WO2017004667A1

WO2017004667A1 - Apparatus and method for monitoring performance of street lights

Info

Publication number: WO2017004667A1
Application number: PCT/AU2016/050578
Authority: WO
Inventors: Richard Dluzniak
Original assignee: The Active Reactor Company Pty Ltd
Priority date: 2015-07-03
Filing date: 2016-07-01
Publication date: 2017-01-12

Abstract

Apparatus is disclosed for monitoring performance of a street light having at least one luminaire for illuminating an associated roadway. The apparatus comprises a sensor module associated with the street light for detecting light output from the at least one luminaire and a monitoring module operatively associated with the sensor module. The monitoring module includes means for monitoring the light output detected by the sensor module, means for determining when the detected light output falls to or below a reference level and means responsive to the means for determining, for indicating that the detected light output has fallen to or below the reference level. A method for monitoring performance of a street light is also disclosed.

Description

Title of Invention

Apparatus and Method for Monitoring Performance of Street Lights

Technical Field

[0001] The present invention relates to an apparatus and method for monitoring

performance of street lights and in particular LED street lights.

Background of Invention

[0002] Because LED (light emitting diode) technology is relatively new in its application to street lights there is little historical knowledge on long term operation of LED street lights and in particular their maintenance and/or failure characteristics. As a result future maintenance requirements for LED street lights are not well known and even less understood.

[0003] Unlike traditional HID lamps, LED lights typically may not fail by "burning out" after a period of time. Rather, over long periods of time, light output levels of LED lights may gradually degrade and become dimmer. Moreover, LED lights used in street lights on the market today may still be producing over 80% of their initial light output after 60,000 hours of operation in the field (about 15 years in typical applications).

[0004] Although it is not possible to predict the direction of lighting technology during the next 15 to 20 years, it may reasonably be assumed that LED light products on the market today may no longer be available. It may also reasonably be assumed that if LED light products need to be replaced, suitable products in the marketplace in 15 or more years' time may be more efficient, physically different, and/or may not be mechanically compatible with current luminaires.

[0005] Consequently it may not be practical to plan for "changing light bulbs" as is the case with HID lamps. Also, it may not be practical to specify "replaceable LEDs" or "power supplies" etc., since at some point it may become more economical to simply replace the luminaires with the latest technology product available.

[0006] To facilitate electrical utilities, local councils and road authorities to plan for future maintenance and replacement of LED street lights, it may be desirable to have available a record of operating history of the LED street lights. The operating history of traditional HID lamps spans over 50 years, the technology is well understood and maintenance regimes are well in place. In contrast there is little operating history and few proven maintenance programs relevant to LED street light technology. [0007] Given the relatively long life of LED light products, a paradigm shift may be needed on how to approach a long term maintenance program in connection with LED street lights. There appear to be at least two relevant issues to consider, namely spot replacement of components and luminaire cleaning.

[0008] Because of the projected long life of LED light products, it may not be practical to stock replacement LED components, e.g. diodes, power supplies, etc. Moreover since an entire luminaire may typically be covered by a manufacturer's warranty for the first 5 years or so, it may be practical to replace a complete unit in the event of an occasional failure. Such an approach may allow greater flexibility when different manufacturers and/or different product generations are used over a lighting network.

[0009] In common with all luminaires, LED street lights are subject to dirt depreciation that reduces light output over time. Because LED street lights are relatively new there is little field data available to prescribe a reasonable cleaning program for various environments.

Additionally since less heat is generated on lenses by LED light products compared to HID lights, so less dust may be expected to adhere and fuse to the lens than historically has been experienced in outdoor luminaires. For this reason lower Luminaire Dirt Deprecation (LDD) may be expected on LED based luminaires.

[0010] One prior art approach for monitoring performance of street lights is disclosed in PCT application GB89/01073. The latter document discloses a system for recording the condition of street lights by travelling along a route of street lights in a vehicle. The prior art system includes an array of photo sensors mounted on the roof of the vehicle for detecting the output of the street lights as the vehicle travels along the route.

[0011] The prior art system is relatively complex and expensive and also requires the position of the vehicle to be logged by means of a computer together with the measured output of the street lights. Moreover the system lacks accuracy in determining when a street light is giving less than "normal" illumination because it is relatively difficult to replicate the conditions that prevailed when an initial or "base level" performance record for a street light was obtained with the prior art system.

[0012] On the other hand an accurate comparison with such a base record is desirable to ascertain when a defined performance standard has been breached. Since readings made with the system disclosed in PCT application GB89/01073 may vary significantly depending on multiple variables including the position of the vehicle relative to the roadway/street lamps, the system is generally more suited for detecting gross deterioration of performance such as a complete failure of the street light or a very significant deterioration or degradation of light output or brightness. [0013] The present invention may provide an apparatus and method for monitoring performance of street lights such as LED street lights. The monitoring method may include at least periodic measurement and/or recording of light level output from the street light.

[0014] A reference herein to a patent document or other matter which is given as prior art is not to be taken as an admission that that document or matter was known or that the information it contains was part of the common general knowledge in Australia or elsewhere as at the priority date of any of the disclosure or claims herein. Such discussion of prior art in this specification is included to explain the context of the present invention in terms of the applicant's knowledge and experience.

[0015] Throughout the description and claims of this specification the words "comprise" or "include" and variations of those words, such as "comprises", "includes" and "comprising" or "including", are not intended to exclude other additives, components, integers or steps.

Summary of Invention

[0016] According to one aspect of the present invention there is provided an apparatus for monitoring performance of a street light having at least one luminaire for illuminating an associated roadway, said apparatus comprising: a sensor module associated with said street light for detecting light output from said at least one luminaire; and a monitoring module operatively associated with said sensor module, said monitoring module including means for monitoring said light output detected by said sensor module, means for determining when said detected light output falls to or below a reference level and means responsive for said means for determining for indicating that said detected light output has fallen to or below said reference level.

[0017] The sensor module may be adapted to be retrofitted to said street light. The sensor module may include a photo diode for receiving the light output from the at least one luminaire. The reference level may be associated with a specified or defined threshold or design level. The reference level may be associated with a desired or minimum illumination level on the roadway. The reference level may be established when the apparatus and/or at least one luminaire is first commissioned.

[0018] The means for indicating that the detected light output has fallen to or below the reference level, may include a display LED that is visible from the roadway. The display LED may include a blue LED. The means for indicating may include a digital or analog signal adapted to be interfaced to a remote location via wired or wireless communication.

[0019] The monitoring module may include a microprocessor and a software program. The at least one luminaire may include an LED source. The street light may include a pole and the sensor module may be mounted on the pole. The pole may include a base and cross arms for receiving the at least one luminaire and the sensor module may be mounted between the base and the cross arms. In one form the sensor module may be mounted at least 2 meters above the base of the pole. The sensor module may be mounted not higher than 1 meter below the at least one luminaire.

[0020] According to a further aspect of the present invention there is provided a method for monitoring performance of a street light having at least one luminaire for illuminating an associated roadway, said method comprising: retrofitting a sensor module to said street light for detecting light output from said at least one luminaire; monitoring said light output detected by said sensor module; determining when said detected light output falls to or below a reference level; and indicating that said detected light output has fallen to or below said reference level.

[0021] In some embodiments, the sensor and monitoring modules may be housed within an integrated package or self-contained sensor unit. The integrated package/sensor unit may be mounted on the outside of the light pole thus avoiding a need to penetrate the light pole. The integrated package/sensor unit may include an internal power source. The power source may include a primary cell battery that will need replacement at regular intervals or it may include a rechargeable battery. The rechargeable battery may be recharged using solar cell technology. Since the integrated package/sensor unit is intended for external mounting, there should be access to sunlight. To minimize power usage, the or each visual indicator may include a high efficiency LED with a reduced duty cycle when battery charge is getting low, and/or a mechanical flag that is flipped using an electromagnetic pulse (similar to indicators used in petrol pumps).

[0022] It may be desirable with an internal power source to also know when to replace the battery and/or clean a solar cell. While rechargeable batteries may have a long life, a percentage of batteries may perform poorly due to manufacturing process tolerances and the solar cell may be covered by bird droppings. Battery life may be estimated but an indication that it needs service may be provided in any suitable manner. The latter may include a visual indicator, such as a different LED colour or a different mechanical indicator.

[0023] Interrogation of the apparatus may be by way of (very) short range RF such as Bluetooth communicating with a smart phone, laptop or the like. This may avoid a need for additional infrastructure costs. An app on the smartphone may be adapted to automatically connect to the apparatus and query its current status including relative illuminance level when last measured and battery status/life/quality. This data may be collected, logged and time tagged since records from the sensor may facilitate better understanding of performance of the street light and sensor power usage over time. The integrated package or sensor unit may include a real time clock and means for communication with network systems.

[0024] One advantage of a real time clock is that the sensor unit may know the time of day and therefore when best to check illumination of the street light. Another advantage is that it may improve a commissioning process. For example, most sensor units will be installed during daylight hours. It may not be possible to commission a sensor unit at the time of installation because sunlight may affect a baseline reading. Therefore, the sensor unit may be configured to check illumination at a specific time later that day. An example may be around 3am when there is minimal likelihood of sensor readings being affected by passing traffic.

[0025] The sensor unit may take measurements over a number of nights to allow it to compensate for individual high readings. The sensor unit may be readily configured using a Bluetooth link to recalibrate when a lighting fixture or luminaire is changed.

[0026] A known issue with silicon based photo sensors is that they age. This means that the composition of the photo sensor may change over time due to thermal diffusion and other related effects. As a result readings may change over time. This is a predicable

characteristic that may be compensated for using a model of the photo sensor based on manufacturers aging curves and operating time from the real time clock.

[0027] The apparatus may be arranged such that the solar cell has access to sky light. The photo sensor may be mounted so that it has view of the lighting fixture being monitored. In order to reduce effects due to rainwater the sensor unit may include a sloped outer surface to facilitate runoff of rainwater. If a visual indicator is included, this should be visible from below to facilitate viewing from the ground. If Bluetooth interrogation is used, the enclosure preferably is non-metallic to minimise absorption of RF signal.

[0028] The apparatus of the present invention may measure light output from a streetlight such as an LED streetlight, may store the light output level and may determine, via an "a priori" rule, if the light output level is at or below a desired, threshold or reference level. The desired output level may include a design or minimum or mandated output level for light in the street and/or associated roadway. If the measured level is above the desired output level the apparatus may increment a night counter and keep on measuring. If the measured level falls below the desired level the apparatus may activate an indicator light such as a blue LED to indicate that the streetlight requires maintenance. [0029] The present invention will hereinafter be particularly described with reference to an LED based street light although it is to be appreciated that it is not thereby limited to such applications.

Brief Description of Drawings

[0030] Figures 1 and 1 a show a typical layout of an LED based street light;

[0031] Figure 2 shows details of a sensor module (photo sensor and display LED) installed on the face of a light pole;

[0032] Figure 3 shows a monitoring module located in the base of the pole;

[0033] Figure 4 shows a block diagram of components associated with the sensor and monitoring modules;

[0034] Figure 5 shows a flow diagram of a software program associated with the monitoring module;

[0035] Figure 6 shows a monitoring module interfaced to a lighting controller;

[0036] Figure 7 shows details of an integrated sensor and monitoring module installed on the face of a light pole; and

[0037] Figure 8 shows a block diagram of components associated with the integrated sensor and monitoring module.

Detailed Description

[0038] Figure 1 shows a typical layout of a street light 10 for illuminating an associated roadway. Streetlight 10 comprises LED based luminaires 1 1 , 12 mounted on pole 13 via respective cross arms 14, 15. Retrofitted to lamp pole 13 is sensor module 20 for detecting light from luminaires 1 1 , 12. Sensor module 20 may typically be mounted on pole 13 between its base and cross arms 14, 15. Sensor module 20 may be mounted at a position at least 2 meters above the base of pole 13 and not higher than 1 meter below luminaires 1 1 , 12. Preferably sensor module 20 is mounted at a position 1 to 3 meters above the base of pole 13.

[0039] Luminaries 1 1 , 12 exhibit respective light polar patterns 16, 17 (in the plane of pole 13 and arms 14, 15) representing luminous intensity relative to angle Θ. For example the intensity of light in the direction 18 of sensor module 20 is indicated via light vector l_s1 on polar pattern 16. Associated with sensor module 20 is a monitoring module 30 located behind pole access door 19. Monitoring module 30 may be housed in a weatherproof plastics box which may be located within pole 13. Access door 19 may be opened to access monitoring module 30 eg., to reset monitoring module 30 and/or read the number of quarters and years that luminaires 1 1 , 12 have operated satisfactorily. The range of acceptable locations for locating sensor module 20 along pole 13 is indicated via sector 12A defined by arc length 12B.

[0040] Illumination level of the associated roadway may be substantially proportional to illumination at sensor module 20. Hence a reduction of illumination on the road way, eg. due to LED streetlight failure, LED depreciation and/or LED dirt accumulation, may be

accompanied by a proportional reduction in illumination at sensor module 20.

[0041] Figure 1 A shows how polar pattern 16 varies as light output from luminaire 1 1 decreases due to source lumen depreciation, luminaire dirt accumulation and/or other lumen depreciation effects. Polar pattern 16 is associated with a relatively new luminaire while polar pattern 16A is associated with an older luminaire at point of threshold. The point of threshold may be a point when light output falls to its design or minimum acceptable lumen level.

[0042] The luminous intensities of polar patterns 16 and 16A may be related by a

Maintenance Factor (MF) used in the design of the street lighting. That is, the intensities associated with polar pattern 16A may be a scalar multiple of the intensities associated with polar pattern 16. Since the MF is always less than 1 (typically 0.7-0.8) polar pattern 16A will always be smaller than polar pattern 16. At the threshold value the luminous intensities of polar pattern 16A may be substantially equal to MF x luminous intensities of polar pattern 16.

[0043] For example the luminous intensity of light from luminaire 1 1 in the direction 18 of sensor module 20 is indicated via light vector I_S1 (candela) when luminaire 1 1 is new or has just been commissioned. When luminaire 1 1 is older and/or has depreciated to its threshold value, its luminous intensity of light is indicated via light vector l_S2 = MF x I_S1.

[0044] A reduction in luminous intensity to the roadway (l_R1) will produce a proportional reduction in luminous intensity to photo sensor 21 , since l_R1 = kl_Si wherein k >1 . Hence by monitoring light level (luminous intensity) on photo sensor 21 for a new luminaire (polar pattern 16) the threshold condition for an old luminaire may be determined.

[0045] The above holds true when sensor module 20 is positioned anywhere along pole 13 as indicated in Figures 1/1 A although accuracy of the apparatus may degrade if sensor module 20 is placed too high up pole 13 where luminous intensity from the street light may be relatively low or even zero.

[0046] Figure 2 shows details of sensor module 20 installed on the face of pole 13 shown in partial cross-section. Sensor module 20 includes photo diode 21 , display LED 22 and associated electronic components. Photo diode 21 and display LED 22 are mounted on PCB 23 with photo diode 21 mounted on a top side of PCB 23 and display LED 22 mounted on an underside of PCB 23. PCB 23 is inserted in cover 24 comprising a clear plastics cylinder with a semi-spherical end. PCB 23 preferably is tilted at an angle alpha (a) relative to the horizontal such that the direction 18 of light from luminaire 1 1 (or 12) impinges substantially normally (90 degrees) relative to the sensor plane of photo diode 21 mounted on PCB 23. Cover 24 is attached to sensor base 25 via threaded portion 26. Clear cover 24 allows optimum light to fall on photo diode 21 and also enhances visibility of light generated by display LED 22. Sensor module 20 is mounted or fixed on pole 13 via self-tapping screws 27. Because luminaires 1 1 /12 are also mounted or fixed relative to pole 13 there exists a defined or fixed spatial or geometric relationship between sensor module 20/photo diode 21 and luminaires 1 1/12. This fixed relationship facilitates performance of luminaires 1 1 /12 to be easily compared to a 'base level' of performance obtained when luminaires 1 1/12 were first installed or commissioned. Display LED 22 may include blue light to make it easier to distinguish against light from luminaires 1 1 , 12 and/or other sources. Sensor module 20 is operatively connected to monitoring module 30 (not shown) via cable 29 such as Cat 5e cable.

[0047] Figure 3 shows details of monitoring module 30 located in the base of pole 13.

Monitoring module 30 includes power input cable 31 , reset button 32 to start a new monitoring session and 2-LED array 33-34 for displaying burning time of luminaires 1 1 , 12 mounted on pole 13. Power input cable 31 may be tapped into mains power cable 36 supplying power to luminaires 1 1 , 12. When interrogated, LED array 33-34 may be arranged to flash intermittently a number of times corresponding to a number of elapsed burning years/quarters. The electronic components may be mounted on PCB 23 as shown in figure 2. PCB 23 may be inserted into plastics housing 37 and housing 37 may be filled with an epoxy material to make it substantially waterproof. Housing 37 may be fixed to mains power cable 36 via plastics coil 38 or the like.

[0048] Figure 4 shows a block diagram of components associated with sensor module 20 and monitoring module 30. Sensor module 20 includes photo diode 21 for receiving light from luminaries 1 1 , 12 and display LED 22 for producing light to be seen at the base of pole 13. Sensor module 20 includes amplifier 40 for amplifying the small signal from photo diode 21 , low pass filter 41 to average the signal from amplifier 40 and variable gain amplifier 42 to scale the signal. The scaled signal may be routed to monitoring module 30 via Cat 5e cable 29.

[0049] Monitoring module 30 includes 8 Bit microprocessor 43 for controlling measurement of light levels from luminaires 1 1 , 12 and/or for controlling display of burning time and/or for providing an indication of a low or degraded lighting level. Indication of low/degraded lighting level may be via display LED 22 and/or digital output 48. Microprocessor 43 may also provide a real time clock and time stamp for critical events. The scaled output signal from sensor module 20 may be routed to the A/D input of microprocessor 43.

[0050] Monitoring module 30 includes linear power supply 44 for driving the electronics. Power supply 44 may include a transformer, rectifier and voltage regulator (not shown).

[0051] Monitoring module 30 includes analog input and output LED drivers 45, 46 for driving LEDs 33, 34 and analog LED driver 47 for driving display LED 22. In some embodiments digital output 48 may be used to communicate an indication of low/degraded lighting level to a remote location. Communication may be via a wired or wireless interface (eg. Wi-Fi, Bluetooth). Monitoring module 30 also includes reset button 32 to start a new monitoring session and 2-LED array 33-34 for displaying burning time of luminaires 1 1 , 12 in years and quarters. LED 33 may include a green LED and LED 34 may include a red LED.

[0052] Microprocessor 43 contains a stored software program for controlling lighting measurements, processing measurement data, displaying lamp burning time and/or displaying a warning when light output level falls below a specified or defined threshold or design level. The software program may be written in Assembly Language for 8 bit microprocessor 43. Microprocessor 43 may include at least 2K RAM and 32 bytes of nonvolatile memory such as E2PROM. The non-volatile memory may be adapted to store a history of operating data relating to a burning session, including a total number of burning hours since reset button 32 was last pressed and a total number of burning hours since the means for indicating (display LED 22) was first activated.

[0053] The software program may accept the scaled output signal from sensor module 20 and may use this signal together with input from push button 32 to turn on various indicator LEDs. Display LED 22 (blue) may be illuminated to indicate that street lighting level is degraded or below a desired level. In one display mode red LED 34 may indicate whether the level of light at photo diode 21 is above threshold, at threshold range or below design level. As indicated above green and red LEDs 33, 34 may indicate in another display mode the number of years and quarters that have elapsed since monitoring module 30 was last reset.

[0054] In one form the software program may include functionality at least for:

i. measuring and/or recording light emanating from the luminaire;

ii. measuring and/or recording operating time of the luminaire (burning time);

iii. indicating via one flashing mode of indicator light when the light level falls below a predetermined threshold level (such as a design or desired level); iv. indicating via another flashing mode of indicator light or lights burning time of the street light; and/or

v. enabling a reset button to reset all parameters and start monitoring from the start.

[0055] Figure 5 shows flow diagram 50 of the software program stored in microprocessor 43 including functional blocks 51 to 64. The function of each block 51 to 64 is set forth below:

Block 51 Program counters and parameters are initialized

Block 52 Check to see if RESET button 32 has been pressed

Block 53 Reset blue indicator LED 22 to OFF

Block 54 Wait 7 seconds

Block 55 Check if RESET button 32 is still pressed

Block 56 Read light level with photo diode 21 . An initial or reference light level may be obtained when light falls within a threshold range and push button 32 is pressed to capture this level. This may be done when the apparatus and/or luminaire 1 1/12 is first installed, commissioned and/or and set-up. All subsequent light readings may be referenced to this initial reading. Threshold = MF x light level wherein MF= 0.7-0.8.

Block 57 Set Count to zero

Block 58 Read light level

Block 59 Check if light level > reference light level

Block 60 Check if 12 consecutive light readings are below reference light level. A light reading may be taken every 5 minutes. If 12 consecutive readings are low (ie. below the reference light level) a flag may be set to turn on (blue) indicator LED 22. Logic of 12 successive low values may be used to cater for any temporary drop in light level due to various short term conditions such as abnormal electrical and/or atmospheric conditions.

Block 61 Increase night Count by one

Block 62 Calculate number of quarters and years from Count value

Block 63 Is street light operating data to be displayed?

Block 64 Display years and quarters of luminaire operation

[0056] The software program may loop continuously taking light readings from sensor module 20 and may be interrupted only when RESET push button 32 is pressed. The software program may perform different functions depending on how long push button 32 is held pressed. [0057] The apparatus may be reset to start monitoring a new street light or continue monitoring a street light which has been cleaned and/or serviced.

[0058] The apparatus may be interrogated to indicate number of years and quarters that the street light has been burning properly and/or number of years and quarters since it failed. The interrogation may be performed on site via a wired or wireless (eg. Wi-Fi, Bluetooth) interface (not shown) connected to microprocessor 43. The interrogation may be performed remotely via a wired or wireless internet connection and/or via a smartphone or laptop with suitable app using short range RF (Bluetooth). In some embodiments indication of a low/degraded lighting level may be communicated directly to a remote location via a digital (or analog) signal obtained from microprocessor 43. The digital (or analog) signal may be communicated to the remote location in any suitable manner and by any suitable means including via a wired (eg. via power lines) or wireless link (eg. via a cellular network). The wired or wireless link may be interfaced to a third party or proprietary system such as a wireless networking system.

[0059] After a few years when light levels have dropped by more than say 10%, a high pressure wash may be applied to the lens from the ground and then light levels may be rechecked. If there is no significant improvement it may be necessary to visit the luminaires and wash the lenses with a wet cloth. Light levels may be rechecked periodically to ultimately design a luminaire cleaning program based on frequency required to maintain desired illumination levels.

[0060] Definitions

Count No of nights of operation of street light

Quarters No of quarters of operation

Years No of years of operation

Threshold Low light level/design level

Design level Initial light level x Maintenance factor (MF)

MF Maintenance factor

[0061] Figure 6 shows an alternative arrangement wherein monitoring module 30 is interfaced to a lighting controller 67 fitted inside luminaire 12. Digital output 48 from monitoring module 30 may be connected to controller 67 via Cat 5e cable 66. Signals from lighting controller 67 may pass via power cable 36 and power line 65 (power line

communication) to a central monitoring system (not shown). In some embodiments lighting controller 67 may communicate with the central monitoring system via a wireless link. [0062] The reference numerals in figure 6 show features described above with reference to the drawings wherein like numerals refer to like features including sensor module 20, photo diode 21 , display LED 22 and pole 13. As previously described light from luminaire 12 passes along direction 18 to photo diode 21 . Display LED 22 produces light 68 to be seen at the base of pole 13.

[0063] In addition to the standard working of the apparatus, a measured threshold value may trip a relay in monitoring module 30 which may send a signal to a lighting controller via an LED light. The lighting controller may then transmit a corresponding signal via the power line to the central monitoring system. The monitoring system may then display status of LED light as being faulty or that light output is below design level.

[0064] Figure 7 shows plan and sectional views of an integrated sensor and monitoring module 70 installed on the face of pole 13. Module 70 includes photo diode 21 , display LED 22 and associated electronic components including solar cell 71 and rechargeable battery 74. Photo diode 21 and display LED 22 are mounted on PCB 76 with photo diode 21 mounted on a top side of PCB 76 and display LED 22 mounted on an underside of PCB 76. PCB 76 is inserted in cover 70A comprising a clear plastics housing. Photo diode 21 preferably is tilted at an angle relative to the horizontal such that the direction 18 of light from luminaire 1 1 /12 impinges substantially normally (90 degrees) relative to the sensor plane of photo diode 21 mounted on PCB 76. Clear cover 70A allows optimum light to fall on photo diode 21 and also enhances visibility of light generated by display LED 22.

[0065] Module 70 is mounted or fixed on pole 13 via a strap passing through slot 78.

Because luminaires 1 1 /12 are also mounted or fixed relative to pole 13 there exists a defined or fixed spatial or geometric relationship between module 70/photo diode 21 and luminaires 1 1/12. This fixed relationship facilitates performance of luminaires 1 1 /12 to be easily compared to a 'base level' of performance obtained when luminaires 1 1 /12 were first installed or commissioned. Display LED 22 may include blue light to make it easier to distinguish against light from luminaires 1 1/12 and/or other sources.

[0066] Figure 8 shows a block diagram of components associated with integrated sensor and monitoring module 70. Module 70 includes photo diode 21 for receiving light from luminaries 1 1 /12 and display LED 22 for producing light to be seen at the base of pole 13. Module 70 includes amplifier 40 for amplifying the small signal from photo diode 21 , low pass filter 41 to average the signal from amplifier 40 and variable gain amplifier 42 to scale the signal. The scaled signal may be routed to Bluetooth module 72 via printed circuit board track 29A. In one form Bluetooth module 72 may comprise a Nordic nRF51822 multiprotocol Bluetooth 4.0 low energy 40 pin IC device. Bluetooth module 72 includes a 16 Bit microprocessor for controlling measurement of light levels from luminaires 1 1/12 and/or for controlling display of burning time and/or for providing an indication of a low or degraded lighting level. Indication of low/degraded lighting level may be via display LED 22 and/or digital output 48. Bluetooth module 72 may also provide a real time clock and time stamp for critical events. Module 70 includes a self-contained power supply for driving the electronics. The power supply includes solar (photovoltaic) cell 71 , battery charger 73, rechargeable battery (Lithium-Ion) 74 and battery manager 75. Module 70 includes RF output 77 in Bluetooth format for reception via a smartphone or laptop, and analog LED driver 47 for driving display LED 22.

[0067] In some embodiments digital output 48 may be used to communicate an indication of low/degraded lighting level to a remote location. Module 70 includes reset button 32 to start a new monitoring session. Bluetooth module 72 contains a stored software program for controlling lighting measurements, processing measurement data, providing lamp burning time and/or providing a warning when light output level falls below a specified or defined threshold or design level. The software program may be written in Assembly Language for a 16 bit microprocessor. Bluetooth module 72 may include at least 16K RAM and 128 K bytes of flash memory. The flash memory may be adapted to store a history of operating data relating to a burning session, including a total number of burning hours since reset button 32 was last pressed and a total number of burning hours since the means for indicating (display LED 22) was first activated. The software program may accept a scaled output signal from module 70 and may use this signal together with input from push button 32 to turn on display LED 22 (blue) to indicate that street lighting level is degraded or below a desired level. The software program may include functionality at least as described herein.

[0068] Finally, it is to be understood that various alterations, modifications and/or additions may be introduced into the constructions and arrangements of parts previously described without departing from the spirit or ambit of the invention.

Claims

1 . Apparatus for monitoring performance of a street light having at least one luminaire for illuminating an associated roadway, said apparatus comprising:

a sensor module associated with said street light for detecting light output from said at least one luminaire; and

a monitoring module operatively associated with said sensor module, said monitoring module including means for monitoring said light output detected by said sensor module, means for determining when said detected light output falls to or below a reference level and means responsive to said means for determining for indicating that said detected light output has fallen to or below said reference level.

2. Apparatus according to claim 1 wherein said sensor module is adapted to be retrofitted to said street light.

3. Apparatus according to claim 1 or 2 wherein said sensor module includes a photo diode for receiving said light output from said at least one luminaire.

4. Apparatus according to claim 1 , 2 or 3 wherein said reference level is associated with a specified or defined threshold or design level.

5. Apparatus according to any one of the preceding claims wherein said reference level is associated with a desired or minimum illumination level on said roadway.

6. Apparatus according to any one of the preceding claims wherein said reference level is established when said apparatus and/or at least one luminaire is first commissioned.

7. Apparatus according to claim any one of the preceding claims wherein said means for indicating includes a display LED that is visible from the roadway.

8. Apparatus according to claim 7 wherein said display LED includes a blue LED.

9. Apparatus according to any one of the preceding claims wherein said means for indicating includes a digital or analog signal adapted to be interfaced to a remote location via wired or wireless communication.

10. Apparatus according to any one of the preceding claims wherein said monitoring module includes a microprocessor and a software program.

1 1 . Apparatus according to any one of the preceding claims wherein said at least one luminaire includes an LED source.

12. Apparatus according to any one of the preceding claims wherein said street light includes a pole and said sensor module is mounted on said pole.

13. Apparatus according to claim 12 wherein said pole includes a base and cross arms for receiving said at least one luminaire and wherein said sensor module is mounted between said base and said cross arms.

14. Apparatus according to claim 13 wherein said sensor module is mounted at least 2 meters above said base of said pole.

15. Apparatus according to claim 13 or 14 wherein said sensor module is mounted not higher than 1 meter below said at least one luminaire.

16. A method for monitoring performance of a street light having at least one luminaire for illuminating an associated roadway, said method comprising:

associating a sensor module with said street light for detecting light output from said at least one luminaire;

monitoring said light output detected by said sensor module;

determining when said detected light output falls to or below a reference level; and indicating that said detected light output has fallen to or below said reference level.

17. A method according to claim 16 wherein said associating includes retrofitting said sensor module to said street light.

18 A method according to claim 16 or 17 wherein said sensor module includes a photo diode for receiving said light output from said at least one luminaire.

19. A method according to claim 16, 17 or 18 wherein said reference level is associated with a specified or defined threshold or design level.

20. A method according to any one of claims 16 to 19 wherein said reference level is associated with a desired or minimum illumination level on said roadway.

21 . A method according to any one of claims 16 to 20 wherein said reference level is established when said at least one luminaire is first commissioned.

22. A method according to claim any one of claims 16 to 21 wherein said indicating is performed via a display LED that is visible from the roadway.

23. A method according to claim 22 wherein said display LED includes a blue LED.

24. A method according to any one of claims 16 to 23 wherein said indicating is performed via a digital or analog signal adapted to be interfaced to a remote location via wired or wireless communication.

25. A method according to any one of claims 16 to 23 wherein said monitoring is performed via a microprocessor and a software program.

26. A method according to any one of claims 16 to 25 wherein said at least one luminaire includes an LED source.

27. A method according to any one of claims 16 to 26 wherein said street light includes a pole and said retrofitting includes mounting said sensor module on said pole.

28. A method according to claim 27 wherein said pole includes a base and cross arms for receiving said at least one luminaire and wherein said sensor module is mounted between said base and said cross arms.

29. A method according to claim 28 wherein said sensor module is mounted at least 2 meters above said base of said pole.

30. A method according to claim 28 or 29 wherein said sensor module is mounted not higher than 1 meter below said at least one luminaire.