JPH0568131U - 2-wire sensor switch - Google Patents

Abstract

(57) [Summary] [Purpose] To maintain high output characteristics of leakage current and residual voltage while enabling the lighting of the indicator lamp. [Structure] A mode change switch 23 can switch between a normal close mode and a normal open mode. In the normally closed mode, when the stability indicator lamp 25 is turned on, the first and third transistors 27, 2
9 is turned off, the second transistor 28 is turned on, and the stability indicator lamp 25 is turned on by the operating current IOP flowing into the detection circuit 22. In the output-on state of the normally open mode, both the first and third transistors 27 and 29 are on, the second transistor 28 is off, and the operation indicator lamp 24 and the stability indicator lamp 25 are in parallel with the output transistor 21. .. Therefore, the residual voltage VON is VON = VOP + Vreg3
Is relatively low.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a two-wire sensor switch that is connected to a load in series and controls the on / off of the load.

[0002]

[Prior Art]

 An example of this type of sensor switch is a two-wire photovoltaic switch in which the measurement target is light. This is because, for example, as shown in FIG. 4, the sensor body 1 having an output transistor built therein is connected in series with the power source 2 and the load 3, and the light from the light emitting element of the light projector 4 is directed toward the light receiving element of the sensor body 1. Set to be projected.

In this configuration, the object to be detected is detected by passing through it so as to block the optical axis between the light projector 4 and the sensor body 1, but this is detected at the time of detection. There are two types: normal open mode, which turns on the output transistor, and normal close mode, which turns off the output transistor when it is detected.

For example, in a normally open mode sensor switch, when the light from the projector 4 is incident on the sensor body 1, the output transistor of the sensor body 1 is in an off state. However, if the light is blocked by a not-shown detection target and the amount of light incident on the sensor body 1 decreases, the output transistor turns on when the measurement signal level of the amount of incident light falls below a predetermined operating level and the load is reduced. 3 is energized.

Now, in this type of photoelectric switch, an operation indicator lamp is generally provided in order to display whether or not the sensor body has detected the detected object. As a configuration therefor, for example, as shown in FIG. 5, a configuration in which a series circuit of an operation indicator lamp 5 and a switching element 6 is connected in parallel with the output transistor 1a is provided. At the time of detection, the switching element 6 is turned on by a signal from the detection circuit 1b.

In addition, in this type of two-wire sensor switch, not only is the operating state displayed, but it is displayed whether or not the amount of light incident on the light-receiving element when light is incident is appropriately secured. It is desirable to be able to confirm with a light. In this way, whether the intensity of light emitted from the light projector 4 is sufficient, whether the optical axis is properly set, or whether the incident light amount is reduced too much due to dirt on the lens, etc. This is because it can be easily determined, which is convenient for sensor setting and maintenance.

To this end, there has been conventionally provided a structure in which a stability indicator lamp 7 is provided as shown in FIG. The stability indicator lamp 7 is also generally connected in parallel with the output transistor 1a together with the switching element 8. With this configuration, when the amount of light incident on the light receiving element of the sensor body exceeds the stable region level and is a sufficient value, the switching element 8 is turned on by the signal from the detection circuit 1b and the stability indicator lamp 7 is turned on.

[0008]

[Problems to be solved by the device]

 By the way, in the two-wire type sensor switch, since the sensor body 1 is used by being connected in series to the load 3, it is required that its output characteristics be as close as possible to the mechanical contact. Specifically, it is desired that the leakage current IOFF when the output is off is as small as possible and the residual voltage VON when the output is on is as low as possible.

However, in the above-described conventional configuration, there is no problem in the normal open mode, but in the normally closed mode, the leakage current IOFF when the output is off becomes large, which causes a problem.

That is, in the normally closed mode, the operation indicator lamp 5 and the stability indicator lamp 7 are turned on when the output transistor 1a is in the off state. Therefore, the lighting current ILED of each of the indicators 5 and 7 must be regarded as a leakage current IOFF. Moreover, since a small operating current IOP always flows into the detection circuit 1b, the leakage current IOFF when the output is off is, in the end, the operating current IOP of the detection circuit and the lighting currents 2 and 2 of the two indicator lamps 5 and 7. ILED is added (IOFF = IOP + 2 · ILED), which is a value that cannot be ignored. For this reason, it may not be able to be used especially for a load such as a sequencer that is considered to be in the ON state even with a small current.

In order to avoid this, it is conceivable to use the technique disclosed in Japanese Patent Laid-Open No. 57-84534, for example. As shown in FIG. 6, the operation indicator lamp 9 and the limiting resistor 9a are provided in the power supply path to the detection circuit 1b, and the bypass transistor 10 is connected in parallel with them. When the operation indicator lamp 9 is to be turned on, the operation indicator lamp 9 is turned on by the operation current flowing into the detection circuit 1b by turning off the bypass transistor 10.

However, in the above configuration, although there is no problem in the normally closed mode, this time, in the normally open mode, there arises a problem that the residual voltage VON becomes large when the output is turned on.

That is, in the normally open mode, the operation indicator lamp 9 is turned on when the output is turned on. When the operation indicator lamp 9 is turned on, since it is connected in series with the detection circuit 1b, the shared voltage VL is added to the operation voltage VOP of the detection circuit 1b. That is, the residual voltage VON between both terminals of the output transistor 1a in this case is the sum of the operating voltage VOP of the detection circuit 1b and the shared voltage VL of the operation indicator lamp 9 and the limiting resistor 9a (VON = VOP + VL). It will be a relatively large value. In the above configuration, if not only the operation indicator lamp 9 but also the steady state indicator lamp is to be turned on, the shared voltage will be further applied for that, so the residual voltage VON when the output is on It gets even higher.

As described above, in the conventional two-wire type sensor switch, when the operation indicator lamp and the stable state indicator lamp are provided, the leakage current increases in the normally closed mode and the residual voltage increases in the normally open mode. That caused the problem.

The present invention has been made in view of the above circumstances, and therefore an object thereof is to maintain a high level of output characteristics such as leakage current and residual voltage while being able to light an operation indicator lamp or the like. It is an object of the present invention to provide a two-wire sensor switch that can be used.

[0016]

[Means for Solving the Problems]

 The two-wire type sensor switch of the present invention is connected in series to a power supply and a load, and a detection circuit that outputs a switching operation signal by comparing a measurement signal level of an object to be measured such as light, sound wave, and magnetic field with a predetermined operation level. An output switching circuit that performs a switching operation based on a switching operation signal from the detection circuit, an indicator lamp, and a parallel connection state in which the indicator lamp is parallel to the output switching circuit and a power supply path to the detector circuit. The switching element group that can be switched to the series connection state that is interposed in series with the output switching circuit, and when the indicator lamp is lit in the normally closed mode of the output switching circuit, the indicator lamp is in the serially connected state, and the indicator lamp is switched in the normally open mode. Control that controls the switching elements so that the indicators are connected in parallel when they are turned on. Characterized in configuration to and a road.

[0017]

[Action]

 The operation will be described based on FIG. 1 which illustrates the configuration of the present invention. The output switching circuit 11 is connected in series with the load 12 and the power supply 13 as shown in the figure. From the detection circuit 14, a switching operation signal Ss is output according to the measurement signal level of the measurement target such as light, sound wave, magnetic field. Further, the switches 15 to 17 constitute a switching element group. When the switch 16 is opened and the switches 15 and 17 are closed, the indicator lamp 18 can be connected in parallel to the output switching circuit 11 and vice versa. Further, when the switch 16 is closed and the switches 15 and 17 are opened, the indicator lamp 18 can be brought into a series connection state in which the indicator lamp 18 is inserted in series with the power feeding path to the detection circuit 14.

Here, for example, in the normally closed mode, the output switching circuit 11 is normally closed and is opened when the switching operation signal Ss is output. At the same time, a signal from the control circuit 19 causes the switching element group to bring the indicator lamps 18 into a serial connection state, and the indicator lamps 18 are lit by the operating current flowing in the power supply path to the detection circuit 14. Therefore, no extra lighting current flows in, and the leakage current when the output is off is small.

On the other hand, in the normal open mode, the output switching circuit 11 is always open and is closed when the switching operation signal Ss is output. Along with this, in response to a signal from the control circuit 19, the switching element group sets the indicator lamp 18 in parallel connection, and the indicator lamp 18 is lit in parallel with the output switching circuit 11. Therefore, since the indicator lamp 18 is not in series with the detection circuit 14, the shared voltage of the indicator lamp 18 is not added to the operating voltage of the detection circuit 14, and the residual voltage VON when the output is on can be kept small. ..

[0020]

[Effect of the device]

 As described above, according to the two-wire sensor switch of the present invention, it is possible to keep the output characteristics such as leakage current and residual voltage at a high level while being able to light the indicator lamp. Produce an effect.

[0021]

【Example】

 Hereinafter, a first embodiment of the present invention will be described with reference to FIG. In this embodiment, the present invention is applied to, for example, a reflection type photoelectric switch. As is well known, the sensor body is provided with a light projecting element and a light receiving element, and the light projecting element and the light receiving element are arranged so as to face the passage area of the object. The light from the light emitting element is reflected by the object to be detected and is incident on the light receiving element, so that the object to be detected is detected.

The electrical configuration on the light-receiving side of the sensor body 20 is as shown in FIG. 2, and the power supply is provided between the collector and emitter (output terminals A and B) of the output transistor 21 corresponding to the built-in output switching circuit. 40 and load 50 are connected in series.

The detection circuit 22 is provided with a light receiving element, the light receiving signal is amplified by a light receiving amplifier, and the output transistor 21 is switched based on a comparison between the level of the amplified measurement signal and a predetermined operation level. The operation signal Ss is output.

The sensor body 20 is provided with a mode changeover switch 23 for giving a signal to the detection circuit 22, so that the normal close mode and the normal open mode can be selectively changed over. Is becoming

When the mode changeover switch 23 is set to the normally closed mode, the switching operation signal Ss from the detection circuit 22 is high when the detected object is not detected (the amount of light incident on the light receiving element is small). At the level, the output transistor 21 is on. Then, when the object to be detected is detected (when the amount of light incident on the light receiving element is increased), the switching operation signal Ss from the detection circuit 22 becomes low level and the output transistor 21 is turned off.

If the mode changeover switch 23 is set to the normal open mode, the switching operation signal Ss from the detection circuit 22 is at the low level and the output transistor 21 is in the off state when the detected object is not detected. It is in. When the object to be detected is detected, the switching operation signal Ss from the detection circuit 22 becomes high level, and the output transistor 21 is turned on.

The diode indicated by reference numeral 24 is an operation indicator lamp, which is a red light emitting diode. Further, the diode indicated by reference numeral 25 is a stability indicator lamp and is a green light emitting type light emitting diode. Of these, the operation indicator lamp 24 is connected in series with the operation indicator transistor 26 and is connected in parallel between the output terminals A and B, and the stability indicator lamp 25 is connected in series with the first transistor 27 and is also connected to the output terminals A and B. They are connected in parallel.

Here, the common connection point between the cathode of the stability indicator lamp 25 and the collector of the first transistor 27 is connected to the positive power supply terminal V + of the detection circuit 22 via the second transistor 28. ing. The third transistor 29 is connected to the series circuit of the stability indicator lamp 25 and the second transistor 28 so as to bypass, and the negative power terminal Vo of the detection circuit 22 is connected to the output terminal B. Has been done.

The first to third transistors 27 to 29 described above include a parallel connection state in which the stability indicator lamp 25 is in parallel with the output transistor 21, and a detection circuit, as will be apparent from the operation description given later. A switching element group for switching between a series connection state in which a power supply path to 22 is interposed in series is formed, and is turned on / off by a control circuit 30 together with the operation display transistor 26. Further, particularly in this embodiment, the second and third transistors 28 and 29 not only function as switching elements for switching the current path of the stability indicator lamp 25, but also function as regulator transistors. That is, when each of the transistors 28 and 29 is turned on, the base current is analog-controlled by the control circuit 30 to supply a constant operating voltage VOP to the power supply terminal V + of the detection circuit 22.

Next, the operation of this embodiment will be described. The photoelectric switch of the present embodiment can select a normal open mode or a normal close mode by switching the mode changeover switch 23. Therefore, each mode will be described separately.

(1) In the case where the normal close mode is set When no detection is performed When the detection target is not detected, the operation display transistor 26 and the third transistor 29 are in the ON state, and the first and second Both transistors 27 and 28 are in the off state. Therefore, the operation indicator lamp 24 is turned on and the stability indicator lamp 25 is turned off, and power is supplied to the detection circuit 22 via the third transistor 29. At this time, since the switching operation signal Ss from the detection circuit 22 is at the high level and the output transistor 21 is in the ON state, the load 50 is energized.

Note that the residual voltage VON between the output terminals A and B in this case is shared by the third transistor 29 and the constant operating voltage VOP supplied to the detection circuit 22 in this embodiment. It is relatively low because it corresponds to the sum of Vreg3 (VON = VOP + Vreg3).

At the time of detection (turning off the operation indicator lamp 24) Now, when the detected object enters the detection area, the light reflected by the detected object enters the light receiving element, so that the received light signal When the measurement signal level rises and exceeds the predetermined operation level, the switching operation signal Ss from the detection circuit 22 becomes low level. As a result, the output transistor 21 is turned off and the load 50 is cut off. At the same time, since the operation display transistor 26 is also turned off by a signal given from the detection circuit 22 to the control circuit 30, the operation indicator lamp 24 is extinguished and the output is turned off.

At this time, the leakage current IOFF flowing between the output terminals A and B is equal to the operating current IOP of the detection circuit 22 (IOFF = IOP) and extremely small, because the indicator lamps 24 and 25 are both turned off.

At the time of detection (lighting of the stability indicator lamp 25) When the amount of light emitted from the light projecting element is sufficient and the optical axis is set appropriately, the amount of reflected light entering the light receiving element from the object to be detected is also It rises sufficiently, the measurement signal level of the received light signal becomes sufficiently high, and enters the stable region. Then, the stable display signal Sst is given from the detection circuit 22 to the control circuit 30, and the first and third transistors 27 and 29 are turned off and the second transistor 28 is turned on based on the signal from this. As a result, the stability indicator lamp 25 is connected in series in the power supply path to the detection circuit 22, and the stability indicator lamp 25 is turned on by the operating current IOP flowing into the detection circuit 22. become.

Therefore, the leakage current IOFF flowing between the output terminals A and B at this time is also extremely small, being equal to the operating current IOP of the detection circuit 22 (IOFF = IOP) while the stability indicator lamp 25 is turned on.

(2) When set to the normal open mode When not detected When the detected object is not detected, the operation display transistor 26 and both the first and second transistors 27 and 28 are in the off state. , The third transistor 29 is in the on state. Therefore, power is supplied to the detection circuit 22 via the third transistor 29, and the operation indicator lamp 24 and the stability indicator lamp 25 are turned off. At this time, the switching operation signal Ss from the detection circuit 22 is at the low level and the output transistor 21 is in the off state, so that the load 50 is cut off.

At the time of detection (lighting of the operation indicator lamp 24) When the object to be detected enters the detection area, the measurement signal level of the light reception signal rises, and when it exceeds a predetermined operation level, the detection circuit 22 Since the switching operation signal Ss from the high level becomes high level, the output transistor 21 is turned on and the load 50 is energized. At the same time, since the first transistor 26 is turned on by the signal given from the detection circuit 22 to the control circuit 30, the operation indicator lamp 24 is turned on to indicate that the output is turned on.

Conventionally, when such an output is turned on, there has been a problem that the residual voltage VON between the output terminals A and B becomes high. However, in this embodiment, since the indicator lamps are not in series in the power supply path to the detection circuit 22, the residual voltage VON is the constant operating voltage VOP supplied to the detection circuit 22. Corresponds to the sum of Vreg3 shared by the third transistor 29 (VON = VOP + Vreg3), which is relatively low.

At the time of detection (lighting of the stability indicator lamp 25) When the amount of light emitted from the light projecting element is sufficient and the optical axis is appropriately set, the amount of reflected light entering the light receiving element from the object to be detected is also It becomes sufficient, the level of the received light measurement signal becomes sufficiently high, and enters the stable region. Then, the stable display signal Sst is given from the detection circuit 22 to the control circuit 30, and this time the operation display transistor 26 is turned off and the first transistor 27 is turned on.

As a result, the operation indicator lamp 24 is turned off and the stability indicator lamp 25 is turned on. If the operation indicator lamp 24 is turned off when the stability indicator lamp 25 is turned on as described above, there is an advantage that the minimum load current can be reduced.

As described above, according to the present embodiment, in the normally closed mode, the stability indicator lamp 25 is turned on by the operating current flowing into the detection circuit 22. Therefore, the leakage current IOFF, which is easy to cause a problem in this mode, is reduced. It can be kept extremely small. Also, in the case of the normal open mode, the operation indicator lamp 24 and the stability indicator lamp 25 are connected in parallel with the output transistor 21, so that the residual voltage VON at the time of output ON, which is apt to be a problem in this mode, is extremely low. can do.

As a result, it is possible to obtain excellent output characteristics such that the leakage current IOFF is small and the residual voltage VON is low while providing the operation indicator lamp 24 and the stability indicator lamp 25. Of course, the operation indicator lamp 24 is provided so that the output status can be easily checked, and the stability indicator lamp 25 is provided so that the measurement signal level can be easily confirmed, and the adjustment work at the time of installation and maintenance is remarkable. It goes without saying that it will be easier.

FIG. 3 shows a second embodiment of the present invention. The difference from the first embodiment resides in that a regulator transistor 31 for making the operating voltage VOP supplied to the detection circuit 22 a constant voltage is provided exclusively. The other points are similar to those of the first embodiment, and the same parts are designated by the same reference numerals and the description thereof will be omitted.

Besides, the present invention is not limited to each of the above-described embodiments, and various modifications can be carried out without departing from the scope of the invention, for example, as described below.

(A) Although the mode changeover switch 23 is provided in each of the above-described embodiments, if the configuration is such that the normally closed mode and the normally open mode are set at the time of factory shipment, the switch 23 is omitted. You can also In this case, for example, either mode is set depending on whether the jumper line is connected or the pattern of the printed circuit board is cut, and the control circuit is switched according to the set mode. It may be configured to control the element group.

Even with such a configuration, it is of course possible to turn on the indicator light without impairing the output characteristics, and it is possible to manufacture the sensor switches of two types of modes by using common parts, which leads to cost reduction. There is also the advantage of being possible.

(B) In each of the above embodiments, the two-wire type sensor switch connected to the DC power source is illustrated, but the present invention is not limited to this, and the configuration may be such that the AC power source is connected via a rectifier circuit.

(C) In each of the embodiments, the case where two indicator lamps of the operation indicator lamp 24 and the stability indicator lamp 25 are lit is shown, but the present invention is not limited to this, and only one of the indicator lamps is lit. It may be configured to be turned on.

In addition, the present invention is not limited to a photoelectric switch, but a proximity switch for detecting the approach of a metal detection object by using electromagnetic operation, an ultrasonic sensor for measuring ultrasonic waves, and a pressure sensor. It can be widely applied to pressure sensor switches, etc. to be measured.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention.

FIG. 2 is a circuit diagram showing a first embodiment of the present invention.

FIG. 3 is a circuit diagram showing a second embodiment of the present invention.

FIG. 4 is a block diagram showing a connection state of a transmission type photoelectric switch.

FIG. 5 is a circuit diagram showing a conventional example provided with an indicator lamp.

FIG. 6 is a circuit diagram showing another conventional example provided with an indicator lamp.

[Explanation of symbols]

 21 ... Output transistor (output switching circuit) 22 ... Detection circuit 24 ... Operation indicator lamp 25 ... Stability indicator lamp 27 ... First transistor 28 ... Second transistor 29 ... Third transistor 30 ... Control circuit 40 ... Power source 50 ... load

Claims (1)

[Scope of utility model registration request] 1. A detection circuit for comparing a measurement signal level of an object to be measured such as light, sound waves, a magnetic field with a predetermined operation level to output a switching operation signal, and a detection circuit connected in series to a power supply and a load. An output switching circuit that performs a switching operation based on a switching operation signal, an indicator lamp, and this indicator lamp are connected in series in a parallel connection state in parallel with the output switching circuit and a power supply path to the detection circuit. Switching element group that can be switched to a serial connection state, and when the output lamp is turned on in the normally closed mode of the output switching circuit, the indicator lamp is connected in series, and the indicator lamp is turned on in the normally open mode. Sometimes the switching element group is controlled so that the indicators are connected in parallel. Two-wire sensor switch that comprises a control circuit.