A heated magnetic stirrer

Abstract

The application discloses a heating magnetic stirrer, a stirring driving device, a temperature measuring device and a temperature control device, wherein the stirring driving device is used for mixing the solution in a beaker and making the temperature distribution of the solution in the beaker more uniform; the temperature measuring device comprises a solution temperature measuring device and a heating table temperature measuring device; the solution temperature measuring device is used for measuring the solution temperature in the beaker and taking the solution temperature as a feedback amount of a main ring; the heating table temperature measuring device is used for measuring the temperature of the heating table and taking the temperature as a feedback amount of a secondary ring; and the temperature control device adopts a fuzzy-serial PID control mode and is used for precisely controlling the solution temperature in the beaker. The heating magnetic stirrer can realize high-precision control of the medium solution temperature, has a small overshoot amount and good stability, and is suitable for different medium solutions.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of stirrers, in particular to a heating magnetic stirrer. BACKGROUND

[0002] The heating stirrer is a common experimental equipment in chemical experiments, and the temperature control mode of the medium in the heating magnetic stirrer configured on the market currently adopts fuzzy PID control. Compared with ordinary temperature control, the fuzzy PID control realizes online modification of P, I and D three parameters through error and error change rate, and indeed further improves the temperature control of the medium. However, the temperature rise of the medium of the heating magnetic stirrer is through the heating table to transmit heat to the medium, and the hysteresis is large. Although the fuzzy PID has further improved the temperature control, the overshoot and stability cannot meet the requirements of the experiment, and therefore the present application proposes a new type of heating magnetic stirrer with temperature control. SUMMARY

[0003] In order to overcome the deficiencies in the prior art, the present application provides a heating magnetic stirrer.

[0004] In order to achieve the above application purposes and solve the technical problems, the technical scheme adopted is as follows:

[0005] A heating magnetic stirrer, comprising a stirring driving device, a temperature measuring device and a temperature control device, wherein:

[0006] The stirring driving device is used for mixing the solution in the beaker and making the temperature distribution of the solution in the beaker more uniform.

[0007] The temperature measuring device comprises a solution temperature measuring device and a heating table temperature measuring device. The solution temperature measuring device is used for measuring the temperature of the solution in the beaker and taking it as the feedback of the main loop. The heating table temperature measuring device is used for measuring the temperature of the heating table and taking it as the feedback of the secondary loop.

[0008] The temperature control device adopts a fuzzy-serial PID control mode and is used for accurately controlling the temperature of the solution in the beaker.

[0009] Further, the stirring driving device comprises a DC brushless motor, a magnet and a magnetic stirring sub, wherein:

[0010] The DC brushless motor is fixed to the bottom of the upper shell of the stirrer by screws, and three Hall elements arranged at 120° are arranged in the inside of the DC brushless motor and are used for detecting the position of the rotation of the DC brushless motor.

[0011] The magnet is fixed above the output shaft of the brushless DC motor, and the brushless DC motor drives the magnetic stirring rod immersed in the beaker to rotate through the magnetic attraction principle.

[0012] Further, the solution temperature measuring device comprises a first platinum resistance, a long pin hole and a wire, the first platinum resistance is put into the long pin hole, ceramic glue is added in the long pin hole for fixation, and the wire is connected with the intelligent control PCB fixed on the lower casing of the stirrer.

[0013] Further, the intelligent control PCB comprises a main control chip, a motor driving device, a temperature acquisition device, a heating resistance wire power adjusting device and a switching power supply.

[0014] Further, the solution temperature measuring device is fixed by a cross-shaped support composed of a support column and a transverse plastic clamping shell, the transverse plastic clamping shell is fixed on the support column by a screw, one side of the support column is provided with a screw thread, the rear side of the upper casing is provided with a screw hole matched with the screw thread of the side of the support column, the support column is fixed on the upper casing, and the transverse plastic clamping shell rotates left and right and moves up and down on the support column.

[0015] Further, the heating table temperature measuring device adopts a second platinum resistance, a stud is welded at the bottom of the heating table, the second platinum resistance is put into the stud hole corresponding to the stud, and the second platinum resistance is sealed with ceramic glue.

[0016] Further, the stirrer further comprises a heating device placed at the bottom of the heating table, the heating device comprises a heating resistance wire, a high-temperature mica sheet and a heat preservation and insulation device, the heating resistance wire is embedded in the high-temperature mica sheet, and the high-temperature mica sheet is fixed in the heat preservation and insulation device.

[0017] Further, the heating table is made of copper-aluminum alloy, the heating resistance wire is placed at the bottom of the heating table, the temperature of the heating table is controlled by controlling the power of the heating resistance wire, and the heating resistance wire is wound into a ring shape, so that the temperature distribution of the heating table is more uniform.

[0018] Further, the stirrer further comprises a man-machine interaction device, the man-machine interaction device is mainly completed through a touch screen, and the touch screen is provided with buttons of temperature setting, motor speed setting, timing time, real-time solution temperature, real-time speed and table temperature.

[0019] Further, the temperature control device adopts a fuzzy-serial PID controller, wherein:

[0020] The main ring adopts a fuzzy-PID controller, and the secondary ring adopts a PID controller; the temperature set by the man-machine interaction device is used as the input value of the main ring, the temperature of the solution in the beaker measured by the solution temperature measuring device is used as the feedback value of the main ring, the output value of the main ring fuzzy-PID controller is used as the input value of the secondary ring PID controller, the temperature of the heating platform measured by the heating platform temperature measuring device is used as the feedback value of the secondary ring, and finally the power of the heating resistance wire is controlled in real time to complete the processing of the preset temperature.

[0021] Compared with the prior art, the application has the following advantages and positive effects:

[0022] The heating magnetic stirrer can realize high-precision control of the temperature of the medium solution, has small overshoot and good stability, and is suitable for different medium solutions. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can also be obtained according to these drawings without creative labor for those skilled in the art. In the drawings:

[0024] Figure 1 is a side view of the heating magnetic stirrer of the application;

[0025] Figure 2 is an automatic control principle diagram of temperature control in the heating magnetic stirrer of the application;

[0026] Figure 3 is a main interface diagram of the man-machine interface of the heating magnetic stirrer of the application.

[0027]

MAIN SYMBOL DESCRIPTION

[0028] 1-lateral plastic card shell; 2-support column; 3-solution temperature measuring device; 4-conductor; 5-beaker; 6-solution; 7-magnetic stirring rod; 8-heating platform temperature measuring device; 9-magnet; 10-direct current brushless motor; 11-heating platform; 12-heating resistance wire; 13-stirring driving device; 14-upper machine shell; 15-switching power supply; 16-intelligent control PCB; 17-lower machine shell. DETAILED DESCRIPTION

[0029] The technical solutions of the present application will be described clearly and completely below in conjunction with the drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0030] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", "third" are only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0031] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be connected inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0032] As shown in Figures 1-3 The present embodiment discloses a heating magnetic stirrer, comprising a stirring driving device 13, a temperature measuring device and a temperature control device, wherein:

[0033] The stirring driving device 13 is used to mix the solution 6 in the beaker 5, so as to make the temperature distribution of the solution in the beaker 5 more uniform;

[0034] The temperature measuring device comprises a solution temperature measuring device 3 and a heating table temperature measuring device 8, the solution temperature measuring device 3 is used to measure the temperature of the solution in the beaker 5 and take it as the feedback quantity of the main ring; the heating table temperature measuring device 8 is used to measure the temperature of the heating table 11 and take it as the feedback quantity of the secondary ring;

[0035] The temperature control device adopts a fuzzy-serial PID control mode, which is used to accurately control the temperature of the solution in the beaker 5, so as to realize the temperature point of the solution 6 required by different experiments.

[0036] Further, the stirring driving device 13 comprises a direct-current brushless motor 10, a magnet 9 and a magnetic stirring rod 7, wherein:

[0037] The direct current brushless motor 10 is fixed on the bottom of the upper casing 14 of the stirrer by screws, and has three Hall elements arranged at 120° inside, for detecting the position of rotation of the direct current brushless motor 10.

[0038] The controller of the direct current brushless motor 10 adopts a PI controller, and the parameters of P and I should be smaller than the normal values. The purpose of this is: first, the motor slowly starts to operate and slowly approaches the target speed. Second, the overshoot is reduced and the oscillation time is shortened. Because the magnetic stirring rod 7 and the magnet 9 in the container are attracted by magnetic force, if the speed changes too much in a short time, it is easy to appear "jumping" (the magnetic stirring rod 7 cannot follow the rotation of the magnet 9, and the magnetic stirring rod 7 jumps up and down in the solution 6). In addition, although the control of the direct current brushless motor 10 is not very complex, some protection measures should be taken to prevent the direct current brushless motor 10 from stalling and causing accidents. For example, the current value of the direct current brushless motor 10 during operation can be collected, and when the direct current brushless motor 10 stalls, the motor output should be immediately cut off to protect the safety of the system.

[0039] The magnet 9 is fixed above the output shaft of the direct current brushless motor 10, for rotating the magnetic stirring rod 7 immersed in the beaker 5 by the principle of magnetic attraction. In this embodiment, it should be noted that the distance between the magnet 9 and the direct current brushless motor 10 should be greater than 5 cm, otherwise the magnetism of the magnet 9 will interfere with the Hall signal of the motor.

[0040] Further, the solution temperature measuring device 3 includes a first platinum resistance, a long needle hole, and a wire 4. The first platinum resistance is placed inside the long needle hole and is fixed by adding ceramic glue inside the long needle hole. At the same time, the wire 4 is connected with the intelligent control PCB board 16 fixed on the lower casing 17 of the stirrer. In this embodiment, the first platinum resistance adopts a PT1000 platinum thermal resistance.

[0041] Further, the intelligent control PCB board 16 includes a main control chip, a motor driving device, a temperature collecting device, a heating resistance wire power adjusting device, and a switching power supply 15. The main control chip adopts a TM32f103VET6 single-chip microcomputer as the main control chip of the stirrer. The chip has multiple IIC, SPI, serial port, advanced timer, and other peripherals integrated inside, which meets the requirements of this design. In this embodiment, all devices are placed on a PCB board, which reduces the wiring connection and saves space. However, it should be noted that the heating resistance wire 12 is controlled by alternating current, while other elements belong to direct current. In order to avoid electromagnetic interference, the alternating current part and the direct current part must be cut off.

[0042] With reference to the above description, it is understood that the above-mentioned embodiments are only used to illustrate the technical solutions of the present application, and are not used to limit the scope of the present application. Figure 1The solution temperature measuring device 3 is fixed by a cross support composed of a support column 2 and a transverse plastic clamping shell 1, the transverse plastic clamping shell 1 is fixed on the support column 2 by screws, one side of the support column 2 is provided with an M5 thread, the rear side of the upper machine shell 14 is provided with an M5 threaded hole matched with the thread of the one side of the support column 2, the support column 2 is fixed on the upper machine shell 14, and the transverse plastic clamping shell 1 rotates left and right and moves up and down on the support column 2.

[0043] Further, the heating table temperature measuring device 8 adopts a second platinum resistance, in order to make the measured temperature closer to the heating table 11, an M3 stud is welded at the bottom of the heating table 11, the second platinum resistance is placed in the corresponding stud hole of the stud, and is sealed by ceramic glue. In the embodiment, the second platinum resistance adopts a PT100 platinum thermal resistance.

[0044] Further, the stirrer further comprises a heating device placed at the bottom of the heating table 11, the heating device comprises a heating resistance wire 12, a high-temperature mica sheet and a heat preservation and insulation device, the heating resistance wire 12 is embedded in the high-temperature mica sheet, and the high-temperature mica sheet is fixed in the heat preservation and insulation device. In the embodiment, the power of the heating resistance wire 12 is 600W. In order to control the power of the heating resistance wire 12 to be controllable, the voltage value of the alternating current must be controlled, so as to control the power of the heating resistance wire 12. Here, the light coupling and bidirectional thyristor are adopted to realize the adjustment of the alternating voltage. The IO port output PWM (pulse width modulation) wave of the single-chip microcomputer controls the conduction and cut-off of the light coupling, and then the alternating voltage control is realized, and the power of the heating resistance wire 12 is controllable.

[0045] Preferably, the heating table 11 adopts a copper-aluminum alloy material with a high thermal conductivity. The heating resistance wire 12 is placed at the bottom of the heating table 11, the temperature of the heating table 11 is controlled by controlling the power of the heating resistance wire 12, and the heating resistance wire 12 is annular, so that the temperature distribution of the heating table 11 is more uniform.

[0046] As shown in Figure 3 , the stirrer further comprises a man-machine interaction device, which is mainly completed through a touch screen. The user can know the real-time temperature and real-time rotating speed of the system through the touch screen. Similarly, the user can set the target solution temperature value, motor rotating speed value and heating mode selection (the heating mode is divided into rapid heating and accurate temperature control) through the touch screen.

[0047] Further, in order to improve the temperature control precision of the system and reduce the overshoot, the temperature control device adopts a fuzzy-serial PID controller, wherein:

[0048] The main ring as the main loop of the system control belongs to a customized control system, and adopts a fuzzy-PID controller. Figure 2 The temperature set by the user through the man-machine interaction device is used as the input value of the main ring, the temperature of the solution 6 in the beaker 5 measured by the solution temperature measuring device 3 is used as the feedback value of the main ring, and the difference between the feedback value and the input value of the solution temperature is used as the error of the closed loop. Since the system requires a small overshoot (exceeding the set value will affect the activity of the microorganisms in the container), the main ring adopts a fuzzy-PID controller, which reduces the overshoot of the system and has higher stability compared with the ordinary PID controller. For the cascade control system, the introduction of the secondary ring is to reduce the overshoot of the system and increase the stability of the system, so the control accuracy of the secondary ring is not as high as that of the main ring. The output value of the main ring fuzzy-PID controller is used as the input value of the secondary ring PID controller, and the heating table temperature measured by the heating table temperature measuring device 8 is used as the feedback value of the secondary ring. Finally, the power of the heating resistance wire 12 is controlled in real time to complete the processing of the preset temperature.

[0049] Specifically, the user sets the target temperature value through the touch screen as the input value of the main ring, and the controller converts the actual temperature value of the solution 6 in the beaker 5 from the voltage value between the two ends of the PT1000 platinum thermal resistance in the solution 6. The difference between the temperature value and the temperature value set by the user is used as the error value of the main ring. The percentage of the output value of the main ring is used as the input value of the secondary ring PID controller, and the feedback value of the secondary ring is the table temperature value, which is measured by the PT100 platinum thermal resistance temperature sensor at the bottom of the table. The power of the heating resistance wire 12 is changed through the output value of the secondary ring, so as to achieve the purpose of controlling the table temperature.

[0050] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any changes or replacements within the technical range disclosed by the present application can be easily thought by those skilled in the art, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A heated magnetic stirrer characterized by, The device comprises a stirring driving device, a temperature measuring device, a temperature control device and a man-machine interaction device, wherein: The stirring driving device is used for mixing the solution in the beaker to make the temperature distribution of the solution in the beaker more uniform. The temperature measuring device comprises a solution temperature measuring device and a heating table temperature measuring device, the solution temperature measuring device is used for measuring the temperature of the solution in the beaker and taking it as the feedback value of the main loop, and the heating table temperature measuring device is used for measuring the temperature of the heating table and taking it as the feedback value of the secondary loop. The temperature control device adopts a fuzzy-serial PID control mode and is used for precisely controlling the temperature of the solution in the beaker. The man-machine interaction device is mainly completed through a touch screen, and the touch screen is provided with buttons of temperature setting, motor speed setting, timing time, real-time solution temperature, real-time speed and table temperature. The temperature control device adopts a fuzzy-serial PID controller, wherein: The main loop adopts a fuzzy-PID controller, and the secondary loop adopts a PID controller; the temperature set by the user through the man-machine interaction device is taken as the input value of the main loop, the temperature of the solution in the beaker measured by the solution temperature measuring device is taken as the feedback value of the main loop, the output value of the main loop fuzzy-PID controller is taken as the input value of the secondary loop PID controller, and the temperature of the heating table measured by the heating table temperature measuring device is taken as the feedback value of the secondary loop, so that the power of the heating resistance wire is finally controlled in real time to complete the processing of the preset temperature.

2. A heating magnetic stirrer according to claim 1, characterized in that The stirring driving device comprises a DC brushless motor, a magnet and a magnetic stirring rod, wherein: The DC brushless motor is fixed to the bottom of the upper casing of the stirrer by screws, and three Hall elements arranged at an angle of 120° are arranged in the DC brushless motor for detecting the position of the rotation of the DC brushless motor; The magnet is fixed above the output shaft of the DC brushless motor, and is used for rotating the magnetic stirring rod immersed in the beaker by the magnetic attraction principle.

3. A heating magnetic stirrer according to claim 1, characterized in that The solution temperature measuring device comprises a first platinum resistance, a long needle hole and a wire, the first platinum resistance is put into the long needle hole, ceramic glue is added in the long needle hole for fixation, and the wire is connected with the intelligent control PCB board fixed on the lower casing of the stirrer.

4. A heating magnetic stirrer according to claim 3, characterized in that The intelligent control PCB board comprises a master control chip, a motor driving device, a temperature collecting device, a heating resistance wire power adjusting device and a switching power supply.

5. A heating magnetic stirrer according to claim 1, wherein The solution temperature measuring device is fixed by a cross-shaped support composed of a support column and a horizontal plastic clamping shell, the horizontal plastic clamping shell is fixed on the support column by screws, one side of the support column is provided with a screw thread, the rear side of the upper casing is provided with a screw hole matched with the screw thread of the side of the support column, the support column is fixed on the upper casing, and the horizontal plastic clamping shell rotates left and right and moves up and down on the support column.

6. A heating magnetic stirrer according to claim 1, wherein The heating table temperature measuring device adopts a second platinum resistance, a stud is welded at the bottom of the heating table, the second platinum resistance is put into the stud hole corresponding to the stud, and the second platinum resistance is sealed with ceramic glue.

7. A heating magnetic stirrer according to claim 6, characterized in that The stirrer further comprises a heating device placed at the bottom of the heating table, the heating device comprising a heating resistance wire, a high-temperature mica sheet and a heat preservation and insulation device, the heating resistance wire being embedded in the high-temperature mica sheet, and the high-temperature mica sheet being fixed in the heat preservation and insulation device.

8. A heating magnetic stirrer according to claim 7, characterized in that The heating table is made of copper-aluminum alloy material, the heating resistance wire is placed at the bottom of the heating table, the temperature of the heating table is controlled by controlling the power of the heating resistance wire, and the heating resistance wire is wound into a ring shape, so that the temperature distribution of the heating table is more uniform.

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