JPH081225U - 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 and the output of the storage circuit 12 and the output of the detection circuit 7 of the photoelectric switch itself from the external control circuit 14 to the external connection terminal 141.
Selection circuit 13 selected by the control signal applied to
In the normal state when a high level control signal is applied to the external connection terminal 141, the selection circuit 13 selects the output from the detection circuit 7, and the semiconductor switch element 9 outputs the detection result of the photoelectric switch. External connection terminal 141
When a low-level control signal is applied to the semiconductor switch element 9, the selection circuit 13 selects the output of the memory circuit 12.
Outputs the self-diagnosis result.

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. In a photoelectric switch including 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 outputs an on / off signal by the output of the first comparator, A memory circuit for storing the output of the circuit, and an output of the first comparator and an output of the memory circuit as input A selection circuit for outputting to said semiconductor switching element is selected, is applied from the outside, characterized in that an external connection terminal for transmitting a control signal for selecting the input to the selection circuit to the selection circuit.

[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 result of the self-diagnosis circuit during the period is stored in the memory circuit, and the control circuit automatically switches to select the input of the memory circuit by applying the control signal to the external connection terminal if necessary. As a result, the diagnosis result of the self-diagnosis circuit stored in the memory circuit is transmitted to the outside via the semiconductor switch element. When the control signal is no longer applied to the external connection terminal, the selection circuit selects the output of the first comparator, and the original detection output of the photoelectric switch is transmitted to the outside through the semiconductor switch element.

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 differs from the conventional one in that a delay circuit 11, a memory circuit 12 and a selection circuit 13 are provided, and the memory circuit 12 and the selection circuit 13 are controlled by a signal from an external control circuit 14. Reference numeral 141 is an external connection terminal of the photoelectric switch. The memory circuit 12 is connected to the output terminal of the self-diagnosis circuit 8 via a delay circuit 11. The delay circuit 11 is, for example, for noise removal for outputting an output when the diagnosis result from the self-diagnosis circuit 8 continues for a certain time and storing the diagnosis result in the storage circuit 12, and is not always necessary. The selection circuit 13 includes an inverter 15, two AND circuits 16 and 17, and an OR circuit 18. The output end of the detection circuit 7 is connected to one input end of the AND circuit 16 and the other input end is connected to an external control circuit. 14 are connected. The output end of the storage circuit 12 is connected to one input end of the AND circuit 17, and the external control circuit 14 is connected to the other input end via an inverter 15. The output terminals of the AND circuits 16 and 17 are connected to the respective input terminals of the OR circuit 18, and the output terminal of the OR circuit 18 is connected to the base of the FET type output transistor 9.

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, the description thereof will be omitted, and the operation of the delay circuit 11, the memory circuit 12, and the selection circuit 13 will be mainly described below. To do. After the photoelectric switch is started, when the output of the external control circuit 14 is set to the high level, this output is applied to the other input terminal of the AND circuit 16, so that the AND circuit 16 becomes conductive. At this time, the input of the other input terminal of the AND circuit 17 becomes low level via the inverter 15, so the AND circuit 17 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 passes through the AND circuit 16 and the OR circuit 18, and is applied to the base of the output transistor 9. , Is output from the output transistor 9, 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 output of the external control circuit 14 is set to low level, the AND circuit 16 is closed, and the base of the output transistor 9 is connected via the AND circuit 17 and the OR circuit 18. It can be known from the output of the output transistor 9 since it is applied to the. The memory circuit 12 is reset when the output of the external control circuit 14 rises from a low level to a high level or after a predetermined time elapses after the output of the external control circuit 14 becomes a low level, and the memory circuit 12 functions as the next original photoelectric switch. It is designed to be remembered when moving to the action of.

[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. In a photoelectric switch including 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 outputs an ON / OFF signal by the output of the first comparator, the self-diagnosis is performed. A memory circuit for storing the output of the circuit, and one of the inputs of the output of the first comparator and the output of the memory circuit By providing a selection circuit for selecting and outputting to the semiconductor switch element and an external connection terminal for transmitting a control signal applied from the outside to select the input to the selection circuit to the selection circuit, When the applied control signal is changed to high level and low level, the selection circuit automatically switches between the original detection result of the photoelectric switch and the self-diagnosis result of the self-diagnosis circuit stored in the memory circuit. Since the light is sent to the switch element, only one semiconductor switch element is required, and the number of parts and the number of output terminals of the semiconductor switch element can be reduced as compared with the conventional device, whereby the photoelectric switch can be downsized. In addition, even if you do not go to the site where the photoelectric switch is installed, you can obtain the diagnosis result of the self-diagnosis circuit by applying a control signal to the external connection terminal. There is an effect that the self-diagnosis result can be known by an operation from the ground.

[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 ... External control circuit, 141 ... External connection terminal.

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. A storage circuit that stores the output of the self-diagnosis circuit in a photoelectric switch including a self-diagnosis circuit that diagnoses and outputs the result and a semiconductor switch element that outputs an on / off signal according to the output of the first comparator. , The output of the first comparator and the output of the memory circuit are input, and either of the inputs is selected to select the semiconductor switch element. A selection circuit for outputting to, externally applied, the photoelectric switch, characterized in that an external connection terminal for transmitting a control signal for selecting the input to the selection circuit to the selection circuit.