Liquid crystal handwriting board and liquid crystal handwriting board system

Abstract

The utility model discloses a liquid crystal handwriting board which comprises an electric control module, a liquid crystal handwriting film, an electromagnetic antenna board and a handwriting substrate, the liquid crystal handwriting film, the electromagnetic antenna board and the handwriting substrate are sequentially arranged from top to bottom, and the electric control module comprises a power supply unit, a main control unit, an electromagnetic control unit, a liquid crystal driving unit and a data transmission unit. According to the liquid crystal handwriting board, on one hand, the electromagnetic control unit transmits acquired writing / erasing coordinate information to the intelligent display equipment through the data transmission unit, so that the intelligent display equipment synchronously displays writing / erasing handwriting; on the other hand, the electromagnetic control unit transmits the collected erasing coordinate information to the main control unit through the data transmission unit, so that the main control unit completes handwriting erasing by controlling the liquid crystal driving unit.

Description

Technical Field

[0001] This utility model relates to the field of liquid crystal writing tablet technology, and in particular to a liquid crystal writing tablet and liquid crystal writing tablet system. Background Technology

[0002] Most existing handwriting tablets that can connect to computers are electromagnetic handwriting tablets. When a user writes on the handwriting tablet, the computer can not only display what the user has written on the handwriting tablet, but also store the content on the handwriting tablet for the user to recall later.

[0003] However, since the electromagnetic writing tablet itself cannot display what the user writes, the user's eyes need to keep looking at the computer screen while writing, which is not convenient. Utility Model Content

[0004] The main purpose of this invention is to propose a liquid crystal handwriting tablet and a liquid crystal handwriting tablet system, which aims to solve the current technical problems.

[0005] To achieve the above objectives, this utility model proposes a liquid crystal writing tablet, comprising an electronic control module, a liquid crystal writing film, an electromagnetic antenna board, and a writing substrate arranged sequentially from top to bottom. The electronic control module includes a power supply unit, a main control unit, an electromagnetic control unit, a liquid crystal driving unit, and a data transmission unit. The power supply terminals of the electromagnetic control unit, the data transmission unit, the main control unit, and the liquid crystal driving unit are all connected to the power supply unit. The data acquisition terminal of the electromagnetic control unit is connected to the electromagnetic antenna board. The output terminal of the electromagnetic control unit is connected to the input terminal of the data transmission unit. The first output terminal of the data transmission unit is connected to the first input terminal of the main control unit. The control terminal of the main control unit is connected to the controlled terminal of the liquid crystal driving unit. The output terminal of the liquid crystal driving unit is connected to the liquid crystal writing film. The data transmission unit further includes a second output terminal for connecting to a smart display device. When a user performs writing or erasing actions on the liquid crystal writing tablet, the data transmission unit transmits a signal corresponding to the writing or erasing action to the smart display device, so that the smart display device responds to the writing or erasing action.

[0006] Preferably, the liquid crystal driving unit includes a negative voltage pre-generation circuit, a negative voltage generation circuit, a bias voltage generation circuit, a horizontal liquid crystal driving circuit, and a vertical liquid crystal driving circuit. The controlled terminal of the negative voltage pre-generation circuit is connected to the main control unit. The output terminal of the negative voltage pre-generation circuit is connected to the input terminal of the negative voltage generation circuit. The output terminal of the negative voltage generation circuit is connected to the output terminal of the bias voltage generation circuit. The first output terminal of the bias voltage generation circuit is connected to the input terminal of the horizontal liquid crystal driving circuit. The second output terminal of the bias voltage generation circuit is connected to the input terminal of the vertical liquid crystal driving circuit. The controlled terminal of the vertical liquid crystal driving circuit is connected to the main control unit. The horizontal liquid crystal driving circuit is used to output a horizontal driving voltage to the liquid crystal handwriting film, and the vertical liquid crystal driving circuit is used to output a vertical driving voltage to the liquid crystal handwriting film.

[0007] Preferably, the negative voltage pre-generation circuit includes resistor R11, resistor R12, capacitor EC2, and N parallel-connected negative voltage control circuits. The controlled terminal of each negative voltage control circuit is connected to the main control unit. The feedback output terminal of each negative voltage control circuit, the second terminal of resistor R11, and the first terminal of resistor R12 are connected to the feedback terminal of the negative voltage generation circuit. The output terminal of each negative voltage control circuit, the second terminal of resistor R12, and the first terminal of capacitor EC2 are interconnected, and their connection node is the output terminal of the negative voltage pre-generation circuit. The first terminal of resistor R11 and the second terminal of capacitor EC2 are grounded, and N≧2.

[0008] Preferably, the negative voltage control circuit includes resistors R1, R2, R3, R4, and R5, transistors Q1, Q2, and Q3. The gate of transistor Q1 is connected to the first end of resistor R1, and this connection node is the controlled terminal of the negative voltage control circuit. The drain of transistor Q1, the gate of transistor Q2, and the second end of resistor R2 are interconnected. The drain of transistor Q2 is connected to the first end of resistor R2. The second end of resistor R3, the first end of resistor R4, and the gate of transistor Q3 are interconnected. The drain of transistor Q3 is connected to the first end of resistor R5, and the second end of resistor R5 is the feedback output terminal of the negative voltage control circuit. The source of transistor Q3 is connected to the second end of resistor R4, and this connection node is the output terminal of the negative voltage control circuit. The source of transistor Q2 and the first end of resistor R2 are both connected to power supply VCC. The source of transistor Q1 and the second end of resistor R1 are both grounded.

[0009] Preferably, the liquid crystal handwriting film includes an upper conductive layer, a liquid crystal layer and a lower conductive layer arranged sequentially from top to bottom. The upper conductive layer includes X horizontal conductive areas and Y vertical conductive areas, with each horizontal conductive area perpendicular to each vertical conductive area. The lower conductive layer includes X horizontal conductive areas and Y vertical conductive areas corresponding to the upper conductive layer.

[0010] Preferably, the data transmission unit includes a Bluetooth control circuit and a Bluetooth antenna. The input terminal of the Bluetooth control circuit is the input terminal of the data transmission unit, the first output terminal of the Bluetooth control circuit is the first output terminal of the data transmission unit, and the second output terminal of the Bluetooth control circuit is connected to the Bluetooth antenna, which is the second output terminal of the data transmission unit.

[0011] Preferably, the Bluetooth control circuit includes a Bluetooth chip control circuit, the data transmission unit further includes a display screen, the input terminal of the Bluetooth chip control circuit is the input terminal of the Bluetooth control circuit, the first output terminal of the Bluetooth chip control circuit is the first output terminal of the Bluetooth control circuit, the second output terminal of the Bluetooth chip control circuit is the second output terminal of the Bluetooth control circuit, and the third output terminal of the Bluetooth chip control circuit is connected to the display screen.

[0012] Preferably, the electronic control module further includes a temperature sensor circuit, the output of which is connected to the second input of the main control unit.

[0013] To achieve the above objectives, this utility model also proposes a liquid crystal writing tablet system, including the liquid crystal writing tablet as described above, a stylus adapted to the liquid crystal writing tablet, and the stylus having a writing / erasing mode selection button.

[0014] Preferably, the LCD handwriting tablet system further includes an intelligent display device adapted to the LCD handwriting tablet, and the stylus is also provided with a stylus / mouse mode selection button.

[0015] Compared to existing ordinary electromagnetic handwriting tablets, the beneficial effects of this utility model's technical solution are as follows:

[0016] On the one hand, by adding an LCD writing film, the handwriting tablet can display handwriting. When a user writes on the tablet, the tablet can display the user's writing content, eliminating the need to constantly focus on the computer screen.

[0017] On the other hand, by setting up a Bluetooth control circuit and Bluetooth antenna in the handwriting tablet, the handwriting information written / erased by the handwriting tablet can be wirelessly transmitted to the smart display device, avoiding the limitation of connection cable when the user uses the handwriting tablet.

[0018] On the other hand, by setting X horizontal conductive areas and Y and vertical conductive areas on the conductive layer of the liquid crystal handwriting film, and setting X horizontal conductive areas and Y and vertical conductive areas corresponding to the upper conductive layer on the lower conductive layer of the liquid crystal handwriting film, the local erasing function of the handwriting tablet can be realized.

[0019] This LCD handwriting tablet can display the user's handwriting and transmit writing / erasing information to a smart display device without wires, enabling the smart display device to respond to the writing / erasing information. It also has a partial erasing function, making it very convenient to use. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of an embodiment of the liquid crystal handwriting tablet of this utility model;

[0021] Figure 2 for Figure 1 A functional module diagram of an embodiment of the central electronic control module;

[0022] Figure 3 This is a schematic diagram of another embodiment of the liquid crystal handwriting tablet of this utility model;

[0023] Figure 4 This is a schematic diagram of another embodiment of the liquid crystal handwriting tablet of this utility model;

[0024] Figure 5 This is a schematic diagram of another embodiment of the liquid crystal handwriting tablet of this utility model;

[0025] Figure 6 for Figure 1 A schematic diagram of the structure of an embodiment of a liquid crystal handwriting film. Detailed Implementation

[0026] The solutions in the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this utility model, and not all of them. Based on the embodiments of this utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this utility model.

[0027] Please see Figure 1 and Figure 2This utility model proposes a liquid crystal handwriting tablet, including an electronic control module 500, a liquid crystal handwriting film 200, an electromagnetic antenna board 300, and a handwriting substrate 400 arranged sequentially from top to bottom. The electronic control module 500 includes a power supply unit 510, a main control unit 540, an electromagnetic control unit 520, a liquid crystal driving unit 550, and a data transmission unit 530. The power supply terminals of the electromagnetic control unit 520, the data transmission unit 530, the main control unit 540, and the liquid crystal driving unit 550 are all connected to the power supply unit 510. The data acquisition terminal of the electromagnetic control unit 520 is connected to the electromagnetic antenna board 300. The output terminal of the electromagnetic control unit 520 is connected to the input terminal of the data transmission unit 530. The first output terminal of the data transmission unit 530 is connected to the first input terminal of the main control unit 540. The control terminal of the main control unit 540 is connected to the controlled terminal of the liquid crystal driving unit 550. The output terminal of the liquid crystal driving unit 550 is connected to the liquid crystal handwriting film 200.

[0028] The data transmission unit 530 also includes a second output terminal for connecting to the smart display device 600. When the user performs writing or erasing actions on the LCD handwriting pad, the data transmission unit 530 transmits a signal corresponding to the writing or erasing action to the smart display device 600 so that the smart display device 600 responds to the writing or erasing action.

[0029] The specific location of the electronic control module 500 can be set according to user needs or preferences, and there are no restrictions here. For example, with the same writing area, if the user wants the LCD writing tablet to be as small as possible, the electronic control module 500 can be placed below the writing substrate 400 to avoid occupying the side space of the LCD writing film 200 and increasing the size of the LCD writing tablet. If the user wants the LCD writing tablet to be as thin as possible, the electronic control module 500 can be placed on the side of the LCD writing film 200 to avoid the electronic control module 500 increasing the thickness of the LCD writing tablet.

[0030] The power supply unit 510 includes a charging interface 511, an energy storage battery 512, and a power conversion circuit 513. When the LCD handwriting tablet is connected to an external power source, on the one hand, the energy storage battery 512 obtains external power for charging through the charging interface 511; on the other hand, the power conversion circuit 513 converts the external power into a power supply voltage compatible with each functional unit in the electronic control module 500 to power each functional unit. When the LCD handwriting tablet is disconnected from the external power source, the power conversion circuit 513 converts the power output from the energy storage battery 512 into a power supply voltage compatible with each functional unit in the electronic control module 500 to power each functional unit. The type of the charging interface 511 can be set according to common standard interface types (such as Type-C interface), and there is no restriction here.

[0031] The smart display device 600 contains an application program that can respond to writing / erasing information transmitted by the LCD writing tablet and synchronously display the content on the LCD writing tablet. In a preferred embodiment, the smart display device 600 may be a computer, an all-in-one teaching machine, or a smart projector; no limitation is made here.

[0032] In this embodiment, when a user writes on the LCD handwriting tablet, the handwriting is directly displayed on the LCD handwriting film 200. Simultaneously, if the LCD handwriting tablet is connected to a smart display device 600, the electromagnetic control unit 520 collects the handwriting through the electromagnetic antenna board 300 and transmits the handwriting information to the smart display device 600 through the data transmission unit 530. The smart display device 600 then synchronously displays the content on the LCD handwriting tablet based on the received handwriting information.

[0033] When a user erases an item on the LCD writing pad, the electromagnetic control unit 520 collects the erasure information via the electromagnetic antenna board 300 and transmits it to the main control unit 540 via the data transmission unit 530. The main control unit 540 then controls the LCD driving unit 550 to drive the LCD writing film 200 to erase the writing on the LCD writing pad. Simultaneously, if the LCD writing pad is connected to a smart display device 600, the data transmission unit 530 also transmits the erasure information to the smart display device 600, which then synchronously erases the content on the LCD writing pad based on the received erasure information.

[0034] Compared to existing ordinary electromagnetic handwriting tablets, this embodiment adds a liquid crystal handwriting film 200 to achieve the function of displaying handwriting. When the user writes on this handwriting tablet, the tablet can display the user's writing content, eliminating the need to constantly focus on the smart display device 600 (such as a computer screen).

[0035] Please see Figures 3 to 6In one optional embodiment, the liquid crystal driving unit 550 includes a negative voltage pre-generation circuit 551, a negative voltage generation circuit 552, a bias voltage generation circuit 553, a horizontal liquid crystal driving circuit 554, and a vertical liquid crystal driving circuit 555. The controlled terminal of the negative voltage pre-generation circuit 551 is connected to the main control unit 540, the output terminal of the negative voltage pre-generation circuit 551 is connected to the input terminal of the negative voltage generation circuit 552, the output terminal of the negative voltage generation circuit 552 is connected to the output terminal of the bias voltage generation circuit 553, the first output terminal of the bias voltage generation circuit 553 is connected to the input terminal of the horizontal liquid crystal driving circuit 554, the second output terminal of the bias voltage generation circuit 553 is connected to the input terminal of the vertical liquid crystal driving circuit 555, and the controlled terminal of the vertical liquid crystal driving circuit 555 is connected to the main control unit 540. The horizontal liquid crystal driving circuit 554 is used to output a horizontal driving voltage to the liquid crystal handwriting film 200, and the vertical liquid crystal driving circuit 555 is used to output a vertical driving voltage to the liquid crystal handwriting film 200.

[0036] In an optional embodiment, the liquid crystal handwriting film 200 includes an upper conductive layer (not shown), a liquid crystal layer (not shown), and a lower conductive layer (not shown) arranged sequentially from top to bottom. The upper conductive layer includes X transverse conductive regions and Y longitudinal conductive regions, with each transverse conductive region perpendicular to each longitudinal conductive region. The lower conductive layer includes X transverse conductive regions and Y longitudinal conductive regions corresponding to the upper conductive layer.

[0037] Optional, such as Figure 6 As shown, the conductive layer is an ITO (Indium Tin Oxide) conductive terminal layer. ITO conductive film refers to a high-tech material product obtained by sputtering a transparent indium tin oxide conductive film onto materials such as transparent organic thin films (PET, polyethylene glycol terephthalate) using processing methods such as magnetron sputtering, evaporation, reactive ion plating, or chemical vapor deposition. ITO conductive terminals are formed by etching corresponding conductive film strips with mutually perpendicular X and Y axes, for example... Figure 6 The circuit consists of X-axis conductive strip 1, X-axis conductive strip 2, X-axis conductive strip 3, ... and Y-axis conductive strip 1, Y-axis conductive strip 2, Y-axis conductive strip 3, ... perpendicular to the X-axis. When we want to erase a certain position, after applying sufficient positive and negative AC voltages to the corresponding X-axis and Y-axis conductive strips (controlled by the horizontal liquid crystal driving circuit 554 and the vertical liquid crystal driving circuit 555), the point where the X-axis and Y-axis intersect will be erased, while other positions will not be erased (the applied voltage is controlled by the horizontal liquid crystal driving circuit 554 and the vertical liquid crystal driving circuit 555). This process continues. If positive and negative AC voltages are applied to multiple conductive strips on the X-axis and Y-axis simultaneously, a local area will be erased.

[0038] Optional, such as Figure 5 As shown, the negative voltage pre-generation circuit 551 includes resistor R11, resistor R12, capacitor EC2, and N parallel negative voltage control circuits 5511. The controlled terminals of each negative voltage control circuit 5511 are connected to the main control unit 540. The feedback output terminal of each negative voltage control circuit 5511, the second terminal of resistor R11, and the first terminal of resistor R12 are connected to the feedback terminal of the negative voltage generation circuit 552. The output terminals of each negative voltage control circuit 5511, the second terminal of resistor R12, and the first terminal of capacitor EC2 are interconnected, and their connection node is the output terminal of the negative voltage pre-generation circuit 551. The first terminal of resistor R11 and the second terminal of capacitor EC2 are grounded, and N≧2.

[0039] The negative voltage control circuit 5511 includes resistors R1, R2, R3, R4, and R5, transistors Q1, Q2, and Q3. The gate of transistor Q1 is connected to the first end of resistor R1, and this connection node is the controlled terminal of the negative voltage control circuit 5511. The drain of transistor Q1, the gate of transistor Q2, and the second end of resistor R2 are interconnected. The drain of transistor Q2 is connected to the first end of resistor R2. The second end of resistor R3, the first end of resistor R4, and the gate of transistor Q3 are interconnected. The drain of transistor Q3 is connected to the first end of resistor R5, and the second end of resistor R5 is the feedback output terminal of the negative voltage control circuit 5511. The source of transistor Q3 is connected to the second end of resistor R4, and this connection node is the output terminal of the negative voltage control circuit 5511. The source of transistor Q2 and the first end of resistor R2 are both connected to the power supply VCC. The source of transistor Q1 and the second end of resistor R1 are both grounded.

[0040] Figure 5 In the circuit shown, another negative voltage control circuit 5511 includes resistors R6, R7, R8, R9, and R10, transistors Q5, Q6, and Q7. The gate of transistor Q5 is connected to the first end of resistor R6, and this connection node is the controlled terminal of the negative voltage control circuit 5511. The drain of transistor Q5, the second end of resistor R8, and the gate of transistor Q7 are interconnected. The drain of transistor Q7 is connected to the first end of resistor R10. The second end of resistor R10, the first end of resistor R9, and the gate of transistor Q6 are interconnected. The drain of transistor Q6 is connected to the first end of resistor R7, and the second end of resistor R7 is the feedback output terminal of the negative voltage control circuit 5511. The second end of transistor Q6 is connected to the second end of resistor R9, and this connection node is the output terminal of the negative voltage control circuit 5511. The drain of transistor Q7 and the first end of resistor R8 are both connected to the power supply VCC. The source of transistor Q5 and the second end of resistor R6 are both grounded.

[0041] Here, the control level output by the main control unit 540 (such as...) Figure 5 The V-control-1 and V-control-N values ​​are applied to the multi-channel negative voltage control circuit 5511, resulting in multiple loop control impedances. These impedances are then input to the negative voltage control circuit 5511, ultimately generating 1, 2, 3...n variable negative voltages. These are then superimposed and integrated to obtain the ideal liquid crystal driving voltage. The basic components of the negative voltage control circuit 5511 consist of multiple field-effect transistors and resistors / capacitors, or it can consist of transistors and resistors / capacitors, or a combination of field-effect transistors and transistors. Each negative voltage is composed of one basic circuit; the number of basic circuits required corresponds to the number of negative voltages needed.

[0042] Figure 5 In the circuit shown, the gate of transistor Q1 is connected to a control terminal of the main control unit 540. Resistor R1 is a pull-down resistor; it outputs a low level when not under control and a high level when under control. Resistor R2 is pulled up to the power supply VCC (e.g., 5V) and then connected to the drain of transistor Q1 and the gate of transistor Q2. When the main control unit 540 does not output a control signal, the gate of transistor Q2 is at a high level, and the voltage at the source of transistor Q2 (i.e., VCC) cannot reach the position of resistor R3 through transistor Q2. When a control terminal of the main control unit 540 is given a high level, transistor Q1 is turned on, and the gate of transistor Q2 changes from high to low, thus turning on transistor Q2. The voltage at the source of transistor Q2 (i.e., VCC) increases. Resistor R3 is connected to the gate of transistor Q3, while resistor R4 is a pull-down resistor for transistor Q3, connected to the source of transistor Q3 and then to the negative voltage output VOUT. At this time, the voltage (VCC) of transistor Q2 is directly applied to the gate of transistor Q3, thus turning on transistor Q3. Resistor R5 is connected in series with the drain of transistor Q3. Resistor R11 is the grounding resistor for the feedback pin of the negative voltage pre-generation circuit 551. R12 is connected to the negative voltage output circuit and the feedback pin to form a loop control. When transistor Q3 turns on, resistor R5 is connected in parallel to the feedback resistor R12, resulting in a reduced impedance. Through loop feedback control, the negative voltage generation circuit 552 obtains a new voltage value. Similarly, when the main control unit 540 is controlled by multiple channels, multiple variable negative voltages can be obtained. Depending on the control requirements of the main control unit 540, these multiple voltages are ultimately superimposed and integrated into a desired ideal liquid crystal driving voltage. This ideal liquid crystal driving voltage, when applied to the liquid crystal film, achieves a better localization effect.

[0043] In an optional embodiment, the data transmission unit 530 is wirelessly connected to the smart display device 600, and the data transmission unit 530 can wirelessly transmit writing or erasing signals to the smart display device 600. Preferably, please refer to... Figure 3 The data transmission unit 530 includes a Bluetooth control circuit and a Bluetooth antenna. The input terminal of the Bluetooth control circuit is the input terminal of the data transmission unit 530, the first output terminal of the Bluetooth control circuit is the first output terminal of the data transmission unit 530, and the second output terminal of the Bluetooth control circuit is connected to the Bluetooth antenna, which is the second output terminal of the data transmission unit 530.

[0044] It is understood that in this embodiment, when the smart display device 600 includes a Bluetooth adapter circuit 630 corresponding to the Bluetooth control circuit, the writing or erasing information output by the electromagnetic control unit 520 can be transmitted to the smart display device 600 via Bluetooth. In an optional embodiment, a wireless connection between the data transmission unit 530 and the smart display device 600 can also be achieved by setting a WIFI module (not shown) or an Internet of Things module (not shown).

[0045] It is worth mentioning that you should refer to Figure 3 and Figure 4 To enrich the functionality of the LCD handwriting tablet, in one optional embodiment, the Bluetooth control circuit includes a Bluetooth chip control circuit 531, and the data transmission unit 530 further includes a display screen 532. The input terminal of the Bluetooth chip control circuit 531 is the input terminal of the Bluetooth control circuit, the first output terminal of the Bluetooth chip control circuit 531 is the first output terminal of the Bluetooth control circuit, the second output terminal of the Bluetooth chip control circuit 531 is the second output terminal of the Bluetooth control circuit, and the third output terminal of the Bluetooth chip control circuit 531 is connected to the display screen 532. To further enrich the functionality of the LCD handwriting tablet, in one embodiment, the data transmission unit 530 further includes a memory 533 and a crystal oscillator 534, which are respectively connected to the Bluetooth chip control circuit 531.

[0046] Here, the electromagnetic control unit 520 and the Bluetooth chip control circuit 531 communicate via the USB protocol, transmitting the data signal from the electromagnetic stylus 100 to the Bluetooth chip control circuit 531. The main control unit 540 primarily communicates via a serial port. The Bluetooth chip (not shown) transmits the erasing data signal from the electromagnetic control unit 520 to the main control unit 540 via the serial port. The main control unit 540 ultimately completes the partial erasing function on the liquid crystal writing film 200 through the negative voltage pre-generation circuit 551, the negative voltage generation circuit 552, the bias voltage generation circuit 553, the horizontal liquid crystal driving circuit 554, and the vertical liquid crystal driving circuit 555. The power supply unit 510 provides power to the Bluetooth chip. The crystal oscillator 534 provides two frequencies, 32MHz and 32.768kHz, to the Bluetooth chip control circuit 531. The memory 533 primarily stores the handwriting data via the SPI bus in a data storage memory 533. The display screen 532 primarily communicates data via the I2C serial bus. It displays various information such as the working mode of the electromagnetic stylus 100, operating commands, and battery capacity, allowing users to easily understand their operations. The necessary data signals are transmitted to the Bluetooth adapter circuit 630 via the Bluetooth antenna using the Bluetooth protocol. The Bluetooth adapter circuit 630 and the Bluetooth antenna communicate with the host's Bluetooth chip control circuit 531 via the Bluetooth protocol. The Bluetooth chip control module (not shown in the figure) inside the Bluetooth adapter circuit 630 connects to the interactive whiteboard or computer via a standard USB-A interface, processes and converts the wireless signal acquired by the antenna, and then inputs it to the intelligent display device 600 (e.g., a computer or interactive whiteboard) via the USB port.

[0047] Please see Figure 3 In an optional embodiment, the electronic control module 500 further includes a temperature sensor circuit 560, the output of which is connected to the second input of the main control unit 540. Here, the temperature sensor circuit 560 can obtain analog voltage values ​​at different temperatures and then send the data to the main control unit 540 for automatic control of the liquid crystal driving voltage.

[0048] This utility model also proposes a liquid crystal writing tablet system, including the liquid crystal writing tablet as described above, and an electromagnetic stylus 100 adapted to the liquid crystal writing tablet. The electromagnetic stylus 100 is provided with a writing / erasing mode selection button. Furthermore, the liquid crystal writing tablet system also includes an intelligent display device 600 adapted to the liquid crystal writing tablet, and the electromagnetic stylus 100 is also provided with an electromagnetic stylus 100 / mouse mode selection button.

[0049] The following, combined with Figures 1 to 6 This document details the working principle of the LCD handwriting tablet and its system.

[0050] When the electromagnetic stylus 100 writes or erases on the partially erasable liquid crystal film, it generates magnetic signals of different frequencies on the electromagnetic antenna board 300. The electromagnetic stylus 100 itself has no power source, but when it is placed on the electromagnetic antenna board 300, the inductor coil inside the electromagnetic stylus 100 receives induced voltage and current, thereby generating a signal. The position data of this signal, as well as the tilt angle and pressure value of the electromagnetic stylus 100, are input to the electromagnetic control unit 520. After signal recognition and conversion by the electromagnetic control unit 520, the coordinate data signal of the writing or erasing marks is transmitted to the Bluetooth control circuit via the USB bus. The Bluetooth control circuit splits the obtained data signal into two paths: the writing mark data and the erasing mark data are wirelessly transmitted via the Bluetooth protocol. The erased handwriting data is also transmitted to the main control unit 540 via a serial port signal. After receiving the data signal, the main control unit 540 transmits the data to the liquid crystal driving unit 550. Under the joint drive of the negative voltage pre-generation circuit 551, the negative voltage generation circuit 552, and the bias voltage generation circuit 553, the horizontal liquid crystal driving circuit 554 and the vertical liquid crystal driving circuit 555 are completed, thus completing the function of partial erasing of the liquid crystal handwriting film 200. Additionally, the smart display device 600 (such as an all-in-one teaching machine or computer) has a Bluetooth adapter circuit 630. The Bluetooth adapter circuit 630 has a built-in Bluetooth chip module (not shown in the figure). The USB dongle in this Bluetooth adapter circuit 630 has been paired with the Bluetooth control circuit on the LCD handwriting tablet. Therefore, the data wirelessly transmitted from the LCD handwriting tablet is input into the corresponding application software through the USB dongle in the Bluetooth adapter circuit 630 and then through the USB port of the all-in-one machine or computer. The application software can then display the writing and erasing actions of the handwriting on the all-in-one teaching machine or computer. In addition, the USB dongle defines the Windows HID standard control device protocol. Through mode switching settings, our electromagnetic stylus 100 can work in both handwriting tablet and mouse modes, making it convenient for users to operate the all-in-one teaching machine or computer wirelessly, including opening and closing programs, and performing writing and partial erasing operations in the application software.

[0051] This solution acquires writing and erasing data signals from the electromagnetic stylus 100 on the electromagnetic antenna board 300, and then transmits the data in two paths via a Bluetooth control circuit. One path wirelessly transmits the data signal to the USB Dongle in the Bluetooth adapter circuit 630 via the 2.4G Bluetooth protocol. The USB Dongle then transmits the data signal via USB to an interactive whiteboard or computer for display, saving, and sharing. The second path, erasing data signals, is input to the main control unit 540 via a serial port. The main control unit 540 then controls the multi-channel negative voltage control circuit 5511 to output a suitable negative voltage. Finally, the data drives the corresponding position of the liquid crystal writing film 200 through the horizontal liquid crystal driving circuit 554 and the vertical liquid crystal driving circuit 555, achieving the desired local erasing effect on the liquid crystal writing tablet. This solution defines the communication protocol between the electromagnetic antenna board 300, the Bluetooth chip, and the main control unit 540, enabling writing and local erasing on the writing tablet, wireless Bluetooth transmission to an interactive whiteboard or computer for handwriting display and local erasing, and mouse functionality.

[0052] It should be noted that the technical solutions of the various embodiments of this utility model can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this utility model.

[0053] The above description is only a part or preferred embodiment of this utility model. Neither the text nor the drawings should limit the scope of protection of this utility model. All equivalent structural transformations made using the content of this utility model specification and drawings under the overall concept of this utility model, or direct / indirect applications in other related technical fields, are included within the scope of protection of this utility model.

Claims

1. A liquid crystal handwriting tablet, characterized in that, It includes an electronic control module, a liquid crystal handwriting film, an electromagnetic antenna board, and a handwriting substrate arranged from top to bottom. The electronic control module includes a power supply unit, a main control unit, an electromagnetic control unit, a liquid crystal driving unit, and a data transmission unit. The power supply terminals of the electromagnetic control unit, the data transmission unit, the main control unit, and the liquid crystal driving unit are all connected to the power supply unit. The data acquisition terminal of the electromagnetic control unit is connected to the electromagnetic antenna board. The output terminal of the electromagnetic control unit is connected to the input terminal of the data transmission unit. The first output terminal of the data transmission unit is connected to the first input terminal of the main control unit. The control terminal of the main control unit is connected to the controlled terminal of the liquid crystal driving unit. The output terminal of the liquid crystal driving unit is connected to the liquid crystal handwriting film. The data transmission unit further includes a second output terminal for connecting to the smart display device. When the user performs writing or erasing actions on the LCD handwriting pad, the data transmission unit transmits a signal corresponding to the writing or erasing action to the smart display device, so that the smart display device responds to the writing or erasing action.

2. The liquid crystal handwriting tablet according to claim 1, characterized in that, The liquid crystal driving unit includes a negative voltage pre-generation circuit, a negative voltage generation circuit, a bias voltage generation circuit, a horizontal liquid crystal driving circuit, and a vertical liquid crystal driving circuit. The controlled terminal of the negative voltage pre-generation circuit is connected to the main control unit. The output terminal of the negative voltage pre-generation circuit is connected to the input terminal of the negative voltage generation circuit. The output terminal of the negative voltage generation circuit is connected to the output terminal of the bias voltage generation circuit. The first output terminal of the bias voltage generation circuit is connected to the input terminal of the horizontal liquid crystal driving circuit. The second output terminal of the bias voltage generation circuit is connected to the input terminal of the vertical liquid crystal driving circuit. The controlled terminal of the vertical liquid crystal driving circuit is connected to the main control unit. The horizontal liquid crystal driving circuit is used to output a horizontal driving voltage to the liquid crystal handwriting film, and the vertical liquid crystal driving circuit is used to output a vertical driving voltage to the liquid crystal handwriting film.

3. The liquid crystal handwriting tablet according to claim 2, characterized in that, The negative voltage pre-generation circuit includes resistor R11, resistor R12, capacitor EC2, and N parallel negative voltage control circuits. The controlled terminal of each negative voltage control circuit is connected to the main control unit. The feedback output terminal of each negative voltage control circuit, the second terminal of resistor R11, and the first terminal of resistor R12 are connected to the feedback terminal of the negative voltage generation circuit. The output terminal of each negative voltage control circuit, the second terminal of resistor R12, and the first terminal of capacitor EC2 are interconnected, and their connection node is the output terminal of the negative voltage pre-generation circuit. The first terminal of resistor R11 and the second terminal of capacitor EC2 are grounded, and N≧2.

4. The liquid crystal handwriting tablet according to claim 3, characterized in that, The negative voltage control circuit includes resistors R1, R2, R3, R4, and R5, transistors Q1, Q2, and Q3. The gate of transistor Q1 is connected to the first end of resistor R1, and this connection node is the controlled terminal of the negative voltage control circuit. The drain of transistor Q1, the gate of transistor Q2, and the second end of resistor R2 are interconnected. The drain of transistor Q2 is connected to the first end of resistor R2. The second end of resistor R3, the first end of resistor R4, and the gate of transistor Q3 are interconnected. The drain of transistor Q3 is connected to the first end of resistor R5. The second end of resistor R5 is the feedback output terminal of the negative voltage control circuit. The source of transistor Q3 is connected to the second terminal of resistor R4, and the connection node is the output terminal of the negative voltage control circuit. The source of transistor Q2 and the first terminal of resistor R2 are both connected to power supply VCC. The source of transistor Q1 and the second terminal of resistor R1 are both grounded.

5. The liquid crystal handwriting tablet according to claim 1, characterized in that, The liquid crystal handwriting film includes an upper conductive layer, a liquid crystal layer, and a lower conductive layer arranged sequentially from top to bottom. The upper conductive layer includes X horizontal conductive areas and Y vertical conductive areas, with each horizontal conductive area perpendicular to each vertical conductive area. The lower conductive layer includes X horizontal conductive areas and Y vertical conductive areas corresponding to the upper conductive layer.

6. The liquid crystal handwriting tablet according to claim 1, characterized in that, The data transmission unit includes a Bluetooth control circuit and a Bluetooth antenna. The input terminal of the Bluetooth control circuit is the input terminal of the data transmission unit, the first output terminal of the Bluetooth control circuit is the first output terminal of the data transmission unit, and the second output terminal of the Bluetooth control circuit is connected to the Bluetooth antenna, which is the second output terminal of the data transmission unit.

7. The liquid crystal handwriting tablet according to claim 6, characterized in that, The Bluetooth control circuit includes a Bluetooth chip control circuit, and the data transmission unit further includes a display screen. The input terminal of the Bluetooth chip control circuit is the input terminal of the Bluetooth control circuit. The first output terminal of the Bluetooth chip control circuit is the first output terminal of the Bluetooth control circuit. The second output terminal of the Bluetooth chip control circuit is the second output terminal of the Bluetooth control circuit. The third output terminal of the Bluetooth chip control circuit is connected to the display screen.

8. The liquid crystal handwriting tablet according to claim 1, characterized in that, The electronic control module also includes a temperature sensor circuit, the output of which is connected to the second input of the main control unit.

9. A liquid crystal handwriting tablet system, characterized in that, The invention includes a liquid crystal writing tablet as described in any one of claims 1-8, and a stylus adapted to the liquid crystal writing tablet, wherein the stylus is provided with a writing / erasing mode selection button.

10. The liquid crystal handwriting tablet system according to claim 9, characterized in that, The LCD handwriting tablet system also includes an intelligent display device adapted to the LCD handwriting tablet, and the stylus is also provided with a stylus / mouse mode selection button.

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