GB2382957A

GB2382957A - Detectable components and detection apparatus for detecting such components

Info

Publication number: GB2382957A
Application number: GB0129492A
Authority: GB
Inventors: David Bernard Mapleston; Peter Robert Symons; Colin Philip Brooks; Andrew David White
Original assignee: Innovision Research and Technology PLC
Current assignee: Broadcom Innovision Ltd
Priority date: 2001-12-10
Filing date: 2001-12-10
Publication date: 2003-06-11
Also published as: GB2420861B; GB0129492D0; GB2382876C; GB2382876A; GB0224431D0; GB2419959A; GB2420861C; GB2419959B; GB0604712D0; GB2382876B; GB2420861A; GB0526602D0

Abstract

A detectable component 3 has a first inductive coupler (L;M) adapted to couple inductively to a second inductive coupler (L1) of a detection apparatus 2 when the detectable component is in range of or coupled to the detection apparatus. The first inductive coupler includes a component formed of a material having a resistance that varies with magnetic field (e.g. giant magneto impedance or giant magneto resistive material). In one example, the first inductive coupler has an inductive component (L) formed of Litz wire and a resistive component formed of the material whose resistance varies with magnetic field. In another example, the first inductive coupler consists solely of a coil, for example a single turn, of the material whose resistance varies with magnetic field. In an embodiment, the material is a material exhibiting the giant magneto impedance effect. Applications suggested include the detection apparatus being the main body of an electrical appliance or device and the detectable component being a subsidiary body e.g. tool or accessory for use therewith, for example, a toothbrush head, implement for a food processor or vacuum cleaner, a tool or bit for an electric power tool or drill or an attachment or accessory for a hairdryer.

Description

DETECTABLE COMPONENTS AND DETECTION APPARATUS FOR

DETECTING SUCH COMPONENTS

This invention relates to detectable components and 5 detection apparatus for detecting such components.

There are many forms of electronic devices or electrical appliances that are designed to operate with attachable or detectable components. Examples are electric power 10 tools, medical catheters, food processors, portable vacuum cleaners, hairdryers and so on. In some cases, such electrical appliances may accidentally be operated with an incorrect attachable component or even with no attachable component. This may present safety problems 15 and in the case of battery-operated electronic devices or electrical appliances may be wasteful of battery life.

In one aspect, the present invention provides a detectable component having first inductive coupling 20 means adapted to couple to second inductive coupling means of a detection apparatus when the detectable component is in range of or coupled to the detection apparatus, the detectable component having an inductive element comprising a multistranded coil and a resistive 25 component having a resistance that varies with magnetic

field so that, when the detectable component is subject

to a change in magnetic field, the variation in

resistance of the resistive component results in corresponding amplitude modulation of a carrier or 5 excitation signal supplied to the second inductive coupling means. The detection apparatus can thus detect the presence of the detectable component without the need for any physical electrical connection such as wires connecting the detection apparatus to the component.

In an embodiment, the present invention provides a detectable component having first inductive coupling means adapted to couple inductively to second inductive coupling means of a detection apparatus when the 15 detectable component is in range of or coupled to the detection apparatus, the first inductive coupling means comprising a coil, in an embodiment a coil of Litz wire, and having a resistive component with a resistance that varies with magnetic field so that when a high frequency

20 carrier signal is supplied to the second inductive coupling means and the detectable component is subject to a varying magnetic field, the carrier is amplitude

modulated and this modulation can then be used to detect the presence of the detectable component.

Litz wire is multi-stranded fine wire wherein individual wires are insulated from one another and are bunched or braided together in a uniform pattern. The use of a coil consisting of wire having many such parallel-connected 5 paths, provides a larger surface area than would be provided by a solid conductor without significantly increasing the size of the conductor and so avoids the power losses that occur in solid conductors due to the "skin effect", that is the tendency of radio frequency 10 current to be concentrated at the surface of a conductor making the detectable component more easily detectable.

In an embodiment, the resistive component has a resistance that varies with magnetic field. Generally,

15 the resistive component is a material exhibiting the giant magnetoimpedance effect (GMI), that is the variation of resistance with magnetic field when a high

frequency alternating current is passed through the material. Examples of such materials are, for example, 20 amorphous cobalt alloys and nickeliron plated beryllium-copper wire. Any material that exhibits magnetic impedance properties may be used in place of the GMI material.

In an embodiment, the coil comprises GMI material. For example, the coil may be formed of layers of GMI material separated by a dielectric material and wound to form the coil. In an embodiment, the resistive component is in series with the coil.

In an embodiment, the first inductive coupling means also 10 includes a capacitor. The first inductive coupling means may form an LCR resonant circuit.

In an embodiment, the resistive component comprises a further coil inductively coupled to the coil. In an 15 embodiment, the resistive component comprises a further coil and the two coils form first and second transformer windings. Where the resistive component forms a coil, then the coil 20 may consist of a single closed-loop turn.

According to one aspect of the present invention, there is provided a detectable component having first inductive coupling means adapted to couple inductively to second 25 inductive coupling means of a detection apparatus when

the detectable component is in range of or coupled to the detection apparatus, the first inductive coupling means consisting solely of a coil formed of a material having a resistance that varies with magnetic field to cause

5 modulation with magnetic field of a carrier signal

supplied to the second inductive coupling means of the detection apparatus.

The resistive component may have a skin resistance that 10 varies with magnetic field. The resistive component may

be a material exhibiting the GMI effect such as, for example, an amorphous cobalt alloy.

In an embodiment a detectable component as set out above 15 also includes a passive device that is operable, when the detectable component is coupled to or is in range of the detection apparatus, to derive power from the detection apparatus and to communicate with the detection apparatus. In an embodiment, the passive device is a 20 passive data storage device which may have a memory storing data. In an embodiment, the passive data storage device derives power from a carrier signal supplied by the detection apparatus and communicates data by modulating that carrier signal in accordance with data 25 read from a memory. The carrier signal may be the

carrier signal supplied to the second inductive coupling means. As used herein, the term "passive" means that the device is not self-powered but derives power from the detection apparatus when coupled thereto.

The passive data storage device may have write means for writing data to the memory.

The detectable component may comprise or form part of a 10 subsidiary body usable with a main body. For example, the subsidiary body may be couplable or attachable to and/or detachable from the main body. The main body may be the main body of an electrical appliance or electronic device and the subsidiary body may be a tool or accessory 15 for use therewith, for example, a toothbrush head, an implement for a food processor or a vacuum cleaner, a tool or bit for an electrical power tool or drill or the like, an attachment or accessory for a hairdryer and so on, while the detection apparatus may be provided in a 20 main body of the electronic device.

In an aspect, the present invention provides an electrical appliance or electronic device having a main body and a subsidiary body, the subsidiary body having 25 first inductive coupling means and the main body having

second inductive coupling means adapted to couple inductively to the first inductive coupling means when the subsidiary body is in range of or coupled to the main body, the main body having carrier signal supplying means 5 for supplying an excitation carrier signal to the second inductive coupling means and magnetic field generation

means for subjecting the subsidiary body to a varying magnetic field, the first inductive coupling means

comprising a coil having a plurality of electrically 10 conductive paths coupled in parallel and having a resistive component with a resistance that varies with magnetic field to cause modulation of the carrier signal,

the main body having modulation detection means for detecting modulation of the carrier signal caused by 15 variation of the resistance of the resistive component due to changes in the magnetic field when the first and

second conductive coupling means are coupled.

In an embodiment, the present invention provides an 20 electronic device or electrical appliance having a main body and a subsidiary body, the subsidiary body comprising a detectable component having first inductive coupling means and the main body having second inductive coupling means adapted to couple inductively with the 25 first inductive coupling means when the subsidiary body

is in range of or coupled to the main body, the main body having magnetic field generation means for subjecting the

subsidiary body to a varying magnetic field and carrier

signal supplying means for supplying an excitation 5 carrier signal to the second inductive coupling means, the first inductive coupling means consisting solely of a coil of the material that has a resistance that, in the presence of the carrier signal, varies with magnetic field to cause modulation of the carrier signal, the main

10 body having modulation detection means for detecting modulation of the carrier signal caused by variation of the resistance of the coil due to the varying magnetic field when the first and second inductive coupling means

are coupled.

In an embodiment, the magnetic field generation means

comprises means for generating a relatively low frequency varying magnetic field, for example an excitation coil

and low frequency source. In an embodiment, the carrier 20 signal has a frequency of, typically, 13.56 MHz (Mega Hertz) while the low frequency signal has a frequency value that typically lies in the range of from lOOHz (Hertz) to 500Hz, for example 250Hz. The motor drive frequency is selected to avoid any possibility of

mechanical frequency interference and will typically have a value in the range from 20Hz to Just under 90Hz.

In an embodiment, the magnetic field generation means

5 comprises a magnet that moves with a component of the main body, for example the magnet may be mounted on a motor drive shaft.

In one aspect, the present invention provides detection 10 apparatus for detecting a detectable component having first inductive coupling means and a resistive component that, when supplied with a high frequency signal, has a resistance that varies with magnetic field but is

insensitive to magnetic field polarization, the detection

15 apparatus having second inductive coupling means adapted to couple to the first inductive coupling means and the detection apparatus also having carrier signal supplying means for supplying a relatively high frequency excitation carrier signal to the second inductive 20 coupling means, magnetic field generation means for

generating a symmetrically oscillating magnetic field at

a given frequency and modulation detecting means for detecting modulation of the carrier signal at a frequency twice the given frequency. In an embodiment, the

magnetic field generation means generates a sinusoidally

varying field.

In some cases, the electronic device or electrical 5 appliance may simply identify whether or not a subsidiary body is present and, if not present, inhibit operation of the electronic device or electrical appliance. In other cases, where a number of subsidiary bodies can be used with the same electronic device, then the electronic 10 device may be able to recognise the type of subsidiary body and to adjust its operation accordingly. For example, the electronic device may adjust the motor drive speed of the electronic device to be adjusted to meet the requirements of a particular attachable component.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 shows a diagrammatic representation of an 20 electrical appliance embodying the invention with a subsidiary body in the form of an attachable component or tool being shown separated from a main body of the electrical appliance and the main body being shown partly in section;

Figure 2 shows a block diagram of functional components of the main body shown in Figure 1 illustrating one example of a reader or detection apparatus embodying the present invention; 5 Figure 3 shows a functional block diagram similar to Figure 2 but illustrating a different form of reader embodying the present invention; Figures 4a to 4e illustrate circuit diagrams for different forms of detectable components embodying the 10 present invention; Figure 5 shows a very diagrammatic partsectional view of the attachable component shown in Figure 1 to illustrate the incorporation of a detectable component therein; 15 Figures 6a to 6c illustrate how the detectable components shown in Figures 4a to 4c, respectively, may be constructed for incorporation in the attachable component shown in Figure 5; Figure 7 shows a diagrammatic representation of part 20 of the main body of an electrical appliance and an attachable component coupled thereto to illustrate another form of detectable component embodying the invention; Figure 8 shows one way in which a detectable 25 component incorporated in the attachable component shown

in Figure 7 may be formed while Figure 9 shows one way in which a coil of the reader shown in Figure 1 may be incorporated into the main body of the electrical appliance; 5 Figure 10 shows a diagrammatic part-sectional representation of an attachable component for illustrating incorporation therein of a detectable component and a passive data storage device; Figure 11 shows a functional block diagram similar 10 to Figures 2 and 3 illustrating a reader for incorporation in an electrical appliance main body suitable for use with the attachable component shown in Figure 10; Figure 12 shows a functional block diagram of an 15 example of a writeable passive data storage device that may be incorporated into the attachable component shown in Figure 10; Figures 13a and 13b illustrate, respectively, the construction of and the equivalent circuit diagram for 20 another example of a detectable component embodying the present invention; Figure 14 shows another example of a detectable component and a detection apparatus embodying the present invention; and

Figure 15 shows a graph of impedance against magnetic field for a material exhibiting the giant

magneto impedance (GMI) effect.

5 Referring now to the drawings, Figure 1 shows a diagrammatic representation of an electronic device or electrical appliance 1 embodying the invention having a main body 2 and subsidiary body 3 shown separated from the main body 2. In this example, the electronic device 10 is a battery-operated tool and the subsidiary body 3 is any one of a number of different attachable components or tools that enable a user of the tool to carry out different operations. For example the subsidiary body may be an abrading or erasing tool, a sanding tool, a 15 screwdriver tool, a polishing tool, a reaming tool or a routing tool. In the interests of simplicity, the bit or head 14 of the attachable component that actually effects the operation (sanding, abrading, erasing, screwing and so on) is shown very diagrammatically in 20 Figure 1 and with no detail because these details will be substantially identical to those of a conventional head or bit.

The main body 2 is shown part cut away to show the 25 functional components of the electronic device. In this

case, the functional components include a battery 4 which may, as is known in the art, be a rechargeable battery.

The battery 4 provides a power supply for the remaining functional components of the electronic device. In the 5 interests of simplicity, however, the connections from the battery to the other components are not shown.

The other components of the main body include a controller 5 in the form of a micro-controller, micro 10 processor or state machine coupled to a motor controller 6 itself coupled to a motor drive 7. The motor drive 7 consists, as is well known in the art, of a motor and gear train and the motor controller 6 controls activation and the speed of rotation of the motor drive. An output 15 shaft 8 of the motor drive extends through a mechanical coupling connector 9 of the main body. The functional components of the main body also include a user interface which in this case is in the form of an on/off switch 10 but may also include, for example, a light emitting 20 device or devices lea that provide an indication to the user of the status of the device (for example whether the battery is charged) and a rudimentary loudspeaker lob for providing an audible warning beep, for example in the event of low battery power.

The functional components so far described are similar to those present in a conventional electrical power tool although, generally, the controller 5 may not be necessary. In this regard, it will, of course be 5 appreciated that the extent and shape of the motor drive shaft or the actual configuration of the drive coupling to the attachable component will depend upon the particular electronic device.

10 In addition to the controller 5, the functional components of the main body 2 include a reader 11 that, as will be described below, is arranged to detect the presence of a detectable component 12 carried by the attachable component 3 when a coupling connector 13 of 15 the attachable component 3 is pushed onto the coupling connector 9 of the main body 2 in the usual manner.

Although only a simple mechanical connection is shown, it will of course be appreciated that a more sophisticated coupling, such as a chuck and key coupling 20 may be provided.

The head 14 is rotatably mounted to the attachable component body 3a and, as is known in the art, when the attachable component 3 is mounted on the body 2, a free 25 end 8a of the drive shaft 8 engages a drive coupling

arrangement (not shown) provided within the attachable component 3 enabling the motor drive 7 to rotate, oscillate, vibrate or reciprocate the head 14.

5 In the present embodiment, when the user activates the electrical appliance using the on/off switch 10, the controller causes the reader 11 to check for the presence of a detectable component 12. If an attachable component is correctly mounted to the main body, then the reader 10 11 detects the detectable component 12 and provides a signal to the controller 5 causing the controller 5 to activate the motor controller 6 to enable use of the electrical appliance in known manner. If, however, a attachable component 3 is not mounted to or is not 15 correctly mounted to the main body 2 when the on/off switch 10 is actuated, then the reader 11 will not detect the presence of the detectable component 12 and the controller 5 will inhibit operation of the motor controller 6. This prevents accidental actuation of the 20 electrical appliance in transit, for example when placed in a carrying case or bag, and also prevents a user inadvertently activating the electrical appliance without having first mounted an attachable component onto the drive shaft 8 and also prevents a user activating the 25 electrical appliance if the attachable component 3 is not

securely mounted to the body 2 and is therefore in danger of becoming detached during use.

Examples of detectable components will now be described 5 with reference to Figures 4a to 4e in which the detectable component 12 has a first inductive coupler adapted to couple inductively to a second inductive coupler forming part of the reader 11 when the attachable component 3 is correctly mounted on the main body 2. The 10 first inductive coupler has a coil formed of Litz wire and has a resistive component having a resistance that, when a high frequency signal is supplied through the resistive component, varies with magnetic field and so

causes modulation, with magnetic field, of a carrier

15 signal supplied to the second inductive coupler of the reader. The resistive component is formed of a material exhibiting the Giant Magneto Impedance (&MI) effect, that is a material that has a skin resistance that, when a relatively high frequency oscillating signal is supplied 20 through the material, varies with magnetic field. The

resistive component may be formed of, for example, a cobalt amorphous alloy, as described in detail in a paper entitled "High frequency giant magneto impedance in Co rich amorphous wires and films" published in the Journal 25 of the Magnetic Society, Japan volume 19 pages 265-268

in 1995 by LV Panina and K Mohri of the department of Engineering of Nagoya University.

Figure 4a shows a representational circuit diagram of one 5 example of such a detectable component. This detectable component 12a consists of an LCR tuned circuit having a coil L formed of Litz wire (represented schematically in Figure 4a as three parallel inductors It to I3) coupled in series with a capacitor C and a resistor R formed by 10 a length of GMI material. The resulting LCR tuned circuit will typically have a resonant frequency in the range 20kHz to 50MHz with the optimum frequency for the GMI material being dependent upon the particular material. In this example the optimum frequency for the 15 selected GM material is 1 MHz.

In an example, the Litz wire inductive component is a 27 turn conductive component, the capacitor C has a capacitance of 18pF and the resistive component is 20 formed of 2cm of GMI material.

Figure 2 shows a more detailed block diagram of the functional components of the main body 2 to illustrate in greater detail one example of a reader 11 suitable for

use in detecting the detectable component 12a shown in Figure 4a.

As shown in Figure 2, the reader 11 has a second 5 inductive coupler comprising a parallel connection of a coil or inductor L1 and a capacitor C1 coupled in series with a resistor R. A carrier or excitation signal generator 20 is provided so as to supply a high frequency carrier or excitation signal to the coil L1.

The reader 11 also includes a further coil L2 coupled to a relatively low frequency signal generator 21 that generates an oscillating, in this case a sinusoidal, signal that can be pulsed under the control of the 15 controller 5.

The carrier signal has a frequency of, typically, 13.56MHz (Mega Hertz) while the low frequency signal has a frequency value that typically lies in the range of 20 from lOHz (Hertz) to 500Hz, for example 250Hz. The motor drive 7 frequency is selected to avoid any possibility of mechanical movements (in particular movement of magnetic materials) causing interference and, typically, has a value in the range 20Hz to 90HZ.

As shown, the low frequency generator 21 is also coupled to a frequency doubler 22 that provides a "clock signal" for a synchronous demodulator 23. An amplitude modulation (AM) detector 24 is coupled to the inductor 5 L1 and provides an input to the synchronous demodulator 23. A demodulated signal output by the synchronous demodulator 23 is supplied to signal processing circuitry 25 that outputs a digital square wave signal to the controller 5. The signal processing circuitry 25 10 may include, for example, an analogue to digital (A/D) converter and buffering circuitry.

When the user activates the electrical appliance 1 using the user interface or on/off switch 10, then the 15 controller 5 activates the high frequency oscillator 20 to output the high frequency carrier or excitation signal to the coil L1 and activates the low frequency signal generator 21 to produce low frequency pulses causing the coil L2 to create an oscillating magnetic field. If the

20 attachable component 3 shown in Figure 1 is correctly mounted to the main body 2 then the mutual coupling of the first and second inductive couplers will cause a decrease in the amplitude in the carrier signal on the inductor L1 with this amplitude being modulated in 25 accordance with the change in resistance of the resistive

component R due to the magnetic field generated by the

pulsed low frequency oscillator 21.

The GMI material forming the resistive component R of the 5 detectable component 12a is not sensitive to the polarization of the magnetic field. Accordingly, if (as

in the case where the oscillating magnetic field is a

sinusoidally oscillating magnetic field) the oscillating

magnetic field is symmetrical, then the high frequency

10 carrier signal will be modulated by a full-wave rectified version of the modulated sine wave supplied by the low frequency carrier signal generator 21. The amplitude modulation of the high frequency carrier signal is therefore predominantly twice the frequency of the low 15 frequency signal generated by the low frequency signal generator 21.

The frequency multiplier 22 "clocks" the synchronous demodulator 23 at twice the frequency of the low 20 frequency signal generator 21 so that the synchronous demodulator 23 extracts modulation at twice the frequency of the low frequency carrier signal. This means that the amplitude modulated signal can easily be differentiated from the original carrier signal supplied by the low 25 frequency carrier signal generator 21 enabling the

inductors L1 and L2 to be placed in relatively close proximity to one another without any cross-talk between these two coils swamping or interfering with the signal that the reader is designed to detect.

The properties of the GMI resistive component R significantly reduce the possibility of false detections resulting from a metal object or a shorted turn coming into proximity with the coil L1 while the use of the 10 symmetrical, in this example sinusoidal, low frequency excitation signal and the synchronous demodulator 23 clocked at twice the frequency of the low frequency carrier signal reduces the possibility of the amplitude modulated signal being swamped by cross-talk between the 15 coils L1 and L2 enabling these coils to be placed close together and also allowing the reader 11 to detect detectable components 12 at relatively long range, for example over a range of 3cm. Where such cross-talk is not a problem, then the frequency doubler may be omitted 20 and the synchronous demodulator replaced by a simple demodulator. As described above, the controller 5 controls activation of the carrier signal generators 20 and 21. The 25 controller 5 may, however, control activation of a gating

circuit that controls application of the carrier signal to the corresponding coil L1 or L2.

The reader described with reference to Figure 2 generates 5 a magnetic field that affects the resistance of the

resistive component R using the coil L2 and a pulsed low frequency carrier signal provided by the low frequency signal generator 21.

10 Another example of an electrical appliance embodying the present invention will now be described with reference to Figure 3 which shows a functional block diagram of the functional components of the main body. Figure 3 differs from Figure 2 in that the reader lla is not provided with 15 the low frequency signal generator 21 and associated coil L2, frequency multiplier 22 and synchronous demodulator 23. In this embodiment, as shown in phantom lines in Figure 1, a magnetic element 30 is secured to the drive shaft 8 to provide the magnetic field to which the

20 detectable component 12 is subjected. In this case, when the attachable component 3 is correctly mounted on the main body 2 and the motor drive 7 is activated to rotate or oscillate the drive shaft 8, then the magnetic element 30 will rotate or oscillate with the drive shaft 8 and 25 the magnetic field to which the detectable component 12

is subjected will vary dependent upon the rotation angle of the drive shaft. The skin resistance of the GMI resistive component R will thus vary periodically with the rotation or oscillation of the drive shaft and, due 5 to the mutual coupling between the first and second inductive couplers, will cause a periodic change in the amplitude of the carrier signal in the coil L1.

This amplitude modulation is detected by the AM detector 10 24 r demodulated by the demodulator 23a and processed by the signal processing circuitry 25 as described above to provide to the controller 5 a signal representing the change in the resistance of the GMI resistive component and thus the relative location of the magnet and the GMI 15 resistive component. The controller 5 can then determine the periodicity of the modulation of

the carrier frequency and, from this, the rotational speed of the drive shaft 8. The 20 controller 5 is thus provided with feedback regarding the speed of rotation of the drive shaft and the load on the drive shaft exerted by the user during operation of the accessory. In the example shown in Figures 1 and 3, the controller 5 may use the information provided by the 25 reader to cause the motor controller 6 to control or

adjust the motor drive speed and/or to detect the load on the attachable component, for example to determine whether the user is pressing too hard. If the latter is the case, then the controller 5 may cause the motor 5 controller 6 to disable the drive to the accessory or cause a warning light lea forming part of the user interface to flash or, if the user interface 10 includes the loudspeaker lob, to cause the loudspeaker to issue an audio output, such as a warning beep, to the user if 10 the controller determines that the load on the attachable component is too high.

The embodiment described above with reference to Figures 1 and 3 may be implemented in any case where the motor 15 drive causes movement of the permanent magnet, for example where the drive shaft 8 completes a full rotation or oscillates so that the drive shaft only rotates through approximately 60 , by positioning the permanent magnet 30 so that the GMI resistive component of the 20 detectable component 12 is subject to the greatest possible change in field strength as the drive shaft and

magnet rotate.

In each of the embodiments described above, subjecting 25 the GMI resistive component to a magnetic field alters

its resistance and affects the Q factor of a tuned LCR circuit. This, in turn, affects the "loading" or modulation of the high frequency carrier signal by virtue of the mutual coupling between the first and second 5 inductive couplers.

In each of the embodiments described above, the presence of the detectable component 12 in the subsidiary body 3 enables the controller 5 to determine whether or not the 10 subsidiary body 3 is present without the need for there to be any physical electric coupling (for example wires) connecting the main body to the subsidiary body. This means that detection of the presence of the subsidiary body 3 can be effected without having to compromise the 15 integrity of the housing of the main body 2, for example its water-tightness.

In the above described embodiments, the detectable component 12 comprises a series LCR resonant circuit with 20 the resistive component R being formed of GMI material that exhibits a skin resistance that is dependent on magnetic field when a high frequency signal is supplied

therethrough and the inductive component L being formed of a multistranded wire, generally Litz wire, which 25 without any significant increase in the overall conductor

size increases the skin surface area so avoiding or at least reducing the power losses compared to those which are incurred in solid conductors due to skin effects at high frequencies. The use of multi-stranded conductor, 5 such as Litz wire, to form the inductive component greatly improves the Q factor of the inductive component and therefore the Q factor of the resonant LCR circuit.

In addition, Litz wire is available at very low cost as it is used in large quantities within conventional AM 10 radios. Accordingly, the use of Litz wire enables the formation of a relatively cheap inductor with a much improved Q factor. Experiments have shown that replacing a conventional solid conductor formed inductor with a Litz wire formed inductor can increase the modulation of 15 the carrier signal in the reader coil by a factor of three or more.

Figure 4b shows a circuit diagram of another form of detectable component 12b that may be used in the 20 accessory 3 shown in Figure 1. This detectable component 12b again consists of a Litz wire inductive component or coil L coupled to a capacitor C that, again, acts to tune the coil. However, in this case, the GMI resistive component is not coupled in series with the inductive 25 component L. Rather, the GMI resistive component is

formed as a simple closed loop coil M around and insulated from the inductive component L so that there is no physical connection between the two coils. As shown, the closed loop M consists of a single turn. It 5 may, however, have 2, 3 or more turns, depending upon the characteristics required of the circuit.

In this embodiment, the two coils L and M effectively form the primary and secondary windings of a transformer 10 with the GMI closed loop M forming the secondary winding that loads the high Q tuned LC circuit of the primary winding. As in the above described embodiments, the presence of 15 a magnetic field when a high frequency signal flows

through the GMI material causes the skin resistance of the GMI closed loop M to change, changing the loading on the primary high Q tuned circuit LC. This change in Q factor of the primary modulates the loading on the reader 20 coil L1 again providing an amplitude modulation that can be detected by the AM detector 24 as described above with reference to Figures 2 and 3.

In this embodiment, the reflected resistance of the GMI 25 loop M is proportional to the square of the ratio of the

number of turns in the inductive component L coil to the number of turns in the closed loop M enabling the sensitivity to be improved by adjusting this ratio, generally using a single turn for the closed loop M. In the detectable components 12a and 12b shown in Figures 4a and 4b, a separate capacitive component C is used to tune the circuit. The inductive component L may, however, be designed so that the inter-winding 10 capacitance can take the place of the capacitor C. In this case, the capacitor C may be omitted.

Figure 4c shows a circuit diagram for another form of detectable component 12c embodying the present invention.

15 In this case, the detectable component consists of an open-circuit inductive component L formed of about 70 turns of Litz wire around which is provided the closed loop M of GMI material as described with reference to Figure 4b. The floating (open-circuit) Litz wire 20 inductive component L is designed to be self-resonant at the carrier frequency of the high frequency signal generator 20 (13.56MHz in this example). As mentioned above, the closed loop M may consist of more than one turn. However, the arrangement shown should enable the 25 maximum possible coupling to the reader coil L1. In this

embodiment, there is no separate capacitor, rather the detectable component 12c relies upon the inter-winding capacitance of the inductive component L to provide the tuned circuit. The absence of a separate physical 5 capacitor C and the fact that no electrical connections are required to this detectable component 12c makes the construction of this detectable component very simple and of low cost.

10 As shown in Figures 4b and 4c, the normal to the plane of the closed loop M is parallel to the axis AX of the coil forming the inductive component L so that, effectively the inductive component and the closed loop form the primary and secondary of a transformer. The 15 present inventors have found that, surprisingly, the orientation of the closed loop M relative to the longitudinal axis AX of the inductive component L can be rotated through 90 degrees from that shown in the Figures 4b and 4c so that, as illustrated 20 diagrammatically in the Figure 4d, in this detectable component 12d, the closed loop M is oriented along a magnetic flux line and thus affects the resistance of the magnetic field path. Furthermore, the closed loop can be

oriented at any angle between the orientations shown in 25 Figures 4c and 4d, for example at a 45 degree

intermediate position in the detectable component 12e shown in Figure 4e.

The detectable components 12b and 12c shown in Figures 5 4b and 4c may be used with the reader 11 shown in Figure 2 or the reader lla shown in Figure 3.

Examples of ways in which a detectable component may be incorporated into the subsidiary body 3 will now be 10 described with reference to Figures 5 and 6a to 6c where Figure 5 shows the subsidiary body 3 (part cut-away so that the head or bit 14 is not shown) shown in Figure 1 but with a portion of the outer surface 3b of the accessory shown cut away.

In this case, the detectable component 12 is provided on a hollow cylindrical plastics material former 40 that fits into a recess 3c formed in the wall 3d of the accessory 3 and that also provides the coupling connector 20 13 for enabling mounting of the attachable component 3 onto the main body. Figures 6a, 6b and 6c show how the detectable components 12a, 12b and 12c shown in Figures 4a, 4b and 4c, respectively, may be provided on such a former 40. In each case, the Litz wire inductive 25 component or coil L is wound around the outside of the

former 40 so that ends 50 and 51 of the inductor L are secured to the former. In the case of Figure 6a, the end 51 is coupled to the GMI resistive component R which itself is coupled by a connecting wire 52 to the 5 capacitor C which may be mounted to the outside of the former 40 and is itself coupled via a connecting wire 53 to the end 50 of the Litz wire inductive component L. Figure 6b shows the comparable construction for the detectable component 12b shown in Figure 4b. In this IO case, the Litz wire inductor L again is wound around the former 40 and has its ends 50 and 51 secured thereto.

However, in this case, the end 51 is connected by the connecting wire 54 to the capacitor C which itself is connected by a connecting wire 55 to the end 50 of the 15 Litz wire conductor. The single closed loop M of GMI wire is simply wound around the former 40.

Figure 6c shows construction of the detectable component 12c on the former 40. In this case, the Litz wire 20 inductive component L is again wound round the former having its ends 50 and 51 secured thereto and the GMI closed loop M is also wound on the former. The detectable components 12d and 12e may be manufactured in a similar manner with the closed loop M being formed by 25 threading the Litz wire between the former and the

inductive component L. It will, of course, be appreciated that, in practice, the coils and loops will be tightly wound onto the former 40 and that the representations shown in Figure 6a to 6c are only very diagrammatic.

Another example of a detectable component embodying the invention will now be described with reference to Figures 7 to 9 where Figure 7 shows a very diagrammatic representation, part cut away, of an attachable component 10 3 mounted to a main body 2. In this case, the detectable component 12d is again received in a recess 3c in the wall ad of the subsidiary body 3. However, in this case, as shown in Figure 8, the detectable component consists of a single turn or loop M of GMI material wound on to 15 the former 40. As illustrated diagrammatically by Figures 7 and 9, in this embodiment, the reader coil or inductor L1 is located on a former 41 embedded in a portion 2'a of the housing 2a of the main body that extends into the subsidiary body 3 when the subsidiary 20 body 3 is mounted to the main body. In this case, the inductor L1 is formed of Litz wire and when the subsidiary body 3 is mounted on the main body, the inductor L1 and closed loop M effectively form the primary and secondary of a transformer with, as described 25 above with reference to Figure 4b, changes in skin

resistance of the closed loop M due to the presence of a magnetic field when the high frequency carrier signal

is flowing through the loop M changing the loading on the inductor L1 and thus modulating the amplitude of the 5 carrier signal as described above. In this case, the detectable component carried by the subsidiary body 3 needs to consist only of a single loop of GMI wire made so that the additional cost of adding the detectable component to the subsidiary body 3 is minimal.

The reader circuitry shown in Figure 2 or in Figure 3 may be used with the detectable component 12d and coil L1 arrangement shown in Figures 7 to 9.

15 In the above described embodiments, the detectable component can be manufactured relatively cheaply and provides a relatively simple yet sensitive way of detecting whether or not the subsidiary body 3 is present. The detectable component may also include a passive data storage device such as described in, for example, International patent application publication number WO 98/24527. Figure 1O shows a schematic part cut away view 25 of an accessory 3 illustrating the mounting within the

wall 3d of the subsidiary body 3 of a former 42 carrying a magnetic field responsive detectable component 12 and

a passive data storage device 300, that is a device that is not selfpowered but derives a power supply from an 5 external source when coupled thereto.

As described in WO 98/24527, the passive data storage device 300 consists of a memory, a power deriving circuit for deriving power from a carrier signal inductively 10 coupled to the passive data storage device and a clock generator for controlling clocking of data out of the memory with the clock generator being arranged to generate a clock signal in synchronism with the carrier signal or arranged simply to be powered by the power 15 deriving circuitry and so to generate an asynchronous clock signal. Clocking of data out of the memory modulates the loading on the inductive coupling means of the passive data storage device and so on the inductive coupling means of the reader. As described in 20 WO 98/24527, such passive data storage devices generally use a 13.56MHz (Mega Hertz) carrier signal and accordingly the excitation carrier signal generator 20 and inductor L1 of the reader shown in Figure 2 or 3 may be used to provide the carrier signal for both the

passive data storage device 300 and the detectable component 12.

A phase modulation scheme may be used for data 5 transmission as described in WO 98/24527. It may also be possible to use amplitude or frequency modulation although any amplitude modulation scheme must ensure that the signal from the passive data storage device can be distinguished from the modulation caused by the 10 detectable component 12.

The passive data storage device 300 may contain data that identifies the subsidiary body 3 so that where, for example, a number of different accessories may be mounted 15 to the same main body 2, the controller 5 can determine from the data downloaded from the passive data storage device the type of the subsidiary body 3 and control the motor drive 7 accordingly so that, for example, the drive speed is increased or lowered in dependence upon the 20 requirements of the subsidiary body 3. As one example, an electrical appliance may be provided with different subsidiary bodies for use by children and adults and these may have passive data storage devices 300 storing different Ins so that, when the electrical appliance is 25 activated, the controller can determine from the data

downloaded from the passive data storage device whether an adult or children's subsidiary body 3 is mounted to the main body 2 and control the motor speed accordingly.

5 In the above described embodiment, the passive data storage device is a read-only passive data storage device. The passive data storage device may, however, be a writeable passive data storage device as described in, for example, the applicants co-pending UK Application 10 No. 0031518.4.

Figure 11 shows a functional block diagram similar to Figures 2 and 3 of the functional components of a main body having the facility to write data to a passive data 15 storage device 300 of a subsidiary body 3. In this case, the reader llb differs from that described above in that a gate 27 is included to enable the controller 5 to interrupt the high frequency carrier signal as described in the above mentioned UK patent application no. 20 0031518.4 so as to enable digital ones and zeros to be represented by long and short gaps between carrier pulses and a separate demodulator 28, filter 29a and buffer/squaring circuitry 29b are provided for enabling reading of data from and writing of data to the passive 25 data storage device. The controller S will, in this

embodiment, also ensure that, where the low frequency oscillator 21 is provided, this oscillator is deactivated during writing to the passive data storage device 300 to avoid any possibility of the detectable component 5 interfering with the writing operation.

Figure 12 shows a simplified block diagram of functional components of such a writeable passive data storage device 300. As shown, the passive data storage device 10 300 is associated with a further inductive coupler LC that forms a tuned circuit with the inductive coupler L1, C1 of the reader lib. This inductive coupler LC consists of a parallel connection of an inductor L3 and a capacitor C3 across which is coupled a series connection 15 of a capacitor C4 and a FET M1. A carrier signal inductively coupled to the passive data storage device 300 is supplied via a capacitor C5 to a junction J1 between the anode of a first diode D1 and a cathode of a second diode D2. The cathode of the first diode D1 is 20 coupled to a first power supply rail 310 (Vdd) while the anode of the second diode D2 is connected to a second power supply rail 320 (Vss). The diodes D1 and D2 provide a power supply deriver for deriving a power supply for the passive data storage device 300 from the 25 carrier signal. It will, of course, be appreciated that,

in the interests of simplicity, the power supply connections to the remaining components of the passive data storage device 300 are not shown in Figure 12.

5 The remaining components of the passive data storage device consist of a control engine 330 which controls reading and writing of data to and from the memory 340.

The control engine is, in this case, a state machine having its own memory.

A clock signal for the control engine 330 is derived from the carrier signal by a first signal deriver 350 in the form of a fast missing pulse detector coupled to junction J1. The control engine 330 extracts data carried by the 15 carrier signal using the output of the first signal deriver 350 and the output of a second signal deriver 360 in the form of a slow missing pulse detector also coupled to the junction J1. A data output of the control engine 330 is coupled to a control gate of the FET M1 so that 20 then the data is output by the control engine 330 the data switches the FET M1 and the loading across the inductor L3 varies in accordance with whether the FET M1 is conducting or non-conducting, thus causing modulation of the carrier signal with the data. Data output by the 25 control engine 350 is extracted from the modulated

carrier signal, as shown in Figure 12, by the demodulator 28, filter 29a and buffer/squaring circuitry 29b that provides a data input signal to the controller 5. As described thus far the passive data storage device is 5 similar to a read only passive data storage device.

In order to write data to the passive data storage device 300, the controller 5 is arranged to control the gate 27 to interrupt the carrier signal for a first time when the 10 data bit is to be a binary "0" and to interrupt the oscillator signal for a second different time when the data bit to be transmitted is a binary ''1. The time out periods of the fast and slow missing pulse detectors are set so that the output of the fast missing pulse detector 15 will have one of two widths dependent on whether the particular data bit is a binary "O" or a binary. 1 ' while the slow missing pulse detector will provide a pulse only when a particular data bit is a binary "1. The control engine 330 can thus determine from the outputs of the 20 first and second signal derivers 350 and 360 whether a received bit is a binary t'Ot' or a binary ''1. The control engine 330 is arranged to recognize codes (patterns of Os and Is) received from the controller 5 that determines the action that should be taken by the 25 control engine, that is whether the control engine should

simply read out the data in a portion of the memory 340, should erase that data and write new data in and so on.

Further details of the writing and reading operations can be found in UK Patent Application No. 0031518.4.

Where, as described above the passive data storage device can be written to, then the controller 5 may be arranged to store historical use data in the passive data storage device 300. This use data may, for example, indicate the 10 time period for which the subsidiary body 3 was in operation and where the controller 5 has a continually running battery backed up clock, the time since the last use of the subsidiary body. This data would therefore provide a record of the historical degree and frequency 15 of use of the subsidiary body that could be accessed for example during maintenance of the electrical appliance or to check on the user's use or routine of use of the electrical appliance.

20 Figures 13a and 13b illustrate another example of a detectable component embodying the present invention.

In this case, the detectable component 12f is formed as a laminated structure consisting of a dielectric material layer 50 on either side of which is provided GMI material 25 51, as shown in Figure 13a, so that the GMl material

layers 51a and 51b effectively form the plates of a capacitor. This structure is then wound to form an inductive configuration whose equivalent circuit is shown in Figure lab, that is this detectable component 5 comprises a parallel resonant circuit consisting of two highly coupled inductors LX and LY each with a GMI series resistive component RX and RY and a parallel capacitance CX. In this case, the inductive component is formed from two tightly coupled coils LX and LY which appear 10 effectively in parallel and, because the capacitive component CX is formed from the inter-winding capacitance, the parallel inductors combine to provide half the individual inductance value enabling a smaller amount of GMI material to be used to achieve "self 15 resonance" at a given frequency. Such a detectable component 12f may be used in place of the detectable component 12a shown in Figure 4a, for example.

The present invention may be applied to other forms of 20 electronic devices and electrical appliances having attachable components or accessories that, when fitted to the main body of the electronic device, will rotate, reciprocate, oscillate, vibrate and so on. Examples, in addition to power tools such as electric screw drivers, 25 saws, sanders, polishing devices and so on, are medical

devices such as devices including catheters and domestic electrical appliances such as vacuum cleaners, kitchen appliances such as food processors, personal care appliances such as hairdryers, massage, skin care 5 devices, and dental hygiene devices such as electric toothbrushes and so on, when different attachments may be provided for different functions.

The subsidiary body need not necessarily comprise an 10 attachable component but may be an accessory or object that may be used with or associated with the main body of the electrical appliance or electronic device. For example the subsidiary body need not comprise a tool to be driven or operated by the main body but may comprise 15 a guard, lid or the like but needs to be present to ensure safe operation of the device. In this case, the presence of the detectable component within the lid or guard and the reader in the main body would ensure that the electronic device could not be operated in the 20 absence of the lid or guard without the need for complex mechanical and/or electrical interlocks.

As another possibility, the subsidiary body may be an attachment that does not rotate or otherwise move but 25 rather affects the operation of the device, such as a

hairdryer diffuser attachment that effects air flow from the hairdryer.

As a further possibility, the electronic device or 5 electrical appliance may be or form part of a novelty item, toy or game with the subsidiary body being an attachable or detachable component, an accessory or other object such as a playing piece that is used with the main body. The present invention may also have applications 10 for devices that communicate using a standard communications protocol such as BLUETOOTHiRr) As another example, the subsidiary body need not be an accessory or attachable component but could be or form 15 part of a completely separate object whose identity or authenticity is to be determined by detection apparatus.

For example the subsidiary body may be a security pass or secure document carrying the detectable component.

Figure 14 illustrates very diagrammatically such an 20 example. In this case, the detectable component is carried by a document in the form of a sheet of paper or other medium P. In this example, the detectable component 12g has the form of a closed loop M of GMI material that is embedded within the paper during the 25 paper production process and the detection apparatus 400

comprises a pen, wand or other device that can be held in the hand and that contains a reader 11 as described above with reference to Figure 2, a battery 4, a controller 5 in the form of a microprocessor or 5 microcontroller and associated memory and a user interface having for example an on/off switch lO,a display lea (that may consist simply of red and green light emitting devices or may be an LCD display) and possibly also a loudspeaker lOb. In this case, the pen 10 or wand is activated by a user using the onioff switch 10. When the user activates the pen 400, then the controller 5 activates the high frequency oscillator 20 to output continually the high frequency carrier or excitation signal to the coil L1 and activates the low 15 frequency signal generator 21 to produce low frequency pulses causing the coil L2 to create a symmetrically oscillating magnetic field. The user then sweeps the pen

over the paper P and, if the paper P carries the detectable component, then its presence or not will be 20 detected as described above with reference to Figure 2 and in response to the detection by the reader 11, the controller 5 will cause the user to be advised whether the document is a genuine document by controlling the user interface accordingly. For example a green light may 25 be activated when the detectable component is detected

or a beep emitted or a red light may be activated if no detectable component is detected or if a display is included an appropriate message may be displayed.

5 In the above described example, the detection apparatus is provided in a device that the user scans across the paper P. As another possibility, the detection apparatus may be provided in a device that is affixed to a surface and the paper of other medium moved or scanned relative 10 to that device.

The above description assumes that the GMI resistive

component will always have the same effect on the reader 11 (that is they will all have the same "signature") so 15 that only the presence or absence of the detectable component can be determined. As will be described below, this need not necessarily be the case and detectable component having different, identifiable signatures may be provided.

Figure 15 shows a graph of resistance (R) against magnetic field strength B in Teslas for a GMI resistive

component showing the effect of the magnetic field caused

by the low frequency signal generator 21 in Figure 2 when 25 the GMI material is subject to the high frequency signal

generated by the oscillator 20. As can been seen, the graph has a characteristic profile with two peaks PK1 and PK2 disposed on opposite sides of the B=0 line or y axis and separated by a trough T. All of these three 5 significant knee points may be exploited to enable detection of a detectable component incorporating GMI material. Thus, although it is notnecessary for the varying applied magnetic field to change polarity, if,

as described above, the applied magnetic field does vary

10 in polarity, then the GMI material will show a frequency doubling effect. (Of course, where the frequency doubling effect is not present, then the frequency doubler 22 shown in Figure 2 will not be required.) A frequency doubling or phase shift may also be detected 15 if the variation in the applied magnetic field is

centred about one of the knee points. Other features of the characteristic profile may also be used by the reader to detect the GMI material.

20 In another embodiment, the GMI resistive component may be provided with a bias flux from a fixed magnet or electromagnet that may form part of the detection apparatus. In this case, because of the bias, the magnetic field experienced by the subsidiary body 3 will

25 not be a symmetrically oscillating magnetic field even

if the low frequency carrier signal frequency 21 provides a symmetrically oscillating signal. The modulation frequency will be the same frequency as the low frequency carrier signal generator 21.

The response of the GMI resistive component may also be biased by incorporating a permanent magnet into the detectable component so that the GMI resistive component is subject to a magnetic field consisting of the

10 combination of the varying magnetic field applied by the

reader and the magnetic field generated by the permanent

magnet and the controller programmed so as to enable this magnetic field bias (and thus different detectable

components having different strength permanent magnets) 15 to be distinguished from one another. As another possibility, as described in the aforementioned paper by LV Panina and H Mohri, the frequency response of the GMI resistive component may be changed by varying its composition or manufacturing conditions and the 20 oscillator 21 may be a variable frequency oscillator (for example a voltage controlled or numerically controlled (VCO or NCO) oscillator) having a frequency controllable by the controller 5 (or a separate controller in the reader) so that, during the detection process, the high 25 frequency oscillator 21 sweeps over a frequency range

enabling the controller to determine the frequency response of the detectable component and thus to distinguish detectable components having GMI resistive components with different frequency responses from one 5 another. The skin resistance of the GMI resistive component can also be changed by changing the cross-sectional shape or dimensions of the wire or ribbon of GMI material, for example the diameter of the wire.

These effects may be combined increasing the range of 10 uniquely identifiable detectable components.

Further information identifying a particular detectable component may be provided by controlling the relative direction in which the low frequency oscillator or drive 15 coil 21 and any coil carried by the detectable component are wound. Thus, if the coils are wound in the same direction, then the Q modulation will be in phase with the modulating signal provided by the low frequency oscillation carrier signal generator 21 while, if the 20 coils are wound in the opposite direction, then the Q modulation will be 180 out of phase with the carrier signal provided by the low frequency carrier signal generator 21. This provides the possibility of three different states: a subsidiary body having no detectable 25 component; a subsidiary body having a detectable

component whose coil is wound in the same direction as the low frequency carrier signal generator 21 coil; and a subsidiary body having a detectable component whose coil is wound in antiphase to the low frequency carrier 5 signal generator 21 coil. This enables three different types of detectable component to be detected by detecting whether or not any modulation is present and, if so, the phase relationship with the low frequency carrier signal.

Claims

1. A detectable component having first inductive coupling means adapted to couple inductively to second inductive coupling means of a detection apparatus when 5 the detectable component is in range of or coupled to the detection apparatus, the first inductive coupling means having: an inductive component comprising a plurality of electrically conductive paths coupled in parallel; and 10 a resistive component with a resistance that varies with magnetic field to cause modulation of a carrier

signal supplied to the second inductive coupling means of the detection apparatus.

15

2. A detectable component according to claim 1, wherein the inductive component is a coil of Litz wire.

3. A detectable component according to claim 1 or 2, wherein the resistive component comprises a resistive 20 element coupled in series with the inductive component.

4. A detectable component according to claim 1, wherein the resistive component is provided by a coil also forming the inductive component.

5. A detectable component according to claim 1 or 2, wherein the resistive component comprises a closed loop inductively coupled to the inductive component.

6. A detectable component according to claim 1 or 2, 5 wherein the inductive component comprises an open circuit coil and the resistive component comprises a closed loop inductively coupled to the inductive component. 10

7. A detectable component according to claim 1 or 2, wherein the inductive component comprises a coil and the resistive component comprises a closed loop providing a resistive path along a magnetic flux line.

15

8. A detectable component according to any one of the preceding claims, wherein the first inductive coupling means also includes a capacitor.

9. A detectable component according to any one of the 20 preceding claims, wherein the resistive component has a skin resistance that varies with magnetic field.

10. A detectable component according to any one of claims 1 to 8, wherein the resistive component comprises a material exhibiting Giant MagnetoImpedance (GMI).

11. A detectable component according to claim 10, 5 wherein the resistive component comprises a cobalt alloy.

12. A detectable component according to any one of the preceding claims, wherein the first inductive coupling means is a tuned circuit.

13. A detectable component having first inductive coupling means adapted to couple inductively to second inductive coupling means of a detection apparatus when the detectable component is in range of or coupled to the 15 detection apparatus, the first inductive coupling means consisting solely of a coil formed of a material having a resistance that varies with magnetic field to cause

modulation of a carrier signal supplied to the second inductive coupling means of the detection apparatus with 20 magnetic field.

14. A detectable component according to claim 13, wherein the resistive component has a resistance that varies with magnetic field.

15. A detectable component according to claim 13 or 14, wherein the resistive component comprises a material exhibiting Giant MagnetoImpedance (GMI).

16. A detectable component according to claim 15, 5 wherein the resistive component comprises a cobalt alloy.

17. A detectable component according to any one of the preceding claims, further comprising a passive device, the passive device being operable, when the detectable 10 component is coupled to or is in range of the detection apparatus, to derive power from a carrier signal supplied by the detection apparatus and to communicate with the detection apparatus.

15

18. A detectable component according to any one of claims 1 to 16, further comprising a passive device, the passive device being operable, when the first and second inductive coupling means are coupled, to derive power from the carrier signal and to communicate with the 20 detection apparatus.

19. A detectable component according to claim 17 or 18, wherein the passive data storage device includes a memory storing data and is operable, when powered, to modulate

the carrier signal in accordance with data read out from the memory.

20. A detectable component according to claim l9, wherein the passive data storage device also has write 5 means for writing data to the memory.

21. A detectable component according to any one of the preceding claims also incorporating a permanent magnetic element.

22. A subsidiary body for use with an electronic device or electrical appliance, comprising a detectable component according to any one of the preceding claims.

15

23. A tool attachable to an electronic device or electrical appliance, comprising a detectable component according to any one of claims 1 to 21.

24. A medium carrying a detectable component 20 accordance with any one of claims l to 21.

25. A sheet of paper incorporating a detectable component in accordance with any one of claims 1 to 21.

26. An electronic device having a main body and a subsidiary body, the subsidiary body having a detectable component in accordance with any one of claims 1 to 16 and the main body having the second inductive coupling means adapted to couple inductively to the first 5 inductive coupling means when the subsidiary body is in range of or coupled to the main body, the main body having carrier signal supplying means for supplying an excitation carrier signal to the second inductive coupling means and magnetic field generation means for

10 subjecting the subsidiary body to a magnetic field and

modulation detection means for detecting modulation of the carrier signal caused by variation of the resistance of the resistive component due to changes in the magnetic field when the first and second inductive

15 coupling means are coupled.

27. An electronic device having a main body and a subsidiary body, the subsidiary body having a detectable component in accordance with any one of claims 17 to 19 20 and the main body having the second inductive coupling means adapted to couple inductively to the first inductive coupling means when the subsidiary body is in range of or coupled to the main body, the main body having carrier signal supplying means for supplying an

excitation carrier signal to the second inductive coupling means and magnetic field generation means for

subjecting the subsidiary body to a magnetic field,

modulation detection means for detecting modulation of the carrier signal caused by variation of the resistance 5 of the resistive component due to changes in the magnetic field when the first and second inductive

coupling means are coupled and communication means for enabling communication of data with the passive data storage device.

28. An electronic device according to claim 26 or 27, wherein the magnetic field generation means comprises

means for generating a relatively low frequency varying magnetic field.

29. An electronic device according to claim 26 or 27, wherein the magnetic field generation means comprises an

oscillating signal source and an excitation coil.

20

30. An electronic device according to claim 26 or 27, wherein the magnetic field generation means comprises a

magnet movable with a component of the main body and relative to the detectable component.

31. An electronic device according to claim 28, wherein the magnet is coupled to a drive shaft for driving a part of the subsidiary body.

32. An electronic device according to any one of claims 5 26 to 31, having frequency control means for controlling the frequency of the excitation carrier signal.

33. An electronic device according to any one of claims 26 to 32, further comprising identifying means for 10 identifying a detectable component in accordance with a characteristic of the resistive component of the detectable component.

34. An electronic device according to any one of claims 15 26 to 33, further comprising at least one tool attachable to a main body of the electronic device and comprising a detectable component according to any one of Claims

1 to 21.

20

35. Detection apparatus for detecting a detectable component comprising first inductive coupling means including a resistive component having a resistance that varies with magnetic field strength but is insensitive

to the polarization of the magnetic field, the detection

apparatus having second inductive coupling means adapted to couple to the first inductive coupling means, the detection apparatus having carrier signal supplying means for supplying a relatively high frequency excitation carrier signal to the second inductive coupling means and 5 magnetic field generation means for generating a

symmetrically oscillating magnetic field at a given

frequency, the detection apparatus having a modulation detection means for detecting modulation of the carrier signal at the same or twice the given frequency.

36. Detection apparatus for detecting a detectable component according to claim 10 or any one of claims 11 to 20 when dependent on claim 10, the detection apparatus having the second inductive coupling means adapted to 15 couple to the first inductive coupling means, the detection apparatus having carrier signal supplying means for supplying a relatively high frequency excitation carrier signal to the second inductive coupling means and magnetic field generation means for generating a

20 symmetrically oscillating magnetic field at a given

frequency, the detection apparatus having a modulation detection means for detecting modulation of the carrier signal at a frequency the same as or twice the given frequency.

37. Detection apparatus according to claim 35 or 36, having frequency control means for controlling the frequency of the excitation carrier signal.

38. Detection apparatus according to claim 35, 36 or 37, 5 further comprising identifying means for identifying a detectable component in accordance with a characteristic of the resistive component of the detectable component.

39. Detection apparatus in combination with a detectable 10 component according to claim 10 or any one of claims 11 to 20 when dependent on claim 10, the detection apparatus having the second inductive coupling means adapted to couple to the first inductive coupling means, the detection apparatus having carrier signal supplying means 15 for supplying a relatively high frequency excitation carrier signal to the second inductive coupling means and magnetic field generation means for generating a

symmetrically oscillating magnetic field at a given

frequency that, when the first and second inductive 20 coupling means are coupled causes the resistance of the resistive component to vary modulating the carrier signal with a modulation representing a full-wave rectification of the symmetrically oscillating magnetic field, the

detection apparatus having a modulation detection means

for detecting modulation of the carrier signal at a frequency twice the given frequency.

40. An electronic device having detection apparatus in accordance with any one of claims 35 to 39.

41. An electronic device having a main body including detection apparatus in accordance with claim 35 or 36 and at least one subsidiary body comprising a detectable component according to any one of claims 1 to 21.

42. A frequency doubling device comprising a transformer having a primary and a secondary coil with the secondary coil comprising a coil of a GMI material.

15

43. A toy, game or subsidiary body for use in or with a toy or game having a detachable component in accordance with any one of claims 1 to 21.