GB2396065A

GB2396065A - Lighting control

Info

Publication number: GB2396065A
Application number: GB0325585A
Authority: GB
Inventors: Stephen John Foxwell
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-11-01
Filing date: 2003-11-03
Publication date: 2004-06-09
Anticipated expiration: 2023-11-03
Also published as: GB2396065B; GB0325585D0

Abstract

An apparatus 30 is provided for controlling the supply of mains power to a load BL which has a live terminal for connection to a first, live side L1 of the mains supply, a neutral terminal for connection to a second, neutral side N1 of the mains supply and a manual control switch SW1 in series with the neutral side N1. The apparatus has an electrically operable first relay switch RL1, connectable in series with the load BL on the live side L1, for controlling application of the mains power to the load BL. The first switch RL1 is switchable between a first, normally open de-energised state and a second, closed state. A second, low voltage power source in the form of a capacitor C1 is provided together with a control circuit operable in response to the closing of the control switch SW1 to cause the capacitor C1 to discharge through the coil L of the first switch relay RL1 to close the relay.

Description

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e.: Lighting Control The present invention relates to control of a power to an appliance such as a light and particularly, but not exclusively, to a low voltage lighting control apparatus suitable for use in a conventional household lighting circuit or the like.

5 Lighting circuits for houses and other buildings generally comprise a length of 2-core or 2-core-and-earth hi gh voltage cable which runs throughout the building and is connected at one end to the consumer unit or fuse box ofthe building. One core wire ofthe cable is connected to the live rail ofthe consumer unit whilst the other core wire is connected to the neutral rail ofthe consumer unit. Where present, the earth cable is connected to the earth rail of the consumer unit.

10 Frequently, the continuityofthe cable isbrokenbymeans of junctionboxesorthe likewhich, for lighting systems, often comprises one or more ceiling roses of conventional light fittings such as pendant fittings or baton fittings. At each ceiling rose, power is tapped from the cable to supply the bulb connected to the light fitting.

Aconventionalceiling rose foralight fitting such es apendant light fittingis shown schematicallyin 15 Figure I and is described below. The circuit for each light fitting includes a switch, which is conventionallymountedonawall or other fixture or, alternatively, takesthe formofapull switch mounted to the ceiling. As described below, the switch is connected to the light fitting by means of the same or similar high voltage cable used for the main circuit since the manner in which the switch i s conventionally connected to the ceiling rose is such that, in use, a high voltage current is 20 passed through the switch.

This arrangement presents some difficulties both during installation ofthe lighting circuit and during use. For example, the size ofthe cable which runs from the ceilingrose to the wall-mounted switch is relatively large, in the order of I to 1.5 mm2. Such cable is usuallyprovidedwith aPVC or other insulating sleeve which gives the cable as a whore across sectional area of approximately 50-60

À :.: c: mm2 Owing to their size these cables, which must generallyberun downwalls or other fixtures, depending on where the light switch is to be positioned, cannot easily be buried or recessed within the wall or fixture. To the extent that this is possible, a channel must be chiseled out of the brickwork, which is a time consuming and expensive operation. Furthermore, owing to the high 5 voltages applied to the cable, it is a requirement that such cables must be protected by a metal capping. Occasionally, the cables are run across the surface ofthe wall and are covered bymeans of plastic capping which generally looks unsightly. Where a new lighting circuit is to be installed in the pre-existing building, it is extremely difficult to install the cabling into a wall without spoiling the existing decoration.

10 Furthermore, once installed, the high voltages on the cable can present a danger to occupants of the building. For example, during routine decoration or maintenance, it is possible to drill through buried cables inwalls which presents the dangerofelectric shock to the occupant from the high voltages carried by the cable. In addition, faulty switches can also be potentially dangerous and, owing to the high voltages which are switched, are occasionallyprone to arcing whereby a spark 15 is produced which can ignite combustible gasses in the air. Also, when a bulb has brown or been removed the light socket can remain in a live condition.

It would be advantageous to provide an improved lighting control or apparatus for controlling the switching of household lighting or the like which addresses one or more of the above problems.

According to one aspect ofthepresent invention, there is provided an apparatus forcontrolling 20 power to a power circuit having at least one power operated appliance, the power circuit being connected to a first power source, the apparatus comprising: electrically operable switch means, connectable in said power circuit, for controlling application of power from said first, mains, power source to said at least one appliance; a second power source;

: ce.: : À. À: e: À À a and control means for applying power from said second power source to said switch means thereby to cause said switch means to apply power to said at least one appliance; wherein said second power source is a low voltage source.

According to a second aspect of the present invention, there is provided an apparatus for 5 controlling a lighting circuit having at least one light source, the lighting circuit being connected to a first power source, the apparatus comprising: electrically operable switch means, connectable in said lighting circuit, for controlling application of power from said first, mains, power source to said at least one light source; a second power source; 10 and control means for applying power from said second power source to said switch means thereby to cause said switch means to apply power to said at least one light source; wherein said second power source is a low voltage source.

The switch meansmaycomprise arelayor the like. Alternatively, the switch means maycomprise a triac or a silicon controlled rectifier (SCR) or other like control device.

15 The second power source may be provided by a capacitance. A capacitor can be used to hold charge when the lighting circuit is switched off.

The control means preferably comprises a switch, such as a conventional light switch. The switch can advantageously be a low power switch since the second power source is a low voltage power source. 20 The present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

: Àe.: : À À À c: :.:.e À.e À Figure 1 is a schematic illustration of a conventional ceiling rose for a light fitting; Figure 2 is a schematic circuit diagram of apreferred form of apparatus according to the invention; Figure 3 is a schematic circuit diagramofasecondpreferred form of apparatus according to the invention; and 5 Figure 4 is a further preferred form of apparatus according to the invention; Figure 5 is a schematic circuit diagram of a further preferred form of apparatus according to the invention; Figures 6 and 7 are schematic circuit diagrams offurtherpreferred forms of apparatus according to the invention; 10 Figure 8 is a schematic circuit diagram of a furtherpreferred form of apparatus according to the invention; and Figure 9 is a perspective view of a plug containing the circuitry of Figure 8.

Referring firstly to Figure 1, the electrical connections to a conventional ceilingrose are shown schematically generally at 10. The ceiling rose 10 has a generally circular backing plate 12 which 15 is arranged to be mounted to a ceiling or other fixture by means of screws (not shown) or the like which pass through mounting holes 14 in the backing plate. The backing plate 12 is provided with three sets of electrical terminal blocks 16, 18, 20 which are mounted to one surface thereof. The first set ofterminal blocks 16 comprises three separate terminal blocks which are conductively connected together. Likewise, the third set ofterminal blocks 20 also comprises three separate 20 terminal blocks conductively connected together. The second set ofterminal blocks 18 comprises only two terminal blocks electrically connected.

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The ceiling rose 10 is arranged to be connected to a conventional lighting circuit comprising a two-core or two-core-and-earth cable which is connected at one end to a consumer unit or junction box in a conventional manner. Specifically, one core wire, hereaftertermedthe "live" wire is connected to the live rail of the consumer unit whilst the other core wire, hereafter referred to as 5 the "neutral" wire is connected to the neutral rail ofthe consumer unit. Where present, the earth wire (not shown) is connected to the earth rail of the consumer unit.

During installation ofthe ceiling rose 10, the circular plate 12 is mounted to the ceiling or other fixture by means of screws passing throughthe fixing holes 14. The supply cable ofthe lighting circuit is cut to produce two cable ends, one forming the end of the cable connected to the 10 consumer unit and the other forming an end ofthe cable extending further into the building for connection to, for example, a further ceiling rose.

The live wire Lo ofthe first end is connected to a first terminal block 1 6a in the first set ofterminal blocks 16. The neutral cable Nil ofthe first end is connected to a first terminal block 20a in the third set ofterminal blocks 20. The live cable L2 ofthe second cable end is connected to a second 15 terminal block 1 6b in the third set ofterninal blocks 16 whilst the neutral wire N2 ofthe second cable end is connected to a second terminal block 20b in the third set of terminal blocks 20 The switch SW for switching on end offthe light Fitting is connected to the ceilingrosebymeans of acable similarto that used forthemainlightingcircuit, haying two core wires S', S2 (denoted by the dashed lines). The first core wire S is connected at one end to a first electrode of the switch 20 SW and at the second end to a third terminal block 1 6c in the first set ofterminal blocks 16. The second core wire S2 is connected at one end to the second electrode ofthe switch SW and at the other end thereof to a first terminal block 1 8a in the second set of terminal blocks 18.

A light source, in the form of a light bulb BL, is connected to the ceiling rose via a cable similar to that used for the main lighting circuit having two core wires B I, B2. The first wire B is connected 25 at one end to a first electrode ofthe bulb BL and at the other end thereofto the second terminal block 1 8b in the second set ofterminal blocks 18. The second core wire B2 is connected to the

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other electrode ofthe bulb BL and at the other end thereofto the third terminal block 20c in the third set of terminal blocks 20.

In use, when the switch SW is actuated to electrically connect the switch cables S' and S2, electrical current from the consumer unit flows along the first live wire Lo through the first set of 5 terminal blocks 16, through the switch wire S I, the switch SW, the switch wire S2, the terminal blocks 18, the bulb wire B I, the bulb BL, the bulb wire B2, the terminal blocks 20 and back to the consumer unit via the wire Nil. The circuit through the bulb BL is completed and the bulb illuminates. When the switch SW is switched to anoffposition, the circuitbetweenL' Andy is disrupted such that no current flows through the bulb which is thus switched off.

10 It will be understood that the switch wires So, S2 are required to carrythe same current as the bulb BL at the same high level voltage as the mains circuit. As described above, this is a potential danger and poses an inconvenience when installing the light fitting and the cable running to the wall-mounted switch.

Figure 2 shows a circuit diagram 30 of a preferred form of apparatus according to the invention, 15 the illustrated circuit being intended to be incorporated into a conventional ceiling rose for a lighting circuit for a house or other building.

As can be seen, a bulb BL is connected to the live wire Lit ofthe main power cable via aparallel arrangement ofthe contacts of arelayRL1 and areset, normally open switch 36. The bulb BLis connected to the neutral wire Nil of the main power cable via a zoner diode ZD1 which is 20 connected in parallel with a series arrangement of a diode D1, capacitor C1 and a switch SW1 which is the main lighting switch. A coil L ofthe relay RL1 is connected in parallel across the capacitor C1 and switch SW1. The diode D1 has its cathode connected to the capacitor C1 and terminal 32 ofthe relaycoil L. When SW1 is closed the capacitor C1 is connected to the neutral wire N' (which is at earth potential) for complete safety.

25 The reset switch 36 and switch SW1 maybemagneticallyoperatedbyareed relay, replacing the

c: À. Be:: : Àe À: ': :.:-.e À conventional light switch, offering novel switch operation and isolation.

To commission the circuit, for example after installation, the light switch SW 1 is closed and switch 36 is then depressed for a short period. Switch 36 is ofthe "press to make", "release to break" type. This charges the capacitor C I through the bulb BL and diode D 1 during the positive mains 5 half cylc. Switch 36 is then released and switch SWI opened.

When the light switch SW1 is then closed during normal use, C 1 discharges through relay coil L causing the contacts of relay RL to close. Current then flows through the relay contacts, bulb BL and zener diode ZD 1, turning the bulb on. During each positive halfcycle ofthe mains voltage, current flows through the diode D 1 and coil L, maintaining the relay contacts closed and the bulb 10 on. The low level current also charges the capacitor C 1. Because C 1 i s connected to the Neutral side of the bulb BL between BL and ZD 1 the voltage applied to C 1 is relatively low and safe. The switch SW 1 is also on the low voltage side ofthe bulb BL and therefore even when bulb BL is on both sides of the switch SW 1 are at earth potential. The bulb also acts as a fuse, limiting current in the circuit.

15 During each negative halfcycle ofthe mains supply, diode D1 does not conduct but capacitor C1 partly discharges through the coil L to maintain the relay contacts closed and the bulb BL on. Thus, effectively the current through L1 is smoothed DC current.

When SW 1 is opened, capacitor C 1 is open circuit. As a result, it cannot dischargethrough the coil L during the next negative half cycle ofthe mains supply. The relay contacts therefore open and 20 bulb BL is turned off. C1 remains charged for when SW1 is closed again.

Itwill be appreciated that the wires to the switch SW1 are not required to carry the high voltage current required by the conventional light switch arrangement and can therefore be of a considerably lower gauge (i. e. narrower or finer) than in the conventional arrangement. The use of screened cable would provide complete insulation for wires hidden within walls and therefore 25 is recommended.

t; t e e rim 8 The auto disconnect feature is also advantageous and amajorbenefitofthecircuit. If bulb BLgoes open circuit (fails) or ZDI short circuits, C1 discharges and since there is then no voltage to recharge C 1, the switch and the bulb BL are isolated from the mains voltage. ZD 1 is typically 1 2v as a result of which a 1 2v link is provided between bulb BL and the switch SW1, providing a safe 5 environment where SWI can be operated even in, for example, a bathroom.

Another major advantage is the environmental aspect since no voltage or current is drawn from the mains when the light switch is switched off.

The use of so-called low voltage triggering (LVT) also reduces or eliminates the dangers of using high voltage cabling within walls and reduces the likelihood of injury through electric shock to the I O user.

The ability to use extremely fine wire to the switch SW has significant commercial benefits for lighting circuit installations. For example, the wires could be run down the architrave of a room or even between tiling and would be considerably less unsightly than if this were done using existing cabling. The lower voltages permit the use of considerately smeller, lower powered end hence 15 more aesthetic switches.

During the wiring of new houses, the fine wires to the switch can be taped to plasterboard on the ceiling or clown the wall without the need for metal orplastic capping as required byheavy duty cables. It is also possible to more easily connect two-way lighting circuits (as are conventionally used for 20 stair or landing lighting) to the lighting circuit.

In another embodiment (not shown), a transistor is used to switch the relay on or off, the switch SW 1 being connected to the base or gate electrode ofthe transistor. This will be well understood bythe skilled person. Such an arrangement allows the use of an even lower-powered switch SW since the switch is only required to withstand the current needed to switch the transistor on. This

À is usually in the order of milliamps.

Refcrringnow to Figure 3, this shows a circuit 40 similarto that of Figure 2 inwhichtherelayRL is replacedbyatriac orsiliconcontrolledrectifier(SCR) TR1. The circuit arrangement is similar to that of Figure 2 but with Cl coupled to TR1 by way of an Opto triac OPT.

5 The circuitry of Figure 2 or 3 may be made integral with the ceiling rose of the light fitting, or otherwise incorporated therein. Alternatively, the circuitrycan be located as an integral part ofthe light fitting, such as within a spot lamp or fluorescent light fitting. It could be located within the mains plug, or an inline switch.

Although the invention has been described with respect to a lighting circuit it will be appreciated that 10 it can be applied to any appliance such as a lawn mower or power tool.

Advantageously, the circuits described above act to isolate the switch SW from the mains voltages and permits operation even in wet environments.

It will be understood that the present invention provides a much improved lighting control system which eases installation, reduces the unsightly effect of wires extending along walls or other fixtures 15 and additionally reduces the dangers associated with high voltage wires and switches such as are used in conventional lighting systems. It does not require wires to be capped or chased into walls and therefore is inexpensive to install.

Figure 4 shows acircuit similarto that ofFigures 2 and 3 where power to therelayRLisprovided by a solar panel SP. A signal conditioner circuit SC conditions the signal from the solar panel to 20 operate the relay coil L. Referring now to Figure 5 this shows a form of embodiment of the apparatus according to the invention. The circuit of Figure 5 is intended to replace a pull cord switch.

t. t The bulb BL is connected directly to the live wire L' and to the neutral by a parallel combination ofthe contacts oftwo relays RL1 and RL2 in turn connected in series with the zener diode ZD1.

The simple arrangement of capacitor C1, switch SW1 and coil L of Figure 1 are replaced by a more sophisticated arrangement. Diode D 1 is connected in series with a parallel arrangement of 5 relay coils which in turn are connected to the neutral wire Nil through the normally closed contacts of relayRL5. An arrangement ofcapacitors C1 to C4, thecoils forrelaysRL1 and RL5 and light switches SWI, SW2 are also conected to the diode D1 by contacts of relays RL3 and RL4 and to the neutral wire by relay contacts of RL5 Switches SW1 and SW2 can be ganged or separate switches.

10 In the circuit of Figure 5, the capacitors C 1 and C2 can be charged on installation ofthe switch containing the circuitry, using for example a separate charging circuit.

When SW1 is closed, C1 discharges through the coil L1 of relayRL1 closingtherelaycontacts.

This switches the mains voltage across the bulb through zoner diode ZD1 and also applies it to diode D 1. The zoner diode ZD 1 has a breakdown voltage of typically 12 volts. When mains 15 voltage is applied to diode D1, on each positive half-cycle the diode D1 conducts and the coil L2 of relay RL2 is activated and closes the contacts of RL2.

The relay coils L3 and L4 for relays RL3 and RL4 are also energised at the same time, switching the relay contacts and connecting the capacitors C3 and C4 into the circuit and to the diode D 1.

20 As a result, these capacitors are charged bythepositivehalf-cycle and, during the half-cycle when D 1 does not conduct, they maintain the relays RL2, RL3 and RL4, as well as relay RL6 latched closed maintaining the mains voltage supply to the bulb BL. In order to switch the bulb BL off, switch SW2 is closed and discharges part ofthe voltage stored by C2 through the closed contacts of RL6 and the coil L5 of relayRL5. This causes the relay contacts of RL5 to open, de-energising 25 coil L6 of relayRL6. As a result, the contacts of RL6 open, disconnecting C2 from coil L5 and preventing C2 from fullydischarging. This also allows the contactsofrelayRL5 to close again.

:e.e ele:..:e Idle However, the contacts of relay RL5 are open long enough to change the voltage conditions et the relay coils L2, L3, L4 and L6 such that during the negative half-cycle ofthe mains voltage these coils are all de-energised allowing the relevant relays to revert to their de-energised state, as shown in Figure 5, with the relay contacts open. As a result, capacitors C3 and C4 are disconnected from 5 the circuit and connected to the respective capacitors C I and C2 and recharge these capacitors.

The circuit thus remains off until triggered on again.

Referring now to Figure 6, this shows a further embodiment according to the present invention where a transformer T I is used to provide low voltage lighting control. In this circuit, the bulb BL is connected across the transformer secondarybinding S with the terminals ofthe second finding 10 S being connected respectively to the live and neutral mains cables L and N. The secondary binding S is connected to the mains five Lby way ofcontacts of arelayRLI whose coil L1 is connected by way of diode D I across the primary binding P of transformer T 1. Connected in parallel with the coil L1 is a series capacitor C1 and switch SW1.

On installation and commissioning, C1 is charged. When switch SW1 is closed, C1 discharges 15 through coil L1 of relayRL1 closing the relaycontacts and energisingboth the bulb BL andprimary coil P oftransform Tl. This has the effect ofenergising the secondarycoil S which in turn maintains R I energised and the relay contacts of RL 1 closed. It also maintains C 1 fully charged on each positive half-cycle of mains voltagebywayofdiode D1. Thus, when SW1 is opened, on the next negative half-cycle on the secondary induced in the secondary winding S. diode D 1 effectively 20 becomes open circuit, resulting in L1 being de- energised and the contacts of RL1 opening to di sconnect bulb BL and the transformer primary winding P from mains voltage. However, C 1 remains charged, ready to energise L1 again next time switch SWI is closed.

Figure 7 is a circuit similar to Figure 6 but with the transformer T1 replacedby a low level lighting transformer and the bulb or lamp is placed in parallel with coil L1.

25 Referring now to Figure 8, this shows a circuit which can be incorporated into a plug/socket

À À À e À... c À À À.

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. . combination 100 as shown in Figure 9 to provide isolation for a load such as a table lamp plugged into the combination 100, in turn plugged into a wall power socket.

When switch SW1 is closed C1 dischargesthroughRL1 contacts, bulbBL, SWl, D1 and L2.

EnergisingL2 switches over the contacts of RL2, thus allowing C1 to continue to discharge through 5 coi I L1. Energising L1 switches relayRL1 contacts overto connect bulb BL to the mains live wire Lo. The bulb BL is thus turned on but mains current also flows through D1, L2 and L1 maintaining the relays energised and the contacts switched and charging C 1. Because zener diode ZD 1 has a low breakdown voltage, typically 1 2v, the voltage applied to the control circuit is at a very low level. 10 When SW 1 is opened, L1 and L2 are de-energised and the relays RL1, RL2 switch back to their de-energised, normal state ready for when SW1 is next closed.

If bulb BL is short circuited whilst SW1 is closed, then the current flowing through resistorR1 in the neutral wire increases. This is applied to the base ofthe transistor TRl which turns fully on, shorting out coils L1, L2 and discharging C2. Relays RL1, RL2 thus switch from their energised 15 states. D2 prevents C1 from discharging.

Claims

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see a. ee. À 13 CLAIMS

l An apparatus for controlling the supply of mains powerto a load wherein said load has a li ve terminal for connection to a first, live side of said mains supply, a neutral terminal for connection to a second, neutral side of said mains supply and a manual control switch in series with said neutral 5 side, the apparatus comprising: electrically operable first switch means, connectable in series with said load on said live side, for controlling application of said mains power to said load, said first switch means being switchable between a first, normally open de-energised state and a second, closed state; a second, low voltage power source; 10 and control means operable in response to the closing of said control switch to cause said power storage means to apply power to said first switch means thereby to energise and close said switch means.
2 An apparatus as claimed in claim 1 wherein said control means includes latch means to latch said first switch means closed whilst said control switch is closed.

15
3 An apparatus as claimed in claim 2 wherein said latch means is actuable in response to current flowing through said load and said control switch and deactuable in response to interruption of said current.
4 An apparatus as claimed in claim 2 or 3 wherein: said first switch means in its first state connects said low voltage power source to said load 20 and manual switch; and said latch means includes a second switch means switchable between a first, normally open state and a second state wherein said switch means connects said second, low voltage power source to energise said first switch means; and said second switch means is switchable from said first to said second state in response 25 to current flowing through said load and said control switch.

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see Àe e.e À
5 An apparatus as claimed in any of claims 1 to 4 wherein: said second, low voltage power source is a do power source.
6 An apparatus as claimed in claim 5 wherein said second, low voltagepower source is a capacitor end said first switch means is energisedbydischarge of said capacitor through said load 5 and said control switch.
7 An apparatus as claimed in claim 6 wherein said capacitor is connected so as to be charged by current flowing through said load when said control switch is closed.
8 An apparatus as claimed in claim 6 wherein said capacitor is connectable to said neutral side of said control switch so as to be charged by current flowing through said load when said to control switch is closed.
9 An apparatus as claimed in claim 2 wherein said latch means is a relay.
l O An apparatus as claimed in any of claims 1 to 9 wherein said first switch means is a relay.
1 1 An apparatus as claimed in any of claims I to 10 wherein the switch means comprises a triac or a silicon controlled rectifier (SCR).

l 5
12 An apparatus as claimed in anypreceding claim wherein the control switch is amanually operable switch.
13 An apparatus for controlling the supply of mains power to a load wherein said load has a live terminal for connection to a first, live side of said mains supply and a neutral terminal for connection to a second, neutral side of said mains supply, the apparatus comprising: 20 electricallyoperable first switch means, connectable in series with said load on said live side, for controlling application of said mains power to said load, said first switch means being switchable between a first, normally open de-energised state and a second, closed state;

À . À . À À a second, low voltage power source; and a control switch; and control means operable in response to the closing of said control switch to cause said power storage means to apply power to said first switch means thereby to energise and close said 5 first switch means.
14 An apparatus as claimed in claim 13 wherein said control means includes latch means to latch said first switch means closed whilst said control switch is closed.
15 An apparatus as claimed in claim 14 wherein said latch means is actuable in response to current flowing through said load and said control switch and deactuable in response to interruption 10 of said current.
16 An apparatus asclaimedin any ofclaims 13to 15 wherein: sai d second, low voltage power source is a dc power source in the form of a capacitor and said first switch means is energised by discharge of said capacitor.
17 An apparatus as claimed in claim 16 wherein said capacitor is connected so as to be 15 charged by current flowing through said load when said control switch is closed.
18 An apparatus as claimed in claim 16 wherein said capacitor is connectable to said neutral side of said control switch so as to be charged by current flowing through said load when said control switch is closed.
19 An apparatus as claimed in any of claims 13 to 15 wherein the second power source is 20 provided by the secondary coil of a transformer.
20 An apparatus as claimed in claim 19 wherein the primary coil of the transformer is connectable to the first power source.

Àe.e e À.. À À A 2 l An apparatus as claimed in anyofclaims 13 to 20 wherein the control switch is a manually operable switch.