AU2004201668B2 - An Improved Energiser for Energising Multi-Zone Electric Fences - Google Patents

Description

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AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT Name of Applicant(s) Actual Inventor(s) Address for Service: Invention Title: Pakton Developments Pty Ltd Paul Thompson CULLEN CO Patent Trade Mark Attorneys, 239 George Street Brisbane Qld 4000 Australian An Improved Energiser for Energising Multi-Zone Electric Fences Details of Associated Provisional Application 2003902630 filed 28 May 2003 The following statement is a full description of this invention, including the best method of performing it, known to us: Field of the Invention The present invention relates generally to multi-zone electric fences and, in particular, to energisers for energising multi-zone electric fences.

Although the invention will be described with particular reference to energisers that are used in security fencing applications, it will be appreciated that the invention may be employed with energisers that are used in other fencing applications such as agricultural fencing applications.

Brief Discussion of the Prior Art Electric fences are often used for security purposes to restrict unauthorised entry to certain areas such as industrial premises. Electric fences normally include a plurality of posts between which one or more non-insulated wire conductors are strung such that the conductors are electrically insulated from the posts. The conductors are coupled to an energiser that periodically outputs a high voltage pulse to energise the conductors so that intruders will receive a small electric shock if they contact the energised conductors.

In Australia, the maximum amplitude and frequency of the pulses that are able to be generated by an electric fence energiser are restricted by safety standards such as Australian Standard 3350.2.76. These standards also state that conductors that are connected to different energisers must be separated from each other by a minimum distance so as to make it difficult for a person to simultaneously touch the conductors.

This prevents a person from receiving an electric shock from more than one energiser which is of a greater magnitude or of a higher frequency than is safe.

When an electric fence is used for security purposes it is desirable to divide the fence into independently energised sections, called zones, so that a load on one zone will not affect the voltage on other zones and will not leave the other zones ineffective as a barrier. Dividing an electric fence into zones has the added advantage that it enables the location of a load on the fence to be more accurately identified so that a more targeted response can be made if a load condition is detected. Moreover, it allows for individual zones to be energised or de-energised independently of each other.

Previously, multi-zone electric fences have been constructed which use a single energiser whose output is split using a series of resistors so that the energiser can energise a plurality of zones. The presence of the resistors reduces the effectiveness of the pulse which is generated by the energiser owing to power dissipation by the resistors. Moreover, it can be difficult to trim the series resistances to achieve a balance between good power on the different conductors and reducing cross loading between the conductors. Furthermore, very high voltage relays or switches must be employed to energise or de-energise the conductors independently of each other.

Some prior art electric fence energisers have multiple outputs from which electrical pulses are simultaneously output so as to prevent pulses from different outputs being combined to produce a series of pulses having a frequency which exceeds a prescribed maximum frequency. However, if the amplitude of the pulses from the different outputs is large enough, pulses from different outputs may be combined to produce a pulse whose amplitude exceeds a prescribed maximum amplitude. This problem has been overcome to a certain extent by outputting pulses of opposite polarities from the different outputs, however a problem with this solution is that inevitably there will be sites where more zones are required than the energiser has outputs.

Australian patent no. 705977 discloses a method of coordinating the generation of pulses by several electric fence energisers so that pulses generated by some of the energisers cannot be combined to produce a series of pulses whose amplitude exceeds a prescribed amplitude or whose frequency exceeds a prescribed frequency. The method entails coordinating the generation of the pulses by the different energisers in such a way so as to lower the frequency of pulse generation by each energiser so that the frequency of a train of pulses produced by combining the pulses generated by some of the energisers is less than a prescribed maximum frequency. A problem with this method is that it becomes difficult to implement as the number of zones which the energisers must energise increases beyond four. Also, the method is reliant on the layout of the electric fence and the correct installation of the energisers so that a person who simultaneously touches two or more conductors that are energised by respective energisers will not receive an electric shock from a series of electric pulses from the cross wired energisers which exceeds the prescribed amplitude and frequency.

It is an object of the present invention to provide an electric fence energiser or a method of energising an electric fence that overcomes, or at least ameliorates, one or more of the deficiencies of the prior art mentioned above, or that provides the consumer with a useful or commercial choice.

Other objects and advantages of the present invention will become apparent from the following description, taken in connection with the accompanying drawings, wherein, by way of illustration and example, a preferred embodiment of the present invention is disclosed.

Summary of the Invention According to a first aspect of the present invention there is provided an energiser for energising a plurality of electric fence conductors. The energiser includes a plurality of electrical pulse generators that are each operable to repeatedly generate a respective electrical pulse for energising a respective fence conductor. The energiser also includes a controller for coordinating the operation of the pulse generators such that the generators repeatedly generate a series of pulses with each pulse in the series generated by a respective generator. The energiser is characterised in that each pulse in the series is offset from an immediately succeeding pulse in the series by substantially the duration of the succeeding pulse so that the pulses in the series are unable to be combined to produce a pulse having an amplitude which exceeds a prescribed maximum amplitude. Also, the duration of the series does not exceed a prescribed maximum duration, and the series is repeated at a rate which does not exceed a prescribed maximum rate.

The energiser may also include a detector for detecting whether an electrical pulse generator is cross wired with another generator. The electrical pulse generator may be operable to reduce the amplitude of the pulses generated thereby if it is detected that the generator is cross wired with another generator. The electrical pulse generator may be operable to stop generating pulses if it is detected that the generator is cross wired with another generator. The energiser may raise an alarm if it is detected that the electrical pulse generator is cross wired with another generator.

Preferably, the electrical pulse generators generate pulses in the same sequence for each series of pulses that they generate. Alternatively, the electrical pulse generators may generate pulses in a different sequence for different series of pulses that they generate.

The energiser may also include a monitor for monitoring a load presented to an electrical pulse generator.

According to a second aspect of the present invention there is provided a method of energising a plurality of electric fence conductors. The method includes the step of repeatedly generating a series of electrical pulses by a plurality of electrical pulse generators such that each pulse in the series is generated by a respective generator. The method is characterised in that each pulse in the series is offset from an immediately succeeding pulse in the series by substantially the duration of the succeeding pulse so that the pulses in the series are unable to be combined to produce a pulse having an amplitude which exceeds a prescribed maximum amplitude. Also, the duration of the series does not exceed a prescribed maximum duration, and the series is repeated at a rate which does not exceed a prescribed maximum rate.

The method may include the further step of detecting whether an electrical pulse generator is cross wired with another generator. The method may also include the further step of reducing the amplitude of the pulses generated by the electrical pulse generator if it is detected that the generator is cross wired with another generator. Alternatively, the method may include the further step of stopping the generation of pulses by the electrical pulse generator if it is detected that the generator is cross wired with another generator. The method may include the further step of raising an alarm if it is detected that the generator is cross wired with another generator.

The electrical pulse generators may generate pulses in the same sequence for each series of pulses that they generate. Alternatively, the electrical pulse generators may generate pulses in a different sequence for different series of pulses that they generate.

The method may include the further step of monitoring a load presented to an electrical pulse generator.

Brief Description of the Drawings In order that the invention may be more fully understood and put into practice, a preferred embodiment thereof will now be described with reference to the accompanying drawings, in which: Figure 1 is a block diagram of an electric fence energiser according to the preferred embodiment of the present invention; Figure 2 is a diagram of a four-sided enclosure whose sides are each protected by respective electric fence conductors that are each energised by a respective electrical pulse generator of the energiser illustrated in figure 1; Figure 3 is a schematic circuit diagram of a module which forms part of the energiser illustrated in figure 1; Figure 4 is a flowchart of the operation of the module illustrated in figure 3; Figure 5 is a waveform diagram of a series of electrical pulses that are each generated by a respective electrical pulse generator of the energiser illustrated in figure 1; and Figure 6 is a waveform diagram similar to that illustrated in figure 5 but with one of the electrical pulses emitted from the series.

Detailed Description of the Preferred Embodiment A block diagram of an electric fence energiser 10 according to an embodiment of the present invention is depicted in figure 1. The energiser includes modules 11 to 14 which are linked together by a communications bus The communications bus 15 could for example be a wire bus, an optical bus, or an RF bus. Also, the modules 11 to 14 could be located at a central location or could be located remotely from each other.

Each module 11 to 14 includes an electrical pulse generator that is operable to repeatedly generate a high voltage electrical pulse for energising a Mmmff respective fence conductor of an electric fence. Also, each module 11 to 14 has an output terminal 16 for connecting an end of a fence conductor to the output of the module's electrical pulse generator, an earth terminal 17 for earthing the module, and an input terminal 18 for connecting the other end of the fence conductor to the module.

Each module 11 to 14 may energise a respective section or zone of an electric fence which extends around the perimeter of an enclosure such as the foursided enclosure 19 illustrated in figure 2. Enclosure 19 is divided into four zones that each protect a respective side of the enclosure 19. The fence conductors of different zones are electrically isolated from each other.

A schematic circuit diagram of module 11, which is identical to modules 12 to 14, is illustrated in figure 3. Module 11 includes a micro-controller 20 which is powered by a power supply 21. Power input terminals 22 are provided for connecting the power supply 21 to either an extra low voltage (ELV) AC electricity supply or a DC source of electricity such as a battery.

The electrical pulse generator circuit of module 11 is also powered by the power supply 21. The pulse generator circuit includes a capacitor 23 which is charged to a predetermined voltage through a diode 24 by a charging circuit 25 which is connected to the power supply 21 and the micro-controller 20. A voltage divider circuit comprising resistors 26 and 27 is connected across the capacitor 23 and scales the voltage appearing across the capacitor 23 for input to the micro-controller 20. The primary winding of a step-up output transformer 28 and a silicon-controlled rectifier (SCR) 29 are connected in series across the capacitor 23 such that the anode of the SCR 29 is connected to the primary winding and such that the cathode and gate of the SCR 29 are respectively connected to ground and an output of the micro-controller The micro-controller 20 periodically triggers the SCR 29 so that the charged capacitor 23 is periodically discharged through the primary winding of the transformer 28. Discharging the capacitor 23 through the primary winding of the transformer 28 causes a high voltage output pulse to appear across the secondary winding of the transformer 28. It is this high voltage output pulse which is used to energise a fence conductor. The secondary winding of the transformer 28 is connected across the output terminal 16 and the earth terminal 17 of the module 11.

The input terminal 18 of the module 11 is connected to one of two input pins of an opto isolator 30 via a current-limiting resistor 31. The other input pin of the opto isolator 30 is connected to a reference earth terminal 32 of the module 11.

The two output pins of the opto isolator 30 are respectively connected to an input of the micro-controller 20 and to ground.

The transformer 28 and the opto isolator 30 function as a high voltage isolation barrier between the low voltage circuitry of the module 11 and the fence conductor which is connected to the module 11.

A communications bus terminal 33 is provided for connecting the module 11 to the communications bus 15. The communications bus terminal 33 is connected to a level shifting circuit 34 which is also connected to the micro-controller A control input terminal 35 is connected to the micro-controller 20 so that the module can be turned on or off.

The micro-controller 20 is also connected to an alarm output terminal 36 via relays 37.

Figure 4 is a flowchart of the operation of the micro-controller 20 of each module 11 to 14 of the energiser 10. The operation of a micro-controller 20 of a particular module is dependent upon whether the micro-controller 20 has been configured as a master or a slave controller. The micro-controller 20 of only one of the modules 11 to 14 is configured as a master controller while the micro-controllers of all the other modules are configured as consecutively numbered slave controllers. In particular, the slave controllers are pre-programmed as slave number 1, slave number 2, and slave number 3, respectively.

The modules 11 to 14 are turned on by applying an appropriate signal to their control input terminals 35. After a module is turned on the module's microcontroller 20 ensures that the module's SCR 29 is turned off and controls the module's charging circuit 25 to commence charging the module's capacitor 23.

If the micro-controller 20 of a module has been configured as the master controller, the micro-controller 20 of that module waits approximately one second after being turned on before transmitting a capacitor discharge command to the microcontrollers 20 of the other modules via the communications bus 15. The capacitor discharge command is transmitted just before the master controller triggers the SCR 29 of its module to discharge the module's capacitor 23 through the primary winding of the module's output transformer 28 to produce a high voltage pulse across the secondary winding of the output transformer 28. After the capacitor 23 has been discharged and the discharge current flowing through the primary winding of the transformer 28 decreases below the holding current of the SCR 29, which is the minimum current required to maintain the SCR 29 switched on, the SCR 29 switches off with the result that the current path from the capacitor 23 to ground through the primary winding of the transformer 28 is no longer available to discharge the capacitor 23. The charge/discharge cycle of the module is repeated once the capacitor 23 has been discharged and the SCR 29 switches off so that the pulse generator of the module periodically generates an electrical pulse.

If the micro-controller 20 of a module has been configured as a slave controller, the micro-controller 20 of that module delays discharging the module's capacitor 23 for a predetermined time after receiving the discharge command from the master controller. The length of the delay is a function of the pre-programmed slave number of the micro-controller 20 such that slave controller 1 waits one delay period, slave controller 2 waits two delay periods, and slave controller 3 waits three delay periods before discharging the capacitor 23 of their respective modules. The delay period of a module whose micro-controller 20 is configured as a slave controller is substantially equal to the duration of the pulse which is generated by the pulse generator of the module. The pulse generator of each module 11 to 14 is able to generate a pulse having a duration of approximately 100 microseconds so that the delay period of a module is substantially equal to 100 microseconds.

Prior to discharging their associated capacitors 23 the slave controllers check their associated opto isolators 30 to see if there is a voltage appearing on the fence conductor which their associated pulse generator is supposed to energise. If a voltage is detected then this infers that the fence conductor on which the voltage was detected is cross wired with a pulse generator of another module. This corresponds to an alarm condition and the slave controller of the module which detects the probable cross wire condition responds by not discharging the module's capacitor 23 and by activating the module's relays 37 so that an alarm signal such as a visual or an audible alarm is output by the energiser The master and slave controllers each monitor the loads presented to their respective pulse generators. This is done by measuring the voltage appearing on their associated fence conductors after triggering their associated SCRs 29 to determine if the voltage lies outside of a predetermined limit. If, for example, the voltage on a particular energised fence conductor is less than the limit then this may correspond to current passing from the conductor to earth which would mean that a person or some 1o other load has contacted the energised fence conductor and formed a connection between the conductor and earth. When such a condition is detected by the master controller or a slave controller, the master or slave controller which detects the condition activates the module relays 37 associated therewith so that an alarm signal such as a visual or an audible alarm is output by the energiser The above-described operation of the modules 11 to 14 results in the pulse generators of the modules 11 to 14 repeatedly generating the series of four pulses A, B, C, and D illustrated in figure 5 provided that a cross wire condition is not detected.

Each pulse in the series is generated by a pulse generator of a respective module 11 to 14. For example, if the micro-controller 20 of module 11 is configured as the master controller and the micro-controllers 20 of modules 12 to 14 are respectively configured as slave controllers 1, 2, and 3, pulse A would be generated by the pulse generator of module 11, pulse B would be generated by the pulse generator of module 12, pulse C would be generated by the pulse generator of module 13, and pulse D would be generated by the pulse generator of module 14. Each pulse in the series is offset from an immediately succeeding pulse in the series by substantially the duration of the succeeding pulse so that the pulses in the series cannot be combined to produce a pulse having an amplitude which exceeds a prescribed maximum amplitude. Also, the duration of the series of pulses does not exceed a prescribed maximum duration, and the series of pulses is repeatedly output by the energiser 10 at a rate which does not exceed a prescribed maximum rate. In the preferred embodiment each pulse has a duration of approximately 100 microseconds. Also, the duration of the series is less than the prescribed maximum duration of 10 milliseconds allowed by the Australian Standards and is repeated at a rate of approximately one series per second which is equal to the maximum rate prescribed by the Australian Standards.

Figure 6 illustrates how the series of pulses illustrated in figure 5 is modified in the event that the slave controller which controls the pulse generator responsible for generating pulse C detects a probable cross wire condition with another pulse generator. The slave controller in question does not trigger the SCR 29 of its associated pulse generator so that pulse C, which is illustrated in phantom, is not generated. Also, the slave controller activates the relays 37 associated therewith so that an alarm signal such as a visual or an audible alarm is output by the energiser Pulse C is omitted until the slave controller no longer detects a probable cross wire condition.

The output stages of the module's pulse generators each have an effective impedance. The effective impedance of a module's output stage can absorb some of the electrical energy which is generated by another module when the modules are cross wired together. Thus, if a person forms a cross wire connection between two or more modules by contacting the fence conductors that are energised by the modules, some of the electrical energy which is generated by a module will be absorbed by the effective impedance of the output stage of the other modules rather than by the person.

If a person simultaneously touches fence conductors that are each energised by a respective module of the energiser 10, the person will not receive an electric shock whose magnitude exceeds a prescribed maximum magnitude because the pulses generated by the modules are offset from one another and are unable to be combined to produce a pulse whose amplitude exceeds the prescribed maximum amplitude. Also, even if the person touches fence conductors that are energised by pulses in the series that are not adjacent to each other pulses A and C) so that the person receives a shock from pulse A and a separate shock from pulse C at a rate which exceeds the prescribed maximum rate, the separate shocks will be imperceptible to the person provided that the duration of the pulses and the series are short enough.

The foregoing describes only one embodiment of the present invention 12 and modifications, obvious to those skilled in the art, can be made thereto without departing from the scope of the present invention. For example, the energiser 10 need not include a means for detecting whether any electrical pulse generator is cross wired with another generator. Moreover, if the energiser 10 does include a means for detecting whether an electrical pulse generator of the energiser 10 is cross wired with another generator, the generator may be operable to reduce the amplitude of the pulses it generates by a suitable amount in the event that a cross wire condition is detected instead of stopping the generation of pulses to ensure that the pulses generated by the cross wired generators do not combine to produce a pulse having an amplitude which exceeds the prescribed amplitude. Furthermore, an alarm does not have to be raised in the event of a cross wire condition being detected.

The pulse generators may generate their pulses in the same sequence for each series of pulses that they generate. Alternatively, the electrical pulse generators may generate their pulses in a different sequence for different series of pulses.

The energiser 10 need not include a means for monitoring the load presented to each electrical pulse generator. However, if the energiser 10 does have a means for monitoring the load presented to each electrical pulse generator, the monitoring means could be in the form of a start of fence monitor such as the start of fence monitor disclosed in Australian patent no. 735681. The contents of Australian patent no. 735681 are incorporated herein by reference. Alternatively, the monitoring means could be of the type which monitors the end of a fence conductor which is opposite to the end of the conductor connected directly to the output of the pulse generator.

The energiser 10 may have more or less modules, however the maximum number of modules is limited by the duration of the pulses generated by the pulse generators of the modules and the prescribed maximum duration of the pulse series.

For example, if the prescribed maximum duration of the pulse series is milliseconds and all of the pulse generators generate pulses having a 100 microsecond duration, the maximum number of modules that the energiser can have is one hundred if there is no overlap between the pulses that they generate.

Also, the energiser 10 is not limited to having the described miaster-slave 13 configuration. The energiser 10 could instead have a central controller which controls all of the modules. Alternatively, the energiser 10 could have a distributed controller so that the modules are able to operate independently of each other.

Moreover, one or more of the modules 11 to 14 may have more than one high voltage output.

Claims (15)

1. An energiser for energising a plurality of electric fence conductors, the energiser including a plurality of electrical pulse generators that are each operable to repeatedly generate a respective electrical pulse for energising a respective fence conductor, and a controller for coordinating the operation of the pulse generators such that the generators repeatedly generate a series of pulses with each pulse in the series generated by a respective generator, the energiser being characterised in that each pulse in the series is offset from an immediately succeeding pulse in the series by substantially the duration of the succeeding pulse so that the pulses in the series are unable to be combined to produce a pulse having an amplitude which exceeds a prescribed maximum amplitude, the duration of the series does not exceed a prescribed maximum duration, and the series is repeated at a rate which does not exceed a prescribed maximum rate.

2. The energiser of claim 1 further including a detector for detecting whether an electrical pulse generator is cross wired with another generator.

3. The energiser of claim 2, wherein the electrical pulse generator is operable to reduce the amplitude of the pulses generated thereby if it is detected that the generator is cross wired with another generator.

4. The energiser of claim 2, wherein the electrical pulse generator is operable to stop generating pulses if it is detected that the generator is cross wired with another generator. The energiser of any one of claims 2 to 4, wherein the energiser raises an alarm if it is detected that the electrical pulse generator is cross wired with another generator.

6. The energiser of any one of the preceding claims, wherein the electrical pulse generators generate pulses in the same sequence for each series of pulses that they generate.

7. The energiser of any one of claims 1 to 5, wherein the electrical pulse generators generate pulses in a different sequence for different series of pulses that they generate.

8. The energiser of any one of the preceding claims further including a monitor for monitoring a load presented to an electrical pulse generator.

9. An energiser for energising a plurality of electric fence conductors, the energiser being substantially as herein described with reference to figure 1, 3, 4, 5 and 6 of the accompanying drawings, A method of energising a plurality of electric fence conductors, the method including the step of repeatedly generating a series of electrical pulses by a plurality of electrical pulse generators such that each pulse in the series is generated by a respective generator, the method being characterised in that each pulse in the series is offset from an immediately succeeding pulse in the series by substantially the duration of the succeeding pulse so that the pulses in the series are unable to be combined to produce a pulse having an amplitude which exceeds a prescribed maximum amplitude, the duration of the series does not exceed a prescribed maximum duration, and the series is repeated at a rate which does not exceed a prescribed maximum rate.

11. The method of claim 10 including the further step of detecting whether an electrical pulse generator is cross wired with another generator.

12. The method of claim 11 including the further step of reducing the amplitude of the pulses generated by the electrical pulse generator if it is detected that the generator is cross wired with another generator.

13. The method of claim 11 including the further step of stopping the generation of pulses by the electrical pulse generator if it is detected that the generator is cross wired with another generator.

14. The method of any one of claims 11 to 13 including the further step of raising an alarm if it is detected that the electrical pulse generator is cross wired with another generator. The method of any one of claims 10 to 14, wherein the electrical pulse generators generate pulses in the same sequence for each series of pulses that they generate.

16. The method of any one of claims 10 to 14, wherein the electrical pulse generators generate pulses in a different sequence for different series of pulses that they generate. I __I 16

17. The method of any one of claims 10 to 16, including the further step of monitoring a load presented to an electrical pulse generator.

18. A method of energising a plurality of electric fence conductors, the method being substantially as herein described with reference to the accompanying drawings. DATED this 2 2 d day of April 2004 Pakton Developments Pty Ltd By its Patent Attorneys CULLEN CO.