Liquid level control system

Abstract

This invention relates to a liquid level control system, comprising a controller, a first processing unit, a first probe, at least one second probe, and at least one second processing unit. The controller has one output terminal and at least one input terminal. The second probe, the second processing unit, and the input terminal of the controller correspond one-to-one. The output terminal of the controller is connected to the input terminal of the first processing unit, and the output terminal of the first processing unit is connected to the first probe. The first and second probes are disposed within a liquid storage device, with the first probe positioned lower than the second probe. Each second probe is at a different height within the liquid storage device. Each second probe is connected to the input terminal of a corresponding second processing unit, and the output terminal of the second processing unit is connected to the corresponding input terminal of the controller. The controller generates a control signal, which is an AC signal with a frequency of 2-20Hz.

Description

Technical Field

[0001] This invention relates to the field of industrial automation control, and more specifically to a liquid level control system. Background Technology

[0002] In industrial production, water supply and drainage, and liquid storage equipment, liquid level control is a crucial aspect. Existing liquid level control systems typically employ a dual-probe level detection structure, placing two probes at the high and low liquid level positions of the storage device. The controller's output is electrically connected to one probe, and its input is electrically connected to the other. When the liquid level rises to the high-level probe, the liquid's conductivity allows the two probes to connect through the liquid, forming a conductive loop between the controller's input and output. Upon receiving the liquid level detection signal, the controller activates actuators such as pumps to draw out liquid, causing the liquid level to drop, thus achieving automatic liquid level control.

[0003] However, the aforementioned traditional liquid level control system has significant drawbacks in practical applications: when the installation distance between the controller and the liquid storage device is long, a long cable is required to connect the controller and the probe. The cable itself has impedance, which causes control signal attenuation, reduces signal transmission accuracy, and can even lead to problems such as the controller failing to accurately identify the liquid level signal or control malfunction. Therefore, the traditional dual-probe liquid level control system is only suitable for scenarios where the controller and the liquid storage device are close together, and it cannot meet the needs of long-distance liquid level control, greatly limiting its application scope. Summary of the Invention

[0004] The purpose of this invention is to provide a liquid level control system to achieve remote liquid level control.

[0005] To achieve the above objectives, the present invention provides a liquid level control system, comprising a controller, a first processing unit, a first probe, at least one second probe, and at least one second processing unit. The controller has an output terminal and at least one input terminal. The second probe, the second processing unit, and the input terminal of the controller correspond one-to-one. The output terminal of the controller is connected to the input terminal of the first processing unit, and the output terminal of the first processing unit is connected to the first probe. The first probe and the second probe are disposed within a liquid storage device. The position of the first probe is lower than that of the second probe. Each second probe is at a different height within the liquid storage device. Each second probe is connected to the input terminal of a corresponding second processing unit, and the output terminal of the second processing unit is connected to the corresponding input terminal of the controller.

[0006] The controller generates a control signal, which is an AC signal with a frequency of 2-20Hz. The first processing unit processes the control signal for the first time and transmits the processed control signal to the first probe. Each second probe is configured to electrically connect to the first probe via liquid when the liquid level in the liquid storage device rises to contact the second probe. After the second probe is electrically connected to the first probe, the processed control signal is transmitted to the corresponding second processing unit via the second probe. The second processing unit processes the processed control signal for the second time and transmits the processed control signal back to the corresponding input terminal of the controller. The controller is configured to determine the liquid level status based on the signal information received at each input terminal.

[0007] Optionally, the controller is connected to the pump, and the controller is further configured to control the pump according to the liquid level state, so that the pump pumps liquid out of the liquid storage device or pumps liquid into the liquid storage device from the outside.

[0008] Optionally, the first processing unit is connected to the first probe via a cable.

[0009] Optionally, the first processing unit includes a power amplifier, a first capacitor, and a current limiting module. The input terminal of the power amplifier is connected to the output terminal of the controller, the power supply terminal of the power amplifier is connected to a power source, the output terminal of the power amplifier is connected to the first terminal of the first capacitor, the second terminal of the first capacitor is connected to the first terminal of the current limiting module, and the second terminal of the current limiting module is connected to the first probe.

[0010] Optionally, the current limiting module is formed by multiple resistors connected in parallel.

[0011] Optionally, the first processing unit further includes a first TVS diode, a second TVS diode, a third TVS diode, and a fourth TVS diode. One end of the first TVS diode and one end of the second TVS diode are both connected to the power supply. The other ends of the first TVS diode and one end of the third TVS diode are both connected to the output terminal of the power amplifier. The other ends of the second TVS diode and the third TVS diode are both grounded. One end of the fourth TVS diode is connected to the second terminal of the current limiting module, and the other end of the fourth TVS diode is grounded.

[0012] Optionally, the first processing unit further includes a self-resetting fuse, which is disposed between the first capacitor and the current limiting module.

[0013] Optionally, the power amplifier is an audio amplifier chip.

[0014] Optionally, each of the second processing circuits includes a fifth resistor, a sixth resistor, a seventh resistor, a diode, a light-emitting diode, and a second capacitor. One end of the sixth resistor is connected to the second probe, and the other end of the sixth resistor is connected to the anode of the diode and the cathode of the light-emitting diode, respectively. One end of the fifth resistor, one end of the second capacitor, one end of the seventh resistor, and the anode of the diode are interconnected. The other ends of the second capacitor, the other end of the seventh resistor, and the anode of the light-emitting diode are all grounded. The other end of the fifth resistor is connected to the corresponding input terminal of the controller.

[0015] Optionally, the controller is a microcontroller unit. Attached Figure Description

[0016] Figure 1 This is a structural block diagram of a liquid level control system according to an embodiment of the present invention;

[0017] Figure 2 This is a schematic diagram of the connection circuit of the liquid level control system according to an embodiment of the present invention. Detailed Implementation

[0018] The preferred embodiments of the present invention are given below with reference to the accompanying drawings and described in detail.

[0019] In existing industrial liquid level control systems, to prevent polarization and scaling of the liquid level probe due to DC electrolysis, a 50Hz AC signal supplied by the secondary winding of the control motherboard transformer is typically used to drive the probe. However, when transmitting this 50Hz AC signal over long distances, the distributed capacitance of the transmission cable can cause short circuits, leading to significant signal energy attenuation and even the generation of contaminated signals. This makes it difficult to meet the needs of long-distance liquid level control scenarios such as large storage tanks and deep wells. Furthermore, long-distance external signal lines are susceptible to induced lightning strikes, threatening equipment safety, and current technology lacks effective protective measures against this.

[0020] like Figure 1As shown, this embodiment of the invention provides a liquid level control system, which includes a controller 100, a first processing unit 200, a first probe 300, at least one second probe 400, and at least one second processing unit 600. The controller 100 has one output terminal and at least one input terminal. The second probe 400, the second processing unit 600, and the input terminal of the controller 100 correspond one-to-one. The output terminal of the controller 100 is connected to the input terminal of the first processing unit 200, and the output terminal of the first processing unit 200 is connected to the first probe 300. The first probe 300 and the second probe 400... The first probe 300 is positioned higher than the second probe 400 within the liquid storage device 500. When there are multiple second probes 400, each probe 400 is positioned at a different height within the liquid storage device 500. Each second probe 400 is connected to the input terminal of a corresponding second processing unit 600, and the output terminal of the second processing unit 600 is connected to the corresponding input terminal of the controller 100. The controller 100 generates a control signal, which is an AC signal with a frequency of 2-20Hz. The first processing unit 200 performs initial processing on the control signal and outputs the signal to the second processing unit 200. The control signal after the first processing is transmitted to the first probe 300. When the liquid level in the liquid storage device 500 rises to contact any of the second probes 400, the liquid will inevitably submerge the first probe 300. The first probe 300 will then be electrically connected to the second probe 400 through the liquid. The control signal after the first processing will be transmitted from the first probe 300 to the second probe 400, and then from the second probe 400 to the corresponding second processing unit 600. The control signal after the first processing is processed a second time, and the second processed control signal is fed back to the corresponding input terminal of the controller 100. When the liquid level in the liquid storage device 500 drops to the point where it is no longer in contact with the second probe 400, the first probe 300 and the second probe 400 are no longer electrically connected. At this time, the control signal after the first processing will not be transmitted to the corresponding second processing unit 600, and the corresponding input terminal of the controller 100 will not receive the control signal after the second processing. Therefore, the controller 100 can determine the liquid level status based on whether its input terminal receives the feedback signal. For example, suppose there are N second probes 400, numbered from 1 to N from low to high, corresponding to the N input terminals of the controller 100. When the i-th input terminal receives a return signal, but the (i+1)-th input terminal does not receive a return signal, it means that the liquid level is between the height of the i-th second probe 400 and the height of the (i+1)-th second probe 400. When none of the input terminals receive a return signal, it means that the liquid level is lower than the height of the lowest second probe 400. When all input terminals receive a return signal, it means that the liquid level is higher than the height of the highest second probe 400.

[0021] In some embodiments, the controller 100 may be connected to a pump used to pump liquid out of the liquid storage device 500 or pump liquid into the liquid storage device 500 from the outside. The controller 100 is configured to control the pump according to the liquid level status to achieve liquid level control of the liquid storage device 500. For example, when the controller 100 determines that the liquid level has reached a preset position, it may control the pump to pump liquid out of the liquid storage device 500 so that the liquid level in the liquid storage device 500 does not exceed the preset position; or, when the controller 100 determines that the liquid level is lower than the preset position, it may control the pump to pump liquid into the liquid storage device 500 from the outside so that the liquid level in the liquid storage device 500 does not fall below the preset position. It is understood that the above are only some exemplary descriptions of liquid level control, and in practical applications, any suitable control can be performed as needed.

[0022] The number and height of the second probes 400 can be set as needed. Each second probe 400 is used to indicate a liquid level height so that the controller 100 can determine the approximate height of the liquid level based on the backflow signal.

[0023] Understandably, although Figure 1 Only one second probe 400 and second processing unit 600 are shown in the diagram. However, in the actual circuit, the second probe 400 and the second processing unit 600 can be added as needed. The structure of each second probe 400 and the second processing unit 600 is the same, except that the height of the second probe 400 is different.

[0024] The first processing unit 200 can be connected to the first probe 300 via a cable 700 to achieve long-distance signal transmission; for example, the length of the cable 700 can reach 2000 meters. According to the capacitive reactance formula Xc=1 / (2πfC), the lower the signal frequency f, the higher the capacitive reactance Xc of the cable, thus reducing signal attenuation during long-distance transmission and enabling long-distance signal transmission. This allows the liquid level control system to achieve long-distance liquid level control.

[0025] like Figure 2As shown, the first processing unit 200 includes a power amplifier 210, a first capacitor C1, and a current limiting module. The current limiting module includes four resistors connected in parallel: a first resistor R1, a second resistor R2, a third resistor R3, and a fourth resistor R4. The output terminal of the controller 110 is connected to the input terminal of the power amplifier 210. The power supply terminal of the power amplifier 210 is connected to the power supply VCC. The output terminal of the power amplifier 210 is connected to the first terminal of the first capacitor C1. The second terminal of the first capacitor C1 is connected to the first terminal of the current limiting module. The second terminal of the current limiting module is connected to the first probe 300 via a cable 700. The power amplifier 210 amplifies the control signal, and the first capacitor C1 isolates the DC component in the amplified control signal, allowing only AC signals to pass through. After passing through the current limiting module, the amplified control signal is transmitted to the first probe 300 via the cable 700.

[0026] It is understood that although the above description uses a current-limiting module comprising four resistors as an example, in other embodiments, the number of resistors can be set as needed, for example, it can be two, three or more, and this invention does not limit this. The current-limiting module is formed by multiple resistors connected in parallel, which not only serves the purpose of current limiting, but also constitutes an "N+1" redundant backup system. Even if multiple resistors are damaged and open-circuited due to lightning strikes, the remaining resistor can still ensure the normal operation of the basic circuit functions, ensuring the continuous and stable operation of the system.

[0027] The first processing unit 200 may further include a first TVS (transient voltage suppressor) diode D1, a second TVS diode D2, a third TVS diode D3, and a fourth TVS diode D4. One end of the first TVS diode D1 and one end of the second TVS diode D2 are both connected to the power supply VCC. The other end of the first TVS diode D1 and one end of the third TVS diode D3 are both connected to the output terminal of the power amplifier 210. The other ends of the second TVS diode D2 and the third TVS diode D3 are both grounded. One end of the fourth TVS diode D4 is connected to the second terminal of the current limiting module, and the other end of the fourth TVS diode D4 is grounded. The first TVS diode D1, the second TVS diode D2, and the third TVS diode D3 are used to clamp positive and negative transient overvoltages at the output terminal of the power amplifier 210; the fourth TVS diode D4 is used to clamp negative transient voltages. The first to fourth TVS diodes D1-D4 are all bidirectional TVS transient absorption diodes.

[0028] The first processing unit 200 may also include a self-resetting fuse F1, which is disposed between the first capacitor C1 and the current limiting module, for automatically cutting off the current when the circuit is overcurrent or short-circuited, and automatically restoring conduction after the fault is cleared.

[0029] For example, such as Figure 2As shown, the power amplifier 210 can be an existing low-power audio amplifier chip (such as HP511K chip, LM386 chip, etc.), where port 2 is its input terminal, connected to the output terminal of controller 100, ports 1 and 8 are power supply terminals, connected to power supply VCC, port 7 is the output terminal, ports 3, 4 and 6 are ground terminals, used for grounding; port 5 is an unused pin.

[0030] The controller 100 can be an MCU (microcontroller unit). The control signal can be a sine wave signal, a square wave signal, or any other suitable waveform signal, preferably a square wave signal.

[0031] The second processing circuit 600 may include a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, a diode D5, a light-emitting diode D6, and a second capacitor C2. One end of the sixth resistor R6 is connected to the second probe 400, and the other end of the sixth resistor R6 is connected to the anode of diode D5 and the cathode of light-emitting diode D6, respectively. One end of the fifth resistor R5, one end of the second capacitor C2, one end of the seventh resistor R7, and the anode of diode D5 are interconnected. The other ends of the second capacitor C2, the other end of the seventh resistor R7, and the anode of light-emitting diode D6 are all grounded. The other end of the fifth resistor R5 is connected to the corresponding input terminal of the controller 100. When the first probe 300 and the second probe 400 are electrically connected to each other through a liquid, the AC control signal will pass through the second processing circuit 600 and flow back to the controller 100. After the initial processing, the control signal is current-limited by the sixth resistor R6. During the positive half-cycle of the signal, it is rectified by diode D5, filtered by the second capacitor C2, and discharged and clamped by the seventh resistor R7. The rectified DC signal is then current-limited by the fifth resistor R5 and connected to the input terminal of controller 100. If the signal is in the negative half-cycle, LED D6 is illuminated. LED D6 serves not only as a signal indicator but also as a discharge capacitor for C1. LED D6 indicates whether the corresponding second probe 400 is connected to the first probe 300, thus determining the liquid level.

[0032] The liquid level control system of this invention utilizes the controller 100 to generate a 2-20Hz low-frequency AC signal, which significantly increases the capacitive reactance of the cable and effectively overcomes the adverse effects of cable distributed capacitance on signal transmission, thereby significantly improving the transmission distance of the control signal. The power amplifier 210 can use existing low-power audio amplifier chips, which are general-purpose components, inexpensive, easy to procure and replace, reducing the system cost. The first processing circuit 200 also includes four TVS diodes, which can clamp the voltage within a safe range when transient high voltages are generated in the cable due to lightning strikes or other induction, forming multi-level protection to ensure that the power amplifier 210 and other devices are not damaged. The light-emitting diode D6 not only provides intuitive status indication but also participates in the signal rectification process, simplifying circuit design. The liquid level control system of this invention integrates multiple functions such as long-distance transmission, lightning protection, and status indication, and has significant technological advancements and practical value.

[0033] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Various variations can be made to the above embodiments of the present invention. That is, all simple and equivalent changes and modifications made based on the claims and description of this invention fall within the protection scope of the claims of this patent. All aspects not described in detail in this invention are conventional technical content.

Claims

1. A liquid level control system, characterized in that, The device includes a controller, a first processing unit, a first probe, at least one second probe, and at least one second processing unit. The controller has one output terminal and at least one input terminal. The second probe, the second processing unit, and the input terminal of the controller are in one-to-one correspondence. The output terminal of the controller is connected to the input terminal of the first processing unit, and the output terminal of the first processing unit is connected to the first probe. The first probe and the second probe are disposed inside a liquid storage device. The position of the first probe is lower than that of the second probe. The height of each second probe inside the liquid storage device is different. Each second probe is connected to the input terminal of the corresponding second processing unit, and the output terminal of the second processing unit is connected to the corresponding input terminal of the controller. The controller generates a control signal, which is an AC signal with a frequency of 2-20Hz. The first processing unit processes the control signal for the first time and transmits the processed control signal to the first probe. Each second probe is configured to electrically connect to the first probe via liquid when the liquid level in the liquid storage device rises to contact the second probe. After the second probe is electrically connected to the first probe, the processed control signal is transmitted to the corresponding second processing unit via the second probe. The second processing unit processes the processed control signal for the second time and transmits the processed control signal back to the corresponding input terminal of the controller. The controller is configured to determine the liquid level status based on the signal information received at each input terminal.

2. The liquid level control system according to claim 1, characterized in that, The controller is connected to the pump and is also configured to control the pump according to the liquid level state so that the pump pumps liquid out of the liquid storage device or pumps liquid into the liquid storage device from the outside.

3. The liquid level control system according to claim 1, characterized in that, The first processing unit is connected to the first probe via a cable.

4. The liquid level control system according to claim 1, characterized in that, The first processing unit includes a power amplifier, a first capacitor, and a current limiting module. The input terminal of the power amplifier is connected to the output terminal of the controller, the power supply terminal of the power amplifier is connected to a power source, the output terminal of the power amplifier is connected to the first terminal of the first capacitor, the second terminal of the first capacitor is connected to the first terminal of the current limiting module, and the second terminal of the current limiting module is connected to the first probe.

5. The liquid level control system according to claim 4, characterized in that, The current limiting module is formed by multiple resistors connected in parallel.

6. The liquid level control system according to claim 4, characterized in that, The first processing unit further includes a first TVS diode, a second TVS diode, a third TVS diode, and a fourth TVS diode. One end of the first TVS diode and one end of the second TVS diode are both connected to the power supply. The other ends of the first TVS diode and one end of the third TVS diode are both connected to the output terminal of the power amplifier. The other ends of the second TVS diode and the third TVS diode are both grounded. One end of the fourth TVS diode is connected to the second terminal of the current limiting module, and the other end of the fourth TVS diode is grounded.

7. The liquid level control system according to claim 4, characterized in that, The first processing unit further includes a self-resetting fuse, which is disposed between the first capacitor and the current limiting module.

8. The liquid level control system according to claim 4, characterized in that, The power amplifier is an audio amplifier chip.

9. The liquid level control system according to claim 1, characterized in that, Each of the second processing circuits includes a fifth resistor, a sixth resistor, a seventh resistor, a diode, a light-emitting diode, and a second capacitor. One end of the sixth resistor is connected to the second probe, and the other end of the sixth resistor is connected to the anode of the diode and the cathode of the light-emitting diode, respectively. One end of the fifth resistor, one end of the second capacitor, one end of the seventh resistor, and the anode of the diode are interconnected. The other ends of the second capacitor, the other end of the seventh resistor, and the anode of the light-emitting diode are all grounded. The other end of the fifth resistor is connected to the corresponding input terminal of the controller.

10. The liquid level control system according to claim 1, characterized in that, The controller is a microcontroller unit.

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