This invention includes a device of the type included in the introduction to Claim 1, for control of lighting fixtures, especially indoor lighting system.

With such a control unit, the individual fixture, or groups of fixtures, can be dimmed or disconnected when the necessary level of lighting in the appropriate section of the room is maintained by a sufficient supply of daylight/sunlight. This will have a favorable effect on the indoor climate, especially during periods of high outdoor temperatures. Disengaged lighting sources can mean a direct savings of energy costs, and can, in many cases, reduce maintenance costs. To attain this, one formerly had to use local or central control units that engage or disengage, or dim fixtures or groups of fixtures by way of photo cell measurement of the illumination at a reference point, and/or with the help of a clock switch. (This is described in Elektro-Elektro-teknisk Tidsskrift 91, no.7, April 11, 1978, pp.12-15; Lampetten, no.3, 1977; brochures from Notika A/S, DK-9400 Nørresundby, about the product LUXSTAT [trademark]). One can also find manual remote control units based on transfer of control signals via infrared rays for local engagement or disengagement, or dimming of fixtures or groups of fixtures (one such device is described in Siemens Elektrodienst 26, Heft 3, 1984, p.23). Such units

are also .found in combination with the automatic control units mentioned above, for example, in Philips Technical Information "Light" and "Integrated Function System". The known automatic control systems use an individual detector (photo cell) to register at an eligible reference point, either the sum of the daylight/sunlight and the artificial lighting in the room, or the illumination outside the building.

In all the rooms with access to daylight, illumination varies strongly for daylight alone from place to place, and also over time due to changes in the sun's position combined with the room's architecture. The need for additional artificial lighting varies from place to place, and over time, in the room. It is therefore a considerable problem to find a reference point for the detector, which can be said to be representative for the room in its entirety.

It is also a problem that the need for illumination can vary from one work station to another. It is also a disadvantage that the existing technical solutions for automatic control demand extra installations of control signal leads or their own power courses for the lighting installations. This produces extra installation costs with new equipment and expensive additional installations with use of existing systems.

The main object of this invention is to create a device that allows automatic control of the individual fixtures in such a way that the control of the individual fixture doesn't influence the corresponding controls of the other fixtures in the room, thus preventing instability.

It must be possible to calibrate the control unit of a single armature individually, in accordance wj.th the illumination that is appropriate for the part of the room that is concerned.

This can be achieved by developing a device according to the characterizing part of claim 1.

The invention makes possible local control of light sources in new or existing systems without extra costs tied

to the introduction of control signal leads or seperate power courses for the lighting installations.

Other advantages of the invention are illustrated in the sub-claims. The invention will be described in more detail below with reference to the illustrations:

Fig. 1 illustrates an example of the geometric relationship of a fixture connected to a ceiling.

Fig. 2 illustrates schematic graphs for the various components of the light flux, which can be measured in the working area of fig.l.

Fig. 3 illustrates schematically the electrical circuit for a fixture with a luminous tube, which is supplied with a device in accordance with the invention. Fig. 4 illustrates schematically the optical and electronic components of one embodiment of the invention.

A fixture 11 with a luminous tube placed under a ceiling 12 to. illuminate a desk 13 is shown in fig. 1.

The fixture 11 is supplied with a device 14 developed in accordance with the invention to control the on/off connection ^' s. The details of this device will be described below. Only its optical system 15 with a detector

16, which captures light from the place of work will be described here. The detector 16 is placed in a tube-shaped shield 17 which is covered with an optical filter 18. The shield 17 limits the opening angle -^ of light that falls on the detector 16.

Fig. 2 shows graphs for the variation of illumination- on the area of measurement dependent on the time. A constant daylight/sunlight component E orginates from a window (not shown) up to the work area in fig. 1. In addition, we get illumination due to the electric light,

E . This will vary with the electrical signal, i.e. with the double frequency of the power frequency 100 HZ, between E A_max and E A_,mm. . A certain illumination will also exist when the electrical signal is zero due to sluggishness of the lighting system within the luminous tube.

How the device, according to the invention, reacts to combined light signals that falls on the detector 16 ^' will be described in more detail below.

Fig. 3 illustrates the electrical components of the luminous tube fixture 11. The main element here is a luminous tube 20 with a starter 21, a reactor 22 and a phase condensor 23. These components are connected in a wellknown manner to each other and to an inlet clamp 24. The device, according to the invention, which is generally referred to by its reference number 14, includes an electrical part 25 that is connected in series between the net and the tube fixture 11, and an optical part 15 with the detector 16.

Fig. 3 shows an example of a lighting unit 25 for on/off connection. It includes an electronic switch 27 that is connected -in series between a grid inlet and the luminous tube fixture 11. The electronic switch 27 is guided on and off through signals from a compara-tor circuit 28. This can be compared to an entry signal from the detector 16 over a circuit 29, which will be described in more detail with a reference signal that is controlled by a potentiometer 30. The electronic circuit 29 includes an electronic filter, a time delay mechanism and an amplifier. The function of these parts will be described in more ' detail below. It is presupposed that the circuit will be built up on principally known methods by available components.

Fig. 4 also illustrates in more detail the development of a telescopic, tube-shaped shield 17, which is fastened to a housing 31 outside the detector 16. In the example, the optic filter 18 is fastened over the inner opening of the shield 17.

The housing 31 can be used to fasten existing fixtures, for independent coupling, or for concealed mounting.

To achieve the object of the invention, it is necessary that measurement of the light and the treatment

of the signal that is registered occur in one or more of the following ways:

1. The optical filter 18 must be developed to transmit light in an area of the spectrum where the relationship between the inherent optical signal and the main optical signal, namely created of foreign light, is at a minumum. In one example, this would mean that a filter is used that allows light through that is near the infrared zone. 2. The detector 16 can be made of a material with especially high spectral sensitivety in the zone mentioned above. This also contributes, first and foremost, to the measurement of the foreign light entering the area of measurement. 3. The electronic circuit 29 contains components that calculate the main signal, i.e. the component of foreign light E , on the basis of the registered variation of illumination during the period of alternating current, as shown in fig. 2 According to the invention, it is possible with a control unit to guarantee correct illumination in the fixture's area of illumination by individual calibration. This implies that only the number of fixtures that are

necessary to maintain correct illumination is working at any given time.

A more detailed description of the signal treatment in the control circuit 29 will now follow.

The electrical signal from the detector contains an almost completely constant section that can be -relayed to the daylight/sunlight component E in the illumination of the area of measurement, and a section that can be relayed to the illumination E that is caused by electrical light sources. This is illustrated in fig. 2. The electrical signal can be amplified. Under the assumption of a characteristic value of the relationship

EA,mm. /EA-.ma , the section EA_ can be filtered out, and the reamaining p *ortion of EA_.mm. is minimized as far as possible, in principle, it is eliminated completely. Thus,

the final electrical signal contains information only on component E and possible re enants of E . This is then treated in the comparator.

The amplifier circuit's time delay hinders random variations of short duration in the illumination of the target area, leading to an on or off movement of the fixture.

The final electrical signal in the comparator circuit will be compared to manual regulating levels for illumination and hysteresis'. The level for hysteresis is adjusted by a potentiometer 32. The hysteresis operates such that the level of illumination that leads to an off movement of the fixture lies higher than the equivalent that leads to an on movement, thereby avoiding the existence of mutal influence and unstability for the individual fixture and the fixtures among themselves. The signal from the comparator circuit 28 then activates the electronic switch 27 in or out.

The invention can be modified in different ways in relation to the example. The electronic switch 27 can be replaced with a circuit that can control the lighting fixture without steps or step by step, for example, a phase-controlled triac. In this way an even more exact adjustment of the illumination can be carried out. The invention will be suitable for use with individual lighting fixtures. In principle, it can also be used for groups of two or more fixtures that are controlled under one system. In this case, the device will have a central placement in the complete light field from the fixtures. For example, a number of fixtures along a wall with windows can be controlled individually and fixtures that are placed farther within the room can be controlled individually.

The control system, in accordance with the invention, can also be combined with a system for connection and disconnection with the help of an IRT sender, that corresponds to that which is described in the report on the known technique above.