming and disarming means for arming and disarming the circuit 1 comprises a radio receiver 27 which receives a signal from a remote transmitter through the aerial 54. Such transmitters will be well known to those skilled in the art, and usually comprise a button activated transmitter which transmits a predetermined code number in digital form. The signal received by the receiver 27 is fed to an amplifier 28 which in turn is fed to an analyser circuit 29 which conditions the signal and extracts the code number from the signal. The analyser circuit 29 delivers the code number to a pin 30 of the microcontroller 16 which compares the code number with a reference code number stored in the microcontroller 16. If the code numbers match, then the received signal is a valid signal and the circuit 1 changes state.For example, if prior to the signal being received the circuit 1 is armed, the valid signal appearing on the pin 30 causes the microcontroller 16 to disarm. On disarming the circuit 1, the microcontroller 16 also through a driver 21 oeprates the relay RL1 to close the contacts 52 of the relay RL1 thereby short circuiting the terminal sockets 6 and 7. This thus enables the ignition of the vehicle to be operated. On the circuit 1 being armed, the microcontroller 16 through the driver 21 operates the relay RL1 to open the contacts 55, thereby opening the circuit between the terminals 6 and 7 and thus preventing the ignition of the vehicle from being switched on.

Referring now to Fig. 2 the voltage drop detector circuit 18 is illustrated. The circuit 18 comprises an AC amplifier 40 which is AC coupled by an AC coupling means, namely a capacitor C10 and a resistor R9 to the terminal 3. The resistor R9 is of 6.8 Kohms and the capacitor C10 is of 1 microF. On power being drawn from the battery 10 the voltage across the battery 10 drops. This voltage drop thus causes an AC voltage to be placed on an input pin 41 of the AC amplifier 40 through the AC coupling capacitors C10.

The AC amplifier 40 amplifies the AC signal on the input pin 41, in this case 70 times. The amplified signal is fed from an output pin 42 of the amplifier 40 through a resistor R13 of 10 Kohms onto one input pin 43 of a voltage comparator 44. The other input pin 45 of the comparator 44 is fed with a reference voltage which is derived from the regulated voltage VCC across a potentiometer formed by resistors R16 and R17. The resistors R16 and R17 are of 100 Kohms and 68 Kohms respectively, thus giving a reference voltage of 4.5 volts. While the voltage on the input pin 43 remains below the reference voltage, a logic low remains on the output pin 46 of the comparator 44. On the voltage on the input pin 43 rising above the reference voltage, a logic high is placed on the output pin 46.This in turn brings the pin 19 of the microcontroller 16 high and causes the microcontroller to activate the drivers 20 and 21 as already described. The amplifier 40 and voltage comparator 44 are powered by the regulated voltage VCC. The resistors R16 and R17 are chosen to give the sensitivity desired for detecting the voltage drop in the battery. In this particular case providing a reference voltage of 4.5 volts provides adequate sensitivity for detecting a voltage drop caused by the interior light of a vehicle being activated. The interior light of the vehicle would typically be switched on by opening a door, boot lid or bonnet of a vehicle, where the opening of the door, boot lid or bonnet closed a courtesy switch in the appropriate frame of the door, boot lid or bonnet.Typically switching on the interior light in a vehicle causes a voltage drop of between 7 and 10 millivolts across the battery. This causes an AC voltage of 0.6 voltage peak to peak to be placed on the output pin 42 of the amplifier 40. Thus, on the voltage on the pin 43 of the comparator 44 rising to 0.3 volts above normal the voltage on the pin 43 exceeds the reference voltage, thereby putting a logic low on the pin 46.

In use, the apparatus 1 is mounted in an inaccessible place in the vehicle, either under the bonnet or behind the dashboard of the vehicle. The ultrasonic transmitter and receiver 14 are mounted in suitable locations in the vehicle, normally at opposite ends of the dashboard, and are directed into the vehicle. The terminal 3 is connected to the positive terminal of the battery, while the terminals 4 and 5 are respectively connected to the lights 11 and siren 12 of the vehicle. The terminals 6 and 7 are connected into the ignition circuit for isolating the circuit.

The terminals 8 and 9 are connected to the transducers 14 and 15.

When the circuit 1 is armed as a result of the receiver 27 receiving a valid signal, the ignition is isolated by the relay RL1, and should the ultrasonic receiver 15 detect movement in the vehicle, or should the detector circuit 18 detect a voltage drop in the battery, the microcontroller 16 activates the light 11 and horn 12. On the receiver 27 receiving a further valid signal from the remote transmitter the circuit 1 is disarmed. On receiving a further valid signal from the remote transmitter, the circuit 1 again becomes armed, and so on.

While the circuit 1 has been described as comprising ultrasonic receiver and transmitter units, if desired these could be dispensed with. Furthermore, it is envisaged in certain cases that means to arm and disarm other than a radio receiver could be used, for example, a keypad input means could be used, in which case a personal identification code would be keyed into the keypad to arm and/or disarm the unit. In which case, it is envisaged that the keypad would be mounted within the vehicle and a timing circuit would be provided to prevent the microcontroller 16 activating the drivers immediately upon the detector circuit 18 detecting a drop in voltage, or the ultrasonic receiver 15 detecting movement in the vehicle.

The timer circuit would be set to give the vehicle owner sufficient time to enter vehicle to key in a personal identification number to disarm the circuit.

Alternatively, the means to arm and disarm the circuit could be provided by a key switch which may be mounted internally or externally of the vehicle. In the event of the key switch being mounted internally, a timer circuit would also be provided to prevent immediate activation of the alarm.

It will of course be appreciated that means other than drivers could be provided to activate the siren, lights and to deactivate the ignition circuit.

Indeed, it will readily be appreciated that it is not necessary for the lights and siren to be activated on an alarm condition being detected, in certain cases, it is envisaged that only the siren or lights would be activated. Indeed, in certain cases, it is envisaged that a separate siren may be provided to be activated only by the circuit 1. Needless to say, other circuits and/or components of the vehicle could be either activated or deactivated in the event of an alarm condition occurring.

Further, it will be appreciated that while in this particular embodiment of the invention, the control means for the apparatus has been described as being a microcontroller under the control of suitable software, any other suitable control means could be used.

While it is preferable, it is not essential that a power supply should be provided. Furthermore, in certain cases it is envisaged that the terminal 3 would be connected to the negative terminal of the vehicle battery.

Claims

1. Vehicle intruder detecting apparatus comprising a control means, detector means for detecting power being drawn from the vehicle battery, the detector means being connected to the control means, means for activating an alarm means controlled by the control means and means to arm and disarm the apparatus, wherein the detector means is provided by a voltage detector circuit, the voltage detector circuit comprising an AC coupling means for AC coupling the detector circuit to the vehicle battery, and a voltage comparator connected to the AC coupling means and a reference voltage for comparing the AC coupled voltage with the reference voltage, the output of the voltage comparator being connected to the control means, so that on the AC coupled voltage passing across the reference voltage the alarm activating means is activated by the control means.

2. Vehicle intruder detecting apparatus as claimed in Claim 1 in which the detector circuit comprises an amplifier for amplifying the voltage output from the AC coupling means for delivery to the comparator.

3. Vehicle intruder detecting apparatus as claimed in Claim 1 or 2 in which the AC coupling means comprises a capacitor.

4. Vehicle intruder detecting apparatus as claimed in Claim 3 in which the AC coupling means comprises a resistor in series with the capacitor.

5. Vehicle intruder detecting apparatus as claimed in any of Claims 1 to 4 in which a power supply is provided to deliver the reference voltage to the voltage comparator.

6. Vehicle intruder detecting apparatus as claimed in Claim 5 in which the reference voltage for the voltage comparator is derived across a potential divider.

7. Vehicle intruder detecting apparatus as claimed in any preceding claim in which the output from the comparator goes from a logic low to a logic high on the value of the AC coupled voltage going above the value of the reference voltage.

8. Vehicle intruder detecting apparatus as claimed in any preceding claim in which the control means is provided by a microcontroller.

9. Vehicle intruder detecting apparatus as claimed in any preceding claim in which the alarm activating means is provided a driver controlled by the control means.

10. Vehicle intruder detecting apparatus as claimed in Claim 9 in which the driver is adapted to activate the vehicle siren.

11. Vehicle intruder detecting apparatus as claimed in any preceding claim in which the means to arm and disarm the apparatus comprises a radio wave receiving circuit to receive a remotely transmitted signal, the radio receiving circuit being connected to the control means.

12. Vehicle intruder detecting apparatus as claimed in any preceding claim in which a trasmitter/receiver circuit is provided for connection to an intruder detector transducer, the transmitter/receiver circuit being connected to the control means.

13. Vehicle intruder detecting apparatus as claimed in Claim 12 in which the transmitter/receiver circuit generates an ultrasonic signal for transmission.

14. Vehicle intruder detecting apparatus substantially as described herein with reference to and as illustrated in the accompanying d-awings.

15. A method for detecting an attempt to enter a vehicle comprising the steps of monitoring the voltage across the vehicle battery by AC coupling the vehicle battery to a comparator, and comparing the AC coupled voltage with a reference voltage, and activating alarm means in the event of the AC coupled voltage exceeding a predetermined level.

16. A method for detecting an attempt to enter a vehicle, the method being substantially as described herein with reference to the accompanying drawings.