阅读说明：本技术 一种基于电变液的盲文显示器装置 (Braille display device based on electrorheological fluid ) 是由 王伟然 陈伟 李可礼 杜昭平 张芊 闫景昊 杨冠军 于中奇 于 2019-11-08 设计创作，主要内容包括：本发明属于残疾人特殊装备制造领域,具体地说,是一种基于电变液的盲文显示器装置,包括供电单元、控制单元、显示单元、保护单元,供电单元为控制单元、显示单元、保护单元提供电源支持,供电单元由电源模块组成,电源模块设定为2个输入端口和3个输出端口,控制单元由盲文输入模块、MCU模块、译码模块、锁存模块、光耦隔离模块组成,显示单元是由高强度不导电防渗透纤维编制而成的点阵材料,保护单元包括电流传感器和报警装置。(The invention belongs to the field of manufacturing of special equipment for disabled people, and particularly relates to a Braille display device based on electro-rheological fluid, which comprises a power supply unit, a control unit, a display unit and a protection unit, wherein the power supply unit provides power support for the control unit, the display unit and the protection unit, the power supply unit consists of a power module, the power module is set to be 2 input ports and 3 output ports, the control unit consists of a Braille input module, an MCU module, a decoding module, a latch module and an optical coupling isolation module, the display unit is a dot matrix material woven by high-strength non-conductive anti-seepage fibers, and the protection unit comprises a current sensor and an alarm device.)

1. The utility model provides a braille display device based on electrorheological fluid, its characterized in that, includes power supply unit, the control unit, display element, protection unit, the power supply unit does the control unit, display element, protection unit provide the power and support, the power supply unit comprises power module, power module sets for 2 input ports and 3 output ports, the control unit comprises braille input module, MCU module, decoding module, latch module, opto-coupler isolation module, the display element is the dot matrix material of being worked out by the non-conductive prevention of seepage fibre of high strength, the protection unit includes current sensor and alarm device.

2. A braille display device based on electro-rheological fluid is characterized in that the power module is provided with 2 input ports which cannot work simultaneously, a direct current DC-36V input port and an alternating current AC-220V input port, the power module is provided with 3 output ports which are a DC-2-5 kV output port, an AC-0.8-2 kV output port and a DC-5V output port, and the input and output ports of the power module are provided with an electric energy conversion circuit.

3. The braille display device based on electro-rheological fluid of claim 2, wherein the display unit is a dot matrix material woven by high strength non-conductive anti-seepage fibers, the electro-rheological fluid material is poured through the injection port during manufacturing, after the injection port is heat sealed, the hot-pressed liquid bubble pad is formed by using a hot-pressing device with convex warp and weft strips and concave round points, the electro-rheological fluid material flows in the warp and weft channels preset by the liquid bubble pad, and is gathered at the braille convex points preset by the liquid bubble pad after being extruded, and the liquid bubble is formed after the flow channel of the heat sealed liquid bubble pad, and comprises 2 lines, 24 squares in each line, 6 convex points in each square and 288 convex points in total, the display unit can be connected in a cascade connection mode, and I is used²The hardware structure design and the data frame of the C bus enable a plurality of display modules to be spliced into a large screen for use.

4. A braille display device based on electro-rheological fluid, characterized in that the display unit further comprises therein a DC high-voltage line that solidifies the vacuoles and an AC high-voltage line that oscillates the solidification-recovery vacuoles.

5. A braille display device based on electro-rheological fluid, characterized in that the control unit employs an MCU core control board.

6. A braille display device based on electro-rheological fluid, characterized in that the MCU core control board adopts Arduino map 2560.

7. A braille display device based on electro-variable fluid according to any preceding claim 1-6, characterized by further comprising an earth leakage protection device.

Technical Field

The invention belongs to the field of manufacturing of special equipment for disabled people, and particularly relates to a Braille display device based on electro-rheological fluid.

Background

The reading of the blind is a special education problem for the disabled: learning and education are necessary for all human beings, and the right to educate and enjoy education is the basic right of all human beings, which cannot be deprived due to the vision loss of the blind, but the blind cannot read any image-related media such as normally printed books, drawing albums, movie programs and the like due to the congenital defect of the blind. In order to solve the problem of blind people reading, the Law of the French man creates Braille in 1824, or the Braille is also called braille or convex character, which is specially designed for the blind people and is sensed by touch. Braille is a pinyin character, the braille of each square is composed of six dots, the left side is 123 from top to bottom, the right side is 456, and the braille is called one party. The national committee on standardization approval is approved by the national committee on language and character work, and the 'national universal sign language common word list' and 'national universal braille scheme' are issued as the specification on the language and character of the Chinese braille and are implemented from 2018, 7 and 1 days.

At present, the braille display at home and abroad mainly adopts the following scheme:

(1) the voice type braille display is to convert the words into language and play the contents of the words by using audio, so that the blind can acquire knowledge. The voice type braille display device is low in price, and with the deep application of artificial intelligence in character recognition, the voice type braille display device has no technical barrier. However, the voice-type braille display cannot display non-text images, and long-time audio playback may impair human hearing.

(2) The core element of the piezoelectric ceramic type braille display is piezoelectric ceramic, the piezoelectric ceramic has reversibility, when two piezoelectric ceramics with opposite polarization directions are tightly attached together, when positive voltage is applied to a piezoelectric bimorph, the piezoelectric ceramics contracts in one direction and extends in the other direction, so that the piezoelectric ceramics can deform and bend, and a driving needle on the piezoelectric ceramics also moves upwards along with the piezoelectric ceramics.

(3) Memory alloy type braille display the memory alloy type braille display is developed and manufactured according to the shape memory effect. The braille display uses a two-way shape memory alloy. The shape of the two-way memory alloy can be recovered to the shape in the high-temperature state when the two-way memory alloy is heated, and can be recovered to the shape in the low-temperature state when the two-way memory alloy is cooled.

(4) Electromagnetic braille display the electromagnetic braille display is the most widely used equipment at present, and the driver made of electromagnet is adopted, and the driver is controlled by a computer to drive the rubber needle to lift so as to display braille information.

(5) The pneumatic braille display device is characterized in that compressed air is introduced into the sealing device through an air compressor to form pressure difference with outside air, and under the action of internal pressure, the surface of a thin film touch screen made of high polymer molecular materials is protruded to form braille contacts.

(6) The electric stimulation type braille display does not have a mechanical driver to generate pressure or vibration touch sense, only directly stimulates nerve fibers in the skin through the surface current of the microelectrode, and the blind person can recognize braille through the electric pulse stimulation of the tip of a finger.

(7) The temperature-controlled braille display has a plurality of temperature-controlled contacts, and the braille contact points are indicated by controlling the temperature of the temperature-controlled contacts made of each semiconductor, thereby displaying braille.

TABLE 1 comparison of advantages and disadvantages of existing Braille displays

As can be seen from table 1, the voice type braille display is cheap, simple in device, but cannot display images, and the blind can hurt hearing for a long time when listening, and is easily interfered by ambient sounds; the piezoelectric ceramic type braille display has high speed, but the device structure is complicated; the memory alloy type braille display has simple structure, but the temperature change rate is slow, so the real-time performance of the device is poor; the principle of the electromagnetic Braille display is simple, but each contact pin needs an independent electromagnetic device, so that the structure of the multi-Braille display device is complex; the pneumatic braille display needs an air pump, and has the disadvantages of complicated device, large volume and inconvenient carrying; the electrical stimulation type braille display is small in size and simple in structure, but the sensitivity of the finger ends of each person or the same person is different at different moments, so that the reliability of the device is poor, and images cannot be displayed; the temperature control type braille display has a novel structure, but the temperature change rate is slow, and the real-time performance of the system is poor.

With the progress of society, the knowledge is further explosively increased, the requirement of human beings on the knowledge is higher and higher, how to design a Braille display which has the advantages of low price, quick response, small size, portability, capability of displaying images and long-term use has an extremely important role in solving the self-learning problem of people with visual disabilities, and the Braille display has the significance of theoretical research and practical application.

Disclosure of Invention

In order to solve the technical problems, the invention discloses a Braille display device based on electro-rheological fluid, which can solidify and restore special liquid according to different applied currents.

The invention adopts the following specific technical scheme:

the utility model provides a braille display device based on electrorheological fluid, including the power supply unit, a control unit, a display unit, the protection unit, the power supply unit is the control unit, a display unit, the protection unit provides the power support, the power supply unit comprises power module, power module sets for 2 input ports and 3 output ports, the control unit comprises braille input module, the MCU module, the decoding module, latch module, opto-coupler isolation module, the display unit is the dot matrix material of being worked out by high strength non-conductive prevention of seepage fibre, the protection unit includes current sensor and alarm device.

The power supply module is further improved, the power supply module is provided with 2 input ports which cannot work simultaneously, a direct current DC-36V input port and an alternating current AC-220V input port, and the power supply module is provided with 3 output ports which are a DC-2-5 kV output port, an AC-0.8-2 kV output port and a DC-5V output port. Therefore, the electric energy conversion circuit of the input and output ports of the power module is designed.

The invention further improves, the display element is the dot matrix material woven by the high strength non-conductive anti-seepage fiber, pour the electrorheological fluid material into from the sprue first while making, after the heat-seal sprue, use and have protruding warp and weft, the hot-pressing bubble pad of concave dot heating pressing apparatus, the electrorheological fluid material flows in the preset longitude and latitude channel of the bubble pad, gather on the preset braille salient point of the bubble pad after squeezing, after the heat-seal bubble pad flow channel, form the liquid bubble, including 2 rows, 24 squares of each row, 6 salient points of each square, total 288 salient points; the display unit also comprises a DC high-voltage line for curing the vacuole and an AC high-voltage line for oscillating, curing and restoring the vacuole. And is based on²The C bus designs a cascade driver and a data frame of the display unit, and a plurality of display units can be spliced to form a large screen for use.

The invention further improves and designs an electric leakage protection module for preventing high-voltage electric shock accidents, in particular to a high-voltage direct current electric leakage protection module.

The invention has the beneficial effects that:

① Braille display uses a bubble pad as a display device, which is an insulating and high-strength fiber soft material, and can be bent and folded at will when not in use, thereby facilitating storage and carrying.

② the Braille display adopts modular design, including power module, Braille display module, and controller module, which is convenient for equipment maintenance and repair, and can be combined with different specifications according to different requirements and environment.

③ the Braille display has small structure, can be carried and used when selecting battery power supply, and can be further reduced when selecting AC220V power supply.

④ the Braille display has quick response, uses DC current to solidify special liquid to make it crystallize, uses AC current to oscillate the crystal to make it restore, the whole process is ms grade, the whole process is extremely quick, can meet the real-time requirement, and the liquid has stronger shearing stress after crystallization, can be obviously felt by the blind.

⑤ the Braille display can be designed with a large area of bubble pad as required, and has a large area of display area to display images.

⑥ along with the development of science and technology, after the new electro-rheological fluid material is invented, the performance of the Braille display can be optimized by only replacing the new material and optimizing the software program without changing the structure.

Drawings

FIG. 1 shows the electric field strength and yield strength of an electrorheological fluid containing Ba-Ti-O nanoparticles coated with urea.

Fig. 2 is a hardware topology of the present invention.

Fig. 3 is a power supply composition logic topology.

FIG. 4 is a schematic diagram of DC-36V to DC-5V conversion of a power supply.

FIG. 5 is a schematic diagram of AC-220V to DC-36V power supply.

FIG. 6 is a schematic diagram of DC-36V conversion from DC-2 kV to DC-5 kV.

FIG. 7 is a schematic diagram of a power supply converting DC-36V to AC-0.8-2 kV.

Fig. 8 is a schematic diagram of a display module.

Fig. 9 is a schematic diagram of a cascaded driver based on PCF 8574.

FIG. 10 is a diagram of a data frame in the I2C bus PCF8574 write mode.

FIG. 11 is a data frame diagram of an I2C bus single PCF 8574.

Fig. 12 is a schematic diagram of leakage detection for a high voltage ac input drive.

Fig. 13 is a schematic diagram of leakage detection in the high voltage dc input drive.

Detailed Description

For the purpose of enhancing the understanding of the present invention, the present invention will be described in further detail with reference to the accompanying drawings and examples, which are provided for the purpose of illustration only and are not intended to limit the scope of the present invention.

An electrorheological fluid, also called electrorheological fluid, is generally a suspension formed by mixing semiconductor solid particles with an insulating liquid, and this material has a rheological property that can change with the intensity of an electric field, that is, as the intensity of the electric field increases, the viscosity of a colloid in the liquid increases, and when the electric field increases to a threshold value, the rheological property of the colloid changes rapidly, and usually between several millimeters, the liquid is cured into an elastic solid. When the external electric field is removed, the process is reversible, namely, the elastic solid can be recovered into liquid after the external electric field is removed. The 'electrorheological fluid' braille display device in the patent adopts 'giant electrorheological fluid' containing composite nano particles, such as urea coated Ba-Ti-O nano particle electrorheological fluid, Ca-Ti-O nano particle based electrorheological fluid and the like, and the specific characteristics of the 'giant electrorheological fluid material' can be found in related documents and research reports.

According to the urea-coated Ba-Ti-O nano-particle electrorheological fluid developed by Wenweijia and the like in 2003, the relationship between the electric field strength and the yield strength is shown in figure 1. It can be seen that the electric field strength and the yield strength are approximately in a linear relationship, when the electric field strength is DC4.5kV, the yield strength is about 100kPa (100kPa is equivalent to the force of 1cm2 receiving a weight of 1 kg), and the yield strength can solidify Braille points in the vacuole cushion, so that the blind can feel. Furthermore, according to the literature, the current density is very low, below 1 μ A/cm2, and the curing time is only 15 ms.

The Braille reading speed is slow, about 200-400 characters per minute, and the character refreshing time requirement is as follows:

as can be seen from the formula (1), when the braille reading speed is the fastest, one word needs to spend 150ms of distinguishing time, and the solidification time of the electro-rheological fluid material is 15ms and the subsequent liquefaction time is 30ms, so that the braille display device designed by the patent can completely meet the refreshing rate of braille display technically.

According to the specification of national standard GB/T15720-:

when an external direct current DC electric field of 4kV is applied and the current density is 1 muA/cm 2, the active power of each bump is as follows:

P＝4kV×1μA/cm²×3.14mm²＝1.256×10^-4W (3)

then 2 rows are designed, each row has 24 vacuole pads of the electrorheological fluid braille display, the vacuole pads have 288 convex points, and the power required by the vacuole pads is only:

P＝288×1.256×10^-4＝3.61728×10^-2W (4)

therefore, the electrorheological fluid Braille display designed by the patent has low overall power consumption and is beneficial to portability and commercialization.

Fig. 2 is a hardware topology of the present invention. As shown in figure 2, the 'electrorheological fluid' Braille display device designed by the invention consists of a power supply module, a control module, a display module and a protection module.

(1) Power supply module

The power supply module can be input by direct current DC-36V, namely the human body safety voltage standard, and the specification voltage enables the device to be powered by a battery, so that the device is convenient to carry. In addition, the power supply module can be input by alternating current AC-220V, namely the commercial power standard of China, and the device can be powered by the commercial power by the voltage of the specification, so that the problem of power supply continuity is solved. The output of the power supply module is 3 grades of output voltage:

① DC-2-5 kV, the variable DC high voltage output is 2-5 kV, the level voltage is used for solidification of 'electrorheological fluid' material in the braille display module liquid bubble pad, therefore, when the DC 5kV voltage field intensity is added, the giant electrorheological fluid material is solidified, the yield strength is about 100kPa, the actual use does not need the high yield strength, therefore, the variable DC high voltage output power supply is designed, and the control module controls to obtain the proper yield strength, so that the liquid bubble salient point in the braille display is solidified, has certain strength, and can be successfully felt by the blind.

② AC-0.8-2 kV, the variable alternating current high voltage output is 0.8-2 kV, the voltage of this level is used to make the solidified 'electrorheological fluid' material restore to liquid state, it can be known from the above-mentioned characteristics about the 'electrorheological fluid' material that along with the removal of the applied high voltage electric field, the 'electrorheological fluid' can restore to liquid state automatically along with the time, but the braille display designed by this patent has the requirement of 150ms character refreshing time, so the variable alternating current high voltage output module is designed here, the control module controls the output voltage level and output frequency, the 'electrorheological fluid' material used for oscillating the solidification makes it restore to liquid state as soon as possible.

③ DC-5V, and outputs DC voltage of 5V for supplying power to MCU, latch, and optical coupling isolation power supply chip in the control module.

(2) Control module

The control module consists of a Braille input module, an MCU module, a decoding module, a latching module and an optical coupling isolation module.

① Braille input module, which translates the external characters, images and so on into Braille code format.

② MCU module, this patent braille display device require not highly to MCU operation speed, but need more IO (input/output) mouth, lectotype Arduino mega2560 in the prototype development, it has 54 way digital input/output ports, cooperation decoding module and latch module control, control the vacuole pad after the opto-coupler is kept apart.

③ decoding module for I/O port output expansion the Braille display designed by this patent (2 rows, 24 squares in each row, 6 bumps in each square) has 288 bumps, each bump needs to be individually controllable, the number is much larger than the number of I/O ports of MCU, therefore, the control output must be encoded, and its parallel output is converted into serial input to reduce the I/O ports occupied by MCU.

④ latch module for latching output control quantity, because the decoding module is used to convert the parallel output into serial input, the latch module is needed to store the output, and no output confusion is caused by the MCU calling the output I/O port.

⑤ optical coupling isolation module, because the controller module is a low voltage device working under DC-5V and the display module is a high voltage device working under DC-2-5 kV and AC-0.8-2 kV, in order to prevent the current from flowing backwards and burning the control module, the optical coupling isolation module is used for the isolation of the control end and the output end.

(3) Display module

The display module is a dot matrix material woven by high-strength non-conductive impermeable fibers. The method comprises pouring electrorheological fluid material into the injection hole, hot-pressing the bubble pad with equipment having convex warp and weft strips and concave dots after heat sealing the injection hole, flowing the electrorheological fluid material in the warp and weft channels preset in the bubble pad, extruding and collecting the electrorheological fluid material at the Braille convex points preset in the bubble pad, and forming the bubble after heat sealing the flow channels of the bubble pad. In addition, the display module contains a DC high-voltage line for curing the vacuole and an AC high-voltage line for oscillating, curing and restoring the vacuole.

(4) Protection module

As the equipment adopts high-voltage curing and liquefying 'electro-change' of DC-2-5 kV and AC-0.8-2 kV, a reliable safety device is required to be arranged to ensure the running safety of the equipment and the personal safety of an operator. The electric shock injury of people is mainly caused by that a certain amount of current flows through the human body, namely, the electric shock state reaches a certain power. The protection module can be through the electric current on current sensor real-time supervision safety casing or safety protection layer surface, when the electric current is greater than a certain predetermined threshold, sends the action signal and gives power module, and power module interrupts all high-voltage output in order to prevent to electrocute the phenomenon.

The detailed description and the limitation are further developed for the important parts in the braille display device based on the 'electric changing liquid' in the patent.

(1) Power supply

The power supply topology designed by this patent is shown in fig. 3 below.

As can be seen from fig. 3 and the above description: the power module has 2 input and 4 output.

The 2-path input is respectively direct current DC-36V and alternating current AC-220V. The direct current input and the alternating current input can not be used simultaneously, so that two paths of power supplies can not be input simultaneously by using exclusive OR logic.

(a) After passing through the converter, the alternating current AC-220V can be transformed into:

① DC-36V for participating in subsequent voltage conversion;

② DC-40V, which is used to charge DC-36V energy storage batteries, the charging voltage must be greater than the battery voltage.

(b) The direct current DC-36V can be transformed into:

① DC-5V, which is used to supply power for controller, optical coupler, low voltage sensor, etc.;

② direct current DC-2-5 kV, which is used for curing the electro-variable liquid material;

③ alternating current AC-0.8-2 kV, which is used for recovering a cured 'electric-variable liquid' material;

the specific power converter principle is as follows:

① DC-36V to DC-5V

As shown in FIG. 4, L_p、L_sIs the primary side and the secondary side of the transformer T, n is the turn ratio of the transformer, C_p、 C_sFor filter capacitors, in operation, switch S₁And S₃Driven simultaneously by a signal, S₂Driven by the inverse of this signal. Let S₂With a duty cycle of T and a duty cycle of D, the output voltage U_oComprises the following steps:

U_o＝D·U_i/n (5)

② AC-220V to DC-36V

As shown in FIG. 5, an STSR2 intelligent driver is used to convert the commercial AC-220V into DC-36V, wherein Vcc is the power supply voltage terminal; PWMGND and SGLGND are reference terminals of power signals and control logic signals; CLOCK is the synchronous signal input end; OUT1 and OUT2 are high current complementary output terminals; the SET SETs an expected cutoff period for OUT; INHIBIT is an enable control terminal. Similarly, the intelligent driver using STSR2 can convert AC-220V into DC-40V, which is used to charge the accumulator.

③ direct current DC-36V-to-DC-2-5 kV

FIG. 6 is a schematic diagram of DC-36V conversion DC-2-5 kV of power supply

Since the total power of the device is small (designed as 5W), the power required by the vacuole pad of the main part is only 3.61728 x 10^-2W is added. Wherein U is_out1The end outputs direct current DC-5 kV.

As can be seen from equation 6, when the duty ratio is set to 50%, i.e., t_on-s6/t_off-s6When it is 1, U_inThe end is DC-36V, U_out1End is DC-5kV, and the ratio of the number of turns of the primary side to the number of turns of the secondary side is N₂/N₁1250/9, although changing the duty cycle can change U without changing the turns ratio_out1End output, but considering the voltage variation ratio is large, the power electronic device S₆The switching frequency of (2) is that a U is additionally arranged at the rear end of a power supply_out2A terminal, the voltage output of which is:

it can be seen that U_out1Terminal and U_out2The terminal voltage changes little and changes S₇Can adjust U_out2The required regulation range of the output voltage of the terminal is direct current DC-2-5 kV.

④ DC-36V converted AC-0.8-2 kV

FIG. 7 is a schematic diagram of a power supply DC-36V to AC-0.8-2 kV

As can be seen from the above, U_inThe input is DC-36V, u_oThe end output is AC-0.8-2 kV. Similarly, equation 6, sets the appropriate windingAfter that, change S₁₂Can change U_out1The direct current output of (2).

The power factor is 0.85 at the moment of the power factor angle of the load, and according to the formula 8, if the AC-0.8-2 kV is required to be obtained, the input U is_out1The terminal is DC-612.6126-1531.5315V. Following the same equation 6, when S₁₂At a duty cycle of 50%, the recommended ratio of the number of primary side turns to the number of secondary side turns is N₂/N₁800/9, when U_out1The direct current output of the transformer can reach 1600V (more than 1531.5315V), and S is regulated₁₂Can be made U_out1The end outputs DC-612.6126 ~ 1531.5315V. Therefore, the output design of alternating current AC-0.8-2 kV is realized.

(2) Display module

① vacuole pad structure

As shown in the schematic diagram of the module shown in fig. 8, the circle in the diagram is filled with an electrorheological fluid material, and the solid line connecting the circles is direct current DC-2-5 kV input and is used for curing the electrorheological fluid material; the dotted line of the connecting circle is AC-0.8-2 kV input and is used for vibrating and solidifying the electrorheological fluid material to quickly recover the liquid state. For the next step of designing the drive, the input terminals of the blister pads in the display module need to be numbered. As shown by the dashed box, every 6 vacuoles constitute a braille display character, marked as 1 square. The vacuole numbers in each side are: A/B_i(x,y)Wherein, the letter A represents a direct current DC-2-5 kV input terminal (referred to as a direct current end for short), and the letter B represents an alternating current AC-0.8-2 kV input terminal (referred to as an alternating current end for short); i in the subscript is the number of the square, and the numbers are sequentially from left to right and from top to bottom; subscripts (x, y) indicate the row and column number of the vacuole, x being the row and y being the column of the vacuole. In fig. 8, a liquid bubble pad with m rows and n columns is set as a display unit, and a plurality of display units can be cascadedAre groups of display elements.

② driver structure of vacuole pad

As shown in fig. 8, each bubble in the bubble pad has 2 sets of dc and ac inputs, each set of inputs has 2 input pins, the input pins are arranged in rows and columns, and the bubble can be solidified or liquefied only when the voltages of the 2 input pins have potential differences. The Braille display of this patent design both can the exclusive use also can cascade use, and a vacuole pad is as a display element, and it has 2 lines of Braille to show, and every line shows 24 square (24 Braille characters), and every side has 6 bumps. If a single control scheme is used, 288 x 2-576I/O ports are required, and such a number of I/os is unacceptable for the resources and cost of the controller. The input pins are arranged in rows and columns and then are combined into a matrix form, so that 24 input pins are needed for the row sequence and 24 input pins are needed for the column sequence, namely 48I/O ports which can be controlled independently are needed. This number still requires too much for the number of I/O ports of the controller, so this patent design encodes 48I/O input ports, and adopts PCF8574 to convert the parallel control signal into I²C signal input, thus can greatly reduce I/O input port, save the resources of the controller. To solve the output signal retention problem, latch 74HCN14 also needs to be incorporated.

As shown in FIG. 9, it is based on I²Schematic diagram of cascaded drivers for C bus, through I²C bus, the controller MCU only needs 2I/O ports, namely SDA and SCL. Each I²The C-bus parallel port chip PCF8574 has independent addresses, i.e. different PCFs 8574 can be invoked by different access addresses. In addition, each I²The C-bus parallel port chip PCF8574 has 8-bit I/O outputs, i.e., 48I/O input ports require 6 blocks of PCF8574 and need to be cascaded together. Since the controller MCU output information changes faster, like a scan out, each PCF8574 needs to connect a latch 74HC14 for holding the output information during one output cycle, maintaining the output state. Because the output signal needs to control the direct current DC-2-5 kV and the alternating current AC-0.8-2 kV, PCF8574 and 74HC14 can not be directly connected, otherwise, the current flows backwards,the chip is burnt out, so that the designed output signal passes through the optical coupling isolation module and then controls a high-voltage direct-current power supply (direct current DC-2-5 kV) and a high-voltage alternating-current power supply (alternating current AC-0.8-2 kV), and therefore solidification and liquefaction of the 'liquid bubble pad' are controlled.

③ drive signal data frame definition

The Braille display device of the patent is composed of²The chip PCF8574 is formed by cascading C bus parallel port chips and needs to be based on I²The C protocol defines the data frames of the drive signals. A data frame is a protocol data unit of the data link layer. This patent only applies the "write mode" therein.

As shown in fig. 10, the data frame first sends a start bit (S) indicating the start of transmission, the data frame sends the address of PCF8574_01, the contents of which are sent, a send cascade bit (C) indicating whether the subsequent display units are cascaded, a send cascade length indicating the number of subsequent display units, and a send verification bit (V) verifying whether the data before verification is correct. Then sends the relevant contents of PCF8574_02 in the above order until PCF8574_06 terminates.

As shown in FIG. 11, wherein I²The frame format of a single PCF8574 of the C bus is as follows, first sending a start bit (S) indicating the start of transmission, sending the address 010A2A1a0 of the current PCF8574, sending a read-write status bit (R/W)0 indicating that the current status is write, sending a response bit (a) to wait for a response, then sending a data block 01, which consists of an 8-bit data bit and A1-bit response bit, sending a data block 02, up to a data block n.

(3) Protection module

The power supply module and the display module are the most prone to electric shock accidents, and therefore protective measures need to be designed for the power supply module and the display module. The power supply module provides four voltage class outputs, wherein direct current DC-36V, DC-5V belongs to human body safety voltage, but direct current DC-2-5 kV and alternating current AC-0.8-2 kV belong to high voltage output category, and a special leakage protection circuit needs to be designed.

As shown in fig. 12, an induction detection coil is arranged to detect current at a specific detection point of the "electric changing liquid" braille display module device, and the current measured by the induction detection coil is smaller than a preset threshold value under the condition that electric leakage does not occur normally, so that the control module does not interfere with the current power supply state; when the electric leakage phenomenon occurs, the current value in the power supply module is increased sharply, the current measured by the induction detection coil is larger than a preset threshold value, the control module sends an action signal to order the tripper to separate the main circuit of the power supply module, so that the electric shock accident of personnel is avoided, and the tripper gets electricity through the alternating current input circuit through the rectification circuit.

As shown in fig. 13, the high-voltage dc circuit is different from the ac circuit, and when the voltage and current of the dc loop are constant, there is no alternating magnetic field, so that the current information cannot be directly sampled by using the induction coil, and a hall sensor with an iron core needs to be used, and the hall sensor needs to pass through the dc loop wire, so that nondestructive measurement can be performed. When the high-voltage direct-current circuit does not generate the electric leakage phenomenon, the current change is constant, and the magnetic field around the conducting wire is constant according to the Faraday's law of electromagnetic induction; when the high-voltage direct-current circuit has an electric leakage phenomenon, the current suddenly changes, the amplitude of the instantaneous current changes obviously, the Hall sensor can accurately acquire the amplitude of the instantaneous current change, and the control module judges whether the electric leakage occurs or not according to the comparison result of the amplitude of the change and the threshold value. When electric leakage occurs, the control module sends an action signal to instruct the release to separate the main circuit of the power supply module, so that the electric shock accident of personnel is avoided. And an optical coupler is adopted between the control module and the tripper to carry out signal transmission and physical isolation.

(4) Control module

The control module core is MCU core control board, and Arduino mage 2560 is adopted to this patent, because Arduino belongs to the equipment of open source, fixed pin, consequently does not expand the narration here.

The foregoing illustrates and describes the principles, general features, and advantages of the present invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.