Field of the Invention

The present invention relates to a capacitive touch-enabled article, such as a capacitive- touch enabled magazine, poster or book.

Background

Electronic components are increasingly being incorporated into printed items, such as books, magazine, posters and greeting cards, to allow these items to become interactive. In particular, capacitive touch sensors are being incorporated into items to allow a user to provide input and the item or a device, such as mobile phone, wirelessly connected to the item to respond. Examples of such items are described in GB 2 464 537 A and WO The battery life of such a capacitive touch-enabled printed article is limited. One approach to increasing the lifetime of the electronic part of the printed article is to fit the battery at point of sale or point of use, rather than during assembly. However, this approach maybe impractical.

Summary

According to a first aspect of the present invention there is provided a capacitive touch- enabled article. The article comprises a substrate, at least two conductive pads disposed on the substrate, the at least two conductive pads including first and second conductive pads, a controller including a capacitive sensor input terminal and a ground terminal connected to the first and second pads respectively. The printed article further comprises a conductive strip removably bridging the first and second conductive pads. The controller is operable in a low-power state and a high-power state. In the low-power state, the controller is configured to measure capacitance of the first conductive pad at intervals and to compare the capacitance with a predetermined threshold. The controller is configured, in response to determining that the

capacitance is greater than the predetermined threshold, to continue in the low-power state and, in response to determining that capacitance is less than the predetermined threshold, to switch to the high-power state.

Thus, the battery can be fitted when assembling the printed article. Unless and until the conductive strip is removed so as not to bridge the first and second pads, the controller lies in the low-power state. When the conductive strip is removed, for example at point of sale or by the user when the article is used, then the controller switches to the high-power state in which capacitive touch functionality is enabled.

A period of time between two measurements of capacitance may be at least ι second, 2 seconds, 5 seconds, 10 seconds or 20 seconds. The given period of time maybe not greater than 1 minute or 2 minutes. Measurements maybe periodic, i.e. the period of time may be the same between adjacent measurements.

The substrate may comprise wood-fibre-based material, such as paper or card. The substrate may comprise a plastics material. The substrate may comprise a laminate of two or more layers of material.

The at least two conductive pads may comprise conductive ink, for example, carbon- based conductive ink. The substrate may support conductive tracks, each conductive track providing a conductive path between a respective pad and a landing pad on the substrate for coupling to a corresponding landing pad on a circuit board or integrated circuit. Each conductive pad and/or track may comprise a region of a first conductive ink (e.g. carbon-based ink) having an outer edge and the pad and/ or track may further comprise a line of a second conductive ink (e.g. silver-based ink) having a greater conductivity than the first conductive ink running along the outer edge so as to reduce the sheet resistance the conductive pad and/ or track.

The conductive strip may be supported on a peel-off sticker. In other words, the conductive strip may be a removable conductive strip. Once removed, the peel-off sticker may be discarded. Thus, the conductive strip may be removed at point of sale or by the user when the article is first used, without the intention of re-applying the sticker.

The controller may be configured, in the high-power state, to measure capacitance of the first conductive pad at intervals and to compare the capacitance with the predetermined threshold. The controller may be configured, in response to

determining that the, or each, capacitance in a series of one or more measurements is greater than the predetermined threshold, to switch to the low-power state.

Thus, the conductive strip may be used to return the printed article into a low-power state. For example, this may be achieved by re-applying the sticker over the first and second pads. Alternatively, the conductive strip may be provided on a page of a book or a wing of a card or pamphlet or the like, such that the conductive strip bridges the first and second conductive pads when the book, card or pamphlet is closed. The controller may comprise a microcontroller or system-on-a-chip for capacitive touch sensing. Alternatively, the controller may comprise a capacitive touch sensor controller and a microcontroller or system-on-a-chip operatively connected, for example via PC, to the capacitive touch sensor controller. A pad and a corresponding terminal may be connected by an ohmic coupling, i.e. by a continuous conductive path, for example, a conductive track(s) and a pair of landing pads/terminals joined by conductive glue, conductive ink or conductive tape. A pad and a corresponding terminal may be connected by a capacitive coupling, for example as described in WO 2014/096772 Ai. The controller may comprise an integrated wireless network interface module, such as a WiFi module or a Bluetooth module, preferably a Bluetooth low power module.

Alternatively, the printed article may comprise an external wireless network interface module, such as a WiFi module or a Bluetooth module, preferably a Bluetooth low power module.

The printed article may further comprise at least one transducer, such as a speaker, for example in the form of a piezo sounder, and/or one or more light-emitting diodes. The capacitive sensor input terminal may be a general purpose input/ output terminal.

The ground terminal maybe a general purpose input/output terminal which is grounded. Thus, two general purpose input/output terminals may be used. Two terminals may alternate between being the capacitive sensor input terminal and the ground terminal. For example, for a given measurement, a first terminal maybe the capacitive sensor input terminal and a second terminal may be the ground terminal and, for the next measurement, the first terminal may be the ground terminal, and the second terminal may be the capacitive sensor input terminal. Thus, for the given measurement, a first pad may be the sensor and a second pad may be ground and, for a following measurement, the first pad may be ground and a first pad may be the sensor.

The controller, in low-power state, may be configured not to measure the capacitance of any other conductive pads.

The controller, in the relatively low-power state, may be configured to lie in a sleep mode for a given time period, to wake up to an active mode so as to measure the capacitance and determine whether the capacitance is greater than or less than the threshold and to return to the sleep mode.

The printed article may comprise a sheet supporting the at least two capacitive touch switches and the controller. This allows capacitive touch functionality to be

incorporated easily into the article, for example, in the form of an insert. The sheet may be bonded, e.g. using an adhesive, to an inner face of a cover of a magazine or book or the underside of a poster or pamphlet. The sheet may comprise wood-fibre-based material, such as paper or card. The article may be a printed article, such as a multiple-fold pamphlet, magazine, poster, disposable product packaging (i.e. packaging which does not form part of another article), greeting card, board game or point-of-sale display.

According to a second aspect of the present invention there is provided a method of operating a controller including a capacitive sensor input terminal and a ground terminal connected to first and second pads respectively. The method comprises, in a low-power state, measuring capacitance of the first conductive pad at intervals, comparing the capacitance of the conductive pad to a predetermined threshold and, in response to determining that the capacitance is greater than the threshold, continuing in the low-power state and, in response to determining that the capacitance is less than the threshold, switching to a high-power state. The method may comprise, in the low-power state, not measuring the capacitance of any other conductive pads.

Being in the low-power state may comprise lying in a sleep mode for a given time period, waking up to an active mode so as to measure the capacitance and compare the capacitance to the threshold and returning to the sleep mode.

According to a third aspect of the present invention there is provided a computer readable medium (for example memory in microcontroller or peripheral memory) storing the computer program according to the third aspect.

Brief Description of the Drawings

Certain embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of a magazine;

Figure 2 is a schematic block diagram of a capacitive touch sensor circuit including a controller;

Figure 3 illustrates circuit diagrams of two conductive pads with and without a tab in place for capacitively coupling the two pads; and

Figure 4 is a process carried out by the microcontroller shown in Figure 2.

Detailed Description of Certain Embodiments

Referring to Figure 1, a capacitive touch-enabled printed article 1 is shown. The printed article 1 takes the form of a magazine, i.e. a periodical publication. The capacitive touch device 1 is pairable with a Bluetooth (RTM) enabled mobile device, such as a smart phone, and can be used to provide input signals for controlling the mobile device as described, for example, in WO 2013 117917 A2.

The magazine 1 has front and back covers 2, 3 and a set of pages 4 bound, e.g. using perfect binding, between the covers 2, 3 along a spine 5. The front cover 2 has a first, front face 6 and a second, inside face 7.

The magazine 1 includes an insert 8 lying behind the front cover 6, preferably glued to the inside face 7 using an adhesive (not shown). The insert 8 may be covered by a cover sheet (not shown) thereby sandwiching the insert 8 between the front cover 2 and the cover sheet. The insert 8 provides a capacitive touch device 11 (Figure 2) which can be used to detect user input when a user touches the front cover 2.

The insert 8 comprises a sheet 12 supporting a set of conductive pads 13 suitable for providing capacitive touch switches, a set of conductive tracks 14 and a set of connection terminals (not shown). Each pad 13 preferably has an area of at least 0.5 cm ² . The conductive pads 13, the conductive tracks 14 and connection terminals (not shown) preferably comprise carbon-based conductive ink printed on the sheet 12, e.g. using lithographic printing, ink-jet printing or gravure printing. However, the conductive pads 13, the conductive tracks 14 and the connection terminals (not shown) may comprise a silver-based conductive ink or foil. The conductive pads 13 may be arranged in an array to form an x-y touchpad and position may be found by

interpolation. Reference is made to WO 2014/057251 Ai.

The insert 8 includes a circuit board 16 supporting a set of one or more connection terminals (not shown) for coupling to the corresponding connection terminals (not shown) on the sheet 12, a mixed-signal microcontroller 17 which is suitable for capacitive touch sensing and a battery 18. The connection terminals (not shown) on the sheet 12 and the connection terminals (not shown) on the circuit board 16 are coupled capacitively through the sheet 12, as described in WO2014/ 096772 Ai.

The microcontroller 17 includes a set of general purpose input/output terminals 191, 192, 19 ₃ . The input/output terminals 191, 192, 19 ₃ can be used for capacitive-touch sensing. For example, a terminal 191, 192, 19 ₃ can measure capacitance of a conductive pad 131, 132, 13 ₃ by charging the conductive pad 131, 132, 13 ₃ and then measuring the time taken to discharge the conductive pad 131, 132, 13 ₃ through a resistor (not shown). A resistor-based capacitive measurement as described, for example, in Zack Albus: "PCB-Based Capacitive Touch Sensing With MSP430", Texas Instruments Application Report, SLAA363A (2007) (http:/ / www.ti.com/lit/ an/ slaa303a/ slaa363a.pdf). Other types of capacitive measurement may be used.

A first input/output terminal 191 of the microcontroller 17 is coupled to a first conductive pad 131 and is used for capacitive touch sensing. A second input/output terminal 192 is coupled to a second conductive pad 132 and is programmed to be grounded. The first and second terminals 191, 192 are connected by a resistor, R. A second input/output terminal 192 need not be used. Instead, a dedicated ground terminal GND can be used. The first and second terminals 191, 192 may alternate between being the sensor and being grounded.

A tab 20 in the form of a removable sticker is disposed over first and second switches. The tab 20 comprises a substrate 21 and a region of conductive material 22 supported on the substrate 21.

Referring to Figure 2, the microcontroller 17 comprises at least one processor core 23, at least one analogue-to-digital converter 24 and non-volatile memory 25 storing application software 26. The microcontroller 17 may include an integrated wireless network interface module 27, such as Bluetooth (RTM) Smart module. Alternatively, a separate wireless network interface module (not shown) provided by separate IC may be used.

The capacitive touch device 11 may include one or more external output devices 28, such as a speaker, for example in the form of piezo sounder, and/ or one or more light emitting diodes (LEDs).

The front cover 2 may include text and images (not shown) which the user can touch. This action can be detected by underlying capacitive pads 13. This can be used to control an external device, such as a mobile phone or tablet, for example as described in WO 2013/117917 Ai, and/or to control an embedded output device 28.

Figure 3 is a flow diagram illustrating operation of the device 11. Referring to Figures 1 to 3, when the magazine 1 is bound, the tab 20 is placed over the first and second conductive pads 131, 132 and the battery 18 is inserted into a holder (not shown).

The controller 17 is in a first state which consumes little power (step Si). In the low- power state, the controller 17 wakes up from a sleep cycle (step S2) and polls the first conductive pad 131 (step S3). The controller 17 compares the capacitance, C, of the first conductive pad 131 with a pre-determined threshold Cth (step S4).

If the capacitance is high, i.e. the capacitance equals or exceeds the threshold C _t h, then this indicates that the conductive strip 22 is in place. The controller 17 goes back to sleep for a given period of time, t (step S5). A watchdog timer (not shown) is used to wake up the controller 17.

The period of time, t, may be greater than 1 second. The period of time may be as long as 10 seconds or more. The period of time may be chosen, on the one hand, to be as long as possible so as to extend battery life and, on the other, to be not so long that a user is not forced to wait too long before being able to use the device. The period of time generally depends on the type of article and may depend on whether the conductive strip 22 is to be removed at point of sale, by the user and whether a delay is tolerable. If the capacitance is low, i.e. the capacitance falls below the threshold C _t h, then this indicates that the conductive strip 22 is no longer in place. The controller 17 then switches into a second state which provides touch functionality (steps S6 & S7).

Optionally, the controller 17 may cause an output device 28 to emit an audible tone and/ or to illuminate an LED to indicate that the device is ready for use.

The roles of the first and second conductive pads 131, 132 may alternate from one measurement cycle to the next. Touch functionality may involve polling at least one other capacitive touch switch 13 ₃ (step S7).

The switch from first to second state may be irreversible, i.e. once the controller 17 has switched from the first state to the second state, it stays in the second state regardless of whether or not the magazine 1 is subsequently closed. However, in some

embodiments, the controller 17 may re-enter the first state after a given period of inactivity has elapsed, e.g. 1 minute or more, or by detecting that the conductive strip 22 has been replaced over the first and second pads 131, 132. Thus, while in the first state, the device 11 can consume little power which can help to extend battery life.

The first and second conductive pads 131, 132 may be used exclusively for the purpose of controlling power consumption. Thus, the first and second conductive pads 131, 132 may be placed to minimise visual impact, e.g. by being placed close to an edge of a page or sheet or next to the spine or in the region where there a block of colour and/ or no text. The first and second conductive pads 131, 132 may be shaped to promote coupling though a sticker. For example, one conductive pad 131, 132 may be a circular disc and the other conductive pad 131, 132 may be concentric ring. Alternatively, the conductive pads 131, 132 may comprise a set of interdigitated electrodes. Alternatively, the first and second conductive pads 131, 132 may be separated sufficiently far from each other so as to avoid accidental coupling.

It will be appreciated that many modifications may be made to the embodiments hereinbefore described. Additionally or alternatively, the insert may be provided for the back cover.

A system on a chip (SoC) and external (i.e. off-chip) memory maybe used instead of a microcontroller. The controller may comprise a dedicated touch controller integrated circuit and a separate microcontroller.

The printed article may take other forms, such as a poster, pamphlet or greeting card, a book, point of sale advertising or disposable product packaging (i.e. packaging which does not form part of another article).