JPH081224U - Photoelectric switch - Google Patents

Abstract

(57) Abstract: A semiconductor switch element outputs a photoelectric switch detection output and a self-diagnosis result. A memory circuit for storing an output of a self-diagnosis circuit 8
12, a selection circuit 13 for selecting the output of the storage circuit 12 and the output of the detection circuit 7 of the photoelectric switch itself according to the presence or absence of the control power supply Vcc, and a power holding circuit 14 for backing up the storage circuit 12 are provided. Normally, when Vcc is applied,
The selection circuit 13 selects the output from the detection circuit 7, whereby the semiconductor switch element 9 outputs the detection result of the photoelectric switch, and when the control power supply Vcc is cut off, the selection circuit 13 is selected.
The output of the memory circuit 12 is selected by the, and the self-diagnosis result is output from the semiconductor switch element 9.

Description

[Detailed description of the device]

[0001]

[Technical field to which the device belongs]

 The present invention relates to a photoelectric switch that determines the presence or absence of a target object based on the amount of light emitted from a light emitting element reaching a light receiving element.

[0002]

[Prior art]

 A photoelectric switch shown in FIG. 2 is conventionally known as this type of photoelectric switch. The circuit shown in FIG. 2 and its operation will be described with reference to the waveform chart of FIG. In FIG. 2, the output terminal of the oscillation circuit 1 is connected to the light emitting element 3 via the resistor 2, and the pulse current Ip as shown in FIG. The light receiving element 4 facing the light emitting element 3 is connected to the amplifier 5, and the amplifier 5 amplifies the output signal of the light receiving element 4 into a waveform indicated by the voltage Vp. The output terminal of the amplifier 5 is connected to the comparator 6a, and the comparator 6a discriminates the waveform of the voltage Vp at a predetermined reference level VL0 to obtain a digital signal Vd suitable for logic processing and connect it to the output terminal of the comparator 6a. A detection signal V01 is obtained by the detected detection circuit 7 and applied to the base of the output transistor 9 to turn on / off the transistor 9 to confirm the presence or absence of a target object (not shown). The output terminal of the amplifier 5 is further connected to a comparator 6b having a predetermined reference level VL1 higher than that of the comparator 6a and a comparator 6c having a predetermined reference level VL2 lower than that of the comparator 6a, and each comparator 6b, 6c has a respective level VL1, The output of the amplifier 5 is discriminated by VL2 and the voltages Vd1 and Vd2 are output. The self-diagnosis circuit 8 to which the output terminals of the comparators 6b and 6c are connected diagnoses whether the received light signal is sufficient or whether the received light signal is completely cut off without leakage light. When the output Vp of the amplifier 5 is less than the reference level VL2 of the comparator 6c, the light emitted from the light emitting element 3 does not enter the light receiving element 4 and is sufficiently shielded. , When the output Vp of the amplifier 5 exceeds the reference level VL1 of the comparator 6b, it is selected so as to be in a sufficient light receiving state. Therefore, the self-diagnosis circuit 8 determines that the output Vp of the amplifier 5 exceeds the reference level VL2 of the comparator 6c. Is output when the reference level VL1 of the comparator 6b is not exceeded. This is obtained by taking the logical product of the output Vd2 of the comparator 6c and the inverted signal of the output Vd1 of the comparator 6b. Here, the state where the output Vp of the amplifier 5 is between the reference levels VL1 and VL2 of the comparators 6b and 6c means that the light emitted from the light emitting element 3 is received by the light receiving element 4 and the detection signal from the detection circuit 7 is detected. Although V01 is obtained and is in the detection state, the photoelectric switch does not have a sufficient light reception output for stable operation. Such a state occurs, for example, when the lens surface of the light emitting / receiving lens is soiled during use of the photoelectric switch. In such a case, before the function as the photoelectric switch is impaired, an alarm is issued from the self-diagnosis circuit 8 to prompt cleaning of the lens surface and the like to prevent failure of the entire device using the photoelectric switch.

[0003]

[Problems to be solved by the device]

 The photoelectric switch with such a self-diagnosis function has the advantage of stable operation and high reliability, but on the other hand, it has an output transistor for self-diagnosis in addition to the output transistor of the detection circuit. There were problems that the number of output elements as photoelectric switches increased, and the number of lead wires connected to external devices also increased, which led to increased wiring costs and other obstacles to miniaturization. Moreover, in order to input these outputs to the sequence controller, the number of input circuits of the sequence controller must be increased, and there is a problem that a large and expensive sequence controller is required.

Therefore, an object of the present invention is to eliminate the drawbacks of the conventional device described above, and to output the self-diagnosis result to the outside from one semiconductor switch element in addition to the output as the original photoelectric switch. To provide a switch.

[0005]

[Means for Solving the Problems]

 In order to achieve the above-mentioned object, the present invention provides a light-receiving element that receives an optical signal emitted from a pulse-lighted light-emitting element and converts it into an electrical signal, and outputs the light-receiving element after discriminating the output of the light-receiving element at a predetermined level. 1 comparator, a second comparator having a discrimination level higher than the first comparator, a third comparator having a discrimination level lower than the first comparator, and outputs of the second and third comparators. A self-diagnosis circuit comprising: a self-diagnosis circuit that diagnoses an input to the light-receiving element according to a force and outputs the result; and a semiconductor switch element that is on / off controlled by an output of the first comparator. Inputting the output of the first comparator and the output of the storage circuit, and inputting either of these inputs. The power supply was cut off by providing a selection circuit that selects depending on the presence or absence of a voltage and outputs it to the semiconductor switch element, and a power holding circuit that supplies power to the storage circuit, the selection circuit, and the semiconductor switch element when the power supply is cut off. At this time, the selection circuit outputs the storage content of the storage circuit to the semiconductor switch element.

[0006]

[Embodiment of device]

 Since the attenuation of the received light signal of this type of photoelectric switch does not proceed rapidly, it is not necessary to perform self-diagnosis at all times, and attention is paid to the fact that it can be carried out when necessary or at the time of periodic inspection. The diagnostic results of the self-diagnosis circuit during the period are stored in the storage circuit, and the power supply is temporarily cut off as needed to automatically switch the selection circuit to the storage circuit, and the self-diagnosis stored in this storage circuit. The diagnostic result of the circuit is output to the semiconductor switch element. The output of the self-diagnosis result from the semiconductor switch element continues to be output until the power of the power holding circuit is consumed. After that, when the power of the photoelectric switch is turned on, the selection circuit selects the output of the first comparator and the semiconductor switch element outputs the original detection output of the photoelectric switch.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0008]

【Example】

 An embodiment of the photoelectric switch according to the present invention is shown in FIG. 1, and the same parts as those of the conventional device shown in FIG. 2 are designated by the same reference numerals. In FIG. 1, the light-receiving element 3 emits light with a pulse current generated by the oscillation circuit 1 and the light-receiving element 4 receives the light similarly to the conventional one. Since the amplifier 5 on the light receiving side, the three comparators 6a, 6b, 6c, the detection circuit 7, the self-diagnosis circuit 8 and the like are the same as the conventional ones, the description thereof will be omitted. This embodiment is different from the conventional one in that a delay circuit 11, a memory circuit 12, a selection circuit 13, and a power holding circuit 14 are provided. The output terminal of the self-diagnosis circuit 8 is connected to the storage circuit 12 via the delay circuit 11. The delay circuit 11 is, for example, for noise elimination for outputting an output and storing the diagnostic result in the memory circuit 12 when the diagnostic result from the self-diagnostic circuit 8 continues for a certain time, and is not always necessary. Further, the memory circuit 12 is connected via a diode 16 so as to be reset when the capacitor 17 of the power holding circuit 14 connected so as to be charged with the voltage of the power source Vcc is discharged. The selection circuit 13 includes an inverter 18, two AND circuits 19 and 20, and an OR circuit 21, the output end of the detection circuit 7 is connected to one input end of the AND circuit 19, and the other input end is controlled by the control power supply Vcc. Are connected. The output end of the memory circuit 12 is connected to one input end of the AND circuit 20, and the other input end is connected via an inverter 18. The control power supply Vcc is a signal power supply for control that is formed when power is applied to the photoelectric switch and disappears when the power is cut off. Its voltage level is a voltage suitable for logic processing. It is kept. The output terminals of the AND circuits 19 and 20 are connected to the respective input terminals of the OR circuit 21, and the output terminal of the OR circuit 21 is connected to the base of the FET type output transistor 9. The power source for driving the selection circuit 13 and the output transistor 9 is connected to the connection point of the diode 16 and the capacitor 17 of the power holding circuit 14 which is connected to charge the capacitor 17 via the diode 16 with the control power source Vcc. .

Since the original operation of the photoelectric switch and the operation of the self-diagnosis circuit 8 have already been described with reference to FIG. 2, description thereof will be omitted, and hereinafter, the delay circuit 11, the memory circuit 12, the selection circuit 13, the power holding circuit will be mainly described. The operation of 14 will be described. The memory circuit 12 is reset when the power supply Vcc is stopped for a predetermined time or longer to stop this photoelectric switch, and when the power supply Vcc is turned on, the capacitor 17 is immediately charged via the diode 16. The diagnosis result of the self-diagnosis circuit 8 is stored via the delay circuit 11. When the power supply Vcc to this photoelectric switch is cut off and the capacitor 17 is discharged, when the power supply Vcc is turned on, the control power supply Vcc is applied to the other input terminal of the AND circuit 19 and becomes high level. Therefore, it becomes possible to conduct electricity. At this time, the other input terminal of the AND circuit 20 becomes low level because the control power supply Vcc is applied through the inverter 18, and the AND circuit 20 is closed. Therefore, the signal received by the light receiving element 4, discriminated at a predetermined level of the comparator 6a and detected by the detection circuit 7 is applied to the base of the output transistor 9 through the AND circuit 19 and the OR circuit 21, and the output transistor 9 It is output from and continues to operate as a normal photoelectric switch. During this period, the diagnosis result of the self-diagnosis circuit 8 is stored in the storage circuit 12 via the delay circuit 11.

In order to know the diagnosis result of the optical system of this photoelectric switch, if the control power supply Vcc is cut off, the memory circuit 12, the selection circuit 13, and the output transistor 9 are driven by the electric charge of the capacitor 17 of the power holding circuit 14, and AND The circuit 19 is closed, and the AND circuit 20 is ready for conduction. Therefore, the diagnosis result stored in the storage circuit 12 passes through the AND circuit 20 and the OR circuit 21 and is applied to the base of the output transistor 9, so that the output of the output transistor 9 produces juice powder. The memory circuit 12 is reset when the control power supply Vcc is cut off for a long time and the charge of the capacitor 17 is discharged.

[0011]

[Effect of device]

 As described above, according to the present invention, a light-receiving element that receives an optical signal emitted from a light-emitting element that is pulse-lighted and converts it into an electrical signal, and the output of this light-receiving element is discriminated at a predetermined level and then output. 1 comparator, a second comparator having a discrimination level higher than the first comparator, a third comparator having a discrimination level lower than the first comparator, and outputs of the second and third comparators. A self-diagnosis circuit comprising: a self-diagnosis circuit that diagnoses an input to the light-receiving element according to a force and outputs the result; and a semiconductor switch element that is on / off controlled by an output of the first comparator. Inputting the output of the first comparator and the output of the storage circuit, and inputting either of these inputs. The power supply was cut off by providing a selection circuit that selects depending on the presence or absence of a voltage and outputs it to the semiconductor switch element, and a power holding circuit that supplies power to the storage circuit, the selection circuit, and the semiconductor switch element when the power supply is cut off. At this time, since the selection circuit is configured to output the storage content of the storage circuit to the semiconductor switch element, it is possible to output the self-diagnosis result using the semiconductor switch element that outputs the original detection result of the photoelectric switch. Therefore, the detection result and the self-diagnosis result of the photoelectric switch can be transmitted to the outside by one semiconductor switch element. Therefore, for each output of the detection result by the corresponding semiconductor switch element, The photoelectric switch can be miniaturized by reducing the number of parts and the number of output terminals of the semiconductor switch element. Also, since the number of output terminals is reduced, the number of wires with external devices can be reduced, so that the wiring work can be facilitated and erroneous wiring can be prevented.

[Brief description of drawings]

FIG. 1 is a connection diagram showing a photoelectric switch according to an embodiment of the present invention.

FIG. 2 is a connection diagram showing a photoelectric switch of a conventional device.

FIG. 3 is a waveform diagram of a main part of the photoelectric switch of FIG.

[Explanation of symbols]

3 ... Light emitting element, 4 ... Light receiving element, 6a, 6b, 6c ... Comparator, 8 ... Self-diagnosis circuit, 11 ... Delay circuit, 12 ... Storage circuit,
13 ... Selection circuit, 14 ... Power holding circuit.

Claims (1)

[Scope of utility model registration request] 1. A light-receiving element for receiving an optical signal emitted from a pulse-lighted light-emitting element and converting it into an electric signal, a first comparator for discriminating an output of the light-receiving element at a predetermined level, and outputting the first comparator. A second comparator having a discrimination level higher than that of the first comparator, a third comparator having a discrimination level lower than that of the first comparator, and an input to the light receiving element according to outputs of the second and third comparators. In a photoelectric switch including a self-diagnosis circuit that diagnoses and outputs the result, and a semiconductor switch element that is on / off controlled by the output of the first comparator, a storage circuit that stores the output of the self-diagnosis circuit, The output of the first comparator and the output of the memory circuit are used as inputs, and either of these inputs is selected according to the presence or absence of a power supply voltage. A selection circuit for outputting to a conductor switching element, a storage circuit for supplying power to the storage circuit, the selection circuit, and a semiconductor switching element when the power supply is cut off are provided, and the selection circuit for the storage circuit when the power supply is cut off. A photoelectric switch characterized by outputting stored contents to a semiconductor switch element.