GB2395842A

GB2395842A - Additional switching device

Info

Publication number: GB2395842A
Application number: GB0227646A
Authority: GB
Inventors: Gavin Hancock; Elliot Makin; Antony Jonathan Sanders
Original assignee: Sanders Associates Ltd; Benchmark Electronics Ltd
Current assignee: Sanders Associates Ltd; Benchmark Electronics Ltd
Priority date: 2002-11-27
Filing date: 2002-11-27
Publication date: 2004-06-02
Anticipated expiration: 2022-11-27
Also published as: GB0522907D0; GB0227646D0; GB2416938A; GB2416938B; GB2395842B

Abstract

An additional switching device 16 comprises a control electronics circuit board 24 interposed between a switch plate 8 and a wall socket 4 to control switching of a light. The board is mounted on a frame 20,52 and includes terminals for connection of a power supply and wires to the light switch. The frame has a perimeter 31 not more than 10% larger than the perimeter 33 of the switch plate. A detection device 28 is connected to the circuit board and is a light, and a presence, detector. The board includes a burglar deterrent function to switch on lights after dark on a timed basis. A presence detection function is also provided to switch on the lights after dark when a person is detected. A function switch to switch between those functions is provided.

Description

ADDITIONAL SWITCHING DEVICE

This invention relates to an additional switching device, particularly for lighting applications and 5 security lighting.

Devices which switch lights on and off at regular, random or programmable times are known in the prior art.

These are called "deterrent lighting" as they deter 10 criminals from entering what appears to be an occupied building. Devices which switch lights on and off when an intruder is detected, for example, PIR security systems, are also known. These may be referred to as "burglar detection security lighting".

GB2290418B discloses a support bracket connected between a switch plate and a patress box without disconnecting the wiring to the switch. An auxiliary control unit is disclosed as being to one side of the 20 switch and, as such, enlarges the overall size of the switch, and is relatively obtrusive. Various functions for the control unit are disclosed.

FR2756081 provides a circuit that allows intrusion 25 detection to be reconfigured to provide an automatic light. US5598041 discloses a portable detector unit in communication with a separate power control arrangement.

30 The detection unit detects the presence of a person in the room and switches lights on in response thereto and in dependence on the ambient light conditions. Such lighting is referred to as "presence detection" lighting or "energy saving" lighting (because the light is 35 automatically switched-off when a presence is no longer ..... ..... À À À À À.. À.

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detected). GB2269008 discloses an external PIR sensor to enable switching between permanently "on" during night hours, 5 and "on" only when movement is detected during night hours. GB2231954 discloses an arrangement for switching on lights in a room, and a detector to detect entry and exit 10 of people from the room. Likewise, GB2218552 discloses a ceiling light having various functions incorporated into its base.

GB2155708 discloses a fitting to be disposed between 15 a lamp holder and the bulb. It is activated by toggling the light switch and has options that include an intruder detector. US4570216 discloses a timer arrangement for 20 switching on lighting and appears appropriate for installation in a standard wall switch box, replacing any existing switch plate.

US4103294 discloses burglar deterrent lighting that 25 switches on lights in response to noises. The circuit is disabled when the light switch is turned on normally.

US4021626 discloses a timer switch for replacing an existing light switch.

It is an object of the present invention to provide a compact wall light switch arrangement that provides useful energy saving and other functions.

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' In accordance with a first aspect of the present invention there is provided a wall light switch arrangement comprising a wall socket, a switch plate for connection to the wall socket, a switch, forming part of 5 the switch plate, and an additional switching device comprising a frame; a control electronics circuit board mounted on the frame and including terminals for connection of a power supply and switched-live lines and wires for connection to the switch; and a detection 10 device connected to the circuit board, wherein the frame is positioned between the switch plate and the wall socket, and has a perimeter no more than 10% longer than the perimeter of the switch plate, no part of the frame or circuit board, other than the detection device, 15 projecting substantially beyond said perimeter.

Preferably, the perimeter of the frame is between 380 and 400 mm long. This is long enough to be larger than most standard switch plates, although ideally, the 20 perimeter of the frame is substantially the same as the switch plate perimeter. Certainly, it should not be smaller, otherwise an overhang will pertain between the switch plate and frame, which would be unsightly.

25 Because the entire circuit board is behind the switch plate, the arrangement is unobtrusive. What is more, the existing switch plate can be used, since essentially only the perimeter of the frame is visible.

Therefore, there is no clash of appearance, as there 30 might be if the switch plate was brass, or metal, and the additional switching device was highly visible, and made of plastics material, for example.

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Accordingly, it is a feature of this invention that the additional switching device might be retrofitted.

Therefore, this aspect of the invention also provides an additional switching device for the switch arrangement 5 defined above comprising: said frame; said control electronics circuit board mounted on the frame and including said terminals for connection of said power supply, and said wires, to the switch; and said detection device, connected to the circuit board, the perimeter of 10 said frame being between 380 and 400 mm long.

It is also an object of the present invention to provide an additional switching device that has composite functions. In accordance with a second aspect of the present invention, therefore, there is provided an 15 additional switching device for a wall mounted switch for a light having a wall socket and a switch plate connectable thereto, wherein the device comprises a control electronics circuit board adapted to be interposed between the switch plate and the wall socket 20 to control switching of the light, wherein the control electronics includes a burglar deterrent function comprising a light detector exposed to ambient environment and a timer whereby the light is activated after dark for selected intervals, and a presence 25 detection function comprising a personnel detector exposed to ambient environment to activate the light after dark when a person is detected, and a function switch to switch between said functions.

Preferably, said function switch has a third 30 position permanently switching the light on.

Not all additional switching devices provide a power supply suitable for all light bulb types, especially fluorescent tubes and energy saving bulbs. This is À ÀÀ À. À À

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because these draw such low current that any arrangement which involves drawing-off current to power the control electronics will be completely unsuitable where the light is a normal incandescent light drawing a relatively high 5 current. Consequently, most prior art arrangements that

provide automatic switching are not said to be suitable for low power applications. Moreover, even when designed for higher loads, not all power supplies have low power dissipation. This can lead to inefficiency and 10 undesirable heat losses. Also, some control electronics derive their power from batteries that need replacing or need recharging. In many light switching arrangements, there is no direct connection to a neutral supply, and so deriving a power supply from the mains is not an easy 15 process.

It is therefore desirable to incorporate a power supply in a switch that reduces overall power dissipation when the switched load can vary over a large range. It 20 is also desirable to provide an additional switching device and a power supply that allows fluorescent tubes and energy saving bulbs to be used in addition to conventional light bulbs.

25 In accordance with a third aspect of the present invention there is provided an additional switching device for a switch comprising an ac mains live supply line, a contact breaker, a switched-live line, and control electronics to selectively inter-connect said 30 lines through a triac during "on" periods determined by said control electronics, wherein a power supply for said electronics comprises a zener diode in series with said triad so that the voltage across the diode when the triac is conducting powers the control electronics, and wherein 35 the control electronics switches-on the triac for short À e a a À À À À À a c À a À a a e À as À À À À À À -

t ' durations during "off" periods sufficient to power said electronics during said "off" periods but insufficient to activate significantly a load connected to said switched-

live line, characterized in that a second triac is placed 5 in parallel with the zener diode, said second triac switching out the zener diode during said "on" periods when a predetermined reservoir voltage level across the zener diode is reached.

10 Preferably, during said "on" periods, said second triac is switchedoff for short second durations so that the voltage across the zener is temporarily restored to power the control electronics. Said durations may be about 1 mS per mains cycle.

Preferably, a diode and a capacitor rectify and smooth the power supply to the control electronics.

An embodiment of the invention is further described 20 hereinafter by way of example, with reference to the accompanying drawings, in which: Figure 1 is an exploded side view of an additional switching device in accordance with the present invention; 25 Figure 2 is an exploded perspective view of the additional switching device of Figure 1; Figure 3 is a perspective view of the additional switching device of Figure 1 in an assembled condition and showing some of the control features for a preferred 30 embodiment in accordance with the present invention; Figure 4 is an underneath perspective view of the device of Figures 3 and, shows a housing for a personnel detector and a light detector; Figures 5A to ED are perspective views showing 35 different plates for the device of Figure 3; À':... '': À:. A:..

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Figure 6 is a circuit diagram of the power supply for an additional switching device in accordance with a third aspect of the present invention; and Figure 7 is a schematic diagram of a preferred 5 embodiment of the power supply circuit shown in Figure 6.

With reference to Figures 1 and 2, a wall light switch arrangement 1 comprises a wall socket 4, a switch plate 8 for connection to the wall socket 4, and an 10 additional switching device 16. The additional switching device comprises a frame 20, a control electronics circuit board 24 mounted on the frame 20, and a cover 52.

The device 16 may be clipped together and sold as a retrofit unit. It has through-hole pillars 21 spaced to 15 align with the standard separation of screw retainers 23 of the wall socket 4. The pillars 21 allow passage of screws 10 to fix the switch plate 8, and interposed device 16, to the wall socket 4.

20 The switch plate 8 includes a switch 12 that has terminals 19 for a live supply wire 56 and a switched live wire 64. Depending on the function of the switch, there may be other terminals for further wires in a multi-switch light circuit, for example. The wires 56,64 25 are generally supplied through a port 5 in the wall socket 4 from a light fitting to be operated by the switch. However, in the present arrangement, the wires are not connected directly to the switch. Instead, the circuit board 24 includes terminals 25 for connection of 30 the wires. Flying leads 13 are also provided to connect the board 24 with the switch 12.

The frame 20 has a front aperture 11 through which the switch 12 is received. The cover 52 has a rear 35 aperture 53 through which the wires 56,64 are fed. The .. a.. ... .. .

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board 24 has circuit elements distributed around its periphery, but has a clear section in its middle to accommodate the switch 12.

5 The additional switching device 16 is positioned between the switch plate 8 and the wall socket 4. The frame 20 has a perimeter 31a, and the cover 52 likewise has a perimeter 3lb that corresponds with the perimeter 31a and mates with it. The combined perimeter 31 10 corresponds substantially with the perimeter 33 of the switch plate 8, although it may be up to 10% larger all around without becoming unduly obtrusive. Consequently, when fitted together as shown in Figures 3 and 4, no part of the frame 20 or circuit board 24 projects more than 15 10% beyond the limits defined by the perimeter 33 of the switch plate.

In fact, it would be most desirable if the frame 20 was the same size as the switch plate 8. But, since that 20 depends on the size of the switch plate, and these vary depending on style, it is preferable to select a size of frame which is slightly larger than the largest switch plate likely to be experienced. In the United Kingdom, this is one about 95 mm square, and accordingly the 25 preferred size of the frame is about 98mm square.

However, there are numerous smaller designs of the order of 90mm square. Accordingly, the finish of the front face 35 is arranged to be as clean as the perimeter 31 so that, for smaller switch plates, the part of the frame 30 showing does not detract substantially from the appearance of the switch as a whole.

There is one possible exception to the generality stated above of no element of the additional switching 35 device protruding beyond the perimeter, however. This is :.. '': ':' ':.'.

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because a presence or light detector 28 is provided which must have access to ambient environment. Thus a detector housing 36, provided with a window 37 that is transparent to radiation, at least, to that to which the detector 28 5 responds, protrudes beyond the perimeter 31. The detector 28 is connected to a front face 29 of the circuit board 24 on an extension 27 thereof. The detector is received within the housing 36, which is no larger than necessary to accommodate the detector 28.

The control electronics 24 includes a burglar deterrent function comprising the detector 28 exposed to ambient environment through the window 37. A timer (not shown) of the circuit 24 operates to activate the light 15 for selected intervals after dark, that is to say, when the detector 28 detects that light levels have fallen below the minimum set by a user. However, the minimum set cannot be more than would be detected when the light switched by the circuit is on, otherwise the circuit will 20 constantly switch on and off during hours of darkness, depending on what hysteresis is provided by the circuit.

Alternatively, and this is preferred, once switched-on by detection of falling ambient light, the light remains on for fixed or variable periods.

Additionally, a presence detection function is provided. This may comprise an additional detector (not shown) or comprise a separate function of the detector 28. This detector is also exposed to ambient 30 environment. The control circuit 24 is arranged to activate the light after dark when a person is detected by the presence detector 28. Of course, where both these functions are integrated in the same device 16, a function switch 32 is provided to switch between the two 35 functions, given that they are to a certain extent ace a aBa ala*as a a 8 a 8 8 À i 8 a 8 a 8 a I a a a 8 8 ^ * a a a sa a a a a a À a. a a

exclusive. The personnel, or presence, detector is conveniently a motion detector, being an infra-red detector or a 5 Passive Infra-Red (PIR) detector. As mentioned above, the personnel detector and light detector may be housed in the same detector housing 36. Equally, however, they could be in separate detector housings.

10 In an embodiment of the present invention each detector housing 36 is rotationally adjustable to adjust the field of detection. In another embodiment of the

present invention each detector housing 36 is at the end of a projection, such as, for example, a stalk. The 15 stalk may be in a fixed position or is movable to reposition the detector housing 36. For example, a universal joint may be at either or both ends of the projection. 20 In a preferred embodiment, the detector housing 36 is situated on the underside of the light switch box 1 as shown in Figure 4.

In another embodiment, a light pipe (not shown) is 25 employed to transport ambient environmental radiation (visible or otherwise) from a remote source to the detector. A light pipe avoids line-of-sight obstacles and reduces the necessity for a protruding detector housing. The light detector 28 changes its output when an increasing level of darkness is reached. It is preferable that the level of darkness at which the light detector changes output is adjustable, said adjustment 35 being performed by a first sensitivity adjustment means ::: À.:: À À::::

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40 as shown in Figure 4. In an embodiment of the present invention, the first sensitivity adjustment is preferably placed externally on the underside of the light switch box 1.

When selected, the burglar deterrent mode only switches the lights "on" when the light detector changes output. It does this when it detects less than a threshold quantity of light. However, this burglar 10 deterrent mode suitably has a timer that may be configured to turn-off the light after a fixed, or perhaps variable, period of time. Such variable time may be varied by a first time adjustment means 44. Indeed, a random function can be employed to alternately turn the 15 light on and off.

The personnel detector 28 changes its output when movement of a warm body is detected. It is feasible that the sensitivity to detecting a presence is arranged to be 20 adjustable by a second sensitivity adjustment means (not shown). However, it is hardly disadvantageous to have the presence detector as sensitive as it is possible to make, so that the occurrence of false-negatives is minimized. When selected, the energy-saving mode switches the lights on when the personnel detector 28 detects a presence such as, for example, a human. The energy saving mode keeps the lights on for as long as the 30 personnel detector detects the human presence. However, when that presence is no longer detected for a given fixed, or preferably variable, amount of time, the lights are switched off. The variable time is controlled by a timer which is adjusted by a second time adjustment means 35 48. Alternatively, adjustment means 44 could be Àe2. À:: .......: À::

configured to adjust both time periods, depending on the position of the function switch 32. For example, in energy saving mode, it adjusts the timer that controls how long the lights are left on after a presence can no 5 longer be detected, and it adjusts a different timer controlling the light "on" period when the function switch is in its burglar deterrent mode position.

Neither the presence detection timer (which suitably has a range of 2 to 10 minutes), nor the burglar deterrent 10 timer (which suitably has a range of 2 to 10 hours) is shown in the drawings.

One mechanism by which the energy saving timer may be configured is by it comprising a counter and starting 15 it to count down from some user gettable start number. A detected presence (ie movement) before the count has reduced to zero is arranged to re-set the counter to the start number, and the light stays on. If no movement is detected and the count eventually reaches zero, the light 20 is arranged to switch-off. To avoid the lights switching-off while there is someone in the room, it is necessary that the time period set by the start number is long enough, and the sensitivity of the detector is high enough, that the circuit detects at least one movement 25 before the count gets to zero. However, inordinately long time periods will waste power, since the light will always stay on for the set time period, even if a person pays just a fleeting visit to the room.

30 In a further embodiment of the invention, when the lights are switchedoff, or just before they are to be switched-off, the sensitivity of the personnel detector may be arranged to increase temporarily. This serves to prevent false negative-presence detections from acting to 35 turn off the lights, or at least enables a slight À À À À À

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movement, for example, to reactivate the lights once turned-off. On the other hand, as stated above, there is unlikely to be any disadvantage in having the presence detector as sensitive as it is possible to arrange it in 5 the circumstances.

In a further embodiment of the present invention, a dimming function is incorporated into the control electronics circuit board 24, said dimmer function being 10 turned on or off by user intervention. This dimming function may gradually increase the brightness over a fixed or variable time period when the light is switched on. It may gradually decrease the brightness over a fixed or variable time period when the light is switched 15 off. Or it may control the light intensity by a dimmer control during the period when the light is switched on.

It could be arranged to disable the dimming function when undimmable (eg flourescent) lighting was employed.

20 In all embodiments of the present invention, each adjustment means could be any one of a potentiometer, a variable resistor, a variable capacitor, a switch, a slide switch, or any other means that allows adjustment to be performed. In the embodiments illustrated, the 25 adjustment means 40,44,48 are a potentiometer moved by a control knob.

The frame 20 and the cover 52 provide between them apertures 55 for the adjustment means or any other 30 control feature that needs to be accessed externally.

Accordingly, it can be seem that these do project through the perimeter 31a,b, but not to any significant extent.

With reference to Figures 5A to ED, the switch plate 35 8, 8a,b and c is retained, in each case, allowing the À À À::

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invention to be integrated to the surrounding decoration.

It will be noted that switch plates 8b,c are larger than switch plates 8, 8a. This is fortuitous in some respects because the least expensive materials for electrical 5 switches are white plastics and it is the white plastics material switch plates 8 that are the smallest and therefore expose more of the device 16. Steel switch plates 8a are also smaller, but since these are generally painted, they do not clash with white. So, for these 10 switch plates, there is less clash of appearance with the device 16, and consequently it is of less consequence that more of the device 16, including some of its front face 35, is visible. However, brass switch plates 8b,c tend to be larger. Consequently, they almost completely 15 cover front face 35, which is beneficial because then substantially only perimeter 31 is visible.

The compactness of the circuitry behind the switch plate reduces the intrusion of the device 1. There is 20 preferably only one additional switching device per room.

It will be apparent that longer screws 10 may be required to fix the light switch box 1 closed.

With reference to Figure 6, the additional switching 25 device 1 includes a power supply arrangement 100 disposed on the board 24. The ac mains live supply line 56 to the switch 1 is connected to one side of the contact breaker 60 (effected by switch 12). The other side 57 is connected to the board 24. A switched live line 64 30 issues from the board 24 and is ultimately connected to a load (ie a light) 76, and thence to a remote ac mains neutral line 78. The control electronics 24a is provided to selectively inter-connect said lines 56,64, provided switch 60 is closed. If it is open, the load 76 is 35 isolated from the live supply, and this is important for À:: :. '.:.::

certainty when a bulb needs to be changed, for example, or if it is simply desired that the light be permanently off. By the same token, function switch 32 described above has a third position in which it closes contact 5 breaker 32a, so that the control electronics 24a are permanently bypassed and the light is permanently on (provided switch 12/60 is closed. However, when function switch 32 is in one of its two other positions in which the control electronics are active (either in energy 10 saving or burglar deterrent mode), contact breaker 32a is open. Normally, power from line 57 passes through zener diode 72 and triad 68 to switched-live line 64. However, 15 this only happens when triac 68 is "on", as determined by the control electronics 24a and line 67. The power supply for the electronics 24a comprises the zener diode 72, so that the voltage across it, when the triac 68 is conducting, powers the control electronics 24. A diode 20 80 and a capacitor 84 rectify and smooth the power supply to the control electronics 24.

However, when the control electronics switches-off triac 68, there is no current through the diode 72, and 25 hence no voltage across it with which to power the control electronics 24. Consequently, the control electronics 24 is arranged to switch-on the triad 68 for short durations during "off" periods. These durations (about 1 mS per cycle - ie about 5% of the time) are 30 sufficient to power the electronics 24. However, they are insufficient significantly to activate the load 76 connected to the switched-live line 64.

The present invention provides a second triac 88, 35 which is placed in parallel with the zener diode 72. The a. À:: :...:.::

l control electronics 24a switches-on the second triac 88 along line 87 when a predetermined reservoir voltage across the diode 72 is reached. This reduces the overall power dissipation for larger loads.

However, with this arrangement, there is also no voltage across the zener diode 72 when the triac 88 is conducting. Consequently, here, the control electronics 24a is arranged to switch-off the triac 88 for short 10 durations during "on" periods, as well as to switch-on the triac 68 for such durations (or perhaps slightly longer ones because there is always some small voltage across the triac 88 when it is conducting) during "off" periods. For any of the embodiments of the present invention, any light bulb type can be used.

Although shown switching the live supply to the load 20 76, preferably the middle position of function switch 32 does not itself make and break the live supply. For this, a simple circuit-board-mounted slide switch would not have the requisite current rating. Rather, it is preferred that this position simply signals the control 25 electronics 24a to keep triacs 68,88 permanently conducting. The present invention has been described in detail with respect to various embodiments, and it will now be 30 apparent from the foregoing to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and it is the intention therefore in the appended claims to cover all such changes and modifications as fall within 35 the true spirit of the invention.

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Claims

I CLAIMS

1. A wall light switch arrangement (1) comprising 5 a wall socket (4); a switch plate (8) for connection to the wall socket; a switch (12) forming part of the switch plate; and, 10 an additional switching device (16) comprising a frame (20); a control electronics circuit board (24) mounted on the frame and including terminals (25) for connection of a power supply and switched-live lines and wires for connection to the switch; and a 15 detection device (28) connected to the circuit board, wherein the frame is positioned between the switch plate and the wall socket, and has a perimeter no more than 10% longer than the perimeter of the switch plate, no part of the frame or circuit board, 20 other than the detection device, projecting substantially beyond said perimeter.

2. A wall light switch arrangement as claimed in claim 1, in which the perimeter of the frame is between 3 8 0 and 400 mm long.

25 3. An additional switching device (16) for a wall mounted light switch (1) having a wall socket (4) and a switch plate (8) connectable thereto, wherein the device comprises a control electronics circuit board (24) mounted on a frame (20) adapted to 30 be interposed between the switch plate (8) and the wall socket (4) to control switching of the light, and a detection device (28), wherein the control electronics (24) includes a burglar deterrent mode, in which the detection device has a light detector 35 exposed to ambient environment and a timer is À À ' À:...

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provided to activate the light after dark for selected intervals, and an energy saving mode, in which the detection device has a personnel detector exposed to ambient environment to activate the light 5 after dark while a person is, and remains, detected, a function switch (32) being provided to switch between said modes.

4. An additional switching device as claimed in claim 3, in which the personnel detector is an 10 infra-red motion detector.

5. An additional switching device as claimed in claim 3 or 4, in which the light detector changes output when it detects less than a threshold minimum quantity of light, the level of said threshold 15 preferably being adjustable by a first sensitivity adjustment means (40).

6. An additional switching device as claimed in claim 5, in which the burglar deterrent mode switches the lights on when the light detector 20 changes detects less than said threshold minimum, and keeps the lights on for first period of time before switching the lights off.

7. An additional switching device as claimed in claim 6, in which said first period of time is 25 variable by a first time adjustment means (44).

8. An additional switching device as claimed in any of claims 3 to 7, in which the personnel detector changes output when movement of a warm body is detected.

30 9. An additional switching device as claimed in claim 8, in which the sensitivity to detecting a warm body is adjustable by a second sensitivity adjustment means.

10. An additional switching device as claimed 35 in claim 8 or 9, in which the warm body to which the ...........

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personnel detector is sensitive is an animal, preferably a human animal.

11. An additional switching device as claimed in claim 8, 9 or 10, in which the energy saving mode 5 switches the light on when the personnel detector detects a warm body and keeps the light on for a second period of time after said warm body is no longer detected, whereupon the light is switched-off.

12. An additional switching device as claimed 10 in claim 11, in which said second period is variable by a second time adjustment means (48).

13. An additional switching device as claimed in claim 11 or 12, in which, when the light is, or is about to be, switched-off, the sensitivity of the 15 personnel detector is temporarily increased for a third period of time, which third period is preferably variable by a third time adjustment means.

14. An additional switching device as claimed in any of claims 3 to 13, in which the detection 20 device is housed in a detector housing (36).

15. An additional switching device as claimed in claim 14, in which the detector housing is rotationally adjustable to adjust the detection zone of the detection device.

25 16. An additional switching device as claimed in claim 14 or 15, in which the detector housing is at the end of a projection.

17. An additional switching device as claimed in any one of claims 14, 15 or 16, in which the 30 detector housing is situated on the underside of the light switch (1).

18. An additional switching device as claimed in any of claims 3 to 17, in which the detection device is within the confines of the frame, a light 35 pipe extending from the frame and transporting light . .... e...

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/ l from ambient environment to the detection device.

19. An additional switching device as claimed in any of claims 3 to 18, in which a dimming function is incorporated into the control electronics circuit 5 board (24), said dimmer function being turned on or off by user intervention and performing one or more of: a) gradually increasing the brightness over a fourth time period when the light is 10 switched-on; b) gradually decreasing the brightness over a fifth time period when the light is switched-off; and, c) controlling the light intensity by a 15 dimmer control during the period when the light is switched-on, said fourth and fifth time periods preferably being variable respectively by fourth and fifth time adjustment means.

20 20. An additional switching device as claimed in any of claims 5 to 19, when dependent on any of claims 5, 6, 7, 9, 12 and 13, in which each adjustment means comprises a potentiometer or variable resistor moved by a control knob.

25 21. An additional switching device as claimed in any of claims 3 to 20, in which the frame is separate from said circuit board, and in which the board is captured between the frame and a cover.

22. An additional switching device as claimed 30 in claims 20 and 21, in which apertures providing access to each said adjustment means are defined between the perimeters of said frame and cover and through which said control knobs protrude.

23. An additional switching device for a 35 switch comprising an ac mains live supply line (56), 22, ':':

..:.::..CLME: a contact breaker (60), a switched-live line (64), and control electronics (24) to selectively inter connect said lines through a triac (68) during "on" periods determined by said control electronics (24), 5 wherein a power supply for said electronics (24) comprises a zener diode (72) in series with said triac (68) so that the voltage across the diode (72) when the triac (68) is conducting powers the control electronics (24), and wherein the control electronics 10 (24) switches the triac (68) for short first durations during "off" periods sufficient to power said electronics (24) during said "off" periods, but insufficient to activate significantly a load connected to said switched- live line (64), 15 characterized in that a second triac (88) is placed in parallel with the zoner diode (72), said second triac (88) switching out the zener diode (72) during said "on" periods when a predetermined reservoir voltage level across the zener diode is reached.

20 24. An additional switching device as claimed in claim 23, in which, during said "on" periods, said second triac is switched-off for short second durations so that the voltage across the zener is temporarily restored to power the control 25 electronics. 25. An additional switching device as claimed in claim 23 or 24, in which said durations are about 1 mS per mains cycle.

26. An additional switching device as claimed 30 in claim 23, 24 or 25, in which a diode (80) and a capacitor (84) rectify and smooth the power supply to the control electronics (24).

27. An additional switching device as claimed in claim 2, comprising: said frame; said control 35 electronics circuit board mounted on the frame and 2 'en. À:: ....:.::

including said terminals for connection of said power supply, and said wires, to the switch; and said detection device, connected to the circuit board, the perimeter of said frame being between 380 and 400 mm 5 long. 28. A wall light switch arrangement as claimed in claim 1 or 2, in which said additional switching device is as claimed in any of claims 3 to 26.

29. A wall light switch arrangement, and an 10 additional switching device for a switch, substantially as hereinbefore described with reference to the drawings.

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