Liquid level sensor

Abstract

To solve such a problem that an installation location of a liquid level sensor is limited when an external power source is required.SOLUTION: A liquid level sensor includes: a float device floating on a surface of liquid; an operator moving according to a positional change of the float device in association with a level change of the liquid surface; and a circuit formed to output a first signal related to the level of the liquid surface on the basis of the movement of the operator. The float device includes a microbial fuel cell for generating power by microbes contained in the liquid. The circuit operates by receiving power supply from the microbial fuel cell.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a liquid level sensor. [Background technology]

[0002] Patent Document 1 discloses a water level meter that detects the up and down movement of a float on the water surface as a change in magnetism. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Utility Model Application Publication No. 4-24028 Summary of the Invention

[0004] The water level meter in Patent Document 1 includes a circuit that converts magnetic changes into electric current. To operate the circuit that converts magnetic changes into electric current, an external power supply is required. The need for an external power supply can result in restrictions on the installation location, etc. A solution to this problem is desired.

[0005] One aspect of the present disclosure is a liquid level sensor comprising: a float device that floats on the surface of a liquid; an actuator that operates in response to displacement of the float device due to changes in the liquid level; and a circuit configured to output a first signal related to the liquid level based on the operation of the actuator, wherein the float device comprises a microbial fuel cell that generates electricity using microorganisms contained in the liquid, and the circuit operates by receiving power from the microbial fuel cell.

[0006] Further details will be described in the following embodiments. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing the configuration of a liquid level sensor. [Figure 2] FIG. 2 is a diagram showing the movement of the actuator in response to changes in the liquid level. [Figure 3] FIG. 3 is a graph showing the change in water level and contact voltage over time. [Figure 4] FIG. 4 is a graph showing the change in water level and contact voltage over time. [Figure 5] FIG. 5 is a diagram illustrating an example of a detection circuit. [Figure 6] FIG. 6 is a diagram illustrating an example of a detection circuit. [Figure 7] FIG. 7 is a diagram showing the configuration of a liquid level sensor. [Figure 8] FIG. 8 is a diagram showing the configuration of the float device. [Figure 9] FIG. 9 is a diagram showing an example of installation of a liquid level sensor. [Figure 10] FIG. 10 is a diagram showing an example of installation of a liquid level sensor. [Figure 11] FIG. 11 is a diagram showing a modified example of the liquid level sensor. [Figure 12] FIG. 12 is a diagram showing a modified example of the liquid level sensor. [Figure 13] FIG. 13 is a diagram showing a modified example of the liquid level sensor. DETAILED DESCRIPTION OF THE INVENTION

[0008] <1. Liquid level sensor overview>

[0009] (1) A liquid level sensor according to an embodiment may include a float device that floats on the surface of the liquid, an actuator that operates in response to displacement of the float device due to changes in the liquid level, and a circuit configured to output a first signal related to the liquid level based on the operation of the actuator. The float device may include a microbial fuel cell that generates electricity using microorganisms contained in the liquid. The circuit may operate by receiving power from the microbial fuel cell. Because the circuit can receive power from the microbial fuel cell, it can operate without an external power source.

[0010] (2) The actuator may be a conductive actuator electrically connected to the microbial fuel cell, and the circuit may be configured to receive power from the microbial fuel cell via the actuator.

[0011] (3) The circuit may be configured to include a contactor that contacts the actuator and to receive power from the microbial fuel cell via the actuator and the contactor.

[0012] (4) The actuator may be a conductive actuator electrically connected to the microbial fuel cell. The circuit may include a plurality of contacts in contact with the actuator. The plurality of contacts may be arranged along the direction of movement of the actuator. The circuit may be configured to receive power from the microbial fuel cell via the actuator and the contact with which the actuator is in contact, regardless of which of the plurality of contacts the actuator is in contact with.

[0013] (5) The actuator may be a conductive actuator electrically connected to the microbial fuel cell, and the circuit may include a plurality of contacts that contact the actuator and a plurality of partial circuits connected to correspond to the plurality of contacts. The plurality of contacts may be arranged along the direction of movement of the actuator. When the actuator comes into contact with a corresponding one of the plurality of contacts, at least one partial circuit of the plurality of partial circuits receives power supply from the microbial fuel cell and operates, and may detect that the actuator is located at the corresponding one of the plurality of contacts.

[0014] (6) The circuit may be configured to further output a second signal relating to the state of the liquid based on the electromotive force or current generated by the microbial fuel cell.

[0015] (7) The microbial fuel cell may further include a conductor that electrically connects the microbial fuel cell and the actuator. The conductor may be guided from the microbial fuel cell to the actuator via a pulley.

[0016] <2. Example of a liquid level sensor>

[0017] Hereinafter, an embodiment of the present invention will be described in more detail with reference to the drawings. FIG. 1 shows an example of a liquid level sensor 100 according to an embodiment. The liquid level sensor 100 is used to detect a liquid level LS of a liquid LB, such as wastewater stored in a drainage tank 300 or the like. Note that, hereinafter, the "liquid level LS" may be referred to as the "water level LS." However, the liquid LB is not limited to water.

[0018] The drainage tank 300 may be provided with an inlet pipe 301 and an outlet pipe 302 for drainage. The drainage water flows into the drainage tank 300 from the inlet pipe 301. In the drainage tank 300, the drainage water is subjected to appropriate treatment, such as purification, as necessary. The treated drainage water is discharged from the drainage tank through the outlet pipe 302. The inflow and outflow of the drainage water is appropriately controlled by opening and closing a valve 310 (see FIG. 5) provided in the inlet pipe 301 and a valve 320 (see FIG. 5) provided in the outlet pipe 302. For example, when the liquid level LS in the drainage tank 300 becomes high, the valve 320 provided in the outlet pipe 302 is opened to allow the drainage water to flow out, thereby lowering the liquid level LS.

[0019] A liquid level sensor 100 according to an embodiment can be used to monitor a liquid level LS. The liquid level sensor 100 includes a float device 200 that floats on the liquid LB. The float device 200 floats on the liquid level LS of the liquid LB and displaces up and down as the liquid level LS changes.

[0020] The float device 200 is equipped with a microbial fuel cell. The microbial fuel cell generates electricity using microorganisms contained in the liquid LB. The float device functions as a microbial fuel cell and can float in the liquid LB, so it can be called a floating microbial fuel cell.

[0021] The microbial fuel cell included in the float device 200 includes an anode 30A and a cathode 30B. The float device 200 also includes a float 250 for providing buoyancy to the microbial fuel cell composed of the anode 30A and the cathode 30B. The float 250 floats the microbial fuel cell so that, for example, a portion (e.g., the upper surface) of the cathode 30B comes into contact with the air above the liquid LB, and the cathode 30B comes into contact with the liquid LB. Therefore, the cathode 30B functions as an air cathode that utilizes oxygen in the air.

[0022] The microorganisms in the liquid LB decompose the organic matter contained in the liquid LB. Electrons e- generated when the organic matter is decomposed by the microorganisms are collected by the anode 30A. The collected electrons e- move from the anode 30A to the cathode 30B via the conductors 131 and 132. Protons (H+) are generated at the anode 30A. The protons move to the cathode 30B side in the liquid and react with the electrons e- that moved from the anode 30A to the cathode 30B and oxygen in the air to produce water.

[0023] A current flows from the cathode 30B to the anode 30A in the opposite direction to the movement of the electrons e-. The electrical energy generated by the microbial fuel cell can be used to operate the circuit 140.

[0024] The liquid level sensor 100 according to the embodiment detects the liquid level LS by detecting the displacement of the float device 200 that accompanies changes in the liquid level LS. To detect the displacement of the float device 200, the liquid level sensor 100 is provided with an actuator 120 that operates in response to the displacement of the float device 200. The actuator 120 moves, for example, in response to the displacement of the float device 200. One example of the actuator 120 is a wheel. The actuator 120 may be disposed outside the tank 300 as shown in FIG. 1 , or may be disposed inside the tank 300.

[0025] The liquid level sensor 100 includes a circuit 140 that detects the operation of the operating element 120. Hereinafter, the "circuit 140" may be referred to as the "detection circuit 140." The circuit 140 operates by receiving power from the microbial fuel cell provided in the float device 200. Therefore, the circuit 140 can detect the operation of the operating element 120 without receiving power from any source other than the microbial fuel cell. As an example, the circuit 140 detects the position of the operating element 120.

[0026] The circuit 140 is connected to the microbial fuel cell via conductors 131 and 132 so as to receive an electrode supply from the microbial fuel cell. In an embodiment, power is supplied from the microbial fuel cell to the circuit 140 via a conductive actuator 120 connected to the conductor 132. The conductor 132 is connected to, for example, the cathode 30B. The actuator 120 may be connected to the conductor 131 connected to the anode 30A. The conductors 131 and 132 extending from the microbial fuel cell are guided to the outside of the wastewater tank 300 via, for example, pulleys 151 and 152, and one of the conductors is connected to the actuator 120 provided in the wastewater tank 300.

[0027] To obtain power from the operating element 120, the circuit 140 includes one or more contacts 141A, 142A, 143A, and 144A. In Fig. 1, four contacts 141A, 142A, 143A, and 144A are provided. The contacts are conductive.

[0028] The multiple contacts 141A, 142A, 143A, and 144A are arranged along the movement direction of the operator 120. Here, the operator 120 descends when the float device 200 ascends, and ascends when the float device 200 descends. That is, the operator 120 moves up and down, for example. Therefore, the multiple contacts 141A, 142A, 143A, and 144A shown in FIG. 1 are arranged along the up-and-down direction, which is the movement direction of the operator 120, for example.

[0029] The operating element 120 may be provided so as to move horizontally in accordance with the up and down movement of the float device 200. In this case, the multiple contacts may be arranged along the horizontal direction.

[0030] Each of the plurality of contacts 141A, 142A, 143A, and 144A has a predetermined length in the direction in which the operating element 120 moves, for example.

[0031] As an example, the operating element 120 is a conductive wheel that rolls and makes contact with the multiple contacts 141A, 142A, 143A, and 144A. Each of the multiple contacts 141A, 142A, 143A, and 144A can be configured as a rail having a predetermined length in the direction of movement of the wheel, which is the operating element 120. When the float device 200 moves up and down, the wheel, which is the operating element 120, comes into contact with the multiple contacts 141A, 142A, 143A, and 144A and moves while rolling. Electrical energy generated by the microbial fuel cell is provided from the operating element 120 to the contacts.

[0032] Even if the actuator 120 moves, the actuator 120 may come into contact with any of the plurality of contacts 141A, 142A, 143A, and 144A. Therefore, even if the actuator 120 moves, the circuit 140 can obtain power from the contact with which the actuator 120 is in contact. In other words, regardless of which of the plurality of contacts the actuator 120 is in contact with, the circuit 140 can receive power from the microbial fuel cell via the actuator 120 and the contact with which the actuator 120 is in contact.

[0033] As an example, the circuit 140 may include a plurality of partial circuits 141, 142, 143, and 144 connected to correspond to the plurality of contacts 141A, 142A, 143A, and 144A, respectively. For example, the circuit 140 may include a first partial circuit 141 connected to correspond to the first contact 141A, a second partial circuit 142 connected to correspond to the second contact 142A, a third partial circuit 143 connected to correspond to the third contact 143A, and a fourth partial circuit 144 connected to correspond to the fourth contact 144A.

[0034] Each of the plurality of partial circuits 141, 142, 143, and 144 can receive power from the microbial fuel cell and operate when the corresponding contact is brought into contact with the operating element 120. For example, as shown in Fig. 1, when the operating element 120 comes into contact with the first contact 141A, the first partial circuit 141 can receive power from the microbial fuel cell and operate.

[0035] Each of the plurality of partial circuits 141, 142, 143, 144 receives power supply from the microbial fuel cell and operates, thereby being able to detect that the operating element 120 is located at the contact corresponding to each partial circuit.

[0036] Each of the plurality of partial circuits 141, 142, 143, and 144 generates light or sound, for example, by power supplied from the microbial fuel cell. The generation of light or sound indicates that the actuator 120 is located at the contact corresponding to each partial circuit.

[0037] For example, the partial circuit may be a circuit including an LED that emits light using power supplied from the microbial fuel cell to generate light, or a circuit including a buzzer that emits sound using power supplied from the microbial fuel cell to generate sound.

[0038] Each of the plurality of partial circuits 141, 142, 143, and 144 may output an electrical signal indicating that the actuator 120 is located at the contact corresponding to the partial circuit. The output of the electrical signal serves as detection that the actuator 120 is located at the contact corresponding to the partial circuit.

[0039] The electrical signal output from the partial circuit is, for example, a signal indicating the electromotive force (voltage value) or current value generated by the microbial fuel cell. Each of the multiple partial circuits 141, 142, 143, and 144 may be, for example, a circuit that outputs a signal indicating the voltage or voltage value of the corresponding contact, or a circuit that outputs a current flowing from the corresponding contact or a signal corresponding to the current value.

[0040] Fig. 2 shows an example of the positional relationship between the water level LS and the operating element 120. Fig. 3 and Fig. 4 show changes in voltage generated in each of the four contacts 141A, 142A, 143A, and 144A due to changes in the water level LS.

[0041] In Figure 2, four types of water levels LS are shown. The first water level is the lowest water level, followed by the second water level, the third water level, and the fourth water level. The "Water level" shown in Figures 3(B) and 4(B) is divided into four zones: "Zone 1," "Zone 2," "Zone 3," and "Zone 4." "Zone 1" corresponds to the first water level in Figure 2, and similarly, "Zone 2" corresponds to the second water level, "Zone 3" corresponds to the third water level, and "Zone 4" corresponds to the fourth water level.

[0042] 2(A), when the water level LS is at the first water level, the operating element 120 contacts the first contactor 141A. The first partial circuit 141 corresponding to the first contactor 141A receives power from the microbial fuel cell via the operating element 120 and the first contactor 141A, operates, and outputs a first signal such as light, sound, or an electrical signal. The output of the first signal indicates that the water level LS is at the first water level.

[0043] 2(B), when the water level LS is at the second water level, the operating element 120 contacts the second contact 142A. The second partial circuit 142 corresponding to the second contact 142A receives power from the microbial fuel cell via the operating element 120 and the second contact 142A, operates, and outputs a second signal such as light, sound, or an electrical signal. The output of the second signal indicates that the water level LS is at the second water level.

[0044] 2(C), when the water level LS is at the third water level, the operating element 120 contacts the third contactor 143A. The third partial circuit 143 corresponding to the third contactor 143A receives power from the microbial fuel cell via the operating element 120 and the third contactor 143A, operates, and outputs a third signal such as light, sound, or an electrical signal. The output of the third signal indicates that the water level LS is at the third water level.

[0045] 2(D), when the water level LS is at the fourth water level, the operating element 120 contacts the fourth contactor 144A. The fourth partial circuit 144 corresponding to the fourth contactor 144A receives power from the microbial fuel cell via the operating element 120 and the fourth contactor 144A, operates, and outputs a fourth signal such as light, sound, or an electrical signal. The output of the fourth signal indicates that the water level LS is at the fourth water level.

[0046] Figure 3(A) shows the voltages of the contacts 141A, 142A, 143A, and 144A when the water level LS rises over time as shown in Figure 3(B). In Figure 3(A), "Rail 1" corresponds to the first contact 141A, "Rail 2" corresponds to the second contact 142A, "Rail 3" corresponds to the third contact 143A, and "Rail 4" corresponds to the fourth contact 144A. The same applies to Figure 4(A).

[0047] As shown in Figures 3(A) and 3(B), when the water level LS is in Zone 1 (first water level), the voltage value of Rail 1 (first contactor 141A) is approximately 600 mV. This voltage is the electromotive force generated by the microbial fuel cell. When the water level LS shifts from Zone 1 (first water level) to Zone 2 (second water level), the voltage value of Rail 1 (first contactor 141A) becomes 0, and instead, the voltage value of Rail 2 (second contactor 142A) becomes approximately 600 mV.

[0048] Similarly, when the water level LS shifts from Zone 2 (second water level) to Zone 3 (third water level), the voltage value of Rail 2 (second contactor 142A) becomes 0, and instead, the voltage value of Rail 3 (third contactor 143A) becomes approximately 600 mV. Also, when the water level LS shifts from Zone 3 (third water level) to Zone 4 (fourth water level), the voltage value of Rail 3 (third contactor 143A) becomes 0, and instead, the voltage value of Rail 4 (fourth contactor 144A) becomes approximately 600 mV.

[0049] FIG. 4(A) shows the voltages of the contacts 141A, 142A, 143A, and 144A when the water level LS changes so as to drop over time as shown in FIG. 4(B).

[0050] As shown in Figures 4(A) and 4(B), when the water level LS is in Zone 4 (fourth water level), the voltage value of Rail 4 (fourth contactor 144A) increases. When the water level LS shifts from Zone 4 (fourth water level) to Zone 3 (third water level), the voltage value of Rail 3 (third contactor 143A) increases. When the water level LS shifts from Zone 3 (third water level) to Zone 2 (second water level), the voltage value of Rail 2 (second contactor 142A) increases. When the water level LS shifts from Zone 2 (second water level) to Zone 1 (first water level), the voltage value of Rail 1 (first contactor 141A) increases.

[0051] As shown in FIGS. 3 and 4, the liquid level sensor 100 shown in FIG. 1 can detect the liquid level (water level) by using power supplied by the microbial fuel cell.

[0052] Fig. 5 shows another example of the circuit 140. In Fig. 5, multiple partial circuits 141, 142, 142, 143, and 144 are connected to contacts 141A, 142A, 143A, and 144A via wirings 141B, 142B, 143B, and 144B, respectively. The voltage values ​​of the contacts 141A, 142A, 143A, and 144A are input to the partial circuits 141, 142, 143, and 144 via wirings 141B, 142B, 143B, and 144B.

[0053] Each of the multiple partial circuits 141, 142, 143, and 144 may include, for example, an amplifier that amplifies an input voltage value and a power supply circuit that generates an operating power supply voltage for the amplifier from the input voltage (power). Each of the partial circuits 141, 142, 143, and 144 outputs the output of the amplifier as an input to the signal processor 147. For example, the output of the first partial circuit 141 is input to a first input In1 of the signal processor 147. The output of the second partial circuit 142 is input to a second input In2 of the signal processor 147. The output of the third partial circuit 143 is input to a third input In3 of the signal processor 147. The output of the fourth partial circuit 144 is input to a fourth input In4 of the signal processor 147.

[0054] Furthermore, each of the partial circuits 141, 142, 143, and 144 can provide the generated operating power supply voltage to the signal processor 147 as the power supply voltage Vin of the signal processor 147. Therefore, the signal processor 147 can also operate using electrical energy from the microbial fuel cell.

[0055] The signal processor 147 (signal processing unit) can generate and output a water level signal (first signal) indicating the water level based on the first input In1 to the fourth input In4. The water level signal is output to the outside of the circuit 140 (detection circuit 140), for example, via a communication device 148 connected to the signal processor 147. The communication device 148 can operate by receiving a supply of electric energy from the signal processor 147 or the partial circuits 141, 142, 143, and 144. The communication device 148 transmits the signal to the outside by wired communication or wireless communication.

[0056] The water level signal is sent to, for example, a monitor 350, which can display the water level on a screen to indicate the water level to a remote lifeguard. The water level signal is sent to, for example, a buzzer 360, which can sound the water level to indicate the water level to a remote lifeguard. The lifeguard can adjust the water level by controlling the valves 310 and 320 according to the water level. The signal processor 147 can also generate and output a valve control signal according to the water level. The valve control signal is sent to the valves 310 and 320, which automatically adjust the water level. The valve control signal may also be generated based on the water level signal by a valve controller that receives the water level signal from the communication device 148.

[0057] Furthermore, the signal processor 147 can generate and output a signal (water quality signal; second signal) relating to the state (water quality) of the liquid LB based on the first input In1 to the fourth input In4. Since the amount of power generated by the microbial fuel cell can vary depending on the state (water quality) of the liquid LB, a signal relating to the state of the liquid LB can be generated based on the electromotive force or current generated by the microbial fuel cell. For example, when the organic matter concentration in the liquid LB is high, the microbial concentration also increases, and the electromotive force generated by the microbial fuel cell becomes larger. Therefore, the signal processor 147 can output a water quality signal indicating the water quality based on the signal levels of the first input In1 to the fourth input In4.

[0058] The output water quality signal is sent to, for example, monitor 350, and the water quality can be displayed on the screen to a monitor in a remote location. The monitor can control the opening and closing of valves 310 and 320, taking the water quality into consideration. For example, if the microbial concentration of the liquid LB in tank 300 is high, it is likely that the organic matter concentration of the liquid LB is high. Therefore, it is better to open valve 310 connected to inlet pipe 301 to allow a diluting liquid to flow into tank 300 and reduce the concentration of the liquid LB in tank 300. Once the concentration has sufficiently decreased, valve 320 is opened to discharge the liquid LB from tank 300. If the water quality signal is available, the monitor can understand the water quality from the water quality signal and operate valves 310 and 320 appropriately.

[0059] The controllers of the valves 310 and 320 may automatically control the opening and closing of the valves 310 and 320 based on the water level signal and water quality signal received from the communication device 148. The signal processor 147 may also output a valve control signal that takes the water quality into consideration.

[0060] Fig. 6 shows yet another example of circuit 140. In Fig. 6, multiple contacts 141A, 142A, 143A, and 144A are connected to inputs In1, In2, In3, and In4 of signal processor 147. Signal processor 147 operates by generating a power supply voltage for operating signal processor 147 from the electrical energy of signals input to inputs In1, In2, In3, and In4, and can generate signals such as water level signals or water quality signals based on the signals input to inputs In1, In2, In3, and In4, similar to signal processor 147 shown in Fig. 5.

[0061] 7 and 8 show examples of more specific structures of the liquid level sensor 100 shown in FIG.

[0062] 7(A) and 7(B), the liquid level sensor 100 includes a float guide 160 that guides the movement of the float device 200 in the liquid LB. The float guide 160 is, for example, cylindrical. The float device 200 is disposed inside the float guide 160 so as to be able to move up and down. A plurality of holes 160A are formed in the bottom of the float guide 160 to allow the liquid LB to enter the inside of the float guide 160.

[0063] The conductor 132 (and conductor 131) connected to the microbial fuel cell provided in the float device 200 passes through the inside of the float guide 160 and extends to the outside of the float guide 160. The conductor 132 extending to the outside of the float guide 160 is connected to the operating element 120 located outside the float guide 160.

[0064] As shown in Figures 7(A) and 7(C), the liquid level sensor 100 includes an operator guide 170 that guides the movement of the operator 120. As shown in Figure 7(C), the operator guide 170 includes a guide groove 171. The guide groove 171 is formed along the movement direction (up and down direction) of the operator 120.

[0065] 7(A) and 7(D), the operator 120 includes a slider 121 that is inserted into a guide groove 171 of an operator guide 170. The slider 121 is movable along the longitudinal direction of the guide groove 171 (up and down direction).

[0066] 7(C), the operator guide 170 includes a plurality of contacts 141A, 142A, 143A, and 144A arranged in a row along the longitudinal direction of the operator guide 170. The plurality of contacts 141A, 142A, 143A, and 144A form a track for the wheel, which is the operator 120.

[0067] Figure 8 shows the float device 200 shown in Figure 7. The float device 200 (floating-type microbial fuel cell) includes an anode electrode device 210 and a cathode electrode device 220. In Figure 8, multiple (two) anode electrode devices 210 and cathode electrode devices 220 are provided, but only one may be provided.

[0068] The anode electrode device 210 includes an anode 30A and a support 211 that supports the anode 30A around its periphery. A conducting wire 131 is connected to the anode 30A. The cathode electrode device 220 includes a cathode 30B and a support 221 that supports the cathode 30B around its periphery. A conducting wire 132 is connected to the cathode 30B. The anode 30A is placed below the cathode 30B and floats in the liquid.

[0069] The float device 200 includes a float 250 for providing buoyancy to the microbial fuel cell. The float 250 floats the microbial fuel cell so that, for example, a portion of the cathode 30B is exposed to the air above the liquid LB and the cathode 30B is positioned in the liquid LB.

[0070] The cathode electrode device 220 is mounted inside the float 250. The anode electrode device 210 is disposed below the float 250. The float 250 includes legs 230 that extend downward from the float 250. The anode electrode device 210 is attached to the legs 230.

[0071] An adjustment weight 270 may be attached to the float device 200. The adjustment weight 270 is attached, for example, to the float 250. Since the gravity acting on the actuator 120 acts to pull the float device 200 upward, if the float device 200 is too light, the float device 200 may be pulled upward regardless of the liquid level. The adjustment weight 270 prevents the float device 200 from being pulled upward. This allows the float device 200 to move appropriately according to the liquid level LS.

[0072] Figure 9 shows an example of installation of the liquid level sensor 100 shown in Figure 7(A). As shown in Figures 9(A) and 9(B), the operator 120 and the operator guide 170 are arranged outside the tank 300. The float device 200 and the float guide 160 are arranged inside the tank 300.

[0073] Fig. 10 shows another installation example of the liquid level sensor 100. In the example of Fig. 10, the entire liquid level sensor 100 is installed inside the tank 300. The liquid level sensor 100 of Fig. 10 includes a cover 180 that covers the actuator 120 and the actuator guide 170. The cover 180 is intended to prevent the actuator 120 and the actuator guide 170 from coming into contact with the liquid LB. The cover 180 is attached to the float guide 160. The internal spaces of the cover 180 and the float guide 160 are connected to each other at their upper portions.

[0074] FIG. 11 shows a modified example of the liquid level sensor 100 shown in FIG. 1. The liquid level sensor 100 shown in FIG. 11 includes fixed pulleys 151 and 152, as well as a movable pulley 153. In FIG. 11, the actuator 120 is electrically connected to the microbial fuel cell via conductor 132, movable pulley 153, and conductor 132A. By providing the movable pulley 153, the amount of displacement of the liquid level and the amount of movement of the actuator 120 can be made different. For example, the amount of movement of the actuator 120 can be reduced, making the contactor more compact. Furthermore, by providing the movable pulley 153, it becomes easier to achieve a weight balance between the actuator 120 and the float device 200.

[0075] FIG. 12 shows another modified example of the liquid level sensor 100 shown in FIG. 1. The liquid level sensor 100 shown in FIG. 12 includes a rod 190 extending upward from a float device 200. An actuator 120 is provided at the upper end of the rod 190. When the float device 200 moves up and down in response to changes in the water level LS, the actuator 120 moves up and down accordingly. The actuator 120 is electrically connected to the float device 200 via the rod 190. The actuator 120 comes into contact with any of the multiple contacts 141A, 142A, 143A, and 144A to supply power to the detection circuit 140, thereby operating the detection circuit 140. As shown in FIG. 12, the liquid level sensor 100 does not necessarily have to include a pulley.

[0076] FIG. 13 shows yet another modification of the liquid level sensor 100 shown in FIG. 1. The liquid level sensor 100 shown in FIG. 13 includes a first contact 141A and a second contact 142A. The first contact 141A is for the operating element 120 to contact when the water level LS is relatively low, and the second contact 142A is for the operating element 120 to contact when the water level LS is high. When the operating element 120 contacts the second contact 142A, the partial circuit 142 (alert circuit) connected to the second contact 142A receives power via the operating element 120 and operates, outputting an alert signal indicating that the water level LS is high. On the other hand, when the water level LS is low enough that the operating element 120 contacts the first contact 141A, no alert is necessary, and the power from the microbial fuel cell is used to operate other circuits. The other circuits may be, for example, other sensor circuits for temperature, humidity, etc. Furthermore, the other circuit may be a power storage circuit, and the power stored in the power storage circuit can be used as operating power for various circuits and devices.

[0077] The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, the operating element whose operation is detected by circuit 140 may be pulley 151 or pulley 152 instead of wheel 120. Pulleys 151 and 152 also operate (rotate) in accordance with the displacement of float device 200. In this case, circuit 140 can detect the displacement of float device 200 (liquid level) by detecting the amount of rotation (rotation angle) of pulleys 151 and 152 using a potentiometer or the like. [Explanation of symbols]

[0078] 30A: Anode 30B: Cathode 100: Liquid level sensor 120: Action 121: Slider 131: Conductor 132: Conductor 132A: Conductor 140: Circuit (detection circuit) 141: 1st partial circuit 141A: 1st contact 141B: Wiring 142:Second partial circuit 142A: 2nd contact 142B: Wiring 143:Third partial circuit 143A: 3rd contact 143B: Wiring 144: 4th partial circuit 144A: 4th contact 144B: Wiring 147: Signal Processor 148:Communication equipment 151: Pulley 152: Pulley 153: Moving pulley 160: Float guide 160A: Hole 170: Operator Guide 171: Guide groove 180: Cover 190: Rod 200: Float device 210: Anode electrode device 211:Support 220: Cathode electrode device 221 :Support 230: Legs 250: Float 270: Adjustment weight 300: Drainage tank 301:Inflow pipe 302:Outflow pipe 310: Valve 320: Valve 350: Monitor 360: Buzzer In1: First input In2: Second input In3: Third input In4: 4th input LB:Liquid LS:Liquid level Vin: Power supply voltage

Claims

1. a float device that floats on the surface of the liquid; an actuator that operates in response to displacement of the float device caused by a change in the liquid level; a circuit configured to output a first signal related to the level of the liquid based on the operation of the actuator; Equipped with The float device includes a microbial fuel cell that generates electricity using microorganisms contained in the liquid, The circuit operates by receiving power from the microbial fuel cell. Liquid level sensor.

2. the actuator is a conductive actuator electrically connected to the microbial fuel cell; The circuit is configured to receive power from the microbial fuel cell via the actuator. The liquid level sensor according to claim 1 .

3. The circuit includes a contactor that contacts the actuator and is configured to receive power from the microbial fuel cell via the actuator and the contactor.

3. The liquid level sensor according to claim 2.

4. the actuator is a conductive actuator electrically connected to the microbial fuel cell; the circuit includes a plurality of contacts that contact the actuator; The plurality of contacts are arranged along the moving direction of the operating element, The circuit is configured to receive power from the microbial fuel cell via the actuator and the contact with which the actuator is in contact, regardless of which of the plurality of contacts the actuator is in contact with. The liquid level sensor according to claim 1 .

5. the actuator is a conductive actuator electrically connected to the microbial fuel cell; the circuit includes a plurality of contacts that come into contact with the actuator, and a plurality of partial circuits connected to correspond to the plurality of contacts, respectively; The plurality of contacts are arranged along the moving direction of the operating element, At least one partial circuit among the plurality of partial circuits receives power supply from the microbial fuel cell and operates when the operating element comes into contact with a corresponding one of the plurality of contacts, and detects that the operating element is located at the corresponding one of the plurality of contacts. The liquid level sensor according to claim 1 .

6. The circuit is further configured to output a second signal related to the state of the liquid based on the electromotive force or current generated by the microbial fuel cell. The liquid level sensor according to claim 1 .

7. Further provided is a conductor electrically connecting the microbial fuel cell and the operating element, The wire is guided from the microbial fuel cell to the actuator via a pulley. The liquid level sensor according to claim 1 .

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