GB2383666A

GB2383666A - Proximity alarm and positioning system

Info

Publication number: GB2383666A
Application number: GB0230212A
Authority: GB
Inventors: Alan Dodds; Nigel Carley
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-12-28
Filing date: 2002-12-27
Publication date: 2003-07-02
Also published as: GB0230212D0; GB0131076D0; AU2002356334A1; WO2003056528A1

Abstract

A proximity alarm and positioning system for monitoring the location of a person or child. A master receiver 20, worn or carried by a monitoring person, includes an alarm means and receives a signal transmitted by at least one slave transmitter 10, worn or carried by a person being monitored. The system has two modes of operation. Firstly, the alarm means is actuated when the relative separation of the transmitter and receiver exceeds a preset value. Secondly, the alarm means is activated by the monitoring person and the output of the alarm increases in strength as the transmitter moves closer to the receiver being sought. The alarm may be audible or vibrating, or may incorporate LEDs. The alarm may be triggered if the battery 16, 26 of the master or slave devices is low. The master receiver may recognise a plurality of slave transmitters.

Description

Title: Positioning system The present invention relates to a positioning system, and more particularly, but not exclusively, to a positioning system for children to enable a guardian to monitor his charge within a protective zone.

It is already known from published patent application EP 0969435 A2 in thenarne of Raj Kumar Dhameja of Stoneygate, Leicester to try and provide a personal tracking system enabling a missing child to be found. EP 0969435 A2 discloses a transmitter unit, which transmits an aerial signal, and can be attached to a child. A receiver unit of the size of a typical mobile telephone is kept in the possession of a responsible adult. When the transmitter unit is activated, the aerial signal is transmitted and receivedbythereceiverunit, if inrange, whichdisplays infonnationrelatingto the direction and distance of the transmitter unit from the receiver unit, and the direction in which the transmitter unit is moving. However, this system does not provide for the constant monitoring of a child, but is activated by the child or responsible person to simply determine the position of the child.

It is an object of the invention to provide an improved positioning system which is capable of constantly monitoring the position of a transmitter, which may be in the possession of a child being monitored.

According to the present invention there is provided a positioning system for enabling a guardian tomonitorhis chargewithin aprotectivezonecomprising amasterreceivercapableofbeingwom or carried by a monitoring person, and at least one slave transmitter capable of being worn or carried by a person being monitored; the or each slave transmitter including a power source, and a transmitter device which emits an aerial signal; the master receiver including a power source, a receiver device which is adapted to receive a signal emitted from the or each slave transmitter device, and an alarm means which is activated in

response to a change in the proximity of at least one slave transmitter relative to the master receiver ; characterised in that the positioning system has a first mode of operation in which the alarm means is actuated when a slave transmitter moves outside a protective zone, the perimeter of the protective zone being a preset distance from an active master receiver; and a second mode of operation in which the alarm means is activated by the monitoring person, the output from the alarm increasing in strength as the master receiver moves closer to a slave transmitter being sought.

It is an advantage of the invention that the position of a child can be constantly monitored, and should the child stray outside a protective zone, an alarm sound. It is a further advantage of the invention that if a child should stray outside the proximity ofthe protective zone, out ofthe visibility of the guardian, then the guardian can activate the alarm in the second mode of operation in order to detect the position of the child by moving in a direction which causes the output from the alarm to increase in strength.

The preset distance is preferably entered into the master receiver by the monitoring person, and may be in the range from 5 metres to 100 metres. Optionally, the range may be set in intervals of 5 or 10 metres.

Most preferably, the preset distance is either 5 metres or 30 metres.

This has the advantage of allowing close proximity monitoring of a child, for example in a shopping centre, or distant proximity monitoring, for example in a playground or fairground.

The master receiver may monitor up to three slave transmitters, and an identification means for each slave transmitter may be loaded onto the associated monitoring master receiver.

This enables the master receiver to distinguish the signals of different slave transmitters, and consequently for a guardian to monitor the position of each child being monitored, individually.

The alarm means preferably includes an individual L. E. D. for each slave transmitter and an audible alarm, which increases in volume when the master receiver and slave transmitter move closer together. A vibrating alarm means may also be provided, which creates vibration of the master receiver, the vibration increasing in vigour when the master receiver and slave transmitter move closer together.

The signal transmitted by each slave transmitter can be received by one or more master receivers.

This is advantageous, for example, if two parents each cany a master receiver. Conveniently, the master receivers can be switched on or off as desired.

The alarm maybe activated if the battery of the master receiver or of a slave transmitter being monitored is low. The alarm may also be activated if a slave transmitter being monitored moves out of range of the master receiver.

The power source ofboth the slave transmitter and master receiver is preferably a battery, but may be a kinetic energy device, for example, similar to those used in watches. The battery is preferably rechargeable. One or more light emitting diodes may be provided to indicate the level of charge in each battery.

If the strap of a slave transmitter being monitored is undone, then the alarm may again be activated.

A further alarm is preferably provided on each slave transmitter, which is activated if the slave transmitter being monitored moves out of range of the master receiver.

This is advantageous because a person being monitored is able to tell if he or she has moved out of the realms of safety provided by the system.

A printed circuit board is preferably mounted in or on the housing ofthe slave transmitter. The transmitter device may be mounted on the printed circuit board.

A further printed circuit board is preferably also mounted in or on the housing of the master receiver. The receiver device may be mounted on the further printed circuit board.

The slave transmitter is preferably mounted on or secured within a strap, which can be securedto a person's wrist or ankle. The strap may be fastened with hook and eye fastener, for example, Velcro (RTM). The master receiver is also preferably mounted on or secured within a strap fastened with hook and eye fastener, which can be secured to a person's wrist or ankle.

Alternatively the straps may be fastened with a conventional buckle, or a tamper proof tag.

The invention will now be described by way of example only with reference to the accompanying drawings in which : Fig 1 shows a schematic perspective view of a slave transmitter; Fig 2 shows a schematic plan view of a master receiver; Fig 3 shows a perspective view of a prototype master receiver; Fig 4 shows the L. C. D. display of the prototype master receiver: Fig 5 is a flowchart showing the start-up routine performed by the circuitry of the master receiver and the loading of a first slave transmitter; Fig 6 is a flowchart showing loading of a second slave transmitter; Fig 7 is a flowchart showing loading of a third slave transmitter;

Fig 8 is a flowchart showing the monitoring routine performed by the circuitry of the master receiver; and Fig 9 is a flowchart showing low battery and anti-tamper routines of the master receiver.

A slave transmitter, indicated generally at lOinFig l, comprises ahousing formed as a strap 12, which can be worn as a wrist or ankle band. Hook and eye fastener 14, such as Velcro (RTM) is provided at the ends of the strap 12, enabling fastening. In alternative arrangements, not shown, a conventional buckle or tamper proof tag may be used. A"button"battery and flexible printed circuit board are indicated schematically at 16, and a transmitter device is shown schematically at 18. Both the battery and flexible printed circuit board 16, and transmitter device 18 are mounted on or within the strap 12. The transmitter device 18 emits an aerial signal, which is received and monitored by a master receiver, indicated generally at 20 in Fig 2, and at 40 in Fig 3. An alarm means is also provided on the strap 12, which is activated when the strap is released, either deliberately or accidentally, or when the slave transmitter moves out of range of the master receiver 20.

The masterreceiver20 is similar in construction to atypical watch, and comprises a strap 22, which is fastened by hook and eye fastener 24 provided at the ends of the strap. In alternative arrangements, not shown, a conventional buckle or tamper proof tag may be used, as with the slave transmitter 10. A"button"battery and flexible printed circuit board are indicated schematically at 26, and a receiver device is shown schematically at 28. The battery and flexible printed circuit board 26, and receiver device 28 are mounted in a casing 30 attached to the strap 22. The casing 30 is a two-part plastics moulding, which is held together with adhesive, and is waterproof.

A switch 32 is provided on one side ofthe casing 30, for switching the masterreceiver 20 on and off, and between first and second modes, as described below. An audible alarm means, not shown, is provided in the casing 30, and has an output which varies in volume. In an alternative arrangement, also not shown, the alarm means is a vibrator, which causes the casing 30 to vibrate

with varying vigour, or frequency, as required.

A voice micro-chip (not shown) is provided in each of the slave transmitter 10 and master receiver 20, which indicates when one of the straps 12,22 is undone, thus alerting a wearer to the accidental or deliberate removal of a strap. If the strap 12 of the slave transmitter 10 is undone, the slave transmitter sends a further aerial signal to the master receiver 20, which notifies the master receiver that the slave transmitter 10 has become detached from the a person being monitored.

The slave transmitter 10 can be used repeatedly, or optionally can be provided with the intention of being disposable after a single use.

In alternative arrangements, not shown, the batteries in the slave transmitter 10 and master receiver 20,40 are rep laced with kinetic energy power sources of the type known for use in wrist watches.

The master receiver 20 is capable of monitoring a plurality of slave transmitters 10, and therefore the system is not limited to the protection of, for example, a single child. It is also possible for more than one master receiver 20 to monitor one or more slave transmitters. This has the advantage, for example, that both parents can wear or carry a master receiver 20 when one or more children are under their charge. Each master receiver 20 can optionally be switched off.

In a first mode of operation, a slave transmitter 10 emits an aerial signal which is received and monitored by an active master receiver 20. If the slave transmitter 10 moves further away from the master receiver 20 than a preset distance, ie, outside a protective zone, then the alarm is activated in response to the change in the proximity of the slave transmitter relative to the master receiver. The preset distance is in the range from 10 metres to 100 metres, and can be set in intervals of 10 metres, for example, at 10,20 or 30 metres. The preset distance is entered into the master receiver 20 by the monitoring person.

In a second mode of operation, the alarm is actuated by the monitoring person, and the output from

the alarm increases in strength or volume, as the master receiver 20 moves closer to a slave transmitter 10 being sought. In this mode, it is possible to detect the position of the slave transmitter 10, by moving in a direction which causes the output from the alarm to increase in strength. Similarly, as the master receiver 20 and slave transmitter 10 move further apart, the strength or volume of the alarm decreases.

A prototype masterreceiver is indicated generally at 40 in Fig 3. The prototype master receiver 40 has the features ofthe schematic model shown in Fig 2, and further includes a Liquid Crystal Display (LCD) 42, LED indicators 44, Scroll Keys 46,48 and an Enter Key 50. A battery charge terminal is also provided on the side ofthe masterreceiver (not shown). The LCD 42 is shown in more detail in Fig 4, and will be described further with the operation ofthe master receiver 40. It is envisaged that each slave transmitter will have the appearance and size of a typical children's wrist watch.

In the operation of the positioning system it is first necessary to decide how many slave transmitters are required, and to designate them in order, for example, Cl 1, CX2 and CX3. The master receiver 40 will be designated PX for ease of identification. In order to switch the PX unit 40 on, the Enter Key 50 is held down for around two seconds. The same procedure is followed to switch off the PX unit 40. When the PX unit is switched on the circuit board (processor) tests the charge ofthe battery, and if the battery is low this is indicated on the LCD 42. If the Scroll Keys 46,48 are both pressed, then the memory (EEPROM) is cleared. If there are CX identification codes stored in the EEPROM, then a synchronisation routine is performed for detecting the CX units.

The user is able to choose between monitoring at five metres (near) and monitoring at thirty metres (far). Once a monitoring range is selected using the Enter Key 5 0, proximity monitoring starts as shown in Fig 8.

If there are no CX identification codes in the EEPROM, then a load sub-routine 52 is performed.

The LCD 42 displays"LOAD"and the CX1 icon 54, Fig 4, is lit. When the strap of the CX1 slave transmitter is shut or done up, then the CX1 unit is turned on. The CX1 must be placed

within approximately 20cm ofthe PX unit 40 to enable the PX to detect CXI. Once detected, the CX1 icon 54 will flash, and the Enter Key 50 must be pressed to store the identification codes of the ex 1 unit on the PX EEPROM. Once stored, the identification codes, which are unique to each unit, are stored even when the power is turned off. Referring now to Fig 6, once the CX1 is loaded, the user has the option to start proximity monitoring, indicated at 56 or to load CX2 indicated at 58. If a further CX unit is to be loaded, then the Scroll Key 48 must be pressed, underneath the"+"icon, indicated at 60 in Fig 4.

CX2 and CX3 slave transmitters can be loaded by following the above procedure again, as indicated in the flow charts shown in Figs 6 and 7. After the final CX unit has been loaded, a proximity selectable menu is displayed on the LCD, as explained further with reference to Fig 8.

Firstly, the monitoring range must be selected, as indicated at 62, from the near and far options.

Once selected, the PX unit begins monitoring the radio signals from the CX units. These signals are designated RSSI in the flow chart, and the circuit board (processor) compares the RSSI values with that ofthe range chosen. If the RSSI value is greater than the value of me chosen range, then the CXunithaving the greaterRSSIvalue is identified by its identification code and the alarm is activated.

Whilst monitoring, the PX sends a"wake up"message, indicated at 64 in Fig 9, to all of the CX units every three seconds. The PX waits for an answers from each CX unit. If a CX signal is not received, the PX unit will send the"wake up"message three more times. If the signal from a CX unit is still not detected after the third attempt, the PX alarm will activate and the LCD will display "CX alarm". Also, the appropriate LED 44 will luminate.

Ifthe CX signals are received, then the PX will compare the proximity values as described, and wait for an alarm from all of the CX units. If any of the CX units are outside the set proximity range, then the alarm will activate, and the PX will indicate which CX unit is beyond the proximity range. The alarm will continue, sound and/or vibration, until the out of proximity range CX is

returned to within the selected range. Should the CX move out of radio communication range of the PX unit, then the alarm will continue to sound and the LCD will display an out of range warning. The range warning and alarm will cease when the CX unit comes back into radio communication range.

When the PX unit is switched off, the PX identification codes are stored, and then when the PX unit is switched on subsequently, after a synchronisation routine is performed, the range must be set by the user and then the PX will start monitoring. The sub-routine takes around thirty seconds.

If the user wants to change any ofthe CX units, then the EEPROM must be cleared and the CX units reloaded. The contents of the EEPROM can be erased by holding the Scroll Keys 46,48 down at the same time for two seconds.

When the PX unit is in the second mode of operation, the output from the alarm increases in strength as the PX unit moves closer to a CX unit being sought, i. e., the audible alarm increases in volume and the vibrating alarm increases in frequency and/or amplitude.

The operational features of each CX unit will now be described. The CX unit is switched on when the strap is closed. A message is then transmitted to the PX telling"I am CX (identification code) and I am here", indicated at 66 in Fig 9. In order for the CX to save energy it then goes into sleep mode, and waits for a"wake up"signal 64 from the PX, as described above. When the "wake up" signal is received, the CX sends its identification code to the PX unit in ten strings, ten times. Once the identification code has been sent, the CX checks the charge ofthe battery. If the ten strings have not been sent ten times, then the CX sends the identification code again. If the battery ofthe CX is low, the CX will transmit a"low battery signal"to the PX and will repeat the battery check.

The CX unit also checks for tampering, i. e. has the strap of the CX unit become undone either intentionally or unintentionally ? If the strap is undone, then the CX will transmit a tamper alarm to the PX for one second and will repeat the signal until the battery is flat. If no tampering is detected,

then the CX sends a message"I am okay"to the PX and then goes into sleep (energy saving) mode. If the PX unit is switched off, no alert signal is displayed.

Both the PX and CX units include a transceiver module for proximity detection (Microlinear 2. 45Hz chip) and a communication exchange. The transmission power is 1 OmW, and Omnidirectional antenna are used on the PX unit. Radiation shielding must be provided on the rear of both units in order to meet UK SAR Regulations. Each unit manufactured has a unique identification code which differentiates it from other units.

It is envisaged that the system will be found particularly suitable for use in school playground areas and shopping malls, will be useful in controlling wayward pets, and may have commercial applications in offices and factories.

Claims

CLAIMS 1. A positioning system for enabling a guardian to monitor his charge within a protective zone comprising a master receiver capable of being worn or carried by a monitoring person, and at least one slave transmitter capable of being worn or carried by a person being monitored; the or each slave transmitter including a power source, and a transmitter device which emits an aerial signal; the master receiver including a power source, a receiver device which is adapted to receive a signal emitted from the or each slave transmitter device, and an alarm means which is activated in response to a change in the proximity of at least one slave transmitter relative to the master receiver; characterised in that the positioning system has a first mode of operation in which the alarm means is actuated when a slave transmitter moves outside aprotective zone, the perimeter of the protective zone being a preset distance from an active master receiver; and a second mode of operation in which the alarm means is activated by the monitoring person, the output from the alarm increasing in strength as the master receiver moves closer to a slave transmitter being sought.
2. A positioning system according to claim I characterised in that the preset distance is entered into the master receiver by the monitoring person.
3. A positioning system according to claim 2 characterised in that the preset distance is in the range from 5 metres to 100 metres.
4. A positioning system according to claim 3 characterised in that the preset distance is either 5 metres or 30 metres.

<Desc/Clms Page number 12>
5. A positioning system according to any preceding claim, characterised in that the master receiver can monitor up to three slave transmitters.
6. A positioning system according to claim 5, charactelised in that an identification means for each slave transmitter is loaded onto the associated monitoring master receiver.
7. A positioning system according to claim 5 or claim 6, characterised in that the alarm means includes an L. E. D. for each slave transmitter.
8. A positioning system according to any preceding claim, characterised in that the signal transmitted by each slave transmitter can be received by one or more master receivers.
9. A positioning system according to any preceding claim, characterised in that the alarm is activated if the battery of the master receiver or of a slave transmitter being monitored is low.
10. A positioning system according to any preceding claim, characterised in that the alarm is activated if a slave transmitter being monitored moves out of range of the master receiver.
11. A positioning system according to any preceding claim, characterised in that an alarm provided on each slave transmitter is activated if the slave transmitter being monitored moves out of range of the master receiver.
12. Apositioning system according to any preceding claim, characterised in that the alarm is activated if the strap of a slave transmitter being monitored is undone.
13. A positioning system as according to any preceding claim characterised in that the alarm means is audible.