SWITCH ASSEMBLIES

Abstract: A touch to activate two terminal A.C. switch (10) which comprises a gate controlled semiconductor switch (12) and a controlling switch (11) associated with a controlling circuit (15) connected between the gate (14) and an electrode of the semiconductor switch (12). The controlling circuit (15) is arranged to maintain a negative potential at the gate (14) whereby inductive loads such as fluorescent light can be switched and full power can be applied to a load switched thereby.

Description: SWITCH ASSEMBLIES This invention relates to improved switch assemblies. It has particular application to touch activated switches and the like but it can be utilized with mechanical switches if desired. For illustrative purposes, the present invention will be described hereinafter with reference to touch activated or proximity switches. The presently available touch activated switches fall into four main categories, namely a first type requiring physical pressure for activation; a second type requiring physical contact with electrical conductors for activation, a third, type requiring either of the above and utilizing infra-red light for activation of the actual switch, and fourth type being custom built switches utilizing complicated circuits and custom built panels such as used for controlling lifts and the like. The first type of switch has the disadvantage that they require the application thereto of positive pressure for activation. This is a disadvantage in many situations such as for use as a call switch for invalids. Since these switches utilize mechanical components their service life is limited. The second type of switch uses the person operating the switch as an.electrical link and thus in use there is chance of that person receiving an electrical shock, particularly if the switch is activated with wet or lacerated fingers. These switches are not particularly suited to bathroom installations for this reason. The third type of switch has the disadvantage that they cannot be used in lieu of existing switches unless extensive rewiring is carried out. They are generally adapted for remote mounting utilizing a battery power supply. Thus they are bulky and may be obtrusive in many applications. The remaining custom switches of course are not suitable for mass production or for general application. Furthermore they may not be able to withstand high current or voltage. Many solid state switches for switching alternating current utilize a triac as the main switch. For this purpose a control circuit is coupled between the gate and mains terminal 1 , hereinafter called MT 1. The triac has a further mains terminal, hereinafter called MT 2 and the load and power supply are connected between MT 1 and MT 2. In use, this circuit remains open circuit until sufficient gate energy- is provided by the control circuit from an external power supply tp trigger the triac to connect MT 1 and MT 2. The triac remains on or in conductive mode for the remainder of the one-half cycle in which it is switched. It then switches off whereupon the control circuit again takes the initial energy from the next one-half cycle to switch the triac to its conductive mode. Such switching arrangements cannot supply full power to the load. The power is supplied in bursts with instant power being supplied in a step form. This can cause problems in electric motors and the like and of course irrespective of the load, the full power available cannot be delivered thereto. Additionally such switches cannot be used to switch an inductive load such as a fluorescent light. For the latter application a separate power supply may be used in addition to the triac control circuit to apply a negative voltage to the gate of the triac with respect to one of the electrodes MT 1 or MT 2. However, this arrangement has the disadvantage that an additional power supply connection is required and thus such modified switches cannot -be used to replace conventional light switches without rewiring. The necessary three wire connection as opposed to a conventional two wire switch connection increases the wiring costs involved and generally makes such switches impractical for many new installations. The present invention aims to alleviate the disadvantages associated with the abovementioned types of switches and to provide improved switch assemblies and methods of activating same which will be reliable and efficient in use. Other objects and advantages of this invention will hereinafter become apparent. With the foregoing and other objects in view, this invention in one aspect resides broadly in an A.C switch assembly including a main switch and a controlling switch operable to select conductive mode of said main switch, the latter being a gate controlled semiconductor type A.C. switch having a gate and further electrodes and said controlling switch being associated with a controlling circuit connected to the gate and one electrode of the mains switch whereby when activated by said controlling switch the controlling circuit proves the necessary energy to the gate to switch said main switch to conductive mode. Preferably the switch assembly is a two terminal switch assembly and said main A.C. switch is a three electrode semiconductor A.C. switch such as a triac having a pair of mains electrodes terminal and a gate terminal, and wherein one mains terminal provides one terminal connection of the switch assembly. The other mains terminal is connected to an electronic controlling circuit which provides the other terminal connection. The controlling circuit is associated with said primary switch whereby it may be activated to provide the necessary potential at the gate terminal to cause the main switch to switch from open circuit mode to conductive mode. In the preferred form the electronic controlling circuit provides a continuous negative potential at the gate and indication means are connected between the control circuit and the gate. Preferably the indication means includes a light which glows dimly when the main switch is in open circuit mode and brightly when the main switch is in conductive mode. Preferably the controlling circuit includes a power regulation circuit having a Zenner diode connected in series with first rectification means and in parallel with further rectification means of the opposite sense to said first rectification means. Preferably the controlling circuit provides storage means for storage of voltage developed across the power regulation circuit. The latter may also include a plurality of diodes arranged in series with the Zenner diode and suitably the storage means is a capacitor. However it may be a rechargable battery or other storage device as desired. The controlling switch may be a mechanical switch or it may be a touch or proximity switch. Preferably the controlling switch is in the form of a capacitive . sensor associated with an electronic switch such as a transistor adapted to switch upon variations in capacitance of the sensor resulting from the placement of a mass, such as a persons hand, adjacent the sensor. Preferably the main A.C. switch is a triac having terminal MT 1 connected to neutral through the load and said electronic controlling circuit connected between MT 2 and the gate terminal whereby said switch assembly is load dependant such that removal of the load causes said electronic controlling circuit to reset and said main switch to be in open circuit mode. Alternatively the semiconductor A.C. switch may be a gate turn off device or the like. Preferably the controlling circuit is so made and arranged that the main switch cannot be switched to conductive mode until a pre-selected load has been applied. Suitably this load threshold is greater than that load applied by finger contact with the load terminals. In a further aspect this invention resides broadly in a power outlet assembly including a power outlet and a load dependant switch assembly as defined above for switching the power outlet whereby in use said power outlet assembly will automatically switch to open circuit mode upon removal of an appliance plug therefrom and will not switch back to a conductive mode until a predetermined load is plugged into the outlet. If desired earth leakage protection could be combined with the switching assembly. In order that this invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawings which illustrate a typical switch assembly made according to this invention, and wherein:- FIG 1 is a perspective view of a preferred form of switch assembly; FIG 2 is a block diagram of the switching circuit; FIG 3 is an expanded block diagram of the timing circuit, and FIG 4 is a circuit diagram of the switch assembly. FIG 1 of the drawings illustrates a wall mounted switch assembly 6 having a face plate 7 which is apertured at 8 whereby it may be screwed to a wall and having a small indicator light 9 which glows dimly when the switch is off and brightly when the switch is on. A housing 10 is formed at the back of the face plate 7 to support the solid state switching apparatus illustrated in FIGS 2- to 4 having terminal connections 5 for two wires, as illustrated. The switching apparatus includes a primary switch 11, and a main A.C. switch in the form of a triac 12 arranged with its terminal MT 1 connected to the load 13 and its terminal MT 2 connected to an electronic control circuit 15 which provides a negative potential to the gate 14 of the triac 12 with respect to the terminal MT 2. As illustrated in FIG 1 , the electronic control circuit 15 includes timing circuit 16, a driver 17, energy storage means 18 and a power regulator 19- A snubber circuit 20 is connected across the triac 12 between terminal MT 1 and MT 2 and the indicator light 9 is provided in the connection between the gate 14 and the driver 17. The snubber circuit 20 is provided to limit the rate of rise of the voltage across the triac 12 and to provide sufficient leakage of current to maintain the stored voltage for the control circuit 15. This circuit maintains a small current flow between the gate 14 and the triac terminal MT 2 which is insufficient to trigger the triac but sufficient to illuminate the indicator light 9 with a dull glow for easy location of the switch. When the switch is in ON mode, the energy required to maintain the triac in conductive mode is sufficient to cause the indicator ' 9 'to glow brightly. Referring to FIG 4 it will be seen that the electronic control circuit 15 is controlled by a sensor 21 which may be actuated to change the state of the switch assembly 6. For this purpose a mass such as a persons hand is placed adjacent the sensor 21 whereby the transistor switch 22 therein signals the timing circuit 16 which counts a preselected time and then checks the continued presence of the mass in proximity to the sensor 21. If the mass remains present during the check period, the bistable switch 23 in the timing circuit 16 changes whereby the voltage present at the gate 14 increases and switches the triac 12 to conductive mode. The negative potential at the gate 14 is achieved by connecting a Zenner diode 24 and diodes 25, 26 in Series/Parallel between MT 2 and one power supply connection 27- During the positive half cycle of the power supply with respect to terminal 27, the current will flow through diode 26, through MT 2, MT 1 and thus to the load. However during the negative half cycle of the power supply with respect to terminal 27, diode 26 blocks the current and the current therefore will flow through diodes 25 and Zener Diode 24 through MT 2, MT 1 and thus to the load. During this process however a voltage (negative with respect to MT 2 is developed across Zener diode 24 and this voltage is stored in a storage device 18 which may be a capacitor or a rechargable battery. Accordingly it will be seen that the triac 12 will have, suitably applied, a continuous negative potential to its gate terminal so that full power can be applied to the load when necessary. Preferably the timing circuit 16 is provided with alternate connection means designated LINK # 1 and LINK # 2, whereby the addition of appropriate links converts the switch assembly 6 for use in other modes. Referring to FIGS 3 and 4, if the link # 1 is formed, for example, the bistable switch 23 will be converted for astable operation whereby it will switch off upon removal of the mass from the sensor 21. Alternatively if link # 2 is formed the switch assembly 6. will be converted for a time delay mode whereby the switch assembly will automatically switch off after a pre-selected " time delay. This is achieved by providing the main counter 28 of the circuit 16, with subsidiary timing circuits 29 and 30 which may be interconnected with the main counter 28 by the addition of the links # 1 and 2 as mentioned above. It will be noted that the switch assembly 6 utilizes only two input wires for its operation thus it may be used to replace existing mechanical switches without any wiring changes. Furthermore, provided the load 13 is connected to neutral, then upon removal of the load, all source of power to the switch assembly 6 is removed and the switch assembly 6 will shut down. For this purpose the driver circuit 17 incorporates a load sensing circuit 17a which may be adjusted by the use of suitable value components so that the load threshold is greater than that corresponding to personal contract with the load terminals. Upon re-connection of the load 13 the control circuit 15 utilizes its own power-on reset circuitry 31 which maintains the circuit 15 in the off-state for a pre-selected time period. Thereafter the switch assembly 6 awaits the application of an appropriate mass to the sensor 21 for further operation. From the above it will be seen that no matter what voltage is applied at the two wire terminals A and N, the control circuit is always supplied at say 5 V from the Zenner diode power supply circuit. Thus it can switch both high and low voltages. Furthermore the distance at which a mass must be placed from the sensor 21 to actuate the primary switch 22 can be adjusted by selection of appropriate value components for the sensor 21. The time delay during which the mass must be present at the sensor is also selectively adjustable by varying the count at pin 9 of the counter 30. This delay is adapted to prevent accidental switching by a momentary - presence of any body. A further advantage associated with the above described switching assembly 6 is that it is capable of switching inductive loads as well as pure resistive loads so that it can be utilized for switching fluorescent lights, fans, electric motors and other inductive loads. This is possible because of the continuous negative potential supplied by the storage device as described above. In a preferred form of switch assembly, the circuitry is placed behind the face plate 7 of the switch assembly. This face plate also acts to insulate a conductive sensing plate 32 from a user. The indicator light 9 is also mounted visibly flush with the outer face of the face plate 7- This conductive plate 32 forms one plate of a capacitor the other plate being the mass which is required to operate the switch assembly 6. Thus in use a capacitor is formed as the users hand is brought close to the face plate 7 and the resulting capacative effect cause the primary switch 11 to actuate the timing circuit 16. Also any number of extension switches may be used as indicated at 34. The switch has the further advantage that the extension switches 34 can be connected by two wires only to the switch assembly 16 as opposed to the conventional arrangement in which at least three wires are required. If desired, the switch assembly can be mounted behind wall cladding material including non-conductive ceramic tiles. In such installation the indicator light is not used. Also if desired the whole switch assembly can be mounted within a suitable material, such as poly carbonate material. The material may be moulded in the shape of a building element such as a brick. The brick could be mounted in place of a normal building brick and used as a vandal proof, water proof and time delay off switch for use in public amenities, conveniences, railway stations and the like. Thus it may be located out of sight and adapted to switch on upon the placement of a hand adjacent its mounted position. The power outlet assembly according to this invention is similar to the switch assembly illustrated in FIG 1. However it includes sockets, as illustrated at 40 in dotted outline, for an appliance plug. A three pin socket is illustrated but of course a two pin socket could be provided if desired. The outlet 40 is controlled by the switch assembly described above. Of course the above has been given by way of illustrative example of this invention and it will be realised that all such and other modifications and variations thereto as would be apparent to persons skilled in the art ' are deemed to fall within the broad scope and ambit of the present invention as is defined in the appended claims.

Claims: THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:- 1. An A.C. switch assembly including a main switch and a controlling switch operable to select conductive mode of said main switch, the latter being a gate controlled semiconductor type A.C. switch having a gate and further electrodes and said controlling switch being associated with a controlling circuit connected to the gate and one electrode of the mains switch whereby when activated by said controlling switch the controlling circuit provides the necessary energy.to the gate to switch said main switch to conductive mode. 2. An A.C. switch assembly according to Claim 1 and adapted for two terminal connection in a circuit, wherein one terminal connection is connected to a free electrode of said main switch and the other terminal connection is connected to said controlling circuit. 3. An A.C. switch according to Claim 1 or Claim 2, wherein said main switch is a three electrode semiconductor A.C. switch having a pair of mains terminals and a gate terminal. 4. An A.C. switch according to Claim 3, wherein said controlling circuit includes a power regulation circuit associated with storage means whereby a continuous current flow may be maintained between the gate terminal and said one electrode. 5. An A.C. switch according to Claim 4, wherein an indicator light is provided in the connection between said controlling circuit and said one terminal. 6. An A.C. switch according to any one of Claims 3, 4 or 5, wherein said other terminal connection is connected _ -\ i _ 85/ 0188 directly to active and said controlling circuit is connected to neutral through a snubbing circuit across said main switch whereby the controlling circuit will be de-energised upon disconnection of said one terminal connector from neutral or upon removal of a load connected between said one terminal connection and neutral. 7. An A.C. switch according to Claim 6, wherein said snubbing circuit and said controlling circuit are so made and arranged that application of fingers to the load connections after the load has been removed will not cause energisation of said controlling circuit. 8. An A.C. switch according to any one of the preceding claims, wherein said controlling switch is a touch or proximity switch. 9. An A.C. switch, wherein said controlling circuit includes timing means which checks for the presence of a mass adjacent the controlling switch for a preselected time period before signalling actuation of the controlling switch. 10. An A.C. switch, according to any one of the preceding claims, 2 to 9 wherein said controlling switch is a bistable switch and wherein said control circuit includes timing means which may be configured to convert said controlling switch to a monostable switch. 11. An A.C. switch, according to Claim 10, when said timing means may be adjusted to convert said bistable switch to operate in monostable mode with bistable function still operative whereby the monostable resets the switch to off (open circuit) mode after a preselected period of operation. 12. A switch assembly according to any one of Claims 5 to 11 and adapted as a light or appliance switch and having:- a face plate adapted to be secured to a supporting surface; a component housing supported behind said face plate; an exposed indicator light in said face plate, and a pair of releasable terminal connectors forming said two terminal connections. 13. A switch assembly according to Claim 11, including a housing in the form of a building element, and wherein said controlling switch is a touch or proximity switch and wherein said indicator light is arranged in a normally exposed face of the building element and adjacent said touch or proximity switch which is concealed in said element and said two terminal connections are disposed in a normally concealed face of the building element. 14. A power outlet assembly having a plug socket assembly adapted to be connected to mains through a switch assembly as defined in any one of Claims 1 to 12. 15. A switch assembly substantially as hereinbefore described with reference to the accompanying drawings.

Inventors: EATON GREGORY FRANCIS, EATON, GREGORY, FRANCIS
Applicants: EATON GREGORY FRANCIS, KONINGEN SUSAN PETA, EATON, GREGORY, FRANCIS, KONINGEN, SUSAN, PETA
Application year: 1985
Main classification: H03K17
IPC codes: H03K17, H05B39