System for detecting the orientation of a light sensor

Description

[0001] The invention relates to a system for automatically detecting an orientation of a light sensor, wherein the light sensor is assigned to a first or a second orientation.

[0002] Light sensors are often used in lighting technology to enable demand-based control of lighting. A typical example is switching on a light when the ambient brightness falls below a certain level. This is used, for example, in street lighting. It is important in such applications that, regardless of the orientation of the light sensor used, the light is always switched on at the same ambient brightness. However, depending on the orientation of the light sensor, it measures different brightness levels at the same time.

[0003] To ensure satisfactory operation, it is therefore important to ensure that, for example, a threshold value for the ambient brightness for switching on the lighting is adapted to the respective orientation of the light sensor used. A light sensor whose detection range is directed towards the sky will output a larger value for the incident light than a light sensor mounted on the same luminaire whose detection range is directed towards the ground. This is particularly important if the light sensor can be mounted in different orientations. In order to be able to use the same modules in different applications, it may be required, for example, that the lighting technology module allows a first installation position and a second installation position for a light sensor.Since the orientation of the light sensor is not predetermined, the orientation must be assigned to the light sensor during commissioning. Once the light sensor knows its orientation, the corresponding threshold value can be used to output a switch-on signal and compare it with the measured intensity.

[0004] Currently, the orientation of the light sensor is determined using complex measures. For this purpose, the system can either be configured accordingly, i.e., the orientation of the light sensor is determined in the system or in the light sensor itself during commissioning by an operator. Automated detection is also possible, whereby the respective light sensors have additional sensors. For this purpose, the orientation of the mounted light sensor can be detected using a magnetometer, gyroscope, or similar sensor technology. This additional sensor technology is used to determine the actual orientation of the respective light sensor. The light sensor can then use the threshold value required for operating the lighting based on the detected orientation.

[0005] Document US 2017 / 019976 A1 discloses a lighting system consisting of one or more lighting devices mounted on a post, a photosensor and a controller.

[0006] The disadvantage of existing solutions is that they require additional effort to install the lighting, requiring an operator to enter the relevant inputs into the system. On the other hand, existing automated systems require more expensive sensors than if the light sensors were simply measuring brightness.

[0007] It is therefore an object of the present invention to provide a system in which simple light sensors can be used, while still allowing automated detection of the orientation of the mounted light sensor.

[0008] The object is achieved by the module according to the invention for a street lamp with the features of independent claim 1.

[0009] Advantageous further training is defined in the subclaims.

[0010] The module according to the invention for a street lamp comprises a system for detecting an orientation of a light sensor. In addition to the light sensor itself, the system comprises an information processing unit configured to assign the light sensor to a first orientation or a second orientation based on at least two measurements performed at different times or a comparison of relative spectral components, wherein daylight is detected by the light sensor in the first orientation and reflected light is detected in the second orientation. This utilizes the fact that daylight hitting the light sensor in the first position differs characteristically from reflected light measured by a light sensor mounted in the second orientation.Thus, the orientation of the light sensor toward the sky or toward the ground is determined directly from one or more measurements of the incident light, or at least spectral components thereof. This assignment of the light sensor used to the first or second orientation, respectively, by the information processing unit, can then be used, for example, to set a threshold for switching on a light accordingly.

[0011] It should be noted that the information processing unit can also be integrated into the light sensor itself.

[0012] For this purpose, the system of the module for a street lamp comprises a control device for controlling the light, wherein the control device is configured to perform a first control or a second control depending on the detected orientation of the light sensor. The first control and the second control differ in that they have different threshold values, which are set such that they cause the lighting to switch on when the ambient brightness is actually identical. This control device can also be arranged in the light sensors, so that the respective light sensor outputs a switch-on signal, which is evaluated, for example, in an operating device and the lighting devices controlled accordingly.However, the control device can also be integrated into the operating device for controlling the lamps, in which case the light sensor only transmits a brightness value, which is compared in the operating device with the threshold value suitable for the orientation of the light sensor.

[0013] The information processing unit is preferably configured such that, for analysis purposes, a maximum value is determined from a temporal progression of an intensity value of at least one spectral component of the light detected by the light sensor and is compared with a threshold value. In the simplest case, the total amount of incident light is detected. Alternatively, however, only a spectral component of the total detected light can be analyzed. To avoid incorrect measurements and improve the reliability of the assignment to the orientations, the spectral component can typically be a component that is only present in daylight, or at least predominantly in daylight. Incorrect assignments that could occur due to additional light sources that may be present are thus avoided.A light sensor oriented toward the sky, thus measuring incident daylight, will measure a higher intensity in the same situation than a light sensor directed toward the ground. The threshold is set so that it is only affected by direct light.

[0014] Daylight measurement is exceeded. Such a measured value can be determined empirically.

[0015] A typical application of the system according to the invention is street lighting systems. The period of light measurement to be considered is therefore typically 12, preferably 24 hours. Measurement over a period of 24 hours ensures that the respective daily maximum of incident daylight is included.

[0016] According to an alternative embodiment, the information processing unit can also be configured to determine a difference between a maximum value and a minimum value from a temporal profile of an intensity value of at least one spectral component of the light detected by the light sensor and to compare it with a threshold value. Such a procedure is particularly advantageous if additional light sources could potentially distort the measurement results. If the intensity value of a spectral component that typically only occurs in daylight is used for the analysis, the occurrence of a difference that lies above an empirically determined threshold value can assign the corresponding light sensor the first orientation towards the sky. If, on the other hand, it is not possible to detect that the threshold value has been exceeded based on the difference, the light sensor is assigned the second orientation.

[0017] Alternatively, the information processing unit can also be configured to determine a temporal change in a spectral analysis. The information processing unit performs a comparison with a pattern that corresponds to the typical progression of the intensities of spectral components in daylight over time. If the temporally changing spectral components match this pattern, the measurement was performed by the light sensor oriented toward the sky. If, however, no match is detectable, the sensor is oriented toward the ground. Here, too, it is preferable if a measurement is taken over a period of 12, preferably 24, hours.

[0018] According to a further preferred embodiment, the measurement is repeated cyclically. The information processing unit is configured to store the most recent measured value as the first measured value until a trigger event occurs, which is then compared with a second measured value determined after the trigger event. The trigger event is an event to which a known change in the intensity of the light to be measured can be assigned. In particular, the trigger event is the (first-time) switching on of the lighting. Switching on the lighting immediately leads to an increase in the reflected portion and thus to an increase in the measured intensity for the sensor oriented toward the ground. A light sensor oriented in the first direction, on the other hand, will not react to the switching on process.If a temporal coincidence can be detected between an increase in the measured intensity by the light sensor and the switch-on process, the light sensor is mounted in the second orientation. However, if such an increase in intensity is not observable at the time of switch-on, the light sensor is mounted in its first orientation.

[0019] The module according to the invention for a street lamp integrates the system m for detecting the orientation of a light sensor. The module comprises a circuit board on which light sources are arranged, and has a first interface arranged on the same side as the light sources, and a second interface on the side facing away from the light sources. With such an arrangement of the two interfaces on the circuit board of the module, it is automatically ensured that at one interface approximately exclusively daylight can be measured by the light sensor, while at the other interface practically only reflected light can be measured. For the sake of simplicity, any additional light sources that may be only temporarily in the detection range of the light sensor, such as car headlights, are neglected here.

[0020] The following explanations relate to a system integrated into a street lamp. However, the invention is not limited to such a street lamp. In particular, in contrast to its preferred integration into the light sensor or the control device of the street lamp, the information processing unit can also be implemented as a separate information processing unit, i.e., a dedicated processor. This can also be arranged outside the street lamp, in which case it would have to be connected to the light sensor(s) in order to receive the intensity values measured by the light sensor(s). Alternatively, it is also possible to integrate the information processing unit directly into the sensor. In this case, the light sensor would directly output its orientation as information. The assignment of the light sensor to an orientation would then have to be reported back to the control unit.

[0021] The module according to the invention is explained in detail below with reference to the attached drawings. Fig. 1 shows a schematic representation of a street light with the system according to the invention for detecting orientations of light sensors; Fig. 2 shows an example for evaluating a temporal progression of measured intensity values for a light sensor in the first orientation and a light sensor in the second orientation; and Fig. 3 shows an example for evaluating a jump in intensity in response to a lighting switch-on process.

[0022] The Figure 1shows a street lamp 1 with a housing 2 in which a module is arranged, which comprises a circuit board 3 on which a plurality of LEDs 4 are arranged. The LEDs 4 are supplied with electrical energy by an operating device 5 in order to emit light. For the automated switching of the LEDs 4 on / off, the ambient light must be detected. To accommodate different installation situations, a first interface 6 and a second interface 7 are provided on the circuit board, which are formed on the top and bottom of the circuit board 3, respectively.

[0023] Each of the interfaces 6, 7 can accommodate a light sensor 8, 9. Due to the orientation of the interfaces on the top side of the circuit board 3, a light sensor 8 inserted into the first interface 6 measures only directly incident daylight. A light sensor 9 inserted into the second interface 7, in contrast, measures reflected light. The housing 2 of the street lamp 1 shades the incoming sunlight, so that only reflected light can enter the detection range of the second light sensor 9. The detection ranges of the two light sensors 8, 9 are in the Figure 1 indicated by the dashed lines. Finally, a light exit opening 10 is formed on the underside of the housing 2 of the street lamp 1, which can be closed by a glass or a diffuser.

[0024] Both the first light sensor 8 and the second light sensor 9 will measure changing intensity values for the incident light throughout the day. However, the absolute measured values at the same time differ. According to the invention, these different intensity measured values are used to infer the orientation of the light sensors 8, 9.

[0025] For the correct operation of the street lamp 1, it is now necessary to know whether the measured ambient brightness was detected by the first light sensor 8 or the second light sensor 9, so that a switching-on process of the lighting can be triggered by comparing the measured brightness with a threshold value valid for the respective light sensor 8 or 9 (first control or second control).

[0026] For the following explanations, it is assumed that each of the light sensors 8, 9 has an information processing unit that can be used to assign the orientation of the light sensor 8, 9. Alternatively, it is also possible for the information processing unit to be part of the control unit, which in turn is integrated into the operating device or even external to the streetlight. In this case, the measured values of the light sensors must be fed to the information processing unit.

[0027] If the information processing unit and the control unit are part of the respective light sensor 8 or 9, the first threshold value and the second threshold value are stored in the light sensors 8 or 9. If its installation position is known, the respective light sensor 8 or 9 can then use the threshold value matching its orientation for comparison with the measured ambient brightness and thus transmit a switching signal to the operating device 5 when the ambient brightness required to switch on the lighting is reached. The procedure for assigning the first or second orientation to a light sensor 8, 9 is now described using the Figures 2 and 3 described.

[0028] First, Figure 2 a daily course of a measured intensity, where the upper diagram of the Figure 2qualitatively shows the intensity curve for the first light sensor 8 and the lower diagram qualitatively shows the measured intensity curve for the second light sensor 9. It can be seen that the first light sensor, which is oriented towards the sky and thus also towards the sun, shows a much stronger increase in the measured brightness than the second light sensor 9. This difference in the measured brightness over the course of the day is now used for evaluation.

[0029] In the simplest case, the intensity values are determined over a 24-hour period. From this curve, the maximum intensity value is then determined and compared with a stored limit value E th . This limit value E th is empirically determined and is set such that, when directly incident daylight is detected, the value is reliably exceeded during the daytime maximum. As described in the Figure 2However, as can be seen, the maximum value of the intensity of the reflected light does not reach the limit value E th . Therefore, if the maximum value over a period of 24 hours is above the limit value E th , the light sensor that provides this intensity value must be the first light sensor 8, to which the first orientation is consequently assigned.

[0030] Conversely, a light sensor whose measured maximum intensity does not reach the limit value E th is assigned the second orientation.

[0031] While the orientation of a light sensor 8, 9 can be determined by comparing an absolute value with the limit value E th, it is also possible to evaluate a relative change in the measured value over time. In this case, measured values from the mounted light sensor 8 or 9 are determined at two successive points in time. As can easily be seen from the two curves, the respective orientation of the light sensor can be determined from the gradient, i.e. the increase or decrease over time. The two measured values should be taken at times at which a clear increase or a clear decrease in the measured intensity can be detected. If this is not the case, for example in the area around the respective maximum, the second measurement can be repeated at a later time.The determined difference is compared with a stored, empirically determined limit value. Depending on whether the difference is greater or smaller, the upper or lower light sensor 8 or 9 is used. To ensure that the measured values are determined at times when the curves have a meaningful trend, the measurement times can be fixed, e.g., set during commissioning.

[0032] Instead of using just two individual measured values, it is of course also possible to consider the entire curve over a period of, for example, 12 or 24 hours. For light sensors 8 and 9, the differences between the minimum and maximum values resulting from the observation period are then calculated and compared with a stored, empirically determined reference value. The magnitude of the difference between the minimum and maximum values indicates whether the mounted light sensor 8 or 9 is oriented upwards or toward the ground.

[0033] In a similar way to the above discussion of the intensity of the total incident light, a characteristic (spectral) component of the light can also be used to improve the accuracy or reliability of the determination. It is particularly useful to use a spectral range for the evaluation that can be clearly assigned to daylight.

[0034] The Figure 3 shows a further example of how the orientation of the light sensors 8, 9 can be deduced from their measured intensity values. This exploits the fact that the time at which the LEDs 4 are switched on by the operating device 5 is known. The timing of the switch-on process correlates with a jump in the measured intensity for the second light sensor 9, since the additional light from the LEDs 4 is reflected and thus also measured by the second light sensor 9. This jump in the measured intensity is shown in the bottom sub-diagram.

[0035] The first light sensor 8, however, will not react to the lighting being switched on, since no reflected portion of this additional light source can fall onto the sensitive surface of the light sensor 8. By comparing the temporal position of an intensity change with the time of switching on, the first or second orientation of the corresponding light sensor can be determined. If a coincidence is detectable, the second orientation is assigned to this light sensor; if such a coincidence is absent, the first orientation is assigned.

Claims

1. Module for a streetlight (1), comprising: a system for identifying an orientation of a light sensor (8, 9), a printed circuit board (3) on which lamps (4) are arranged, a first interface (7) which is arranged on the same side as the lamps (4), and a second interface (6) on the side facing away from the lamps (4), wherein each of the interfaces (6, 7) can accommodate the light sensor (8, 9), wherein the system comprises the light sensor (8, 9) and an information processing unit which is configured to assign the light sensor (8, 9) to a first orientation or to a second orientation based on at least two measurements carried out at different times or on a comparison of relative spectral components, wherein the module is designed such that in the first orientation, directly incident daylight is detected by the light sensor (8, 9) and in the second orientation, reflected light is detected.

2. Module according to claim 1, characterized in that the system of the module has a control device for light control, the control device being designed to carry out a first control or a second control depending on the identified orientation of the light sensor (8, 9).

3. Module according to claim 1 or claim 2, characterized in that the information processing unit of the system of the module is designed, for the purpose of an analysis, to determine a maximum value from a temporal profile of an intensity value of at least one spectral component of the light detected by the light sensor (8, 9), and to compare said maximum value with a threshold value.

4. Module according to claim 1 or claim 2, characterized in that the information processing unit of the system of the module is designed, for the purpose of an analysis, to determine a difference between the maximum value and a minimum value from a temporal profile of an intensity value of at least one spectral component of the light detected by the light sensor (8, 9), and to compare said difference with a threshold value.

5. Module according to claim 1 or claim 2, characterized in that the information processing unit of the system of the module is designed to determine a temporal change in a spectral analysis.

6. Module according to any of claims 1 to 5, characterized in that the information processing unit of the system of the module is designed to consider measured values over a period of at least 12 hours, preferably 24 hours, for analysis.

7. Module according to claim 1 or claim 2, characterized in that a cyclical repetition of the measurement takes place and the information processing unit of the system of the module is designed to store the most recent measured value as the first measured value until a trigger event occurs, which first measured value is compared with a second measured value determined after the trigger event.

8. Module according to claim 7, characterized in that the trigger event is a first-time power-on process.