JP7844082B2 - Contact monitoring device - Google Patents

Description

This invention relates to a contact monitoring device.

As described in Patent Document 1, a contact monitoring device used to monitor the status of connected equipment is known. In the technology described in Patent Document 1, when a device's contact switches from an open state to a closed state, the relay board receives a status signal indicating that the device has entered a closed state. The relay board then outputs a signal to an external communication unit. Such a contact monitoring device uses a battery (dry cell battery) to supply power to the relay board and other components.

Such a status monitoring device detects the operation of electrical equipment or sensors by the opening and closing of contacts. The state of the contacts, from open to closed, is monitored by the level (High/Low) of a signal input to an intermediate board. The signal level is determined by the fact that when load current flows from the battery to the mechanical contacts, the contacts open and close, causing a change in potential difference between the battery and ground. This change in potential difference is input to the intermediate board as a status signal, and this status signal is then used to notify external parties.

Japanese Patent Publication No. 2021-190434

Incidentally, when the contacts in external electrical equipment are mechanical contacts, and the closed and open states are switched by the contact of fixed or movable contacts, an arc is generated between the contacts when the voltage between the contacts increases as the contacts move away from the off position or make contact. Repeated arcing causes an oxide (sulfide) film to form on the contacts as arc deposits. This oxide (sulfide) film is an insulator and could potentially hinder electrical conductivity.

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.

The inventors of this invention have attempted to solve this problem through diligent study. 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 device, even when an oxide film has formed on the mechanical contacts of the external electrical equipment, and to extend the battery's lifespan.

To solve the above problems, a contact monitoring device is provided for monitoring the state of mechanical and semiconductor contacts of connected external electrical equipment. This device comprises: a battery mounting section capable of supplying power to the contact monitoring device and mounting a battery used to supply current to the mechanical and semiconductor contacts of the external electrical equipment; a current limiting device capable of reducing the load current flowing from the battery to the mechanical contacts of the external electrical equipment; and a relay board that receives a signal capable of determining whether the mechanical contacts of the external electrical equipment are closed. The relay board outputs a signal to activate the current limiting device when it can determine from the input signal that the mechanical contacts of the external electrical equipment are closed. The current limiting device, upon receiving the output from the relay board, operates to reduce the load current flowing from the battery to the mechanical contacts of the external electrical equipment.

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.

Furthermore, it is preferable that the transistor be a field-effect transistor, which operates by applying a voltage.

Furthermore, it is preferable to have a configuration that allows multiple external electrical devices to be connected to the relay board.

This invention provides a contact monitoring device for monitoring the contact state of external electrical equipment. It enables the device to maintain a state where power can be supplied 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 also allows for extended battery life.

This is a perspective view of the contact monitoring device in the embodiment. Figure 1 is an exploded perspective view of the contact monitoring device shown. However, the battery is installed in this view. Figure 2 is a side view of the base, with the battery installed. 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. This diagram shows the relationship between the contact monitoring device and external electrical equipment in the embodiment. This figure shows the mechanical contact shown in Figure 5 in a closed state. This is a diagram showing the configuration of the current limiting device in the embodiment. 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. This diagram shows an example of connecting multiple external electrical devices to a single contact monitoring device.

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 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 can be mounted, 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 have closed is input. Furthermore, the relay board 30 outputs a signal to activate the current limiting device 20 when it can be determined from the input signal that the mechanical contacts 81 of the external electrical device 8 have 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, which monitors the contact state of the external electrical device 8, it becomes possible to maintain a state where power can be supplied using the battery Ba installed in the contact monitoring device 1 even if an oxide film has formed on the mechanical contact 81 of the external electrical device 8, and to extend the lifespan of the battery Ba.

The contact monitoring device 1 is used to detect the open/closed state of the contacts of the external electrical device 8. Therefore, it is equipped with a relay board 30 capable of detecting the open/closed state of the contacts output from the external electrical device 8. Furthermore, since the contact monitoring device 1 of this embodiment is powered by battery Ba, it is equipped with a battery mounting section 11a. Battery Ba, mounted in the battery mounting section 11a, is used to supply power to the relay board 30 housed inside and to provide power to the contacts of the external electrical device 8.

In this embodiment, the battery mounting section 11a and the relay board 30 are located inside the contact monitoring device 1. As can be seen from Figures 1 and 2, the contact monitoring device 1 of this embodiment is configured so that the base 11 and the cover 12 can be separated. When installing or removing the battery Ba, the cover 12 is removed for the work.

In the example shown in Figure 2, the base 11 is provided with a battery mounting section 11a and a relay board 30. It is preferable to equip the relay board 30 with LEDs, etc., so that the way the LEDs light up varies depending on the situation. In this case, it is preferable to configure the cover 12 to be partially or entirely transparent so that the changes in the LEDs can be observed even when the cover 12 is attached.

In this embodiment, the contact monitoring device 1 is equipped with a gasket 13 that seals the gap between the cover 12 and the base 11. This gasket 13 is installed in an annular shape, making it difficult for foreign matter to enter the area enclosed by the gasket 13. The gasket 13 in this embodiment is waterproof, providing enhanced water resistance in addition to dust resistance. In this embodiment, the gasket 13 is installed so as to fit into a groove provided in the base 11.

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, electrically connecting the external electrical device 8 and the relay board 30. In the example shown in Figure 4, an electric wire 91 connected to one external electrical device 8 is introduced through the introduction section 11b, but the introduction section 11b may be designed to accept electric wires 91 from multiple external electrical devices 8.

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 for electricity to flow from the contact monitoring device 1 to the external electrical device 8, and a route is established for electricity to flow from the external electrical device 8 to the contact monitoring device 1.

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). Conversely, 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, due to the difference in the opening and closing of the contacts of the external electrical device 8, a potential difference is created between the output portion to the external electrical device 8 and the input portion from the external electrical device 8, i.e., between the battery and ground.

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

Incidentally, an oxide film forms 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, after current is supplied, it is not necessary to flow such a large current. Therefore, the contact monitoring device 1 of this embodiment reduces the current flowing through the contacts after current is supplied.

To enable this, the contact monitoring device 1 of this embodiment is equipped with a current limiting device 20 on the output side of the battery Ba, which includes a field-effect transistor (FET) and multiple 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. Furthermore, 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 control of the operation of the field-effect transistor 23, enabling selection whether or not the current supplied from the battery Ba passes through the second resistor 22. Note that the second resistor 22 has a higher resistance than the first resistor 21.

In this embodiment, a field-effect transistor is used as the component for the current limiting device 20. The conduction between the source (S) and drain (D) of a field-effect transistor can be determined by applying a voltage to the gate (G). More specifically, this embodiment uses a P-channel FET, and the system can switch between a first state, where current mainly passes through the first resistor 21 and transistor 23, and a second state, where 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).

Furthermore, hyperpolar transistors can be used as an alternative to field-effect transistors. In this 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, using a field-effect transistor is preferable.

As can be understood from the above, the current limiting device 20 preferably comprises a first resistor 21, a second resistor 22 having a higher resistance than the first resistor 21, and a transistor 23. 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. By applying a voltage or current to the transistor 23 via the output of the relay board 30, it is preferable to have a configuration that allows switching from a state where the current flowing through the first resistor 21 mainly passes through the transistor 23 and energizes the mechanical contact 81, to a state where the current flowing through the first resistor mainly passes through the second resistor 22 and energizes the mechanical contact 81.

If a field-effect transistor is used for transistor 23, the following behavior can be achieved, for example. Since a field-effect transistor typically 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. Therefore, as shown in Figure 7, if the battery voltage Ba is 1.5V, the resistance of the first resistor 21 is 10Ω, and the resistance of the second resistor 22 is 100,000Ω, then typically a current of 150mA flows through the mechanical contact 81.

On the other hand, when a voltage is applied to the field-effect transistor, current stops flowing between the source (S) and drain (D). Therefore, the current flowing from battery Ba mainly passes through both the first resistor 21 and the second resistor 22. For this reason, as shown in Figure 7, when the voltage of battery Ba is 1.5V, the resistance of the first resistor 21 is 10Ω, and the resistance of the second resistor 22 is 100,000Ω, a current of 15μA flows through the mechanical contact 81 when a voltage is applied to the field-effect transistor.

Here, we will explain the process from when the contact is opened to when it is closed, and how the current path changes as a result. As can be understood 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 closes, 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.

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

Up to this point, we have described an example where one external electrical device 8 is connected to one contact monitoring device 1. However, multiple external electrical devices 8 may be connected 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 flow becomes even more important. Therefore, a configuration that allows multiple external electrical devices 8 to be connected to the relay board 30 is a more preferable configuration.

The present invention has been described above using embodiments as examples, but the present invention is not limited to the above embodiments and can be implemented in various forms. For example, multiple batteries may be installed in series. Furthermore, in configurations where many external electrical devices are connected, it is possible to design the external electrical devices that can be powered by each battery to differ depending on where the batteries are installed.

1 Contact monitoring device 8 External electrical equipment 11a Battery mounting section 20 Current limiting device 21 First resistor 22 Second resistor 23 Transistor 30 Intermediate board 81 Mechanical contacts

Claims (4)

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