GB2234869A - Improved electrical switching system - Google Patents

Abstract

A manually controlled switching unit 10 or 11 incorporating a high voltage impulse generator is linked to a receiving unit 13 via an electrically conductive path 14 or 15, and the receiving unit 13 turns a load 16 ON and OFF in response to such impulse. Successive impulses may toggle the load between ON and OFF states or it may be turned ON by a positive pulse and OFF by a negative pulse or vice versa. A plurality of switching units and receiving units may be interconnected by a single line, the switching units producing outputs which can be distinguished from one another on the basis of patterns of positive or negative pulses, or pulses of different widths or amplitudes. The receiving unit may be incorporated in an adaptor interposed between the load and a power supply socket for the load. The impulse generator may be energised by a dynamo, solar coil, battery or particularly a piezoelectric device. The load may be a domestic, commercial or industrial appliance such as a motor, television set or, particularly, a lamp. <IMAGE>

Description

IMPROVED ELECTRICAL SWITCHING SYSTEM This invention relates to an improved electrical switching system which can be used inter alia for lighting or appliance control in domestic, commercial or industrial applications.

Conventional lighting wiring requires the provision of mains wiring between each wall- or ceiling-mounted switch to the lighting fitting controlled thereby. Building Regulations dictate that such mains wiring be of a specified minimum gauge of three core cable and that it be installed in conduit which is generally unsightly if left exposed or is expensive to conceal if it is to be hidden from view. Further, the need to provide conventional conduit means it is difficult to reposition a switch or add further switches or fittings without extensive building work and redecoration.

Conventional wiring conducts mains voltage to a location which is close to a user's fingers in a conventional on/off wall switch, meaning that special safety precautions have to be taken in "earthy" environments such as bathrooms and toilets to avoid the risk of electrocaution.

This invention seeks to provide an improved electrical switching system which avoids the above-discussed disadvantages.

According to one aspect of the invention an electrical switching system comprises a manually-controlled switching unit incorporating a high voltage impulse generator, a receiving unit coupled to the mains or other operating voltage used for powering a load to be switched into and out of circuit with the operating voltage, the receiving unit including an impulse-sensitive switch means for controlling the supply of operating voltage to the load, and an electrical conducting path linking the switching and receiving units to transmit an impulse from the generator to the switch means in the receiving unit.

Desirably the impulse generator is a piezo-electric crystal and the electrical conducting path is a single electrically conducting strand of wire, tape or ribbon.

Since the conducting path is only required to transmit the voltage impulse from the generator to the switch means of the receiving unit and not to carry mains voltage, a crosssectional area of at most 0.2 sq. mm of copper wire is sufficient and wires of this size (e.g. 0.5 mm diameter) can readily be concealed in the gap between a wall- or ceiling-mounted switching unit and a receiving unit controlling the on/off cycles of the load.

Since the conducting path is only required to transmit the voltage impulse so that its presence is detectable at the receiving unit, cross-sectional areas one, two or more orders smaller than 0.2 sq. mm can be used if desired.

Each switching unit could be secured (e.g. adhesively) in any desired location and then linked to the receiving unit by whatever length of conducting path is required and sited where it will be most easily concealed (e.g. in a "scratched" groove in plaster, slipped behind wallpaper, buried in grouting between tiles or as a conducting strip of metal (e.g. evaporated) supported by self-adhesive tape stuck to door furniture, skirting boards, picture rails, wall or ceiling surfaces and optionally painted over.

The power source in the switching unit is desirably self-energising (e.g. a piezo-generator actuated by operating the switch, a moving magnet/coil dynamo device or a solar cell) but the use of a battery is not ruled out.

Desirably the receiving unit is incorporated in an adaptor designed to have a male part of one known type of electrical socket connector on one side and a female part of the same type of connector on the other side so that it can simply be interposed between the load and socket when required. Thus for a screw-in or bayonet-fitting socket the receiving unit would have a male screw-in or bayonet fitting at one end and a female screw-in or bayonet socket at the other. For a power supply, three pins of a plug can protrude from one side and the other side can exhibit the three pin holes of a socket outlet.

The receiving unit includes switching means remotely actuated by the switching unit and thus the only adaptation necessary, say, to convert a conventional domestic room lighting system, would be to ensure the existing switch is permanently "on" and interpose the receiving unit in the existing wiring leading to the room light or lights.

The receiving unit can utilise semi-conductor devices (e.g. bipolar transistors or FETs) to switch the mains voltage on and off to the load in response to detection of whatever vestige of the impulse from the switching unit arrives at the switch means.

A number of switching units can readily be provided for controlling a single receiving unit, each switching unit being linked to the receiving unit by its own lowprofile conducting path.

Alternatively, by using means in the receiving unit to discriminate between the outputs from different switching units, it is possible to link a plurality of switching units to a single receiving unit via a common conducting path.

US Patent 3931514 discloses a switching system which uses piezoelectric devices and also avoids the provision of mains wiring between switching and receiving units, but in this prior art proposal fibre optic links are provided, the receiving unit operating on receipt of a "light" pulse fed along a fibre optic link from a switching unit.

Although it is expected the invention will have its most important application in the control of lighting fittings it will be appreciated that a wide range of electrical loads (such as small appliances like motors or television sets or industrial machines) can be controlled from remote switching units.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic of a simple system for controlling mains voltage supply to a ceiling-mounted lamp via two remote switches, Figure 2 is a schematic of a more complex switching system in accordance with the invention, Figure 3 is a circuit diagram of one workable system in accordance with the invention, and Figures 4 to 6 are circuit diagrams of further modified workable systems.

Figure 1 shows a simple electrical switching system in which two switching units 10, 11 are linked to a receiving unit 13 via respective fine wires 14, 15. As illustrated the unit 13 is a ceiling rose supporting a lighting fitting 16 and connected to mains supply wiring (not shown). Mains voltage is limited to the unit 13, the wires 14, 15 being effectively non-current carrying and merely transmitting on/off voltage pulses from a voltage impulse generator (not shown) in the switching units 10, 11 as and when it is required to change the operating state of the fitting 16.

The best voltage impulse generator I have so far inves tigated is a piezo-electric crystal unit (e.g. a unit of the kind used for generating a spark to ignite a gas flow) but I do not wish my invention to be unnecessarily limited to this type of generator since better generators may exist and/or may shortly be developed.

Figure 2 shows a more involved system. For convenience the same reference numerals have been used in Figure 2 as were used in Figure 1 to designate similar integers.

In the arrangement of Figure 2, two further switching units 20, 21 are provided, switching unit 20 being linked by its own impulse-carrying wire 22 to the unit 21 and unit 21 being linked to the receiving unit 13 by a common wire 23 which can transmit impulses from either of units 20 or 21.

Figure 2 also shows three core mains wiring 24 from a power supply point 25 to the unit 13, wiring 26 from the unit 13 to the load 16, and normal mains wiring links 27 and 28 linking the point 25 to the load 16 via a conventional switch 29. With the system shown in Figure 2, the load 16 can be energised in the conventional manner using the switch 29 or it can be energised by operating any one of the switching units 10, 11, 20 or 21 and de-energised by operating said any one switching unit a second time or operating any of the other three units.

Figure 3 shows one workable system and for convenience only one switching unit 10 has been shown. The unit 10 has a piezo-electric crystal 30 mounted in a housing so that switching pressure (applied in the direction of the arrow X) generates a high voltage (e.g. 10 Kv) short duration pulse which is dissipated in a spark gap 31 while a longmovement earthing switch 32 is temporarily in its opencircuit condition. The wire 14 can be as long as is required but should not be so long that its overall resistance exceeds more than a few megohms, since the attenuation of the pulse when it reaches the receiving unit 13 may then be too great to leave a pulse capable of triggering the switch means in the receiving unit 13.

The unit 13 includes a full-wave rectifier 40 and resistor 41 in series, generating a low DC voltage for powering an "ON" semiconductor switch means 42 and an "OFF" semiconductor switch means 43. Each switch means has three bipolar transistors coupled to a respective relay coil 44, 45, the main switching transistor being a PNP unit 44a in the "ON" switch means 42 and an NPN unit 45a in the "OFF" switch means 43.

The "load" (in this case a bulb 16) is energised when relay coil 44 is energised on receipt of a first impulse via wire 14 and de-energised when the next impulse is received on the wire 14 by energisation of the relay coil 45. All the time there is mains voltage on the load 16, the coil 44 of the "ON" switch means 42 has 12 volts applied across it. When the next impulse arrives from the switching unit 10, it energises relay coil 45 so that the power supply to the coil 44 is interrupted, cutting off the mains supply to the load. To ensure mains voltage cannot get onto the wire 14 a sealed enclosure spark gap 33 can be provided in the unit 13.

The diodes (which could be Zener diodes) shown at 50 in Figure 3 are an optional feature in the circuit. The power supply could include a step-down transformer feeding the bridge 40 with a smoothing capacitor connected across the outputs of the bridge.

The connection shown in dashed lines in Figure 3 provides terminals 34 to which a computer could be connected so that automatic operation of the system can be achieved via impulses generated by the computer.

Figure 4 shows an FET-based circuit, the FET's being shown at 54a and 55a and controlling the supply of power to the relays 44 and 45 on the basis of the appearance of a first and subsequent spark voltage on the line 14.

Figure 5 shows a low-voltage piezo switching system which has a number of features in common with the circuit of Figure 3. To simplify understanding of Figure 5 the same reference numerals have been used in Figure 5 with the addition of 100 to represent components used in the circuit of Figure 3.

In Figure 5 the spark gap 33 is dispensed with and instead the switching impulse is coupled from the conducting path 114 to the receiving circuit 113 using a coil 160 and a wire (or pick-up coil) 161. The power supply to the rectifier bridge 140 could be 6 volts ac, but a low voltage dc supply could also be used, thus obviating the need for the bridge 140.

Figure 5 shows three arrangements of piezo crystal marked as Type 1 (130), Type 2 (130A) and Type 3 (130B).

Type 1 feeds the output pulse from the crystal 130 into a small signal transformer (1:1 or step-down) 132 connected to the conducting path 114. Type 2 has a very high resistance 131 (e.g. 100 meg-ohm) in parallel with the crystal 130A but feeds the generated pulse directly to the path 114. Type 3 employs both a very high resistance 131B and a transformer 132B. I have found that when using types 2 and 3 improved performance may occur if the transistors 144a and 145a are changed over.

In place of the wire or pick-up coil 161, a Hall effect switch could be used. Further, if a constant supply voltage is not available to power the receiver unit 113 a remnance relay can be used in place of the relay 145.

Although Figure 5 shows cascaded transistors in both 143 and 142, it is expected that a single transistor could be used in each part of the circuit. Further rather than have one circuit part responding to a positive-going impulse and another circuit part responding to a negative going impulse, Figure 5 can be simplified to include a latch device which causes it to reverse its stable state each time a pulse is received. A circuit of this general type is shown in Figure 6.

Figure 6 shows a further circuit arrangement which uses a chip 170 (as illustrated a 4013B 14 terminal chip) receiving the impulse from the unit 161 and directly controlling a transistor 171 (e.g. a ZTX300) in the supply to the relay coil 172 (e.g. a RS 351-566 relay).

The piezo crystal 130 shown in Figure 6 could be of the kind (e.g. commonly used in a cigarette lighter) in which a spring-urged impact device is triggered manually to strike the crystal. Such a spring-urged impact device produces positive- and negative-going pulses which are so close that they are most easily treated as two parts of a single pulse and Figure 6 is particularly suitable for dealing with pulses of this kind. Each pulse received alters the state of the relay powered by coil 172, so that succeeding switching pulses appear on different ones of two terminals of the chip 170.

In the circuits of both Figure 5 and Figure 6 the terminals 134 can be used to connect the receiving unit 113 to a computer, a burglar alarm, one or more infra-red sensors, a timer or to other units required to switch on the load independently of the switching unit 110.

Any outside interference upon the single wire 14, 114 is never enough to induce the 10,000 or so volts required to induce the receiver circuits to pick up. But neither does the virtually currentless voltage supply enough energy to be emitted as radio interference. However, screening of the wire 14, 114 can be provided if Regulations should require protection against radio interference to be provided. The pick up is very sensitive and it senses the -ve and +ve voltage output of the piezo crystal. It uses the +ve wave to switch its load on and the -ve to switch its load off, but it is easily reversed. The receiver is completely dormant i.e. unpowered until its activation by either wave and is so small it can be fitted into a volume 3 of 5 cm3 or less.

The receiving unit will respond to any number of piezos that address its requirements without preference.

With modification a series of receiving units can be made to have a preference for certain voltages and discriminate at say 100v intervals. This would allow multiple switching through a single line thus providing "a data transfer" control panel with only one wire going to it.

By interlacing the receiving units a "key wave" can be produced. This is where a series of predetermined -ve and +ve charges are used to activate a predetermined receiver system or matrix and activate a path of current.

A matrix would allow any number of paths, like a telephone exchange.

For instance a piezo system producing characteristic +ve -ve -ve +ve -ve waves in series could influence five designated receiving units each switching itself on and opening the paths to the next, the last receiving unit operating a load e.g. a light. Any error would reset the system. Only the wave +ve -ve -ve +ve -ve would ever operate that light and the piezo could be made to be removable and carried like a door key, an ideal security light for colleges and businesses etc.

Discrimination between a plurality of switching units 10, 110 operating a single receiving unit 13, 113 can be provided on the basis of impulses of different duration or pulse lengths being generated by the different switching units and/or by arranging for impulses of different peak potentials to be generated by the different switching units.

There are a wide variety of different loads 16, 116 which can be used in practice and it is possible to index a piezo motor in the receiving unit so that the total angular rotation of the motor produced is a function of the number of impulses sent to it on the line 14, 114.

Other arrangements are possible for the receiving unit and these other arrangements can make use of Triac devices alone or in conjunction with transistors and/or FETs.

Because of the very high voltage available on the line 14, 114 it is possible to use alternative switching arrangements for the relays 44, 144 and 45, 145. Thus, for example, the piezo-generated voltage spike can be fed through a single wire movably located between a north magnetic pole and a south magnetic pole, whereby the movement of the wire towards one or the other pole can be used to close respective contacts in the relay coil supplies. Such a circuit represents a magnetic switch which may not require the inclusion of any electronic components particularly if the relay coils are designed to run from mains voltage.I am not aware of any relay currently available which can be "latched" and "unlatched" using the output voltage from a piezo-electric crystal but I would expect one to be developed before my patent monopoly expires and would expect to be able to use such a relay in the receiving unit of a switching system in accordance with my invention.

Further, the high voltage generated by a piezoelectric crystal can be used to electrostatically charge an electrically insulating member (e.g. a plastics film disposed adjacent to one or a cluster of charge-emitting needles to which the high voltage spike is fed) and cause the latter to deflect relative to the needle(s) or adjacent "earthy" members. The deflection of the charged insulating member can be used to move an electrically conducting switch part between spaced-apart pairs of switching contacts. The switch part could be a bridge of metal foil or the like to provide a conducting path on the insulating member which is electrostatically deflected between the pairs of switch contacts.Such an electrostatic switch can be very simple, the movement of the insulating member oscillating between switch contact pairs as the polarity of the high voltage spikes change during "straining" and during "unstraining" of the crystal. The insulating member can be charge-attracted to each of its switch-contact-pairengaging positions or charge attracted to one and mechanically biassed (e.g. by spring force or gravity) to the other.

One of the pairs of switch contacts may be redundant, since the necessary control of power supply to a load can be relay controlled using just one set of contacts periodically closed by a conducting bridge member.

By using conventional logic circuit devices (suitably protected from the high voltages in the impulse from the switching unit(s)) it is possible to separately control a number of receiving units simply by generating specified groups of impulses from any given switching unit. By coding series of impulses into control groups in this way, simple on/off switches in the switching units can be used a plurality of times to control several different receiving units in a variety of different combinations.

The system of this invention was designed originally as a safe bathroom light switch, but it soon became apparent that the qualities that it possessed were wasted on that single function. The invention has promise as a safer more versatile domestic and industrial switching system. Wire gauges smaller than the thickness of a human hair, can be used to transmit the impulse from switching to receiving units and wire of such gauge can easily be hidden within existing decor in the home allowing total rewiring or just the addition of switches to be put in place without disturbing the existing decoration. It is not necessary for a continuous conducting path to be provided since the switching pulse can traverse the gap between two wires disposed one adjacent the other but not in electrical contact.

A self adhesive backed switch unit can be stuck to the wall and then either the wire is pressed into a tiny notch in the plaster or hidden beneath paper or painted surfaces or even camouflaged self adhesive wire/strip could be used.

The switch unit only requires one single wire and this is run to a small receiving unit located conveniently out of sight (e.g. hidden in a lightrose). At no time need the conducting path make contact with the operating voltage in the receiving unit so that electrocution from the system outside of the receiving unit is totally impossible.

Indeed a shock of any kind is impossible. This makes the system ideal for dangerous environments such as kitchens, gardens, bathrooms, sheds, garages or other "earthy" environments.

The receiving unit will operate from any number of additional switching units through the same or different wires. It can be interfaced with burglar alarms, infrared, computer, fire alarms, courtesy lights or an existing 240v light switch with only simple modification. It alleviates the requirement for cable conduit. Any switching unit can operate multiple receiving units so complex lighting configurations can be used. It can even be used as a dimmer with modification.

The switching unit requires no batteries or external power of any kind and construction costs are expected to be low.

Claims (14)

1. An electrical switching system comprising a manually-controlled switching unit incorporating a high voltage impulse generator, a receiving unit coupled to the mains or other operating voltage used for powering a load to be switched into and out of circuit with the operating voltage, the receiving unit including an impulse-sensitive switch means for controlling the supply of operating voltage to the load, and an electrical conducting path linking the switching and receiving units to transmit an impulse from the generator to the switch means in the receiving unit.

2. A system according to claim 1, in which the impulse generator comprises a piezo-electric crystal.

3. A system according to claim 1 or claim 2, in which the electrical conducting path is a strand of wire, tape or ribbon.

4. A system according to claim 3, in which the crosssectional area of the material used for the conducting path is at most 0.2 sq. mm.

5. A system according to any preceding claim, in which more than one switching unit is provided for the receiving unit.

6. A system according to claim 5, in which each separate switching unit has its own conducting path linking it to the receiving unit.

7. A system according to claim 5, in which each separate switching unit uses a common conducting path and the receiving unit is adapted to distinguish between the impulses generated by the different switching units con nected thereto.

8. A system according to claim 7, in which the distinguishing is effected on the basis of one or more of, a) a key wave characterised by a chosen train of positive and negative impulses, b) impulse pulses of different duration and/or c) impulses of different peak potentials.

9. A system according to any preceding claim, in which the or each switching unit is adhesively secured in a desired location relative to the receiving unit.

10. A system according to any preceding claim, in which the receiving unit is incorporated in an adaptor designed to have a male part of one known type of electrical socket connector on one side and a female part of the same type of connector on the other side.

11. A system according to any of claims 1 to 4, in which the output from the switching unit is coded to distinguish its output from the output of other switching units.

12. A system according to claim 11, in which the distinguishing is effected on the basis of one or more of, a) a key wave characterised by a chosen train of positive and negative impulses, b) impulse pulses of different duration and/or c) impulses of different peak potentials.

13. A switching system substantially as herein described with reference to, and as illustrated in Figure 1 or Figure 2 of the accompanying drawings.

14. A switching system as herein described using a circuit substantially as illustrated in Figures 3, 4, 5 or 6 of the accompanying drawings.