Device and method for controlling a touch-sensitive screen

Abstract

The invention relates to the field of electronics and can be used in devices intended for testing touch-sensitive screens and in devices for transmitting information via a touch-sensitive screen. A device for controlling a touch-sensitive screen is characterized in that it comprises, mounted on a printed circuit board, a control unit and a harmonic amplifier to which positive feedback is applied by a feedback circuit and a coplanar capacitor containing two plates, one plate of the capacitor being coupled proximate an input of the amplifier, and the other plate being coupled proximate an output of the amplifier, wherein the plates of the capacitor lie in the same plane. The technical result is a simplification of the device and an increase in the operational stability and reliability thereof, as well as compactness.

Description

[0001] DEVICE AND METHOD FOR CONTROLLING A TOUCH SCREEN

[0002] Field of technology to which the invention relates

[0003] The invention relates to the field of electronics and can be used in devices intended for testing touch screens and devices transmitting information via a touch screen.

[0004] State of the art

[0005] The existing level of technology includes methods for controlling touch screens using devices that are used for testing the hardware of the screens, as well as modeling user behavior when interacting with the screen interface (see https: / / www.prorobot.ru / 17 / quality-commander.php, 12 / 28 / 2010; https: / / androidinsider.ru / polezno-znat / kak-testiruyutsya-sensornyie-displei.html, 12 / 22 / 2013).

[0006] For example, various robotic devices, including hands with “fingers” equipped with conductive pads at the ends (see CN201 138361 Y, 22.10.2008; CN203133768U, 14.08.2013) can be used as technical means simulating physical touches of the screen. In other cases, simpler electromechanical drives can be used. The devices are grounded and, when the screen is touched, they trigger the screen sensors and register touch events by the screen hardware and software systems. In addition to testing the technical part to assess the accuracy and responsiveness of screens, the robot can be used to simulate different levels of user skills when using touch screens: in games, when typing, etc. Technical means simulating touches can also be used to transmit information via touch screens.

[0007] The disadvantages of the above mentioned solutions are their inertia, the complexity of the design containing a large number of moving parts, unstable and unreliable operation of the devices, leading to false screen activations, as well as their large dimensions. Disclosure of the essence of the invention

[0008] The technical challenge is to create a simple, portable touch screen control device that does not contain moving parts and is characterized by stable and reliable operation.

[0009] The technical result consists in simplifying the device, increasing stability and reliability of operation, and ensuring compactness.

[0010] The technical result is achieved due to the fact that the touch screen control device contains a control unit, a harmonic oscillation amplifier, mounted on a printed circuit board, covered by positive feedback via a feedback circuit and a coplanar capacitor containing two plates, wherein one plate of the capacitor is connected closer to the input of the amplifier, the other plate is connected to the output of the amplifier, wherein the plates of the capacitor are located in the same plane.

[0011] In addition, the capacitor is designed with the possibility of being applied to the touch screen parallel or perpendicular or in intermediate positions, directly or at a distance not exceeding 1 mm from the surface of the touch screen.

[0012] In addition, the capacitor has a base, which is made of a dielectric material and is integral with the device board or is made separately.

[0013] In addition, the dimensions of the plates of the coplanar capacitor are chosen in such a way that the distance between their geometric centers coincides with the distance between the centers of the touch screen sensors.

[0014] In addition, the capacitor plates have connectors with a feedback circuit, the length of which is no more than 2 mm.

[0015] In addition, the harmonic oscillation amplifier is assembled on three transistor cascades using a common emitter circuit.

[0016] In addition, the harmonic oscillation amplifier is built using a non-inverting circuit with zero phase shift at the frequency of self-generation of excitations in the feedback circuit.

[0017] In addition, the harmonic oscillation amplifier is made inverting at the excitation self-generation frequency with a 180° phase-shifting feedback circuit. In addition, the harmonic oscillation amplifier is made inverting, but shifting the phase by 180° at the excitation self-generation frequency with a feedback circuit and with a zero phase shift, or constituting 360° in sum with the amplifier shift a multiple number of times.

[0018] The method for controlling a touch screen using a control device comprises the following steps:

[0019] - supply voltage from the control unit to the generator-amplifier of the control device, forming an electromagnetic field between the plates of the coplanar capacitor located in the same plane;

[0020] - when harmonic oscillations of voltage appear on the capacitor plates located in one plane, an effect is exerted on the touch screen by applying the capacitor to the touch screen sensors parallel or perpendicular or in intermediate positions, directly or at a distance from the surface of the touch screen, where the alternating electromagnetic field generated in the self-oscillation mode of the amplifier affects the fields formed by the touch screen sensors, changing their capacity up or down depending on the operating mode of the touch screen controller;

[0021] - determine by means of the touch screen controller the change in the capacitance of the touch screen sensors relative to the previously established rest level and register touch screen touch events at a point located inside or at a minimum distance from the projection zone of the capacitor plates onto the screen.

[0022] In addition, the impact on the touch screen is carried out when harmonic oscillations of voltage of average frequency of 1-2 MHz appear on the capacitor plates located in the same plane.

[0023] In addition, the impact on the touch screen by applying a capacitor to the touch screen sensors is carried out at a distance not exceeding 1 mm from the surface of the screen.

[0024] In addition, the coordinates of the touch event registration points are located within an area limited by a radius of 10 mm, with the center lying in the projection zone of the coplanar capacitor.

[0025] In addition, the dimensions of the plates of the coplanar capacitor are selected so that the distance between their geometric centers coincides with the distance between the centers of the screen sensors. Brief description of the drawings

[0026] Fig.1 - Device for controlling a touch screen;

[0027] Fig.2 - Coplanar capacitor (side view);

[0028] Fig.3 - Coplanar capacitor (top view);

[0029] Fig.4 - Distribution of electric fields of a coplanar capacitor and a touch screen when they are arranged in parallel to each other;

[0030] Fig. 5 - Distribution of electric fields of a coplanar capacitor and a touch screen when they are perpendicular to each other;

[0031] Fig.6 - Electric field of the touch screen with measurement of the mutual capacitance of the sensors before interaction with the field of the coplanar capacitor;

[0032] Fig.7 - Interaction of electric fields of a coplanar capacitor and a touch screen with measurement of the mutual capacitance of the sensors;

[0033] Fig.8 - Electric field of the touch screen with measurement of the sensors' own capacitance before interaction with the field of the coplanar capacitor;

[0034] Fig.9 - Interaction of electric fields of a coplanar capacitor and a touch screen with measurement of the sensors' own capacitance;

[0035] Fig.10 - Oscillogram of harmonic oscillations on the plates of a coplanar capacitor;

[0036] Fig.1 1 - Oscillogram of oscillations on the plates of a coplanar capacitor, corresponding to one touch event on the touch screen.

[0037] The following elements are indicated by numbers on the figures:

[0038] 1 - amplifier of electrical signals;

[0039] 2 - feedback circuit;

[0040] 3 - base of the coplanar capacitor;

[0041] 4 - plate of a coplanar capacitor;

[0042] 5 - plate of a coplanar capacitor;

[0043] 6 - control unit;

[0044] 7 - area between the plates;

[0045] 8 - line of force of the electric field strength between the plates of a coplanar capacitor;

[0046] 9 - touch screen base; 10 - screen receiving sensor (upper, sensing electrode);

[0047] 11 - transmitting screen sensor (lower, driving electrode);

[0048] 12 - driver of the transmitting screen sensor;

[0049] 13 - line of force of the electric field strength of the mutual capacitance of the screen sensors;

[0050] 14 - the line of force of the electric field strength between the plate of the coplanar capacitor, located closer to the amplifier output, and the receiving sensor of the screen;

[0051] 15 - the line of force of the electric field strength between the plate of the coplanar capacitor, located closer to the amplifier input, and the receiving sensor of the screen;

[0052] 16 - the line of force of the electric field strength between the plate of the coplanar capacitor, located closer to the amplifier output, and the transmitting sensor of the screen;

[0053] 17 - the line of force of the electric field strength between the plate of the coplanar capacitor, located closer to the amplifier input, and the transmitting sensor of the screen;

[0054] 18 - line of force of the electric field strength of the self-capacitance of the transmitting screen sensor;

[0055] 19 - line of force of the electric field strength of the receiving sensor screen's own capacitance.

[0056] Implementation of the invention

[0057] The created technical solution is a portable electronic device capable of causing registration of touch events when acting on a touch screen. The device does not contain moving parts, including microelectromechanical ones, and is assembled on a printed circuit board with dimensions not exceeding 2 sq. cm. The coordinates of the touch event registration points are within an area limited by a radius of 10 mm, with the center lying in the projection zone of the device element (coplanar capacitor), directly intended for acting on the touch screen. The device is designed to be powered by a battery (accumulator). The action on the touch screen is carried out when harmonic oscillations of medium frequency voltage (1-2 MHz) appear on the capacitor plates located in the same plane.The capacitor is applied to the screen parallel or perpendicular (and can also be in intermediate positions), directly, or at a distance not exceeding 1 mm from the screen surface.

[0058] The touch screen control device is based on a mid-frequency harmonic oscillation generator. The generator is essentially an amplifier covered by positive feedback, and the feedback circuit includes a coplanar capacitor, the plates of which are located in one plane, applied to the screen surface. Due to the open arrangement of the plates, the alternating electromagnetic field formed in the amplifier's self-oscillation mode affects the fields formed by the screen sensors, changing their capacity up or down (depending on the screen controller operating mode). The screen controller determines the change in sensor capacities relative to the pre-established "rest" level and registers screen touch events.Power is supplied to the generator from the control unit of the device, which can be configured to generate both relatively slow (constant) "touches" up to values ​​limited by the capabilities of a particular screen (e.g. 30 Hz). The control unit can also transmit a signal to the device with a touch screen in the form of a digital code, for example, using amplitude manipulation.

[0059] Projective capacitive touch screens have two mutually perpendicular groups of transparent electrodes - sensors, separated by a dielectric layer. There are two main ways of such screens. In one case, the screen controller sends an electric signal to the sensors of the first group in turn, and an electric field arises at the intersection with the sensors of the second group. The screen controller measures the mutual capacitance of the intersection of the sensors, characterized by this field. When the user touches the touch screen with a finger, the charge on the sensor of the second group decreases due to the capacitance of the user's body, then the value of the mutual capacitance of the sensors also decreases. In another case, the controller can measure the proper capacitance of each sensor of both groups. In this case, in the event of a touch, their capacitance will increase. The screen controller determines the change in the capacitance of the sensors and registers a touch at the point of their intersection.There are touch screens that can use both modes of operation. The examples of the technical solution disclosed here allow the touch screen to be controlled using a capacitor with coplanar (located in the same plane) plates. The electromagnetic field of a coplanar capacitor located in close proximity to the surface of the touch screen affects the field of nearby screen sensors and causes its controller to register touch events.

[0060] Fig. 1 shows a device for controlling a touch screen. The electronic circuit is a controlled RC generator. The amplifier (1) is covered by positive feedback via a feedback circuit (2) and a coplanar capacitor (3) with an air dielectric. One plate of the capacitor (4) is connected closer to the input of the amplifier (1), the other plate (5) is connected to the output of the amplifier (1). When supply voltage is supplied from the control unit (6), the amplifier (1) is excited, and an electromagnetic field arises between the plates of the coplanar capacitor (3), which interacts with the sensors of the touch screen, the controller of which registers the event of its touch at a point located inside or at a minimum distance from the projection zone of the plates (4, 5) of the capacitor (3) onto the screen. The device is intended for portable use and its electronic circuit is designed to use a power battery.The alternating electromagnetic field between the plates of the coplanar capacitor (3) induces a floating voltage. At the same time, a floating ground is induced on the plate (4), located closer to the input of the amplifier (1). A mobile device with a touch screen also induces a floating ground, relative to which it determines the capacitance of the sensors - screen sensors.

[0061] The amplifier (1) can be constructed, for example, according to a non-inverting circuit with a zero phase shift at the frequency of self-excitation generation in the feedback circuit (2), which includes a coplanar capacitor (3). In another case, the amplifier (1) can be inverting at the frequency of self-excitation generation with a 180° phase-shifting feedback circuit (2), which includes a coplanar capacitor (3). Also, the amplifier (1) can be inverting, but shifting the phase by 180° at the frequency of self-excitation generation, with a feedback circuit (2) with a coplanar capacitor (3) in its composition and with a zero phase shift (or constituting 360° in sum with the shift of the amplifier (1) a multiple number of times).

[0062] Fig. 2 and Fig. 3 show a coplanar capacitor in more detail. Its base (3) can be made of a dielectric material, such as fiberglass or another. It can be integral with the device board, or it can be made separately. The plates (4 and 5) can be etched, glued, or formed in another way.

[0063] A typical touch screen contains a matrix of sensors arranged in a diamond grid, with the diagonals of the diamonds being equal to or approaching 4 mm. The dimensions of the plates (electrodes) of the coplanar capacitor are chosen so that the distance between their geometric centers mostly coincides with the distance between the centers of the screen sensors (for example, in this case - 4 mm) or is as close as possible with an error of 1-2 mm. In Fig.

[0064] 3 coplanar capacitor is shown from above. When choosing the lengths of the sides of the plates (4 and 5) -

[0065] 2 mm and the distance between them (7) is 2 mm, the distance between the centers of the plates is

[0066] 4 mm. The capacitance of a coplanar capacitor consists largely of parasitic capacitance caused by the edge effect (increase in electric field strength at the edges of the plates). Its exact calculation is difficult due to the need to take into account the degree of penetration of the electric field into the base of the capacitor (3) and into the air or protective coating of the capacitor. Relatively complex formulas are known, but for the implementation under consideration it is sufficient to use the relation:

[0067] C = E р {3 I = 2.7*1.3*0.2 - 0.7 pF where,

[0068] P is an empirical coefficient depending on the width of the plates and the distance between them; the adopted value is used in the case of equality of the sides of the plates (Fig. 3, pos. 4 and pos. 5) and the distance between them - the area (Fig. 3, pos. 7);

[0069] I - the length of the joint boundary of the plates (Fig. 3, pos. 4 and pos. 5) along the region (Fig.

[0070] 3 pos. 7), cm;

[0071] E р - calculated value of relative permittivity: for a capacitor without a protective coating,

[0072] E Р =(1 + E П ) / 2=(1 +4.4) / 2=2.7

[0073] (for a capacitor covered with a protective layer, E Р =( E П + E3) / 2), where E п - relative permittivity of the substrate material (FR4 fiberglass);

[0074] E3 is the relative permittivity of the protective coating. In the embodiment shown in Fig. 1, the amplifier (1) is assembled on three transistor stages using a common emitter circuit. The coplanar capacitor (3) is connected to the input and output matching components of the feedback circuit (2), which is characterized by a zero phase shift. It is known that the condition for the occurrence of self-excitation of the RC generator is the observance of the phase balance: phatr + Cpfb = 2ТТП, where phatr is the phase shift at the amplifier output; φгЬ is the phase shift of the feedback circuit; n is an integer.

[0075] Each amplifier stage of this type is characterized by a phase shift of 180°, provided that there are low-frequency harmonic oscillations at the input. However, when using a coplanar capacitor (3) of a rather small capacity of 0.7 pF, the amplifier autoexcitation frequency in this implementation is 1.8 MHz, which corresponds to the level of the typical value of the phase-frequency characteristic of the bipolar transistors used at this frequency - 60° per stage. Thus, the phase balance index n is 2. The stable operability of the device disclosed here has been experimentally established at a supply voltage of ±25 V, which is maintained when the level is reduced to ±12 V (with parallel arrangement of the plates to the screen surface).

[0076] By introducing additional circuits into the amplifier, the frequency range of the amplifier autoexcitation, at which the device solves the technical problem, was experimentally established - from 600 kHz to 2.3 MHz (at a lower frequency, the effect on the sensor screens disappears; experiments were not conducted at a higher frequency). For a preliminary illustration of this effect, Fig. 4 and Fig. 5 show variants of the mutual arrangement of a coplanar capacitor and two screen sensors without taking into account the interaction. In this case, it can be considered that the moment before the interaction is depicted is shown and the most important lines of force of the electric field strength are shown (one for each pair of charged plates / sensors). In reality, the arrangement of the capacitor relative to the sensors may be different (within the parallel arrangement shown in Fig. 4, the perpendicular arrangement shown in Fig. 5, as well as in intermediate positions between them).The capacitor also interacts with the sensors located near the depicted ones (in the neighboring cells of the screen grid), but to a lesser extent. When the coplanar capacitor is shifted from the depicted pair of sensors along the plane of the screen, it will interact to a greater extent with other sensors, but the principle of their interaction will be similar to that considered. The electromagnetic field between the plates of the coplanar capacitor (8) is considered as quasi-stationary. The vortex fields formed by high-frequency oscillations of the generator are not shown, but they have an additional effect on the screen sensors, under the effects of the coplanar capacitor, considered below. In the case of a perpendicular arrangement relative to the screen (according to Fig. 5), the lines of force (8) will affect the screen sensors due to the edge effect. The sensors are located in different planes of the screen base (9), with the receiving sensor (10) usually higher and the transmitting sensor (1 1 ) lower relative to each other.The driver of the transmitting sensor (12) supplies an electric signal to the sensor (11 ) in the mutual capacitance measurement mode. As a result, field lines (13) are formed. A field line (14) is formed between the plate (5) located closer to the amplifier output (1 ) after the feedback circuit (2) and the sensor (10). Similarly, a field line (15) is formed between the plate (4) and the transmitting sensors. Field lines are also formed between the plates and the transmitting sensors, respectively, a field line (16) is formed between the plate (5) and the sensor (11 ) and a field line (17) is formed between the plate (4) and the sensor (1 1 ). The field lines of the transmitting sensor (18) and the receiving sensor (19) participate in the self-capacitance measurement mode of the sensors.

[0077] Let us consider some of the power lines involved in registering screen touch events in the mode of measuring the mutual capacitance of the sensors. Fig. 6 shows the plates of the coplanar capacitor (4, 5), the sensors (11, 10) and the power line (13) between them before power is supplied to the amplifier. In this case, the sensor (11) periodically charges the sensor (10), and the screen controller periodically measures their mutual capacitance (usually by the charge transfer method - charging the sensor (10) using a reference capacitor, and then discharging it). Some steady-state measured value is taken to correspond to the absence of touch. Fig. 7 shows the interaction of the coplanar capacitor when power is supplied to the amplifier, self-generation occurs and an electric field appears on the plates (or after bringing the capacitor to the screen surface with the amplifier turned on in advance). In this case, the field lines of the capacitor (8) reduce the influence of line (13) on the sensor (10), thus reducing the mutual capacitance of the screen sensors.The screen controller records the touch event. There will be no such influence during the half-periods of the generator self-oscillations corresponding to the opposite polarity of the lines (8) (power lines 14-17 in Fig. 4 or Fig. 5 may be involved). But in this case, with a high probability, a similar influence will be exerted on the adjacent power lines (Fig. 4 pos. 13) and adjacent screen sensors. The reliable operation of the device using this method has been experimentally established both with parallel placement relative to the screen (in Fig. 4) and perpendicular (in Fig. 5). Moreover, with perpendicular placement, the electronic circuit of the device has a smaller influence on the sensors, but positioning must be carried out more carefully. The influence of the electronic circuit with parallel placement, which can lead to false screen responses, can be reduced, for example, by shifting the plane of the device board from the base of the coplanar capacitor above the screen.In this case, it is not recommended to exceed the length of the capacitor plate connectors with the feedback circuit by more than 2 mm.

[0078] Let us consider the process of interaction of a coplanar capacitor with the screen sensors when its controller measures their own capacitance. Fig. 8 shows the lines of force (18 and 19) in a state of rest (the amplifier is switched off, there is no voltage on the plates). Fig. 9 shows the change in the lines of force of the sensors in the case of the appearance of an alternating field on the plates (4 and 5) of the coplanar capacitor. As can be seen, the upper parts of the lines have lengthened, this corresponds to an increase in the sensors' own capacitance. The screen controller records the touch event.

[0079] Fig. 10 shows an oscillogram of harmonic oscillations on the plates of a coplanar capacitor at a high sweep rate. Fig. 11 shows an oscillogram of oscillations on the plates of a coplanar capacitor corresponding to one touch event on the touch screen. A small vertical asymmetry of the signal is present due to the presence of capacitors in the feedback circuit of the amplifier.

[0080] The device disclosed here can also be used to transmit information to mobile devices via a touch screen. For example, by command from the control unit (Fig. 1 pos. 6), which switches on the amplifier (1) at certain times. In this way, manipulation of the signal on the plates of the coplanar capacitor and transmission of messages (for example, passwords) are carried out. The messages can be received, for example, by a special mobile application.

Claims

CLAUSES OF THE INVENTION 1. A touch screen control device characterized in that it contains a control unit mounted on a printed circuit board, a harmonic oscillation amplifier covered by positive feedback via a feedback circuit and a coplanar capacitor containing two plates, wherein one plate of the capacitor is connected closer to the input of the amplifier, the other plate is connected to the output of the amplifier, wherein the plates of the capacitor are located in the same plane.

2. A touch screen control device according to claim 1, characterized in that the capacitor is designed with the possibility of being applied to the touch screen parallel or perpendicular or in intermediate positions, directly, or at a distance not exceeding 1 mm from the surface of the touch screen.

3. A touch screen control device according to claim 1, characterized in that the capacitor has a base that is made of a dielectric material and is integral with the board of the device or is made separately.

4. A touch screen control device according to claim 1, characterized in that the dimensions of the plates of the coplanar capacitor are selected in such a way that the distance between their geometric centers coincides with the distance between the centers of the touch screen sensors.

5. A touch screen control device according to claim 1, characterized in that the capacitor plates have connectors with a feedback circuit, the length of which is no more than 2 mm.

6. A touch screen control device according to paragraph 1, characterized in that the harmonic oscillation amplifier is assembled on three transistor cascades according to a common emitter circuit.

7. A touch screen control device according to claim 1, characterized in that the harmonic oscillation amplifier is constructed according to a non-inverting circuit with a zero phase shift at the frequency of self-generation of excitations in the feedback circuit.

8. A touch screen control device according to claim 1, characterized in that the harmonic oscillation amplifier is designed to be inverting at the excitation self-generation frequency with a 180° phase-shifting feedback circuit.

9. The touch screen control device according to claim 1, characterized in that the harmonic oscillation amplifier is made inverting, but shifting the phase by 180° at the frequency of self-generation of excitations with a feedback circuit and with zero phase shift, or amounting to 360° in sum with the amplifier shift a multiple of a number of times.

10. A method for controlling a touch screen using a control device according to claim 1, characterized in that it contains the following steps: - supply voltage from the control unit to the generator-amplifier of the control device, forming an electromagnetic field between the plates of the coplanar capacitor located in the same plane; - when harmonic voltage oscillations appear on the capacitor plates located in the same plane, an effect is exerted on the touch screen by applying the capacitor to the touch screen sensors parallel or perpendicular or in intermediate positions, directly or at a distance from the surface of the touch screen, where the alternating electromagnetic field generated in the self-oscillation mode of the amplifier affects the fields formed by the touch screen sensors, changing their capacity up or down depending on the operating mode of the touch screen controller; - determine, by means of a touch screen controller, the change in the capacitance of the touch screen sensors relative to a pre-established rest level and record touch events on the touch screen at a point located inside, or at a minimum distance from, the projection zone of the capacitor plates onto the screen.

11. The method according to paragraph 1, characterized in that the action on the touch screen is carried out when harmonic oscillations of voltage of average frequency of 1-2 MHz appear on the capacitor plates located in the same plane.

12. The method according to paragraph 1, characterized in that the action on the touch screen by applying a capacitor to the touch screen sensors is carried out at a distance not exceeding 1 mm from the surface of the screen.

13. The method according to claim 1, characterized in that the coordinates of the points of registration of touch events are located within an area limited by a radius of 10 mm, with the center lying in the projection zone of the coplanar capacitor.

14. The method according to paragraph 1, characterized in that the dimensions of the plates of the coplanar capacitor are selected in such a way that the distance between their geometric centers coincides with the distance between the centers of the screen sensors.

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