Contact monitoring device

Abstract

To provide a contact monitoring device for monitoring a contact state of an external electric apparatus, in which, even when there is occurrence of an oxide film at a mechanical contact of the external electric apparatus, electricity conduction is enabled using a battery mounted to the contact monitoring device, and a service life of the battery is extended.SOLUTION: A contact monitoring device 1 comprises a battery mounting unit to which a battery Ba can be mounted, a current limiting device 20 which is capable of reducing a load current that is flowed from the battery Ba to a mechanical contact 81 of an external electric apparatus 8, and a relay circuit board 30 to which a signal is inputted that determines whether the mechanical contact 81 of the external electric apparatus 8 is closed. When it can be determined from the inputted signal that mechanical contact 81 of the external electric apparatus 8 is closed, the relay circuit board 30 produces output for actuating the current limiting device 20, and the current limiting device 20 having received output from the relay circuit board 30 is operated to reduce the load current that is flowed from the battery Ba to the mechanical contact 81 of the external electric apparatus 8.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a contact monitoring device.

Background Art

[0002] As described in Patent Document 1, a contact monitoring device used for monitoring the state of connected devices is known. In the technique described in Patent Document 1, when the contact of a device switches from an open state to a closed state and the relay board receives a state signal indicating that the device has become closed, the relay board is structured to output a signal to an external communication unit. Such a contact monitoring device uses a battery (dry cell) to supply power to the relay board and the like.

[0003] Such a state monitoring device, for example, detects the operation of an electrical device or a sensor by the opening and closing operation of a contact, and monitors the state from the open state to the closed state of the contact based on the level (High / Low) of the signal input to the relay board. Regarding the level of the signal, when a load current flows from the battery to the mechanical contact and the contact is opened and closed, a potential difference change occurs between the battery and the ground. Therefore, the change in the potential difference is input as a state signal to the input part of the relay board, and notifications and the like are sent to the outside from the state signal.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] By the way, when the contact provided in an external electrical device is a mechanical contact and switches between a closed state and an open state by the contact of a fixed contact or a movable contact, when the voltage between the contacts becomes high when the contact moves away from or contacts the off position, an arc occurs between the contacts. When this arc is repeated, an oxide (sulfide) film is formed on the contact as a deposit of the arc. This oxide (sulfide) film is an insulator and may inhibit electrical conduction.

[0006] Applying sufficient current and voltage to the contacts can remove the oxide (sulfide) film through a process called "cleaning," thereby improving electrical conductivity. However, applying sufficient current and voltage leads to problems such as high battery consumption, including that of dry cell batteries. [Overview of the project] [Problems that the invention aims to solve]

[0007] The inventors of this invention have attempted to solve this problem by diligently considering this issue. The problem that this invention aims to solve is to enable a contact monitoring device for monitoring the contact state of external electrical equipment to conduct electricity using a battery installed in the contact monitoring device even if an oxide film has formed on the mechanical contacts of the external electrical equipment, and to extend the battery's lifespan. [Means for solving the problem]

[0008] To solve the above problems, a contact monitoring device is provided for monitoring the state of mechanical contacts or semiconductor contacts of connected external electrical equipment. The device comprises: a battery mounting section that can accommodate a battery used to supply power to the contact monitoring device and to supply current to the mechanical contacts or semiconductor contacts of the external electrical equipment; a current limiting device capable of reducing the load current supplied from the battery to the mechanical contacts of the external electrical equipment; and a relay board that receives a signal capable of determining whether or not the mechanical contacts of the external electrical equipment are closed. The relay board outputs a signal that, if it can be determined from the input signal that the mechanical contacts of the external electrical equipment are closed, it will operate the current limiting device. The current limiting device, upon receiving the output from the relay board, operates to reduce the load current supplied from the battery to the mechanical contacts of the external electrical equipment.

[0009] Furthermore, the current limiting device includes a first resistor, a second resistor with a higher resistance than the first resistor, and a transistor, with the first and second resistors connected in series. Preferably, the transistor and the second resistor are connected in parallel, and by applying a voltage or current to the transistor via the output of the relay board, it is possible to switch from a state in which the current flowing through the first resistor mainly passes through the transistor and energizes the mechanical contacts to a state in which the current flowing through the first resistor mainly passes through the second resistor and energizes the mechanical contacts.

[0010] Furthermore, the transistor is preferably a field-effect transistor that operates by applying a voltage.

[0011] Furthermore, it is preferable to have a configuration that allows multiple external electrical devices to be connected to the relay board. [Effects of the Invention]

[0012] In this invention, a contact monitoring device for monitoring the contact state of external electrical equipment makes it possible to maintain a state where power can be supplied using a battery attached to the contact monitoring device even if an oxide film has formed on the mechanical contacts of the external electrical equipment, and also makes it possible to extend the battery's lifespan. [Brief explanation of the drawing]

[0013] [Figure 1] This is a perspective view of the contact monitoring device in the embodiment. [Figure 2] Figure 1 is an exploded perspective view of the contact monitoring device, but with the battery installed. [Figure 3] Figure 2 is a side view of the base, with the battery installed. [Figure 4] This diagram shows a contact monitoring device with a battery installed connected to an external electrical device via electrical wires. However, the contact monitoring device has its cover removed. [Figure 5] This diagram shows the relationship between the contact monitoring device and external electrical equipment in the embodiment. [Figure 6] This figure shows the mechanical contacts shown in Figure 5 in a closed state. [Figure 7]This is a diagram showing the configuration of the current limiting device in the embodiment. [Figure 8] This diagram illustrates how the path of current flow changes when the contacts of an external electrical device are changed from an open state to a closed state. [Figure 9] This diagram shows an example of connecting multiple external electrical devices to a single contact monitoring device. [Modes for carrying out the invention]

[0014] The following describes embodiments for carrying out the invention. The contact monitoring device 1 of this embodiment is used to monitor the state of mechanical contacts 81 and semiconductor contacts of an external electrical device 8 to which it is connected. The contact monitoring device 1 includes a battery mounting section 11a to which a battery Ba can be mounted, which is used to supply power to the contact monitoring device 1 and to supply current to the mechanical contacts 81 and semiconductor contacts of the external electrical device 8; a current limiting device 20 capable of reducing the load current flowing from the battery Ba to the mechanical contacts 81 of the external electrical device 8; and a relay board 30 to which a signal capable of determining whether or not the mechanical contacts 81 of the external electrical device 8 are closed is input. Furthermore, the relay board 30 outputs a signal that causes the current limiting device 20 to operate when it can be determined from the input signal that the mechanical contacts 81 of the external electrical device 8 are closed. The current limiting device 20, upon receiving the output from the relay board 30, operates to reduce the load current flowing from the battery Ba to the mechanical contacts 81 of the external electrical device 8. Therefore, sufficient current can be supplied to clean the mechanical contact 81, and after electrical conductivity is established, the current consumption flowing through the mechanical contact 81 can be reduced. As a result, in the contact monitoring device 1 that monitors the contact state of the external electrical device 8, even if an oxide film has formed on the mechanical contact 81 of the external electrical device 8, it is possible to maintain a state where power can be supplied using the battery Ba installed in the contact monitoring device 1, and to extend the lifespan of the battery Ba.

[0015] Note that the contact monitoring device 1 is used to detect the open / closed state of the contacts of the external electrical equipment 8. For this purpose, it includes a relay board 30 capable of detecting the opening and closing of the contacts output from the external electrical equipment 8. Further, since the contact monitoring device 1 of the embodiment uses the battery Ba as a power source, it includes a battery mounting portion 11a. The battery Ba mounted on the battery mounting portion 11a is used to supply the operating power of the relay board 30 housed inside and to energize the contacts of the external electrical equipment 8.

[0016] Note that in the embodiment, the battery mounting portion 11a and the relay board 30 are provided inside the contact monitoring device 1. As can be understood from FIGS. 1 and 2, the contact monitoring device 1 of the embodiment is configured such that the base 11 and the cover 12 can be separated, and when attaching or detaching the battery Ba, the cover 12 is removed for the operation.

[0017] In the example shown in FIG. 2, the battery mounting portion 11a and the relay board 30 are provided on the base 11. However, it is preferable that the relay board 30 is provided with an LED or the like, and the way of lighting the LED varies according to the situation. In this case, in order to be able to grasp the change of the LED even when the cover 12 is attached, it is preferable to configure a part or all of the cover 12 to be transparent.

[0018] Note that the contact monitoring device 1 of the embodiment includes a packing 13 that closes the gap between the cover 12 and the base 11. This packing 13 is attached in an annular shape, and is configured such that foreign matter is unlikely to enter the portion surrounded by the packing 13. The packing 13 of the embodiment is a packing 13 having waterproof performance, and in addition to dustproofness, the waterproof property is also enhanced. Note that in the embodiment, the packing 13 is attached so as to fit into a groove provided on the base 11.

[0019] The contact monitoring device 1 of this embodiment is equipped with an introduction section 11b through which an electric wire 91 can be introduced, so that it can be connected to an external electrical device 8 via the electric wire 91 (see Figures 3 and 4). This electric wire 91 is connected to a relay board 30, and the external electrical device 8 and the relay board 30 are electrically connected. In the example shown in Figure 4, an electric wire 91 connected to one external electrical device 8 is introduced from the introduction section 11b, but the introduction section 11b may be equipped with electric wires 91 from multiple external electrical devices 8.

[0020] Here, an example of a method for monitoring the contacts of an external electrical device 8 using the contact monitoring device 1 of the embodiment will be described. By connecting the contact monitoring device 1 and the external electrical device 8 with an electric wire 91, a route is established through which electricity can flow from the contact monitoring device 1 to the external electrical device 8 and a route is established through which electricity can flow from the external electrical device 8 to the contact monitoring device 1.

[0021] When the contacts of the external electrical device 8 are open, the current flowing from the contact monitoring device 1 to the external electrical device 8 does not return to the contact monitoring device 1 (see Figure 5). On the other hand, when the contacts of the external electrical device 8 are closed, the current flowing from the contact monitoring device 1 to the external electrical device 8 returns to the contact monitoring device 1 (see Figure 6). Therefore, the difference in the opening and closing of the contacts of the external electrical device 8 results in a potential difference between the part output to the external electrical device 8 and the part input from the external electrical device 8, i.e., between the battery and ground.

[0022] The relay board 30 is capable of detecting this change in potential difference, and based on the detection result, it is possible to determine whether the contacts of the external electrical device 8 are closed or open. In this embodiment, a chattering prevention circuit is formed in the microcontroller that determines when the potential difference changes by a predetermined value or after it has changed by a predetermined value, and when the potential difference has stabilized for a predetermined time. By determining whether the contacts are open or closed after confirming that the potential difference has stabilized, false determinations can be suppressed.

[0023] Incidentally, an oxide film is formed on the mechanical contacts 81 of electrical equipment through use. To break through this oxide film and allow current to flow, a sufficient current and voltage must be applied to the mechanical contacts 81. On the other hand, it is not necessary to flow such a large current after the current has been supplied. Therefore, the contact monitoring device 1 of this embodiment is designed to reduce the current flowing through the contacts after the current has been supplied.

[0024] To enable this, the contact monitoring device 1 of this embodiment is provided with a current limiting device 20 on the output side of the battery Ba, which includes a field-effect transistor (FET) and a plurality of resistors (see Figure 7). More specifically, the first resistor 21 and the second resistor 22 are connected in series with respect to the battery Ba. The source (S) and drain (D) of the field-effect transistor 23 are connected so as to straddle the second resistor 22. This is to allow the operation of the field-effect transistor 23 to be controlled so that it is possible to select whether or not the current sent from the battery Ba passes through the second resistor 22. The second resistor 22 has a higher resistance than the first resistor 21.

[0025] In this embodiment, a field-effect transistor is used as the component for the current limiting device 20. By applying a voltage to the gate (G) of the field-effect transistor, the conduction between the source (S) and drain (D) can be determined. More specifically, in this embodiment, a P-channel FET is used, and the system is configured to switch between a first state, in which current mainly passes through the first resistor 21 and transistor 23, and a second state, in which current mainly passes through the first resistor 21 and second resistor 22, depending on whether or not a voltage is applied to the gate (G).

[0026] It should be noted that hyperpolar transistors can also be used as an alternative to field-effect transistors. In that case, the conductivity between the collector and emitter can be selected by applying current. However, since the current consumption of battery Ba required to operate a field-effect transistor can be made smaller than the current consumption of battery Ba required to operate a hyperpolar transistor, it is preferable to use a field-effect transistor.

[0027] As can be understood from the above, the current limiting device 20 is preferably configured to include a first resistor 21, a second resistor 22 having a higher resistance than the first resistor 21, and a transistor 23, wherein the first resistor 21 and the second resistor 22 are connected in series, and the transistor 23 and the second resistor 22 are connected in parallel, and by applying a voltage or current to the transistor 23 from the output of the relay board 30, it is possible to switch from a state in which the current flowing through the first resistor 21 mainly passes through the transistor 23 and energizes the mechanical contact 81 to a state in which the current flowing through the first resistor mainly passes through the second resistor 22 and energizes the mechanical contact 81.

[0028] If a field-effect transistor is used for transistor 23, the following behavior can be achieved, for example. Since a field-effect transistor usually has its source (S) and drain (D) connected, the current flowing from battery Ba passes through the first resistor 21 and then mainly through transistor 23 rather than the second resistor 22. For this reason, as shown in Figure 7, if the voltage of battery Ba is 1.5V, the resistance value of the first resistor 21 is 10Ω, and the resistance value of the second resistor 22 is 100,000Ω, then normally a current of 150mA flows through the mechanical contact 81.

[0029] On the other hand, when a voltage is applied to the field-effect transistor, no current flows between the source (S) and drain (D), so the current flowing from the battery Ba mainly passes through both the first resistor 21 and the second resistor 22. Therefore, as shown in Figure 7, when the voltage of the battery Ba is 1.5V, the resistance value of the first resistor 21 is 10Ω, and the resistance value of the second resistor 22 is 100,000Ω, when a voltage is applied to the field-effect transistor, a current of 15μA flows through the mechanical contact 81.

[0030] Here, we will explain the process from when the contact is opened to when it is closed, until the path of the current changes. As can be seen from Figure 8 (1), when the contact of the external electrical device 8 is open, no current flows from the battery Ba of the contact monitoring device 1 to the external electrical device 8. However, when the contact of the external electrical device 8 is closed, the system is in a state of readiness to allow current to flow mainly through a route that does not pass through the second resistor 22.

[0031] As can be seen from Figure 8(2), immediately after the mechanical contact 81 of the external electrical device 8 is closed, current flows through the waiting route, allowing a relatively large current to flow and clean the mechanical contact 81. Subsequently, if the change in potential difference caused by closing the mechanical contact 81 is continuously detected, a voltage is applied from the relay board 30 to the field-effect transistor (see Figure 8(3)). Applying a voltage to the field-effect transistor moves the field-effect transistor, causing current to flow mainly through the second resistor 22 (see Figure 8(4)). This reduces the current value flowing through the mechanical contact 81.

[0032] Up to this point, we have described an example in which one external electrical device 8 is connected to one contact monitoring device 1, but it is also possible to connect multiple external electrical devices 8 to one contact monitoring device 1. In the example shown in Figure 9, four external electrical devices 8 are connected. Note that although Figure 9 makes it appear as if the contact monitoring device 1 has four batteries Ba, it actually has only one battery Ba. When configuring the system to supply current to the contacts of multiple external electrical devices 8 from a single battery Ba, limiting the current supplied becomes even more important. In other words, it can be said that a configuration that allows multiple external electrical devices 8 to be connected to the relay board 30 is a more preferable configuration.

[0033] The present invention has been described above with reference to the embodiments, but the present invention is not limited to the above embodiments and can be made into various forms. For example, multiple batteries may be installed in series. Also, in the case of a configuration that connects many external electrical devices, it is possible to make it so that different external electrical devices can be powered by the batteries depending on where the batteries are installed. [Explanation of symbols]

[0034] 1. Contact monitoring device 8. External electrical equipment 11a Battery mounting section 20 Current limiting device 21 The First Resistance 22 The Second Resistance 23 Transistors 30 relay boards 81 Mechanical Contacts

Claims

1. A contact monitoring device used to monitor the condition of mechanical contacts of connected external electrical equipment, A battery mounting section that can accommodate a battery used to supply power to the contact monitoring device and to supply current to the mechanical contacts of external electrical equipment, A current limiting device capable of reducing the load current flowing from the battery to the mechanical contacts of external electrical equipment, A relay board to which a signal capable of determining whether or not the mechanical contacts of an external electrical device are closed is input, Equipped with, The relay board, when it can determine from the input signal that the mechanical contacts of an external electrical device have closed, outputs a signal to activate the current limiting device after supplying a sufficient current to remove the oxide film on the mechanical contacts immediately after they have closed. The current limiting device, which receives the output from the relay board, is a contact monitoring device that operates to reduce the load current flowing from the battery to the mechanical contacts of external electrical equipment.

2. The current limiting device includes a first resistor, a second resistor with a higher resistance than the first resistor, and a transistor. The first resistor and the second resistor are connected in series. The transistor and the second resistor are connected in parallel. By applying a voltage or current to the transistor via the output from the relay board, From a state where the current flowing through the first resistor mainly passes through the transistor and energizes the mechanical contacts, The contact monitoring device according to claim 1, which is capable of switching to a state in which the current flowing through the first resistor mainly passes through the second resistor and energizes the mechanical contacts.

3. The contact monitoring device according to claim 2, wherein the transistor is a field-effect transistor that is operated by applying a voltage.

4. A contact monitoring device according to any one of claims 1 to 3, wherein multiple external electrical devices can be connected to the relay board.

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