FI116356B - Condition monitoring system - Google Patents

Description

Background of the Invention

The invention relates to a method according to the preamble of claim 1 for monitoring the condition of one or more LEDs and to a device according to the preamble of claim 7 for monitoring a condition of one or more LEDs.

The standards stipulate that all types of emergency lamps must be periodically inspected. Automatic condition monitoring of tur-10 flashlights with incandescent and discharge lamps is standard. By monitoring the condition of these lamps, the operational status of the light source can be easily determined by measuring the electrical parameters of the lamp.

Light-emitting diode (LED-powered) luminaires are now increasingly used as exit signs and emergency lights. The condition of these 15 lamps must also be monitored in accordance with the standards. In prior art arrangements, the problem of condition monitoring of LED luminaires is to automatically and reliably measure the condition of the luminaire, since the LED may lose its illumination slowly and its current will not change but remain at its original value, thus measuring the current or voltage, i.e. electrical parameters reliably found out.

The condition of LEDs can also be measured by measuring the light they produce from the outside of the luminaire, but it is difficult if the luminaire contains; · There are several LEDs or / and the luminaire is placed in an environment with bright: ,, / backlight. In this case, the light emitted from the outside of the luminaire and produced by adjacent LEDs: '25 light makes the results unreliable

BRIEF DESCRIPTION OF THE INVENTION It is thus an object of the invention to provide a method according to the characterizing part of claim 1 and an apparatus according to the characterizing part of claim 7 so as to solve the above problems. 30 tua. The object of the invention is achieved by a method characterized by: "comprising the steps of: controlling the LEDs with a pulsed current, measuring the light output of the LEDs or LED lamp with one or more light sensors during a minimum and maximum level of pulsed control current, distinguishing between two separate measurement signals from the minimum and maximum levels of pulsed control current from the mit 35 outputs, and deducing measurement signals corresponding to the minimum and maximum levels of control current 116356 by comparing the functional status of the LEDs or LEDs. means for supplying a pulsed control current to the LEDs and / or the LED luminaire, 5 one or more light sensors for measuring the light output of the LEDs and / or the LED luminaire, and signal processing means for receiving signals from the light sensor äsittelemiseksi.

Preferred embodiments of the invention are claimed in the dependent claims.

The invention is based on the fact that an LED lamp comprising one or more light emitting diodes is controlled by a pulsed current, whereby the LEDs alternately illuminate and are switched off or illuminate brightly and dimly. The output of the LEDs or LED luminaires so controlled is measured by one or more light sensors mounted in connection with the luminaire. The light sensor produces a measurement signal, which varies substantially uniformly with the pulsed current. This measurement signal is separated into two separate signals, one corresponding to the minimum level of the pulsed current and the other to the maximum level. The two separated measurement signals are then compared to each other and the result of the comparison is the difference between the light output of the LEDs over a minimum and a maximum of pulsed current. As the light output of the LEDs fades, this difference becomes smaller. . nee LEDs and finally the difference reaches zero at the end of the light output of the LEDs. When the LEDs are lit, the luminous intensity detected by the light sensor is formed by LE-

The sum of the light output produced by the dienes and the light emitted from the surroundings, whereas when the LEDs are off, the measured luminous intensity is formed only by the light emitted from the surroundings, provided that the minimum level of pulsed current is zero. Thus, the difference between the two separate mit results obtained with the light sensor corresponds in each case to the light output produced by the LEDs.

An advantage of the method and system of the invention is that • external ambient light can be eliminated from light sensor measurement results, * * · 30, so that it no longer causes distortion when monitoring the operating condition of the luminaire. Further, the method and apparatus of the invention provide a reliable solution for LED condition monitoring that is independent of the electrical parameters of the LEDs and the LED luminaire.

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BRIEF DESCRIPTION OF THE DRAWINGS »> 1 1» • »35 The invention will now be further described with reference to preferred embodiments, with reference to the accompanying drawings, in which: 3 1 1 6 3 b 6

Fig. 1 is a schematic view of an LED luminaire whose operating condition is monitored in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to Figure 1, there is shown a schematic view of an LED luminaire according to the present invention, comprising means for monitoring the operation of the LEDs. Such an LED lamp comprises one or more LEDs 2, the operation of which is controlled by the power supply means 6. The power supply means 6 are configured to supply pulse-like current to the LEDs, wherein the LEDs are alternately lit and off. The frequency of such pulsed current may vary from e.g. 20 to 500 Hz. An example of a pulsed current 14 is shown in Figure 1. At the maximum level 15 of the pulsed current 14, the LEDs 2 are on and producing light and at the minimum level 13, the LEDs 2 are off and do not produce light.

The frequency of the pulsed current 14 can be selected to suit each luminaire application and / or use situation. Further, the amplitude of this pulsed current 14, which illustrates the intensity of the current supplied to the LEDs 2, can be selected as required. It is also possible to change the pulse ratio of the current supplied to the LED 2 by adjusting the maximum level 15 of the pulsed current 14, whereupon the LEDs 2 receive current, relative to the time length of the mini-20 level 13, whereby the LEDs 2 do not receive current. By changing the pulse ratio as described above, it is possible to adjust the brightness of the luminaire by increasing the length of the maximum level 15 relative to the length of the minimum level 13. This pulse current 14 is utilized here to provide the pulse oscillator, but it can also be generated by any other device that allows pulse current to be generated.

It is also possible to set the current pulse going to the LEDs 2 such that, at the minimum level 13, the LEDs 2 are supplied with a current which, by its pulse-like nature, is smaller than the current supplied at the maximum level 15. However, in the following example, the current at the min level 13 is assumed to be zero.

; According to the present invention, an LED lamp is mounted inside; A light sensor 4 that measures the intensity of light inside the luminaire. The intensity of the light inside the luminaire is constantly the sum of the ambient light, ie:! From the outside, the light coming from and the light output from the LEDs 2.

] (: At the minimum level 13 of pulse current 14 supplied to LEDs 2, this light output generated by LED 2 is zero because LEDs 2 do not illuminate and thus emit light, so that the light intensity inside the luminaire consists only of light from environment 116356 4. Pulse current 14 at a maximum level 15, the LEDs 2 produce light as they receive power, so that the intensity of light inside the luminaire is the sum of the light emitted from the surroundings and the illumination output generated by the LEDs 2. Thus, light sensor 4 automatically measures ambient light 5 pulsed current 14 at minimum level 13 and total light pulsed current 14 at a maximum level 15.

From the measurement results obtained from the sensor 4, two separate measurement signals are distinguished, one corresponding to the measurement result obtained at the maximum level 15 of the pulsed current 14 and the other corresponding to the measurement result obtained at the minimum level 13. The separation of these two separate measuring signals 10 is effected by the separation means 18 in the comparing means 8. The separating means 18 may, for example, be a switch which acts in response to a pulsed current signal from the power supply means 6 as shown in FIG.

The light intensity measurement signals corresponding to the maximum level 15 and the minimum level 13 of the pulsed current 15 applied to and separated by the reference means 8 are compared to each other. The comparison is preferably made by calculating the difference between the two separate measurement results in the resolution means 16. This is done in practice by taking voltage samples from the separated measurement signals of the light sensor 4, which are applied in so-called. a voltage sample representative of the minimum level 13 of the pulsed current 20 when the LEDs are off, is stored in the memory 10. A voltage sample representative of the maximum level 15 of the pulse current 14 when the LEDs are lit is stored in the memory 12. are then compared to each other by calculating the difference for them. These two separate levels of signal 25 stored in the memories 10, 12 can also be averaged over time by suitable averaging means, whereby sudden and transient changes are filtered out of the measurement results. When using the reference means 8 of FIG. 1, the switch 18 responsive to the pulse current 14 controls the output of the light sensor 4 when the LEDs are lit; ; the measurement signal to memory 12 and when the LEDs are off, the light sensor 4 receives ** **. 30 way measurement signal to memory 10.

Since the measurement signal representing the minimum level 13 of the pulsed current 14 contains only the ambient light intensity and the measurement signal representing the maximum level 15 ../ contains both the ambient light intensity and the light output generated by the LE, the ambient light intensity is filtered. 35 from the background results, the difference between the two separate measurement signals. This leaves only the values of the light output 116356 5 generated by the LEDs, of which the value corresponding to the minimum level 13 of the pulsed current 14 is zero in this embodiment because the LEDs do not receive current. Thus, by calculating the difference between the two measurement signals, the light output of the LEDs and hence the condition of the LEDs and / or the LED lamp is continuously determined.

5 The values obtained by the discriminating means 16, which represent the operational status of the LEDs 2 or the whole LED lamp, can be further compared to a predetermined threshold value. Because LEDs tend to fade over long periods of use, this comparison with a predetermined limit allows for a fully automatic monitoring of LED status. In this case, when the representative value of the LEDs obtained from the separating means 16-10 is reduced, an alarm can still be made by means of an alarm device (not shown) connected to the comparing means 8. After the alarm, the LED lamp can be restored to service by servicing or by replacing the lamp.

Monitoring of LED operation can be further facilitated and simplified by connecting the pulse current 14 power supply means 6 and the light sensor 4 to a microprocessor and / or a computer, thereby forming a reference means 8. The processing of the measurement signal from the light sensor 4 can be performed entirely or partially by a microprocessor. In this case, the difference between the measurement signals corresponding to the min level 13 and the maximum level 15 of the pulsed current 14 is stored, stored in the memories 10, 12, compared to them and given an alarm. based on a predetermined threshold, it can be easily accomplished with the help of a micro, V processor and / or a computer and possible software using I * ·.

With the apparatus described above, a method according to the present invention for monitoring the operation of an LED lamp can be carried out. According to the method, the light output of the LED-controlled LED pulse 14 is measured by a light sensor 4 mounted inside the lamp. Due to the wood-like current, the light output varies according to the current variation, whereby: the measurement signal obtained by the light sensor 4 corresponds substantially to a pulse frequency;

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, ···. 30 earth current frequency. This measurement signal is further passed to the comparator means 8, where two separate measurement signals are separated from the measurement signal, one corresponding to the luminous intensity of the LED lamp at a minimum level 13 of pulsed current 14 and the other at a maximum level 15. These two separated measurement signals , 12, and a mean score of 35 to eliminate sudden changes in ambient light. These averaged measurement signals are then compared to each other by calculating 116356 6 their difference and the resulting difference is further compared to a predetermined threshold. When the difference between the measurement signals falls below a predetermined threshold, an alarm is triggered when the LED luminaire is operating below the allowable value.

It will be obvious to a person skilled in the art that as technology advances, the basic idea of the invention can be implemented in many different ways. The invention and its embodiments are thus not limited to the examples described above, but may vary within the scope of the claims.

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Claims (14)

116356 A method for monitoring the condition of an LED luminaire comprising one or more light emitting diodes, characterized in that the method comprises the following steps: 5. controlling the LED (2) with a pulsed current (14) comprising a minimum level (13) and a maximum level (15); - measuring the light output of the LEDs (2) or the LED lamp with one or more light sensors (4) during the minimum level (13) and maximum level (13) of the pulsed control current (14), 10. distinguishing between the minimum level (13) and the maximum level 15) two separate measurement signals from the light outputs measured during the operation, and - deducing measurement signals corresponding to the minimum level (13) and maximum level (15) of the control current (14) by comparing the operation status of the LEDs or LED-15. Method according to Claim 1, characterized in that the comparison of the respective measurement signals of the minimum level (13) and the maximum level (15) of the control current (14) is performed by calculating the difference between them. Method according to claim 1 or 2, characterized in that it further comprises the step of averaging the measurement signals corresponding to the minimum level (13) and maximum level (15) of the control current (14) over a certain period of time before determining the LED or LED lamp operating condition. The method of any one of the preceding claims, characterized in that it further comprises the step of setting a predetermined threshold value for the result of a comparison / difference between the measurement signals corresponding to the minimum level (13) and maximum level (15) of the control current (14). A method according to claim 4, characterized in that the method further comprises the step of providing an alarm with a control signal: (14) of the measurement signal corresponding to a minimum level (13) and a maximum level (15): value. »* · Method according to one of the preceding claims, characterized in that the processing of the measurement signals obtained from the light sensors (4) is carried out wholly or partly by a microprocessor in order to determine the operating condition of the LEDs and / or LED light. »·: ··: 35 Apparatus for monitoring the condition of an LED luminaire comprising one or more light emitting diodes (2), characterized in that the apparatus comprises 116356 power supply means (6) for supplying a pulsed control current to the LEDs and / or the LED luminaire, one or more luminaires (4) for measuring the light output of the LEDs and / or the LED light, and signal processing means (8) for transmitting the cassettes 5 of the measurement signals received from the light sensor (4). Device according to claim 7, characterized in that the power supply means (6) for supplying a pulsed control current to the LEDs and / or the LED lamp comprises a pulse oscillator. Device according to claim 7 or 8, characterized in that the comparison means (8) comprise discriminating means (18) for distinguishing between the minimum level (13) and the maximum level (15) of the pulsed control current (14) with the light intensities measured by the light sensor (4). Apparatus according to any one of claims 7 to 9, characterized in that the reference means (8) further comprises a memory (12) for storing a measurement signal obtained during a maximum level (15) of a pulsed 15 current and a pulsed control current (10) for the memory (10). 14) for recording the measurement signal obtained during the minimum level (13). Device according to any one of claims 7 to 10, characterized in that the signal processing means (8) comprises means (20) for determining the difference between the minimum output level (13) and the maximum output level (15) of the control current. Device according to Claim 11, characterized in that 'the device further comprises an alarm device for providing an alarm, the difference between the light output of the control current mi during the nominal level (13) and the maximum level (15): 25 below a predetermined threshold. Device according to any one of claims 7 and 9 to 12, characterized in that the microprocessor comprises signal processing means (8, 18, 10, 12, 16). Device according to any one of claims 7 and 9 to 13, characterized in that the computer and / or computer software comprises signal processing means (8, 18, 10, 12, 16). 116356