WO 2015/042661 PCT/AU2014/050246 AN IDLER, A METHOD FOR MONITORING A PLURALITY OF IDLERS, AND A CONVEYOR SYSTEM. Technical field The disclosure herein generally relates to an idler, a conveyor system comprising a plurality of 5 idlers, and a method for monitoring a plurality of idlers, Background Conveyors, including but not limited to conveyor belts, may be used to transport objects and materials, examples of which include but are not limited to bulk materials, packages, agricultural products, people and bags, An example of a conveyor belt generally but not necessarily 10 comprises a belt looped around spaced apart terminal wheels. At least one of the terminal wheels may be powered to circulate the belt. An upper portion of the belt and the material conveyed thereon is generally supported by a plurality of idlers located between the tertninal wheels. The plurality of idlers are free to rotate around their respective axis. Idlers are also known as rollers. Figure 1 shows an idler stand 100 having three prior art idlers 102, 104, 106. The idlers 102, 15 104, 106 are mounted to a frame 108 ready to receive the upper portion of the belt Some conveyors, examples of which may be found at a mine, quarry, or port, may be 100's of meters or kilometres long and may carry many tonnes of excavated bulk material for extended periods of time. Because these conveyor belts may have thousands of idlers the probability of an idler failing is relatively high. Idler failure may result in undesirable consequences including: 20 * delayed delivery of excavated bulk material causing significant financial loss. + damage to the conveyor belt which may be time consuming and costly to repair; - a fire, which may be particularly disastrous if the bulk material (e g. coal) is flammable; and - a safety hazard to nearby people. ?5 One current practice is to regularly measure the temperature of idlers by, for example, using a thermographic camera. The camera may identify hot idlers that have or nearly have failed This may be labour intensive. Because it is difficult to simultaneously monitor the temperature of all of a conveyor belt's idlers by this practice, a failed or nearly failed idler may not be detected before an undesirable consequence occurs. Furthermore, it may be considerably inconvenient 10 and expensive to stop the conveyor and replace an idler that has or nearly has failed. 1 WO 2015/042661 PCT/AU2014/050246 Another practice is early replacement of idlers to reduce the probability of idler failure. Replacement of the idler may be conveniently performed during a conveyor maintenance period that is scheduled during the life of the conveyor. It may be difficult to accurately determine the age of an idler, however, and how much longer it may last. Removing an idler too early may be 5 wasteful. Removing an idler too late, however, may present an unacceptable risk of idler failure and an undesirable consequence Summary Disclosed herein is an idler. The idler comprises a rotor configured to rotate around an axis and comprising an outer bearing surface., The idler comprises an information generator configured to 10 generate idler information comprising information about the idler. In an embodiment, the rotor comprises an idler shell. The idler information may be, for example, indicative of at least one property of the idler. The idler information may be used to detect a failure in the idler. The idler information may indicate that an idler is scheduled for replacement. The idler information may indicate the idler's 15 position in a conveyor, some examples of which may have thousands or hundreds of thousands of idlers. This may make locating an idler difficult, In an embodiment, the idler information comprises rotation information that comprises informati on about the rotation of the rotor around the axis. In an embodiment, the rotation information may comprise rotation number information 20 comprising information about a number of rotations of the rotor around the axis. The number of rotations may be indicative of an effective age of the idler Because the number of rotations is known, the replacement of an idler too early or too late may be avoided, which may result in savings while maintaining the risk of idler failure at an acceptable level. The rotation number information may indicate that the number of rotations of the rotor around the axis satisfies a ?5 number of rotations condition, The number of rotations condition may comprise a condition that the number of rotations one of equals a threshold number of rotations and exceeds the threshold number of rotations. Alternatively or additionally, the rotation number information may indicate the number of rotations of the rotor. In an embodiment, the rotation information may comprise rotational velocity information about a 30 rotational velocity of the rotor. An idler for which the idler information indicates that the rotational velocity is less than expected, for example zero, may have failed. The rotational 2 WO 2015/042661 PCT/AU2014/050246 velocity information may indicate that the rotational velocity of the rotor satisfies a rotational velocity condition, The rotation velocity condition may comprise a condition that the rotational velocity of the rotor is one of equal to and less than a rotational velocity threshold. The rotation velocity condition may comprise that the rotational velocity of the rotor is zero. The rotation 5 velocity condition may comprise that the rotational velocity of the rotor is irregular Alternatively or additionally, the rotational velocity information may indicate that the rotational velocity of the rotor. An embodiment comprises an electrical generator arranged to generate electricity from the rotation of the rotor around the axis. The electricity may be for powering the idler, including for 10 example the information generator, There may be no need to individually wire the idler for power. The electricity when so generated may be periodic. The information generator may be in electrical communication with the electrical generator. The information generator may be configured to analyse the electricity for the generation of the rotation information. The information generator may comprise an electricity analyser configured to analyse the electricity 15 for the generation of the rotation information, The information generator may be configured to detect at least one of a plurality of power peaks in the electricity and a plurality of zero power crossings in the electricity for generation of the rotation information. Alternatively or additionally, the information generator is configured to generate sample information by temporally sampling the electricity and using the sample information to compute at least one of ?0 the plurality of power peaks in the electricity and the plurality of zero power crossings in the electricity. An embodiment comprises a stator, In the context of this document, the stator is a stationary part of the idler, The stator may comprise a shaft The electrical generator may comprise a magnet and electrical circuitry. The electrical circuitry may comprise at least one wire coil The 25 electrical circuitry may comprise generator electronics. One of the magnet and the electrical circuitry may be attached to the rotor and the other of the magnet and the electrical circuitry may be attached to the stator, The magnet and the electrical circuitry may be cooperatively arranged to generate the electricity within the electrical circuitry when the rotor rotates around the axis. An embodiment comprises a circuit board disposed around the stator and comprising the 30 electrical circuitry, The circuit board may be a toroidal circuit board. The circuit board may be disposed within an enclosure comprising the magnet. The circuit board may be fixed to the rotor. The enclosure may comprise a magnetic circuit having the at least one magnet. The magnetic 3 WO 2015/042661 PCT/AU2014/050246 circuit may be configured to concentrate the at least one magnet's magnetic field within the electrical circuitry. An embodiment comprises a power storage device in electrical communication with the electrical generator for storing the electricity. The power storage device may comprise a 5 capacitor. A capacitor may not suffer from the limited operational temperature range and limited life span of a battery, for example. A capacitor may be used in an idler operable safely at an elevated temperature for years, Power may be drawn from the capacitor after the rotor has ceased rotating. A capacitor may not suffer from the limited operational temperature range and limited life span of a battery, for example. Power may be drawn from the capacitor after the rotor 10 has ceased rotating. The rotation information, however, may be generated by any suitable alternative. For example, an embodiment comprises at least one of a hall effect sensor, optical encoder, a proximity switch, a contact switch, a rotary potentiometer and a rotary variable differential transformer in communication with the information generator for the generation of the rotation information. [S In an embodiment, the idler information comprises temperature information about a temperature. The temperature may be that of an idler component. The temperature information may indicate that the temperature satisfies a temperature condition. The temperature condition may comprise a condition that the temperature at least one of equals and exceeds a threshold temperature. The temperature condition may comprise a condition that that temperature one of equals and exceeds 20 the threshold temperature for period that one of equals and exceeds a period value. additionally or alternatively, the temperature information is indicative of the temperature. The temperature may be an average of a plurality of temporally spaced apart temperature measurements. A temperature sensor may be in communication with the information generator. The temperature sensor may be in thermal communication with an idler bearing. The temperature sensor may be 25 disposed within an idler bearing aperture. The temperature sensor may be in thermal communication with the idler shell. An embodiment comprises the temperature sensor. In an embodiment, the idler information indicative of information about the idler comprises idler vibration information about a vibration generated by the idler. The idler vibration information 30 may indicate that the idler vibration satisfies a vibration condition. The vibration condition may comprise a condition that a characteristic of the vibration at least one of equals and exceeds a 4 WO 2015/042661 PCT/AU2014/050246 vibration characteristic value. The vibration condition may comprise a condition that the vibration comprises at least one frequency component characteristic of a defective idler. An embodiment comprises a vibration sensor configured to generate a vibration signal. The information generator may have a frequency filter selected to pass a frequency component of the 5 vibration signal characteristic of a defective idler. The frequency filter may comprise a bandpass filter. The vibration sensor may comprise a microphone. Additionally or alternatively, the vibration sensor comprises at least one of an accelerometer, a displacement sensor, and a piezoelectric vibration sensor. An embodiment comprises memory in communication with the information generator. The 10 memory may have idler identification information. The idler information indicative of information about the idler may comprise the idler identification information. The memory may have a location information indicative of the location of the idler. This may simplify and automate idler identification, especially in systems that may have thousands of idlers, An embodiment comprises a Radio Frequency identification (RFID) device. The RFID device [S may comprise the memory or another memory. The RFID device may be configured for the memory or the other memory to be written by a RFID scanner, The RFID device may be configured for the memory to be read by the RFID scanner. Idlers may be easily identified using the RFID scanner. An embodiment comprises a radio transmitter in communication with the information generator 2 The radio transmitter may be arranged to send a radio signal carrying the idler information. An embodiment comprises a network interface configured to send the idler information via a network. The acquisition of the idler information may be automated, and may reduce or eliminate the need for a technician to individually inspect each idler of a conveyor. The network interface may be configured to send a radio signal carrying the idler information via a radio 25 network. There may be no need to individually wire the idler for communications. The network interface may comprise a radio network interface configured to cooperate with a plurality of radio network interfaces of a plurality of idlers to form at least part of the radio network. The network interface may comprise a radio network interface configured to cooperate with the plurality of radio network interfaces of a plurality of idlers and a network gateway to form the 30 radio network, The radio network may comprise a radio mesh network. The radio network interface may comprise a radio mesh network interface. 5 WO 2015/042661 PCT/AU2014/050246 In an embodiment, the idler may have a mode of operation in which the idler information is sent only when an idler information condition is satisfied. Idler information conditions may comprise at least one of the number of rotations condition, the rotation velocity condition, the temperature condition, and the vibration condition, for example. The mode of operation may be the only 5 mode, or it may be one of several modes. The sending of the idler information may be initiated by the idler on confirmation that the idler information condition is satisfied. The idler information may, consequently, be sent only when needed. This may decrease power requirements and radio network load compared to another embodiment in which the idler periodically sends idler information, irrespective of whether an idler information condition is 10 satisfied or not. An embodiment comprises an external aerial. A rotary bearing may be coupled to the shaft and coupled to the rotor. The shaft may be configured to form a passageway between the shaft and the bearing, the rotor comprises an idler shell impenetrable by the radio signal, and an external 15 aerial is in communication with an aerial lead that passes through the passage. The shaft may have a slotted portion defining a slot. The rotary bearing may be mounted on the slotted portion. The aerial lead may be disposed in the slot. The temperature sensor may be disposed in the slot. The slot may comprise a longitudinal slot. The idler shell may be impermeable to the radio signal. ?0 The sensors may be used to detect an impending idler failure. As described, the parameters monitored by the sensors may include the temperature of the idler's bearings, the vibration generated by the rotor, , vibration frequency levels, the number of rotations and the rotational velocity of the idler. By using this information, a system in communication with the idler may be able to detect or predict forthcoming idler failure. Further, by independently monitoring the 25 temperate of each bearing within the idler and / or the idler shell, the system may be able to more accurately detect increases in temperature with a lower cost, Disclosed herein is an idler. The idler comprises a shaft on which is mounted a rotary bearing coupled to an idler shell The idler comprises an information generator disposed within an interior of the idler shell and configured to generate idler information comprising information 30 about the idler. The idler comprises a radio transmitter in communication with the information generator for sending a radio signal carrying the idler information, and comprising an external aerial in communication with an aerial lead that passes from within the interior of the idler shell to an exterior of the idler shell via a passageway located between the shaft and the rotary bearing. 6 WO 2015/042661 PCT/AU2014/050246 An embodiment comprises a temperature sensor in communication with the information generator and disposed within the passageway. The temperature sensor may be in thermal communication with a bearing. A seal may be disposed in the passageway. Disclosed herein is a conveyor system. The conveyor system comprises a plurality of idlers in 5 accordance with the above disclosure. The plurality of idlers comprises a plurality of network interfaces configured to cooperate to form at least part of a radio network for communication of idler information sent by the plurality of idlers. In an embodiment, the radio network comprises a radio mesh network. In an embodiment, the plurality of network interfaces are configured to cooperate with each 10 other and a network gateway to form the radio network for communication of the idler information. An embodiment comprises a processing system. configured to receive idler information sent by one of the plurality of idlers and in response present on an electronic display the identify of the one of the plurality of idlers that sent the idler information. The idler information may comprise idler location information and the processing system may be [S configured to present on the electronic display the location of one of the plurality of idlers that sent the idler information, The location information may be stored in a RFID device of the one of the plurality of idlers that send the idler information. Disclosed herein is a method for monitoring a plurality of idlers The method comprises the step of forming at least part of a radio network with a plurality of network interfaces of the plurality 20 of idlers. The method comprises the step of one of the plurality of idlers sending idler information via the radio network. Each of the plurality of idlers is in accordance with the above disclosure, The radio network may comprise a radio mesh network. An embodiment comprises the step of forming the radio network with the plurality of network ?5 interfaces of the plurality of idlers and a network gateway The plurality of idlers may act as repeaters allowing the gateway to communicate with those of the plurality of idlers that are outside of a gateway radio range. The gateway may be a network master and may be arranged to poll each of the plurality of idlers to obtain idler information from each of the plurality of idlers. The radio network may be automatically configured and structured by a process initiated at the 10 gateway, for example by pressing a button on the gateway or the processor, The gateway may automatically maintain the structure of the radio network to optimise the quality of the radio 7 WO 2015/042661 PCT/AU2014/050246 network. The network may automatically use an alternate route in the event that one of the plurality of idlers fail, or a low quality radio link quality is detected. An embodiment comprises the step of a processor receiving the idler information sent by the one of the plurality of processors. The identity of the one of the plurality of idlers that sent the idler 5 information may be displayed on an electronic display. The processor may be arranged to present human interpretable information generated from the idler information. For example, a visual or audible message may be generated by the processor when an idler has failed or is expected to fail. In an embodiment, the idler information comprises idler location information and the method 10 comprises the step of providing the location of the one of the plurality of idlers. The plurality of idlers may be in accordance with the above disclosure. Any of the various features of each of the above disclosures, and of the various features of the embodiments described below, can be combined as suitable and desired. Brief description of the figures 15 Embodiments will now be described by way of example only with reference to the accompanying figures in which: Figure 2 shows an embodiment of an idler. Figure 3 shows a schematic diagram of on information generator of the idler of figure 2. Figure 4 shows part of an example of a conveyor system. 20 Figure 5 shows a schematic diagram of a radio network Figure 6 shows a flow diagram 46 of an embodiment of a method for monitoring the plurality of idlers Figure 7 shows an exploded view of an embodiment of an idler monitoring module of the idler of figure 2. ?5 Figure 8 shows a cross-section through the idler of figure 2. Figure 9 shows a view of a shaft of the idler of figure 2. Figure 10 shows a block diagram of a vibration detection system of the idler of figure 2. Figure II shows a diagram of RED communications with the idler of figure 2. Figure 12 shows an a diagram of an embodiment of the gateway used with the idler of 10 figure 2. Figure 13 shows a schematic block diagram of the gateway 40 of figure 12. 8 WO 2015/042661 PCT/AU2014/050246 Description of embodiments Figure 2 shows an embodiment of an idler, the idler being generally indicated by the numeral 10. The idler 10 has a rotor 12 configured to rotate around an axis 14, The rotor 12 has an outer bearing surface 1.5 that is shown transparently in figure 2.The idler 10 has an information 5 generator 20, a schematic diagram of which is shown in figure 3. The information generator 20 is configured to generate idler information comprising information about the idler. The idler information may, for example, comprise information that may be used to determine if the idler is defective, requires attention or inspection. 1.0 The information generator 20 is housed within a housing 22 of an idler monitoring module 24 disposed within the idler. In an alternative embodiment, however, the information generator may not be housed in an idler monitoring module 24. The outer bearing surface 15d is an outer surface of an idler shell 16 that is a part of the rotor 12. The inner diameter of the shell is substantially the same as the outer diameter of the idler monitoring module 24, so that there is a 15 friction or interference fit between them. An adhesive may be applied to the outer diameter of the idler monitoring module before being inserted into the shell to ensure attachment therebetween. In the present embodiment, the idler shell 16 comprises a steel cylinder. In alternative embodiments, however, the idler shells 16 may comprise a polymer in the form of, for example, high density polyethylene, nylon, or generally any suitable polymer. The idler shell ?0 16 may be generally form of any suitable material. The idler 10 has a shaft 86 centred on the axis 14 and on opposite ends of which are mounted rotary bearings 88, 89 (best viewed in figure 8), The rotary bearings 88, 89 couple the rotor 12 to the shaft 88. The idler 10 has a radio transmitter 39 in communication with the information generator 20 and 25 is arranged to transmit a radio signal carrying the idler information. The idler information may be received at a remote processor, for example, at which the idler information may be presented to a user or used to activate user alerts. Figure 4 shows part of an example of a conveyor system 26. The conveyor system 26 has a 30 plurality of idlers of which the idlers indicated by numerals 28, 30, and 32 are representative. The idlers 28, 30, 32 are the same as idler 10, in this but not all embodiments. The outer bearing surface of the plurality of idlers 28, 30, 32 in this but not all embodiments support a belt 34 of the conveyor system Figure 5 shows a schematic diagram of a radio network 36 in the form of a radio mesh network formed at least in part by the cooperation of the plurality of network 9 WO 2015/042661 PCT/AU2014/050246 interfaces 38 of the plurality of idlers 28, 30, 32, In alternative embodiments, the radio network may a WiFi radio network. Ahernatively a cabled Ethernet network may be used, or generally any suitable network. The network interfaces 38 are configured to send the radio signal carrying the idler information via the radio mesh network, using the radio transmitter 39. The plurality of 5 network interfaces 38, in this but not necessarily in all embodiments, cooperate with each other and a network gateway 40 from the radio mesh network. The conveyor system 26 has a processing system 42 in the form of an industrial computer in communication with the network gateway 40. The processing system 42 is configured to receive idler information sent by one of the plurality of idlers. In response to receiving the idler information, the processing system 42 10 may present on an electronic display 44 the identity of the one of the plurality of idlers that sent the idler information. In this but not necessarily in all embodiments, the idler information also comprises idler location information, The processing system is configured in this embodiment, to present on the electronic display 44 the location of the one of the plurality of idlers that sent the idler information. 15 Figure 6 shows a flow diagram 46 of an embodiment of a method for monitoring the plurally of idlers 28, 30, 32 that may be executed by the conveyor system 26. The method comprises the step 48 of forming at least part of the radio mesh network 36 with the plurality of network interfaces 38 of the plurality of idlers. The method comprises the step 50 of one of the plurality 20 of idlers send idler information via the radio mesh network 36, In this but not in all embodiments, the method comprises forming the radio mesh network with the plurality of network interfaces 38 of the plurality of idlers 28, 30, 32 and a network gateway 40. In this but not all embodiments, the method comprises the step of the processor 42 receiving the idler information sent by the one of the plurality of idlers 28, 30, 32, and displaying on an electronic 25 display the identity of the one of the plurality of idlers that sent the idler information. The idler information may generally comprise any information about the idler that generated it. In this but not necessarily all embodiments, the idler information generated by the information generator 20 comprises rotation information that comprises information about the rotation of the 10 rotor 12 around the axis 14, In this embodiment, the rotation information comprises rotation number information comprising information about the number of rotations of the rotor 12 around the axis 14. For example, the information generator may determine if the number of rotations of the rotor 12 around the axis 14 satisfies a number of rotations condition. For example, some idlers are be known to the significantly more likely to 'fail after a threshold number, say 1 15 million, of rotations. If the number of rotations equals or exceeds the threshold number of 10 WO 2015/042661 PCT/AU2014/050246 rotations, then the rotation number information indicates that the number of rotations has exceeded the threshold number of rotations. This is an example of an alarm generated by the idler. Additionally or alternatively, the rotation information indicates the number of rotations of the rotor. The number of rotations of the rotor 12 may be communicated to the processor 42 5 either directly or via the gateway 40, which may then store the number of rotations in an idler database, for example. The processor 42 may determine if the necessary conditions are meet for an alert and subsequently may display on the electronic display 44 an alert when the number of rotations of an idler exceeds the threshold number of rotations, The rotation information may also be used to determine the amount of available power to the idler 10. 10 The rotation information, in this but not all embodiments, comprises rotational velocity information about a rotational velocity of the rotor 12. For example, the rotational velocity information in this embodiment indicates that the rotational velocity satisfies a rotational velocity condition, which in this embodiment is that the rotational velocity of the rotor 12 is 15 equal to or less than a rotational velocity threshold, This is another example of alarm generated by the idler. An idler that has failed or failing may have a very low rotational velocity or even a zero rotational velocity. The rotational velocity condition may be that the rotational velocity of the rotor 12 is irregular, which may indicate a failed or failing idler, The rotational velocity may be periodically determined by the information generator and monitored for changes in the 20 rotational velocity. Alternatively or additionally, the rotational velocity information may indicate the rotational velocity of the rotor 12. Using the rotational velocity information indicating the rotational velocity of the rotor 12, the processor 42 may determine if a condition for an alert The processor 42 may display on the electronic display 44 an alert when the velocity of an idler is not what is expected, for example if the rotational velocity is equal to or less than a rotational 25 velocity threshold or the rotational velocity is irregular. The rotations of the rotor 12 may be determined by any suitable rotation monitor 124. For example, the idler may comprise at least one of a hall effect sensor, an optical encoder, a proximity switch, a contact switch, a rotary potentiometer and a rotary variable differential 10 transformer, in communication with the information generator 20 for the generation of the rotation information. In the present embodiment the idler comprises an electrical generator 25 arranged to generate electicity from the rotation of the rotor 12 around the axis 14 The electricity when so generated 15 by a normal idler is periodic, and the information generator 20, which is in electrical 11 WO 2015/042661 PCT/AU2014/050246 communication with the electrical generator, is configured to analyse the electricity for the generation of the rotation information. The information generator 20 has a control circuit in the form of a microprocessor. The 5 microprocessor has an electricity analyser 23 configured to analyse the electricity for the generation of the rotation information, In the present but not all embodiments, the electricity analyser is defined by program instructions executed by the microprocessor. The electricity analyser is, in this embodiment, configured to detect at least one of a plurality of power peaks in the electricity and a plurality of zero power crossings in the electricity. Alternatively, the 10 information generator may be configured to generate sample information by temporarily sampling the electricity and using the sampled information to compute a least one of the plurality of power peaks in the electricity and the plurality of zero power crossings in the electricity, A comparator may be used and the information generator may count the number of state changes of the comparator output. The information generator has a clock 129, which may be used to 15 determine the rotation period and subsequently the rotational velocity, The idler 10 may have a power storage device in electrical communication with the electrical generator for storing the electricity. Consequently, the idler may still transmit idler information for a period after the rotor 12 ceases to rotate. The power storage device may be, for example, a 20 capacitor or a battery. Figures 7 shows an exploded view of the idler monitoring module 24 with a first half 200 of the housing 22 separated from a second half 202 of the housing 22. The idler monitoring module 24 has magnets 116, printed circuit board (PCB) 118 having electrical circuitry including a coil 115 25 and the information generator 20 (on the far side of the PCB). The circuit board 118 is a toroidal circuit board. The magnets 116 are affixed to metal brackets 113. The magnets 116 are arranged on the metal brackets 113 in alternating polarity so that a closed magnetic loop of attracting opposite poles are formed when the housing 22 is assenibled. The metal brackets 113 and the magnets 116 form a closed magnetic path that concentrates the magnetic field travelling across 10 the air gap between each half of the housing 22. The housing 23 is affixed to an inside rotor wall 183 and rotates with the rotor 22. The coil 115 is wound onto a former 117 which are fixed to the PCB 118. The PCB 118 is located within the housing 22 and is attached to an idler shaft 86 by at least one adjustable foot 15 87, Generally any suitable form of attachment - for example a friction fit may be used. 12 WO 2015/042661 PCT/AU2014/050246 Accordingly, the coils 115 and the PCB 118 do not rotate with the rotor and housing 22 but remain stationary with the idler shaft 86 As the housing 22 rotates, the coils 115 pass through the middle of the magnetic fields formed between the opposing magnets 116 and a voltage is generated on each coil. The coils 115 are wired in series on the PCB 118 and in polarity so that 5 their voltages add. The cumulative generated voltage is rectified by the idler power supply 126 and used to power the circuitry. A temperature of the idler 10 may be monitored to detect beating failure, For example, the idler may determine when the magnitude of the temperatures exceeds programmable thresholds. 10 The idler information may comprise temperature information about the temperature. The temperature may be that of the shaft 86 or bearing 88, the idler shell 16, or another part for example. Figure 8 shows a cross-section through the idler 10. The temperature sensor 121 is in communication with the information generator 20 via a temperature sensor lead 200. The 15 temperature sensor 121 is disposed within an idler bearing aperture 202 and is in thermal communication with an idler bearing 88. Figure 9 shows the shaft 86. The shaft 86 is configured to form a passageway between the shaft 86 and the bearing 88. The shaft has a slotted portion 204 at one end thereof defining the slot 206 in which the temperature sensor is disposed (there is another temperature sensor in slot 210), The rotary bearing 88 is mounted on the slotted portion 20 206. Disposed in the slot is a seal 220 in the form of a resilient boot, for example a rubber or silicon boot. The seal 220 may prevent moisture and dust, for example, entering the idler which may degrade performance. In embodiments where the temperature information is that of the shell, a temperature sensing 25 may be attached to the housing 22. The temperature sensor 121 converts temperature produced by the Idler bearings to an electrical signals, which is processed by analogue and/or digital electronics within the idler. This embodiment has a negative temperature coefficient (NTC), however, a thermocouple, for 10 example, may be used, but is more expensive and is more complex to implement, The information generator 20 is in this but not necessarily in all embodiments configured to average a plurality of temporally spaced apart temperature measurements. The information generator 20 may include in the idler information temperature information derived using the 15 temperature sensor 121, for example the temporally averaged temperature measurements. The 13 WO 2015/042661 PCT/AU2014/050246 information generator 20 is configured to test if the temperature satisfies a temperature condition, and if so include in the idler information temperature information indicating that the temperature satisfies the temperature condition, For example, the temperature condition may be that the temperature at least one of equals and exceeds a threshold temperature. A failed or 5 failing bearing may have an elevated temperature, Alternatively or additionally, the idler information may be indicative of the temperature. In an alternative embodiment, the temperature sensor 121 is clamped to the shaft 86, or is on the circuit board. The close proximity of the sensors to each bearing may allows the temperature of each bearing to be measured accurately and within a short time period (low thermal mass). 10 Being of steel, the idler shell 16 is impenetrable by radio signals. The idler has an external aerial 214. The shaft 86 has another slotted portion 208 at another end thereof defining another longitudinal slot 210. Another rotary bearing 89 is mounted on the other slotted portion 208. The slotted portion to defines another passageway 218 located between the shaft 86 and the rotary 15 bearing 89. The external aerial 214 of the idler is in communication with an aerial lead 216 that passes through the passage 218 from within the interior of the idler 10 to the exterior of the idler1 0 The aerial lead 16 is in communication with a digital radio comprising a radio transmitter which forms part of the network interface 38 Disposed in the other slot 210 is a seal 220 in. the forrm of a resilient boot, for example a rubber or silicon boot. Another temperature 20 sensor may also be disposed in the slot 2land within the aperture of the other bearing 89, The vibrations emitted by the bearings within the Idler are monitored to detect bearing failure. Vibrational energy within specific frequency bands are measured. It is determined when the audio energy in these bands exceeds programmable thresholds, When thresholds are exceeded an 25 alarm may be generated. The idler 10 has two vibration sensors 122 and 123 to detect vibrations generated by the idler 10. The vibration sensors convert detected vibrations into electrical signals that are processed in the information generator. Figure 10 shows a block diagram of a vibration detection system of the 10 idler 10. Vibration sensor 122 is arranged to detect vibrations transmitted through the idler 10. In the present embodiment, vibration sensor 122 is a 3-Axis MEMs digital accelerometer which may have low cost and good receiver sensitivity. Vibration sensor 122 may alternatively be, for example, another type of accelerometer, a MEMS device, a displacement sensor, and piezoelectric vibration sensor, or a combination of these. Vibration sensor 123 is configured to 15 detect vibrations transmitted through the air, and is in the form of a microphone. An omni 14 WO 2015/042661 PCT/AU2014/050246 directional Electret condenser microphone is used in the present embodiment due to its low cost, good receiver sensitivity and directionality characteristics, However, the following example microphone technologies may also be used. MEMs; and Boom, Electret Condenser, Magnetic, and Piezoelectric, for example. 5 The vibration sensors 122 and 123 are mounted, in this but not all embodiments, on the PCB 118, located within the idler monitoring module 24 near the middle of the shaft. This allows the sensors to be PCB mounted, which is more convenient than using flying leads. By placing the vibration sensors 122, 123 at the middle of the Idler, that are able to detect left and right bearings 10 equally The PCB 118 is, in this embodiment, potted to protect it from dust, moisture, and the effects of vibration. Accordingly, the microphone will either protrude from the potting mixture or be located within an aperture in the housing 22, so that it is not immersed by the potting mixture. A 15 water proof microphone may be used or alternatively, the microphone may be protected by a thin resilient boot in the form a of silicon rubber boot that allows sound to pass through but not moisture or dust. Alternate locations may include placing microphones directly under each bearing within the slot 206, 210 in the shaft 86. 20 The information generator 20 is in communication with vibration sensors 122 and 123 and receives a first vibration signal from vibration sensor 122 and a second vibration signal from vibration sensor 123. The first and second vibration signals are processed by the information generator 20. The idler information comprises idler vibration information about a vibration generated by the idler, the vibration information being generated by the processing the first and 25 second vibration signals. The idler vibration information may indicate that the idler satisfies a vibration condition. In this but not necessarily in all embodiments, the vibration condition comprises a condition that a characteristic of the vibration at least one of equals and exceeds vibration characteristic value. 10 Figure 10 shows a block diagram of a vibration detection module of information generator (the vibration sensor 122,123 external of the information generator is shown in dashing). For example, the magnitude of the vibration may exceed a vibration threshold. Defective idlers are known to generate characteristic vibration frequencies. The vibration condition may comprise a condition that the vibration comprises at least one frequency component characteristic of a 15 defective idler (or bearing), thus indicating that the idler is likely to be effective. The information 15 WO 2015/042661 PCT/AU2014/050246 generator may have a frequency filter, for example, selected to pass the frequency component of the vibration signal characteristic of a defective idler (or bearing), The bandpass filter may suppress general noise so that the alert is preferentially triggered by sounds that relate to the failure mode frequencies of the bearings/idler. The frequencies of the bandpass filter and other 5 filter characteristics may be modified to suit the specific failure mode frequencies for the different idler/bearing being monitored. The filter is in this but not all embodiments a hardware implemented filter, for example one of a 2nd order active operation amp] ifier bandpass filter, a low pass active operational amplifier bandpass filter, a high pass active operational amplifier bandpass filter, and an inductor-capacitor (LC) passive bandpass filter. The filter may be a finite 10 impulse response (FIR) filter, an infinite impulse response (11R) filter. A fast Fourier transform (FFT) technique may be used. A software implementation of the Bandpass filter may be modifiable to the failure mode frequencies of different idler bearing manufacturers. However, a software implementation may be more power intensive in comparison to the hardware based solution. 15 A peak detector 153 extracts the magnitude of energy of the bearing failure mode frequencies extracted by the bandpass filter 15 1. In this embodiment, the implementation is a hardware peak detector, in the form of an active precision rectifier followed by a low pass filter. This implementation may be cost effective, may be easy to implement and may provides low power 20 characteristics. The peak detector may alternatively be implemented in software in the following methods: Correlation Filter; and Standard Deviation and Variance Statistical Algorithms, for example. 25 A decision algorithm 155 processes the output of the peak detector to determine if the peak exceeds a peak threshold value. A software implementation of the peak detector may be modifiable so that it accommodates the failure mode frequencies of different idler bearing manufacturers. However, it may be more 30 power intensive in comparison to the hardware based solution, The magnitude of energy from the peak detector 1.53 is compared to a threshold. If the threshold exceeds a set level for a configured period of time, an alarm will be triggered. 16 WO 2015/042661 PCT/AU2014/050246 The idler 10 has memory 128 in communication with the information generator 20. The memory has idler identification information, For example, the idler identification information may comprise a series of characters or bits that may constitute a serial number. The information generator 20 may retrieve from memory 128 the idler identification information and include it in 5 the idler information. Consequently, when idler information is sent indicating that an idler may be faulty the idler can be identified, In this that not all embodiments, a memory also has idler location information indicative of the location of the idler. In this embodiment, the idler location information is indicative of the location of the idler on the conveyor 26, 10 The memory 128 is in this but not necessarily all embodiments incorporated in a radio frequency identification (RFD) device comprising the memory 128, Figure 11 shows a diagram of RFID communications with the idler. The RFiD device 127 is configured for the memory to be written and read by a RFID scanner. For example, the manufacturer may write the idler identification information into the memory 128 as a manufacturing step. Information that the manufacturer 15 may write include: part number; software version; manufacture date, and batch identification. In another example, a worker installing the idler 10 may write the location of the idler into the idler memory 128 using the RFID scanner. Information that workers may write into or read from the RFID may include; conveyor identification; idler frame identification; Idler frame 20 position identification; installation date; installers name; site information; and other general text information. The idler 10 has a RFID aerial 214 that in this embodiment is in the form of an external RFID aerial, The signal from an internal RFID aerial may be impeded by the idler shell 16 which 25 comprises metal. Embodiments of the idler 10 with a radio transparent shell, for example a polymer shell, may have an internal RFID aerial mounted to the PCB 118, for example. The RFID device 127 is in the form of a dual RFID EEPROM (referred to as a "Dual RFID"). The Dual RFID is a memory that emulates a passive RFID tag and which can be read or written 10 to by an RFID scanner (i e, a hand held device). Since the Dual RFID is a passive memory it can powered directly from the RFID scanner and programmed whilst the idler is stationary (i e, not generating power). The Dual RFID memory 128 is also connected to the information generator 20. The Information 15 generator is able to read the memory when the rotor is rotating (i.e. generating power). The Dual 17 WO 2015/042661 PCT/AU2014/050246 RFID allows the manufacturer to conveniently tag and identify an idler without needing to power up the Smart-Idler (i e. rotating the idler). The Dual RFID allows the installers to conveniently tag, identify and configure a Smart-Idler without needing the conveyor to be running. This may improve safety as attempting to configure Idlers whilst a conveyor is operational, is a safety 5 hazard for installation personnel The Dual RFID integrated circuit 127 is located on the PCB 118. Accordingly, the Dual RFID is stationary with respect to the rotating idler shell which facilitates routing of the RFID antenna. The RFID loop antenna is accessible via the outside the idler near an end cap 230. 10 The loop antenna is over moulded with rubber or plastic so that it is durable and protected from the elements. The over mould also encapsulates wires connecting the external antenna to the RFID EPPOM integrated circuit. The over mould passes under the bearing via a slot in the shaft. 15 Alternatively, rather than using the radio network to relay data entered via RFID, it is possible to use the RFID scanner to pass configuration information to the Gateway. In this case, the RFID scanner keeps a copy of configuration data in a database within the scanner, which is subsequently transferred from the RFID scanner to the Gateway either by a direct connection or via an interconnected processor. This method may require the operator to transfer the database 20 file to the gateway, so may be more manual and prone to human error. However, in this case, a Dual RFID EEPROM is not required and simple passive tag attached or embedded within the idler 10 may be used. A simple passive tag is less expensive from a parts cost perspective that a Dual RFID EEPROM. For this method to work it is necessary that the unique identification information contained within the passive tag to be associated with a unique radio address within 25 the idler memory 128 (which is in this embodiments not associated with RFID 127). This can be achieved by programming the memory 128 with the tag identification information during manufacture and using this tag identification as a radio ID. Alternatively, it is also possible to store a radio identification within the passive tag In either case a number that represents the radio identification may be read from the tag. 10 The radio identification may be read by the installer using the RFID scanner during installation. This radio identification and along with location infoination (e.g. conveyor identification information, idler frame identification information and location-on-idler-frame identification information) are transferred via the RFID scanner to the gateway 40. The gateway 40 in turn 18 WO 2015/042661 PCT/AU2014/050246 uses the radio address to program each idler processor with its location information which in turn is used to generate a logical network address. Figure 12 shows an a diagram of an embodiment of the gateway 40. Figure 13 shows a 5 schematic block diagram of the gateway 40 of figure 12. The gateway 40 has a circuit board (not shown) mounted within a DIN rail mountable enclosure 131. The circuit board incorporates a digital radio 141 of a radio mesh network interface, controller 144, memory 143, user interface 142, communications interface 145, and power supply 146. The gateway power supply 146 accepts DC power generated from an external mains supply (not shown) and generates voltage 10 rails suitable for powering the gateway circuits, The memory 143 is used to store network configuration parameters, data received from the idler monitoring module and other system information. The memory may be battery backed so that its content are preserved during system power failures. The user interface 144 consists of various indicators 132 and a push button 133. The indicators 132 are used to communicate the gateway's communications and operating status. 15 A button 133 is used to initiate automatic discovery and configuration of the radio mesh network. Alternatively, the gateway may be in the form of a gateway peripheral of a computer. In the illustrated embodiment the gateway 40 acts as the radio network master and manages the radio network configuration. In this embodiment, the network is a ZIGBEE network having a 20 frequency of 2.4 GHz, although generally any suitable network may be used, for example WI-Fl or a proprietary network standard. The gateway has a ZIGBEE master module, and the network interface 38 of the idler 10 may be a ZIGBEE module. The network 3- forms a structure with the gateway 40 as the root. The idler monitoring modules may act as repeaters along each link of the network allowing the gateway 40 to communicate with idler monitoring modules that are outside 25 its radio range. The radio network is automatically configured and structured by pressing a button 133 on the gateway 40 or at the processor 42. The gateway 40 automatically maintains the network structure in such a way as to control the quality of the radio links in the network The network may exhibit self-healing properties and automatically uses alternate routes in the event that an idler failure or a low radio link quality due to high bit error rates or low radio signal 30 strength. In the present embodiment, the idler 10 has a mode of operation in which the idler information is sent only when an idler information condition is satisfied. The sending of the idler information may be initiated by the idler on confirmation that the idler information condition is satisfied, 15 The idler information may, consequently, be sent only when needed, decreasing power 19 WO 2015/042661 PCT/AU2014/050246 requirements and radio mesh network load, Idler information conditions may include at least one of the number of rotations condition, the rotation velocity condition, the temperature condition, and the vibration condition. 5 In the present but not all embodiments, the gateway 40 poles the idlers for the idler information via the network, The idler 10 has another mode in which it sends the idler information when poled. While in the present embodiment the gateway sends the idler information to the processor 40 for processing, in an alternative embodiment the gateway 40 may process the idler information to determine if sensor readings have violated programmed thresholds. Thresholds 10 include minimum and maximum values, or minimum or maximum rates of change. When a threshold is violated a logical alarm condition is generated. The gateway 40 also maintains statistics on each idler, including its serial number, network address, age, operating hours, number of rotations, the number of alarm events, and radio link 15 quality. The gateway 40 may be in communication with processor 42 via communications interface 45. It also accepts configuration commands from the processor 40. The processor 42 is used to display data obtained from the gateway 40 and to configure the system. In other embodiments, The 20 generation of alarm conditions, and the managing of statistics may be performed in the processor, or an external PLC (not shown) for example. The communications interface 145 of the gateway 40 includes any one or a combination of RS485, RS422, RS-232, ModBus, USB and Ethernet interfaces In this embodiment, the gateway 25 is in communication with the processor 42 by a MODBUS interface The processor has PLC emulation software for communicating with gateway 40 and has Supervisory Control and Data Acquisition (SCADA) software for acquiring information about the status of the idlers which are remote from the processor. Alternatively, the processor may be a hardware implementation of SCADA, for example a programmable logic controller (PLC) implementation. 10 The SCADA implementations may provide alarm handling. The processor monitors whether certain alarm conditions are satisfied, to determine when an alarm event has occurred. Once an alarm event has been detected, one or more actions maybe taken (such as the activation of one or more alarm indicators, and perhaps the generation of e-mail or text messages so that management 15 or a remote SCADA users are informed) SCADA user may have to acknowledge the alarm 20 WO 2015/042661 PCT/AU2014/050246 event This may deactivate some alarm indicators, whereas other indicators remain active until the alarm conditions are cleared. Examples of alarm indicators include a siren, a pop-up box on a screen, or a coloured or flashing area on a screen (that may act in a similar way to the "fuel tank empty" light in a car). The role of the alarm indicator is generally to draw the user's attention to 5 the pan of the system 'in alarm' so that appropriate action can be taken. The SCADA. may be also in communication with the conveyor system and cause the conveyor system to stop if a faulty idler is detected. 10 Alternatively, the processor may provide a HTML interface for remote monitoring, wherein web pages displaying idler information and alarms are served to a personal computer, for example, accessible by the user The idler information may be compared against at least one threshold value Threshold values 15 may include minimum and maximum values, or minimum or maximum rates of change. In different embodiments of the system, the comparison of measured data against a threshold value may occur within the idler, the gateway, the processor, In the present embodiment, thresholds levels are configurable and programmed by the user at the processor. When a measured parameter violates a programmed threshold for a programmable time, an alarm condition may be 20 generated in the system, This alarm condition may be displayed by the processor, for example. The alarm for each parameter may be globally enabled, disabled or cleared at the processor. Any idler information or derived status or alarm conditions available in the system may be collected by the Gateway and transmitted to the processor. Now that embodiments have been described, it will be apparent that the some embodiments may 25 provide some of the following advantages. The idler information may be used to determine when to replace an idler. The quantity of rotations may be indicative of an effective age of the idler. Because the quantity of rotations is known, the replacement of an idler too early or too late may be avoided, 10 which may result in savings while maintaining the risk of idler failure at an acceptable level. An idler for which the idler information indicates that the rotational velocity is zero may have failed. 21 WO 2015/042661 PCT/AU2014/050246 The ability to measure not only temperature but also vibration, acoustic level, rotations and rotational speed, and to use this information individually or in combination in order to more accurately identify a failing or failed idler. 5 * The ability to independently measure a temperature of within the idler using a single circuit. By independently monitoring the temperature of each bearing within the idler the system may be able to more accurately detect increases in temperature. Using a single circuit may also lower cost. 10 - The ability to power the electronics embedded within the idler from the rotation of the roller or idler without the use of a battery and to communicate wirelessly. There may be no requirement for special wiring of the conveyor, simplifying installation. - The use of capacitance to store energy for short periods rather than disposable or 15 rechargeable batteries. By not using a battery, the system is able to operate safely at elevated temperatures for extended periods up to 10 years. - The inclusion of an RFID memory within each roller or idler may allow the reading and programming of identification, location and configuration information within the roller or 20 idler. The information may be automatically transmitted to the processor via the radio network, This may simplify and automate the identification of idlers. Variations and/or modifications may be made to the embodiments described without departing from the spirit or ambit of the invention. The present embodiments are, therefore, to be 25 considered in all respects as illustrative and not restrictive Prior art, if any, described herein is not to be taken as an admission that the prior art forms part of the common general knowledge in any jurisdiction. In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word 10 "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, that is to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention. 22