JP3311764B2 - Photoelectric switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric switch having a main body, a light receiver and a light emitter, wherein at least the light emitter is connected to the main body by two signal lines.

[0002]

2. Description of the Related Art As a structure of a photoelectric switch, there is a photoelectric switch in which a light emitter and a light receiver are separated from a main body in which an amplifier, a signal processing circuit and the like are provided. In such a configuration, the light emitter or the light receiver is connected to the main body by a signal line, and signals are transmitted to and received from the main body via the respective signal lines. Therefore, since the size of the light emitter and the light receiver can be reduced, restrictions on the installation location are reduced, so that there is an advantage that the range of use is widened and easy to use.

However, in the case where the main body is separately provided, the detection of light reception is also performed by the main body. Therefore, when a projector or a light receiver is installed, the light reception state must be checked each time. The installation work is troublesome and time-consuming.

In order to solve such a problem, for example, it is considered to provide a light-receiving detection display section in the light projector. In this case, a signal line for supplying a signal for light-receiving detection display from the main body to the light projector is proposed. Will increase,
There has been a problem that the number of wiring steps is increased and the wiring tends to lead to erroneous wiring and a decrease in reliability.

Therefore, conventionally, for example, the following has been considered. In other words, the light emitting diode for display is connected in parallel with the light emitting element on the side of the light emitting element with the opposite polarity while the signal line between the light emitting element and the main body remains two, and light is emitted from the main body via the signal line. A light emitting pulse is applied to the light element to intermittently light, and at the non-output timing of the light emitting pulse, a pulse-like display signal having a polarity opposite to that of the light emitting pulse is supplied from the main body via a signal line to light the display element. It is intended to be.

Thus, even if the projector is provided separately from the main body, the projector can perform the light reception detection display without increasing the number of signal lines, and the above-mentioned problem can be solved.

[0007]

However, in recent years,
Some photoelectric switches have a stable light incident display function for indicating that the level of the light receiving signal exceeds a stable light incident level set to a value higher than the detection level, in addition to the light receiving detection display. It is becoming mainstream. If the two types of display functions are to be realized by the above-described conventional configuration, the number of signal lines must be increased, which leads to an increase in the number of wiring steps and erroneous wiring and reliability. There is a defect that causes a drop.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object the purpose of maintaining at least two signal lines even when at least a light projector is provided separately from the main body, and providing two types of signal lines at the light projector side. The present invention is to provide a photoelectric switch capable of performing the above display.

[0009]

SUMMARY OF THE INVENTION The present invention is directed to a photoelectric switch having a main body, a light receiver, and a light emitter, wherein at least the light emitter is connected to the main body with two signal lines. A signal generation circuit provided in the main body for outputting a pulsed light emission signal, and a first pulsed display provided in the main body having a polarity opposite to that of the light emission signal at a non-output timing of the light emission signal A display drive circuit for selectively outputting a signal and a second pulsed display signal having a higher peak value than the display signal, and energized and lit by the light projection signal provided through the signal line provided in the light projector And a first display element provided in the projector and energized and lit via a resistor in a state where the first or second pulsed display signal is supplied via the signal line. , Provided in the floodlight A transistor that is turned on by the terminal voltage of the resistor when the second display signal is supplied to the first display element; and a second transistor that is provided in the light projector and is energized and turned on when the transistor is turned on. It is characterized by having a display element.

[0010]

According to the photoelectric switch of the present invention, the light emitting element provided in the light projector is energized and turned on by a pulsed light signal supplied from the main body through the signal line, and the pulse light is transmitted to the light receiver. Project. The light receiver receives light from the light emitter and transmits the light reception signal to the main body. The main body outputs a light emitting signal to the light emitting device and selectively outputs the first or second pulsed display signal at a non-output timing of the light emitting signal. In this case, since the first and second pulsed display signals have polarities opposite to those of the light emission signal, the light emission element is not driven and turned on. And the first
When the pulsed display signal is supplied, the first display element is energized through the resistor, so that the first display element is turned on. When the second pulse-like display signal is supplied, the first display element is energized, and the peak value of the second pulse-like display signal is higher than that of the first pulse-like display signal. Becomes large, the transistor is turned on, and the second display element is also energized to be turned on. Thus, for example, two types of display functions can be provided, such as display of stable light detection in addition to display of light reception detection.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

FIG. 2 is a block diagram showing the overall structure of the apparatus. The overall structure comprises a main body 1, a light emitter 2 and a light receiver 3. Of these, two signal lines are provided between the main body 1 and the light emitter 2. 4 and 5 are connected, and two signal lines 6 and 7 are connected between the main body 1 and the light receiver 3.

FIG. 1 shows an electrical configuration of a main part, which will be described below. First, in the light projector 2, the anode of the light emitting LED 8 as a light emitting element is connected to the signal line 4, and the cathode is connected to the signal line 5. The anode of the light-receiving display LED 9 as the first display element is connected to the signal line 5, and the cathode is connected to the signal line 4 via the resistor 10.

An LED for displaying stable light as a second display element
11 is connected to the signal line 5 and the cathode is np
The n-type transistor 12 is connected to the signal line 4 via the collector and the emitter. The base of the transistor 12 is connected to the cathode of the light-receiving display LED 9.

Next, in the main unit 1, the signal generation circuit 1
Reference numeral 3 denotes a pulse-like light emitting signal having a predetermined period, and its output terminal is connected to the base of an npn transistor 15 via the emitter and collector of the pnp transistor 14. The base of the transistor 14 is a resistor 16
Is connected to the signal line 5 via the ground and grounded. The collector of the transistor 15 is connected to the DC power supply terminal 17, and the emitter is grounded via the resistor 18 and the emitter-collector of the pnp transistor 19. The base of the transistor 19 is connected to the output terminal of the signal generating circuit 13, and the emitter is connected to the signal line 4.

One terminal of the display element lighting capacitor 20 is connected to the emitter of the transistor 19, and the other terminal is connected to the DC power supply terminal 17 via the resistor 21 and the collector and emitter of the pnp transistor 22. I have. The other terminal of the capacitor 20 is connected between the collector and the emitter of the npn transistor 23 and the resistor 24.
And an npn transistor 2
5 between the collector and the emitter and via the resistor 26. The base of the transistor 22 is connected to the DC power supply terminal 17 via the resistor 27 and
And grounded through the collector and emitter of the npn transistor 29.

The output terminal of the signal generating circuit 13 is also connected to the input terminal of the monostable multivibrator 30. The monostable multivibrator 30 outputs an "H" level signal for a certain period of time when a pulse signal is supplied to an input terminal.
1 is connected to one input terminal. The other input terminal of the AND circuit 31 is connected to the output terminal of the signal generation circuit 13 via the inverter circuit 32. And
The output terminal of the AND circuit 31 is connected to one input terminal of the NOR circuit 33 and to one input terminal of the AND circuit 34. The other input terminal of the NOR circuit 33 is connected to the output terminal of the signal generation circuit 13 and
The output terminal of the circuit 33 is connected to one input terminal of the AND circuit 35.

The other input terminal of each of the AND circuit 34 and the AND circuit 35 is connected to an output terminal a of a light receiving signal processing circuit 36 provided in the main body 1, and a light receiving detection signal is output from the light receiving signal processing circuit 36. Is to be given. The output terminal of the AND circuit 34 is connected to the base of the transistor 25 and to one input terminal of the AND circuit 37. The output terminal of the AND circuit 35 is connected to the base of the transistor 29. AND circuit 3
The other input terminal 7 is connected to the output terminal b of the light receiving signal processing circuit 36, and the light receiving signal processing circuit 36 supplies a stable light input signal. AND circuit 37
Is connected to the base of the transistor 23.

In the main body 1, a portion excluding the signal generating circuit 13 and the light receiving signal processing circuit 36 is configured as a display driving circuit 38.

Next, the operation of this embodiment will be described with reference to FIG. The main body 1 gives a light emitting signal to the light emitting device 2 to perform (1) light emitting operation. When light is detected by the light receiving device 3 by this light emitting, the presence or absence of an object is detected by the light receiving signal at that time. Is performed, and at the same time, according to the level of the light receiving signal at that time, the projector 2 displays the light receiving state of whether the light is received in a stable state or in an unstable state. Hereinafter, these operations will be described in detail.

(1) Light Projection Operation In the main body 1, the signal generation circuit 13 generates a pulse-like light projection signal having a predetermined period as shown in FIG. With this light emission signal, the transistor 14 is turned on, the transistor 15 is turned on, and the transistor 19 is turned off. As a result, a current flows in a path from the DC power supply terminal 17 to the transistor 15, the resistor 18, the signal line 4, the light emitting LED 8, and the signal line 5, so that the light emitting LED 8
Lights intermittently at a timing corresponding to the light projection signal.

On the other hand, the monostable multivibrator 30 outputs an "H" level signal for a predetermined time as shown in FIG. 3 (e) every time the light emitting signal from the signal generating circuit 13 is applied. The signal is input to the AND circuit 31.

(2) Detection Operation Next, the light output from the light-emitting LED 8 by the above-described light-emitting operation is received by the light-receiving device 3, and the signal lines 6 and 6 are transmitted from the light-receiving device 3.
The light receiving signal is transmitted through the light receiving signal processing circuit 36
A description will be given of the detection operation in the case of applying to. The following cases will be described according to the presence or absence of an object that blocks the optical axis and the light receiving level at that time.

(A) Light-shielded state When an object exists on the optical axis and light does not enter the light receiver 3, there is no light reception signal from the light receiver 3 side. In this state, neither the light reception detection signal nor the stable light detection signal is output from the circuit 36. Accordingly, at this time, only the light projection signal appears between the signal lines 4 and 5, as shown in FIG.

(B) Unstable detection state Next, in the case where light from the light projector 2 is incident on the light receiver 3,
The operation in a state where the level of the light receiving signal of the light receiver 3 reaches the detection level but is not at the stable light input level, that is, the unstable detection state will be described.

That is, when the light receiving signal exceeds the detection level,
The light receiving signal processing circuit 36 of the main body 1
And outputs an "H" level light reception detection signal (see FIG. 3C), which is a pulse-like display signal. In this case, the light reception detection signal is output when the output signal (see FIG. 3E) of the monostable multivibrator 30 is inverted to the “L” level after the light emission signal is output. .

When the light receiving detection signal is output, the output of the NOR circuit 33 goes to the "H" level because the output of the monostable multivibrator 30 is at the "L" level at that time. Becomes "H" level (see FIG. 3 (g)). Thus, when the transistor 29 is turned on, the transistor 22 is also turned on. on the other hand,
At this time, the light emission signal of the signal generation circuit 13 is at the “L” level, so that the transistor 19 is turned on.

Therefore, the capacitor 20 includes the DC power supply terminal 17, the transistor 22, the resistor 21, the capacitor 20,
A direct current flows through the energization path of the transistor 19 to start charging. Next, when the light emission signal becomes “H” level,
The output of the monostable multivibrator 30 is also at "H" level, the output of the AND circuit 35 is inverted to "L" level, and the transistors 22 and 19 are turned off. As a result, the current in the capacitor 20 is cut off, so that the charging is terminated, and the electric charge is accumulated between both terminals of the capacitor 20. The light emitting LED 8 is lit while the light emitting signal is at the “H” level.

Subsequently, when the light emission signal goes to "L" level, while the output of the monostable multivibrator 30 is at "H" level, the output of the AND circuit 34 goes to "H" level. Turned on. This allows
The charge of the capacitor 20 flows through the current path of the transistor 25, the resistor 26, the signal line 5, the light receiving display LED 9, the resistor 10, and the signal line 4, and the light receiving display LED 9 is turned on. At this time, since the resistance value of the resistor 26 is set so that the voltage drop due to the resistor 10 does not cause the transistor 12 to be turned on, the LED 11 for stable light input display is not energized and is turned off.

When the output of the monostable multivibrator 30 is inverted to "L" level, the output of the AND circuit 34 also becomes "L" level, and the transistor 25 is turned off.
As a result, the light receiving display LED 9 is cut off and turned off. Then, before the light emission signal is inverted to the “H” level, the capacitor 20 is charged again in the same manner as described above.

(C) Stable detection state Next, when the light is sufficiently incident on the photodetector 3 and the level of the received light signal exceeds the stable incident light level,
In addition to the light reception detection signal, an output terminal "b" of the light reception signal processing circuit 36 outputs a "H" level stable light detection signal (see FIG. 3D) as a second pulse-like display signal. This stable light detection signal is also output when the output of the monostable multivibrator 30 is inverted to the "L" level in the same manner as the above-described light reception detection signal.

Also in this case, the monostable multivibrator 3
When the output of 0 is inverted to the “L” level, the capacitor 20 is charged in the same manner as described above. After that, the light emission signal becomes “H” level, and the light emission LED 8 is turned on.

Subsequently, when the light emission signal is inverted to the "L" level, while the output of the monostable multivibrator 30 is at the "H" level, the light reception detection signal and the stable light detection signal are at the "H" level. Therefore, the outputs of the AND circuits 34 and 37 become "H" level. As a result, the transistor 23 is turned on in addition to the transistor 25, so that the charge of the capacitor 20 flows through the current path via the transistor 23 and the resistor 24 in addition to the current path. That is, when the stable light incident detection signal is substantially output, the peak value becomes higher than when only the light reception detection signal is output.

Accordingly, the charge of the capacitor 20 flows through the current path in a state where the resistors 26 and 24 are connected in parallel, so that the voltage drop of the resistor 10 on the side of the projector 2 becomes large and the transistor 12 is turned on. Become like As a result, the light receiving display LED 9 and the stable light receiving display LED 9
11 are energized and turned on.

Thereafter, when the stable light receiving state continues, the light receiving signal processing circuit 36 continues to output the light receiving detection signal and the stable light receiving detection signal, and the above-described operation is repeated. When the state changes from the stable light receiving state to the unstable light receiving state, the stable incident light detection signal is inverted to the “L” level, and the above-described operation of the unstable light receiving state is performed.

According to this embodiment, the light-emitting device 2 is connected to the light-receiving detection display LED 9 in anti-parallel with the light-emitting LED 8 via the resistor 10 in series, and is turned on at a predetermined terminal voltage by the resistor 10. Since the transistor 12 and the LED 11 for displaying stable light are connected in series with the transistor 12, the light emitting LED 8 is energized and turned on by the light emitting signal, and the light receiving is detected by the light receiving detection signal in the opposite direction and the stable light receiving detection signal. Display and stable light incident detection display can be performed. Therefore, it is only necessary to provide two signal lines 4 and 5 between the light projector 2 and the main body 1, and by increasing the number of signal lines Incorrect wiring and reduction in reliability can be prevented.

Further, according to this embodiment, the reverse voltage applied to both terminals of the light emitting LED 8 when the light receiving detection display LED 9 and the stable light entering display LED 11 are operated can be made relatively small. Therefore, it is not necessary to separately provide a diode or the like for compensating the withstand voltage. That is, since the forward voltage of the LED 9 is about 2 V and the base-emitter voltage of the transistor 12 is about 0.7 V, the light emitting LED 8
Will take up to 2.7V in the reverse direction.
Since the reverse breakdown voltage is about 3 V, it can be fully tolerated.

FIG. 4 shows a second embodiment of the present invention.
The difference from this embodiment is that a pnp transistor 39 is used instead of the npn transistor 12 of the light projector 2. That is, the cathode of the LED 9 for light reception detection display is connected to the signal line 4, and the anode is connected to the signal line 5 via the resistor 10. LED for stable light display
11 has a cathode connected to the signal line 4 and an anode connected to the signal line 5 via the collector and the emitter of the transistor 39.
It is connected to the.

With this configuration, similarly to the first embodiment, the light emitting LED 8 is intermittently turned on by the light emitting signal from the signal generating circuit 13, and the light receiving detection display LED 9 is intermittently turned on by the light receiving detection signal. The LED is turned on, and the stable light-indicating display LED 11 is also intermittently turned on by the stable light-in detection signal. Therefore, according to the second embodiment, the same operation and effect as those of the first embodiment can be obtained.

FIG. 5 shows a third embodiment of the present invention.
What is different from the embodiment is the connection relation in the light projector 2. That is, the light emitting LED 8 is connected between both terminals of the resistor 10, and the stable light incident display LED 11 is connected to the transistor 1.
2 and the signal line 4.

According to such a configuration, when the light emission signal is given via the signal lines 4 and 5, the light emission LED 8
Current flows through a forward diode portion between the base and collector of the transistor
The ED 8 is turned on. Also, when a light reception detection signal is given, a current flows through the light reception detection display LED 9 and the resistor 10, and the light reception detection display LED 9
Are energized and turned on, and when a stable light incident detection signal is given, the transistor 12 is turned on by the terminal voltage of the resistor 10 and the LED 11 for stable light incident is energized and turned on in addition to the energized lighting of the LED 9 for light reception detection display. Become so. Therefore, the same effects as those of the above-described embodiment can be obtained by the third embodiment.

FIG. 6 shows a fourth embodiment of the present invention. The structure of the fourth embodiment differs from that of the second embodiment in that a light emitting LED 8 is connected between both terminals of a resistor 10 and a stable light input. The display LED 11 is connected between the emitter of the transistor 39 and the signal line 5.

According to this embodiment, the same operation as that of the third embodiment can be obtained, and the same effect as that of the first embodiment can be obtained.

[0044]

As described above, according to the photoelectric switch of the present invention, the first and second pulse-like display signals are supplied to the projector via the signal line at the non-output timing of the projection signal, and the Is composed of the first and second display elements connected in reverse polarity to the light emitting element, a resistor and a transistor,
Since the first display element is turned on by the first pulsed light emission signal, and the first and second display elements are turned on by the second pulsed display signal, erroneous wiring and reliability of signal lines are performed. There is an excellent effect that two display functions can be performed with two signal lines remaining without causing a decrease.

[Brief description of the drawings]

FIG. 1 is an electrical configuration diagram of a main part showing a first embodiment of the present invention.

FIG. 2 is a schematic diagram of the overall configuration.

FIG. 3 is a time chart showing a signal output state of each unit.

FIG. 4 is an electrical configuration diagram of a projector unit according to a second embodiment of the present invention.

FIG. 5 is a view corresponding to FIG. 4, showing a third embodiment of the present invention.

FIG. 6 is a view corresponding to FIG. 4, showing a fourth embodiment of the present invention.

[Explanation of symbols]

1 is a main body, 2 is a light emitting device, 3 is a light receiving device, 4 to 7 are signal lines, 8 is a light emitting LED (light emitting element), and 9 is a light receiving display L
ED (first display element), 10 is a resistor, 11 is an LED for stable light input (second display element), 12 is an npn transistor, 13 is a signal generation circuit, 17 is a DC power supply, 20
Is a capacitor, 30 is a monostable multivibrator, 3
1, 34, 35 and 37 are AND circuits, 33 is a NOR circuit, 36 is a light receiving signal processing circuit, 38 is a display driving circuit,
9 is a pnp transistor.

Claims (1)

(57) [Claims] 1. A photoelectric switch comprising a main body, a light receiver, and a light emitter, wherein at least the light emitter is connected to the main body by two signal lines, and a pulse-like light emission signal provided in the main body is provided. A signal generating circuit for outputting, a first pulse-like display signal having a polarity opposite to that of the light emission signal provided at the non-output timing of the light emission signal and a second peak having a higher peak value than the display signal. A display driving circuit for selectively outputting a pulsed display signal of the above, a light emitting element provided in the light projector and energized and lit by the light emitting signal provided through the signal line, and the signal provided in the light projector A first display element that is energized and lit through a resistor in a state where the first or second pulsed display signal is supplied via a line, and a first display element provided in the light projector, Second pulsed table A photoelectric switch, comprising: a transistor that is turned on by a terminal voltage of the resistor when a signal is supplied, and a second display element that is provided in the light projector and is energized and turned on when the transistor is turned on. .