GB2291289A

GB2291289A - Non-contact incandescent lamp switching and dimming device

Info

Publication number: GB2291289A
Application number: GB9413601A
Authority: GB
Inventors: Robert Ian Murrells; Bernard Wade Murrells
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-07-06
Filing date: 1994-07-06
Publication date: 1996-01-17
Also published as: GB9413601D0

Abstract

A two-terminal circuit is connectable to an AC supply in series with an incandescent lamp and comprises sensor means which produces a control signal when a user's finger interrupts a path between an infrared emitter 4 and a receiver, or when vibrations from a piezo-electric emitter (30, Fig. 3) are reflected by the finger to an ultrasonic detector (31), control means which changes the amount of electrical power supplied to the lamp in response to the control signal, and a power supply for the sensor and control means, the power supply storing electrical power during part of each AC cycle which is sufficiently small to avoid discernible illumination of the lamp. The power supply may store power within about 18 degrees phase angle at the start of each AC cycle. To prevent spurious response, the emitter may give a coded output. Momentary application of the user's finger switches the lamp from OFF to ON, or vice versa, whereas continued application causes the lamp to cycle between maximum and minimum levels for brightening or dimming the lamp. An additional infrared receiver may be provided for remote control of the circuit by a hand-held device. The circuit may be mounted on a face plate which can be secured in a standard wall box, and the plate may have an LED indicator light to aid location in the dark. <IMAGE>

Description

NON-CONTACT SWITCH Field of the Invention This invention relates to a non-contact light switch which can be used to replace a mechanical light switch.

Background to the Invention Conventional mechanical switches for switching electrical power to lamps typically comprise a sprung contact held apart from a fixed contact by a mechanical rocker in its "off' position, and allowed to meet when the rocker is moved to its "on" position. While such switches are inexpensive to manufacture and therefore almost universally used, they suffer from a number of disadvantages: 1. They are subject to wear, eventually rendering their mechanical action less satisfactory and possibly leading to arcing at the electrical contacts; 2. Since they require an appreciable force to operate them, they can be difficult for some physically handicapped people or small children to use; and 3.They are unsafe for use in proximity to water, for example in a bathroom, and are therefore replaced by pull switches, or costly waterproofed switches, in such environments.

To replace the simple mechanical switch for use with incandescent lamps, dimmer switches have become popular. These typically involve a variable-resistor controlled triac and usually incorporate a rotary on-off switch. Dimmer switches of this type share the disadvantages ofthe conventional mechanical switch.

It is desirable to replace switches of these types with a sealed switch having no mechanical moving parts, but while various possibilities are known for achieving this, a difficulty arises from the conventional manner of using light switches which means that it has not been possible simply to remove a mechanical switch and replace it with a non-mechanical device. The problem arises because current electrical wiring practice is to loop the mains supply from ceiling rose to ceiling rose in a chain, taking a tail from the line terminal to the light switch and then back to one terminal of the lamp, the other terminal being connected to the neutral.Thus, the switch is connected in series with the lamp, and it will be appreciated that, while power is required continuously for any electronic device in the switch, the current flowing through the switch will vary considerably depending on whether the lamp is on or off Switches have been proposed which make use of touch pads which depend on an electrical contact with the user's finger to cause them to operate. These are able to operate with a very small amount of power, but are inappropriate for use in moist environments, and do not readily adapt to additional functions such as remote control or the incorporation of a locating light without additional supply wiring.

Summarv ofthe Invention The present invention provides a non-contact switch which can be fitted as a direct replacement for a conventional mechanical on-off or dimmer switch.

According to the invention, there is provided a non-contact switch for connection, in series with an incandescent lamp, to an alternating current supply, the switch comprising sensor means consisting of a spaced emitter and receiver of radiation arranged either such that the path of the radiation therebetween can be interrupted by a user to provide a control signal, or such that the proximity of the user causes reflection of a part of the radiation emitted by the emitter back to the receiver to provide a control signal, control means responsive to receipt of the control signal to change the amount of electrical power delivered to the lamp, and power supply means for the sensor means and control means, the power supply means being arranged to store electrical power during a part of each cycle of the supply current, said part being sufficiently small to avoid discernible illumination of the lamp.

Preferably, the switch is arranged to vary the power supplied to the lamp continuously between a maximum and a minimum, and vice versa, while the control signal continues to be provided, i.e. while the radiation path continues to be interrupted, or the reflected signal continues to be received by the receiver.

The emitter and receiver may operate with infra-red radiation or, in the case of a reflective device, with an ultrasonic piezo-electric emitter. The signals may be coded, with the receiver responding to provide a control signal only if the code is received. In this way, spurious operation by ambient radiation is avoided.

It has been found that about 18 at the start of the cycle is a sufficient proportion to permit adequate power to be extracted to maintain operation of the switch over the remainder ofthe cycle.

The switch may incorporate a separate infra-red receiver arranged to provide a control signal on receipt of a coded signal from a hand-held remote control device, whereby switching ofthe lights may be achieved remotely.

The switch may be a single switch, or part of a multi-gang unit.

The switch may also incorporate a small indicator light, for example a low-power light-emitting diode, to permit the switch to be located more easily in the dark. The indicator light may be powered in the same manner as the switching components in the other embodiments of the invention. The light may be located behind a translucent portion ofthe cover plate.

Brief Description of the Drawings Figure 1 is a perspective view of a light switch according to one embodiment of the invention; Figure 2 is a block circuit diagram for the switch of Figure 1; and Figure 3 is a perspective view of a light switch according to another embodiment of the invention.

Detailed Description ofthe Illustrated Embodiments Referring to Figure 1, the switch comprises a face plate 1 to the rear of which are attached the electronic components described hereinafter with reference to Figure 2. The face plate 1 is formed with a shallow circular depression 2 therein.

An infra-red light-emitting diode (LED) 4 is mounted beneath the face plate 1 so as to direct a beam 3 of infra-red light through the face plate across the depression towards an opposed infra-red photodiode mounted in a corresponding position in the opposite side of the depression. The surface of the face plate may remain unbroken, the LED 4 and the photodiode being located behind portions of the cover plate which are translucent or transparent to infra-red. As hereinafter described with reference to Figure 2, the LED 4 sends a modulated signal to the receiver, either continuously or repeatedly. When a finger is placed into the depression 2 it interrupts the beam, and this causes a control signal to be sent to change the switching state, to switch the light on or off, or to increase or decrease the power supplied to the load, brightening or dimming the light.The face plate 1 has screw holes 5 in conventional manner, to permit the switch to be secured in a standard mounting box, of either the surface-mounted or flush type.

In the block circuit diagram shown in Figure 2, the switch is provided with a triac T1 to provide the main switching function and a spike suppressor S1 to prevent very high voltage spikes from damaging any other components of the device, both connected across the input and output terminals of the switch. A power supply integrated circuit IC1 is also connected between the terminals and is arranged to supply a regulated continuous 12 volts to the other integrated circuits within the switch, using only the first 180 of the mains cycle.The triac T1 is controlled by an on/off dimmer control IC2 which, when synchronised to the mains supply frequency and provided with a logic level pulse, turns the triac T1 on or off, depending on its previous state. A continuous control signal causes the phase angle for the triac to be cyclically varied. An isolated triac driver IC3 triggers the triac T1 from the output of the on/off control IC2. Phase synchronisation information for the on/off control IC2 is provided by an isolated driver IC4.

An infra-red output control and receiver circuit IC5 provides a modulated drive control for the infra-red LED 4 as well as providing a logic output to control the on/off control IC2 according to the receive state. Breaking the infra-red beam momentarily will cause the switch to change from the OFF state, which is the default after initial connection to the AC load and input, to an ON state at maximum brightness. Breaking the beam momentarily again will turn the switch OFF. If the beam is broken for a longer period of time, the phase angle of the AC supplied to the load will cyclically vary from its current position to maximum, and then to a minimum (which need not be zero brightness). Allowing the beam to reconnect leaves the switch in an ON state at the brightness level for the point in the cycle at which the beam was renewed.When the load is turned OFF the phase angle can be retained for when the switch is turned ON again. Other switching sequences may be incorporated into the operating logic for use in different circumstances, or to suit the preferences of the user. The power supply IC 1 has sufficient capacitance associated therewith to continue supplying power to all the components of the switch for the 342" of the cycle when it is not drawing power from the mains supply. In addition, the need for a conventional wound transformer is avoided, thus dramatically reducing space requirements and cost.

It will be appreciated that most or all of the switch control and power supply components, shown here as individual integrated circuits, may be incorporated into a single integrated circuit, possibly with only the triac, the capacitors and the LED/photodiode as externally-connected components.

Typically, the switch will be usable with an incandescent load of 60 to 300 W, although it will be appreciated that this range will be changeable by changing the values ofthe circuit components accordingly.

Figure 3 shows an alternative configuration of switch, having a piezo-electric ultrasonic emitter 30 directed outwardly of the switch and a receiver 31 spaced apart therefrom. As with the embodiment of Figure 1, the emitter and receiver may be located behind portions of the face plate which are transparent to ultrasound.

The emitter 30 is arranged to emit a modulated very low power ultrasonic signal continuously or repeatedly at short intervals. When the user brings a finger 32 into the proximity to the switch, some of the ultrasonic signal is reflected back from the finger to the receiver 31, causing operation of the switch generally in the manner described with the reference to Figure 2. The power ofthe emitter will be limited so that the user's finger (or other reflective surface) will have to be closer to the switch than, say, 25 mm for the switch to be activated.

Claims

1. A non-contact switch for connection, in series with an incandescent lamp, to an alternating current supply, the switch comprising sensor means consisting of a spaced emitter and receiver of radiation or ultrasonic vibrations arranged either such that the path of the radiation or vibrations therebetween can be interrupted by a user to provide a control signal, or such that the proximity of the user causes reflection of a part of the radiation or vibrations emitted by the emitter back to the receiver to provide a control signal, control means responsive to receipt of the control signal to change the amount of electrical power delivered to the lamp, and power supply means for the sensor means and control means, the power supply means being arranged to store electrical power during a part of each cycle of the supply current, said part being sufficiently small to avoid discernible illumination of the lamp.

2. A switch according to Claim 1, wherein the control means is arranged to vary the power supplied to the lamp continuously between a maximum and a minimum, and vice versa, while the control signal continues to be provided

3. A switch according to Claim 1 or 2, wherein the emitter and receiver operate with infra-red radiation.

4. A switch according to Claim 1 or 2, wherein the control signal is provided by reflection from the user's finger, and wherein the emitter is an ultrasonic piezo-electric emitter and the receiver is an ultrasonic detector.

5. A switch according to any preceding claim, comprising means for modulating the emitted radiation or vibrations with a code, and means for detecting the code in the signal received by the receiver.

6. A switch according to any preceding claim, wherein the power supply means is arranged to store electrical power within about 18" phase angle at the start of the cycle.

7. A switch according to any preceding claim, incorporating a separate infra-red receiver arranged to provide a control signal on receipt of a coded signal from a hand-held remote control device, whereby switching of the lights may be achieved remotely.

8. A switch according to any preceding claim, also incorporating an indicator light to permit the switch to be located more easily in the dark.

9. A switch according to Claim 8, wherein the indicator light is a low-power light-emitting diode powered by the power supply means.

10. A switch according to Claim 7 or 8, wherein the light is located behind a translucent portion of the cover plate.

11. A non-contact switch, substantially as described with reference to, or as shown in, the drawings.