STREET LIGHT WITH WEATHER-SENSITIVE LIGHT EMISSION

Description

[0001] The present invention relates to a street lamp which is designed to change a light output depending on the weather.

[0002] The weather has a strong influence on visibility conditions in road traffic. For example, the lighting function of a street light changes in snow or rain. Lighting that is perceived as ideal in dry conditions with good visibility can lead to strong scattering or glare in precipitation, which road users find unpleasant and tiring. This can also impair road safety.

[0003] EP 2 884 312 A1 discloses a street light according to the preamble of claim 1. Further lights and weather sensors are disclosed in the documents US 2018 / 124900 A1, CN 106 704 979 A, ​​GB 966 769 A, JP 2010 107528 A and US 2007 / 132599 A1.

[0004] The object of the present invention is to provide a street light which can fulfil its lighting task in the best possible way even in changing weather conditions.

[0005] The problem is solved by a street lamp according to claim 1.

[0006] A special feature of the street light according to the present invention is a weather sensor that is designed to reliably detect rain and / or snow. For this purpose, the weather sensor has at least one pair of electrodes on an insulating body and is designed to measure the resistance or capacitance between the two electrodes. If the electrodes are spaced apart and there is no conductive material in between, the resistance is naturally very high. However, if moisture gets between the electrodes, the resistance decreases. Alternatively, the moisture between the electrodes can also be determined by determining the capacitance. Therefore, the level of resistance or capacitance can be used directly to adapt the light to the weather conditions. For example, if the resistance or capacitance is reduced.The luminous flux can be adjusted to reduce secondary glare for road users caused by light reflected from the rain or snow surface. Alternatively, or additionally, the light color can also be changed. It is known that the blue component of light causes greater glare than the red component. For example, if snow or rain is detected, the red component can be increased relative to the blue component, thus reducing glare.

[0007] According to the invention, the street light has at least three electrodes, with two electrodes arranged at a shorter distance and the third electrode at a greater distance from one of the first two electrodes. The electronic circuit is configured to measure both the resistance or capacitance between the two more closely spaced electrodes and the resistance or capacitance between the two more widely spaced electrodes. By measuring the resistances or capacitances across two different distances between the electrodes, a more precise statement about the type and intensity of precipitation can be made.For example, by measuring the shorter electrode gap, a precise statement can be made about rain, while the measurement over the larger electrode gap allows a statement to be made about snowfall in particular, because the snow in the form of a closed layer is also able to electrically bridge a larger electrode gap.

[0008] According to a preferred embodiment, the larger of the two electrode spacings is arranged in a vertical direction and the street light has a plane below the two further spaced electrodes on which snow can collect, so that when snow falls the larger distance between the two electrodes can be bridged by snow. The snow accumulating on the plane can successively form an increasingly thick layer, so that the larger distance between the two electrodes is partially or completely bridged. The resistance or capacitance measurement can therefore provide information about whether snow is present and, if applicable, even how much snow is present. This embodiment is therefore particularly advantageous for being able to control the light in response to changed weather conditions with regard to a continuous snow cover.The two other electrodes, which are arranged at a smaller distance from each other, can be used independently to determine rain.

[0009] According to a preferred embodiment, the defined distance between the two electrodes is in the range of 1 mm to 10 mm, and in the embodiment with three electrodes, the larger distance between the second electrode and the third electrode is in the range of 10 mm to 20 mm. The smaller distance of 1 mm to 10 mm is suitable for detecting rain, while the larger distance of 10 mm to 20 mm is particularly suitable for detecting snow.

[0010] According to a preferred embodiment, one of the electrodes consists of a luminaire housing, a luminaire pole or another structural component of the street light which is made of metal. At least one of the two or three electrodes can be formed by a metallic component of the luminaire. In particular, if the weather sensor is arranged, for example, on top of the luminaire housing, the luminaire housing itself can serve as an electrode, since it is made of a metallic material anyway. However, a luminaire pole, a luminaire pole boom or another supporting or covering part of the luminaire can also serve as an electrode, provided that one or the two other electrodes are arranged separately from this component by an insulating body. This simplifies the structure of the luminaire because a separate electrode can be omitted.

[0011] According to a preferred embodiment, the insulating body is a cylindrical body, preferably arranged vertically on the luminaire. The cylindrical insulating body has the advantage of providing the same surface geometry symmetrically on all sides. The electrodes can, for example, be mounted as continuous rings on the cylindrical surface. This structure will always react to the precipitation in the same way with a change in resistance or capacitance, regardless of the direction from which the precipitation hits the sensor.

[0012] According to a preferred embodiment, the insulating body is replaceable in order to adjust the distance between the two electrodes by selecting an insulating body with a thickness corresponding to the desired distance. In this embodiment, the structure of the weather sensor is particularly simple and yet allows adaptation for detecting different types of precipitation. For example, a thicker insulating disc can be selected for detecting snow and a thinner insulating disc for detecting rain. One electrode can be formed, for example, by a cylindrical metallic body on the insulating disc, and the other of the at least two electrodes can be formed by a housing surface or another surface of the luminaire below the insulating disc.

[0013] According to a preferred embodiment, an electrically insulating, absorbent spacer is provided between the two electrodes, wherein at least one side of the absorbent spacer is exposed to weather conditions so that it can absorb moisture from precipitation. During operation, the spacer absorbs moisture when it starts to rain. After the rain has stopped, the absorbent spacer only dries out after a time delay, so that the measurement of the change in resistance or capacitance only responds to the changed weather conditions with a certain time delay. This time delay can be adjusted by selecting the thickness of the spacer so that it corresponds to the drying of the road after the rain has stopped. This allows the light output of the luminaire to be adjusted according to the condition of the road without the need for a time delay in the luminaire's electronic control system.This embodiment is therefore particularly preferred for luminaires that do not have a complex electronic control system in the lamp ballast or other electronic components. This embodiment is therefore also particularly suitable for retrofitting luminaires that do not have a corresponding complex electronic control device. The weather sensor can simply be used to control an existing conventional ballast of the luminaire.

[0014] According to a preferred embodiment, one of the two electrodes on the absorbent spacer body is designed as a grid electrode. The grid electrode ensures that the absorbent spacer body is exposed to weather conditions on at least one side, so that the spacer body can absorb moisture like a sponge when precipitation begins and slowly release the moisture again after the precipitation has stopped.

[0015] According to a preferred embodiment, the spacer is arranged relative to a heat-generating component of the luminaire, in particular a light source, such that the spacer can be heated by the component during operation of the luminaire, e.g., through heat transfer or thermal radiation. Arranging the absorbent spacer near a component that generates heat during operation of the luminaire has the advantage that the drying rate of the spacer after the rain has stopped is increased under the influence of the heat generated by the luminaire during operation. This allows the time constant with which the spacer dries after the rain has stopped to be adapted to the drying rate of the road surface.

[0016] According to a preferred embodiment, the control circuit is configured to reduce the luminous flux and / or shift the ratio of the blue and red light colors further toward red upon a measured reduction in resistance or a measured reduction in capacitance. While on a dry road a relatively large amount of light from the street lamp is absorbed by the dark color of the road surface, on a wet road a higher proportion of the light is reflected or scattered. This reflected or scattered light can dazzle road users. To reduce this glare, the luminaire according to the invention simply reduces the intensity of the luminous flux. Since there is enough light overall due to the additional reflected or scattered light on a wet road, even the reduced luminous flux is sufficient to generate an adequate level of illumination.The same applies to reflection from a snow surface. The luminous flux can be reduced by dimming the light sources or by changing the light distribution of the luminaire to a wider light distribution. According to an additional or alternative embodiment, the ratio of the light colors blue and red can also be adjusted. Blue light is known to cause more glare than red light. By reducing the blue component and increasing the red component, glare can therefore be reduced. While white light is preferred for a true color reproduction of the road in dry road conditions, glare is reduced in rainy or snowy conditions by changing the color rendering. Although this means that the color fidelity is no longer the same as in dry road conditions, this is not necessary in critical weather conditions.

[0017] According to a preferred embodiment of the street light with three electrodes, the control circuit is configured to further reduce the luminous flux and / or change the ratio of the light colors even further toward red light if a reduced resistance or reduced capacitance is measured between the two more widely spaced electrodes. A snowy surface reflects or scatters the light from the street light even more than a rain-soaked surface. Therefore, in this embodiment, the changes in illumination upon detection of a snowy surface are further amplified by the more widely spaced electrodes in order to further reduce the increased secondary glare due to the snowy surface.

[0018] Further advantages and features of the present invention will become apparent from the following description of preferred embodiments, which is given in conjunction with the accompanying figures. The figures show the following: Figures 1a-1c show side views of weather sensors on a street lamp according to various embodiments. Figure 1d shows a top view of a weather sensor according to the embodiments of Figures 1a-1c . Figure 2 shows a side view of an alternative embodiment of a weather sensor of a street light in a further embodiment. Figure 3 shows an exploded view of the structure of the sensor element of the Figure 2 . Figure 4 shows a side view of the sensor element of the Figures 2 and 3 Figure 5 shows a block diagram of an electronic circuit for measuring resistance for a weather sensor according to an embodiment of the invention.

[0019] In the Figures 1a to 1cVarious embodiments of weather sensors for street lights according to the invention are shown. The street light itself is not shown, but only a section 3 of its light housing.

[0020] In the Figures 1a and 1b The weather sensor has a cylindrical insulating body 1, on whose outer surface two electrodes A and B are arranged. In the embodiment according to Figure 1b The electrodes A and B are arranged as concentric rings one above the other with a defined distance between the electrodes, which is, for example, between 1 mm and 10 mm. In the embodiment in Figure 1athe two electrodes are arranged in the longitudinal direction of the cylindrical insulating body 1 and are also spaced apart from one another by a distance of, for example, between 1 mm and 10 mm. The cylindrical insulating body 1 is attached in the vertical direction of the lamp, for example on the housing 3. The cylindrical insulating body 1 is closed at the top with a round cap 4, which promotes the dripping off of rainwater or snow. In these embodiments, an electrical control circuit is provided which measures the resistance or capacitance between the electrodes A and B. From the change in capacitance or resistance, it can be concluded that a film of moisture is present in the area between the two electrodes A and B. These measurements are used to activate an electronic control system for the lamp (not shown in the figures) in order to change the light output of the lamp.

[0021] In the embodiments according to Figures 1a and 1b Furthermore, a third electrode C is provided, which is arranged at a greater distance from one or both of the first-mentioned electrodes A and B. In the example, the distance is between 10 mm and 20 mm. The electrode C is formed by a part of the lamp housing 3 itself. As shown in the top view of Figure 1d As shown, the luminaire housing 3 has a plane from which the cylindrical insulating body 1 extends vertically. Snow can accumulate on the surface of the luminaire housing 3, which, as the layer becomes thicker, bridges the distance between electrode C and A or B. Therefore, a resistance or capacitance measurement between the third electrode C and one of the two electrodes A or B can be used to determine whether snow has formed. This measurement also serves to adapt the light output of the street light to changing weather conditions.

[0022] The Figure 1cshows an alternative embodiment. In this embodiment, an electrode A is designed as a cylindrical body made of metal, e.g., stainless steel. The electrode A sits on a disc, which forms the insulating body 1 in this embodiment. The disc 2 is arranged between the electrode A and an electrode B, which is also designed as part of the luminaire housing 3 in this embodiment. The mode of operation is as previously described. When moisture is detected by rain or snow, the resistance or capacitance between the electrodes A and B changes. By measuring the change in resistance or capacitance, the light output is adapted to the changed weather conditions determined by measurement. The example in the Figure 1c However, without a third electrode is not part of the invention.

[0023] The light output can be adjusted by dimming the light intensity of the lamps in the luminaire when precipitation (rain or snow) is detected in order to reduce glare for road users caused by a rain-soaked surface or a layer of snow. Alternatively or additionally, a color shift from blue to red can be made. Since red light is less glaring than blue light, this can also reduce glare. In addition to the option of reducing the light intensity of the lamps overall or changing the color rendering to reduce glare, the light distribution of the luminaire can also be changed to reduce the light density and thus the glare. In this case, the light distribution is changed to a wider light distribution, so that the illuminance on the rain-soaked or snow-covered surface is reduced.

[0024] The adaptation of the lighting conditions to the weather conditions can also be carried out in stages. In particular, the adaptation can be greater when a layer of snow is detected, e.g., by measuring the change in resistance or capacitance between the two electrodes located further away, than when rain is detected by a change in resistance or capacitance between the two electrodes arranged closer together in the embodiments with three electrodes as in Figures 1a and 1b shown.

[0025] A further embodiment of a weather sensor for the luminaire according to the invention is shown in the Figures 3 to 5shown. In this embodiment, the two electrodes A and B are separated from each other by an absorbent spacer 5. The spacer 5 is made of a material with pores, similar to a sponge, and is therefore able to absorb moisture and slowly release it again through evaporation. One of the electrodes A in this embodiment is designed as a grid electrode, so that the absorbent spacer is exposed to weather conditions. The arrangement of the two electrodes A and B and the spacer 5 is arranged in an insulating body 1, similar to the previously mentioned embodiments. During operation, when it starts to rain, the spacer 5 will gradually absorb moisture, so that the resistance and capacitance between the electrodes A and B change.This change in resistance or capacitance is, as in the previous embodiments, measured by a detection device and used to control the light output. A special feature is that when the rain stops, the moisture in the spacer body 5 only slowly evaporates again. As a result, the decrease in the change in resistance or capacitance will occur with a time delay compared to the end of the rain. However, this time delay is desired because the road surface also dries only slowly after the rain has stopped. The change in resistance or capacitance between the electrodes can therefore be used directly to control the light output of the luminaire because the light output of the luminaire should only slowly adjust to the lighting level for dry road conditions when the road dries out after the rain has stopped.

[0026] The previously mentioned pairs of electrodes (regardless of whether they are arranged at a greater or smaller distance) are connected to an electronic device to measure the resistance. Figure 5 shows an exemplary connection of a pair of electrodes A and B according to one embodiment. Each electrode is electronically contacted via a high-resistance resistor 7 (e.g., from 1 to 10 MOhm). The high-resistance design is preferred because the electrons can be touched from the outside and thus the maximum permissible leakage current must not be exceeded. The next stage is an amplifier 8 to make the change in resistance or capacitance measurable. The measurement is performed by a microcontroller 9. This microcontroller can, for example, be part of an electronic ballast of the luminaire or another component of other electronic units of the street light.

[0027] The weather sensor described above can also be connected to a known lighting control device via an interface. For example, the output values ​​of the capacitance or resistance changes generated by the electronics can be connected to a data bus via a Zhaga interface. The change in illuminance can be implemented, for example, via appropriate DALI commands using state-of-the-art control systems.

[0028] The weather sensors described above also have the advantage of being easy to implement. The high-resistance design allows the electrodes to be exposed. Such solutions are significantly simpler and more cost-effective to implement than other humidity sensors such as RF or optical sensors. LIST OF REFERENCE SYMBOLS

[0029] A, B, CElectrodes 1Insulating body 3Lamp housing 4Cap 5Absorbent, insulating spacer 7High-ohm resistor 8Amplifier 9Microcontroller

Claims

1. Street lamp which is configured to change a light output depending on the weather, wherein the street lamp has a weather sensor in order to detect rain and / or snow, characterized in that two electrodes are arranged at a smaller distance and a third electrode (C) is arranged at a greater distance from one of the two first-mentioned electrodes (A, B) in the weather sensor on an insulation body (1), and an electronic circuit of the weather sensor is configured to measure both the resistance or the capacitance between the two more closely spaced electrodes (A, B) and the resistance or the capacitance between the two more widely spaced electrodes (B, C), and in that the street lamp has a control circuit which is configured to change a luminous flux and / or a luminous color of a light output by the street lamp depending on the measured resistance or the measured capacitance.

2. Street lamp according to Claim 1, wherein the greater of the two electrode distances is arranged in a vertical direction and, below the distance between the two more widely spaced electrodes (B, C), the street lamp has a plane on which snow can accumulate, with the result that, in the event of snow, the greater distance between the two electrodes can be bridged by snow.

3. Street lamp according to one of the preceding claims, wherein the smaller distance between the two electrodes (A, B) lies in the range from 1 mm to 10 mm and the greater distance between the second electrode (B) and the third electrode (C) lies in the range from 10 mm to 20 mm.

4. Street lamp according to one of the preceding claims, wherein one of the electrodes consists of a lamp housing (3), a lamp mast or some other structural component of the street lamp which is formed from metal.

5. Street lamp according to one of the preceding claims, wherein the insulation body (1) is a cylindrical body which is preferably arranged vertically on the street lamp.

6. Street lamp according to one of the preceding claims, wherein the insulation body (1) is exchangeable in order to set the distance between the two electrodes (A, B) by selecting the insulation body with a thickness of the insulation body corresponding to the desired distance.

7. Street lamp according to one of the preceding claims, wherein an electrically insulating, absorbent spacer (5) is provided between the two electrodes (A, B) so that it can absorb moisture from precipitation.

8. Street lamp according to claim 7, wherein one of the two electrodes (A) is formed on the absorbent spacer as a grid electrode.

9. Street lamp according to one of claims 7 and 8, wherein the spacer (5) is arranged opposite a heat-generating component of the street lamp, in particular a lighting means, so that the spacer (5) can be heated by the component during operation of the street lamp, for example by heat transfer or by heat radiation.

10. Street lamp according to one of the preceding claims, wherein the control circuit is configured so that it reduces a luminous flux of the street lamp and / or shifts a ratio of the luminous colors blue and red further in the direction of red in the case of a measured resistance reduction or a measured capacitance reduction.

11. Street lamp according to claim 10, wherein the control circuit is configured to reduce the luminous flux even further and / or to change the ratio of the luminous colors even further in the direction of red light if furthermore a reduced resistance or a reduced capacitance is measured between the two further spaced electrodes (B, C).