JPH0687035B2 - Photoelectric sensor control method and control system - Google Patents

Description

The present invention relates to a control system for a photoelectric sensor including a light emitting element and a light receiving element.

(Prior Art) A photoelectric sensor is used as one of switches in various sequence control processes.

A conventional photoelectric sensor and its switching method are shown in FIG.

In the figure, the photoelectric sensor 21 includes a light emitting element 22 and a light receiving element 23.
The light emitting element 22 emits the optical axis L toward the light receiving element 23. Typically, the light emitting element 22 is a photodiode and the light receiving element 23 is a phototransistor.

A signal from the photoelectric sensor 21 is input to the amplifier section 24, and a signal indicating whether or not an object is present between the light emitting element 22 and the light receiving element 23 is input from the amplifier section 24 to the controller section 25. Based on this input, the controller unit 25 controls the device 26.

Incidentally, in general, the light emitting element 22 of the photoelectric sensor 21 is adapted to be inputted with a pulse wave and be intermittently lit at a constant period, and the amplifier section 24 compares the pulse signal synchronized with the pulse wave of the object. I was judging the existence.

(Problems to be Solved by the Invention) In the above-described configuration, it is easy to be affected by ambient light. That is, as shown in FIG. 5, the output signal of the light receiving element 23 can take three types of waveforms. Figure 5 (a)
(B) and (c) indicate (a) when the light from the light emitting element 22 is not incident, and (b) when light from the light emitting element 22 is incident (c) the disturbance light is incident. Shows the waveform when Of these, (a) and (b) are in a normal operating state, and the amplifier section 24 for the input of (a) and (b) can transmit the presence or absence of an object to the controller section 25.

However, when ambient light is incident, the amplifier section 24 cannot perform detailed data processing. Therefore, it is determined that (a) is input and the same signal is sent to the controller section 25. If the cause of the ambient light is the insertion of the western sun or the leakage of light into the device and the like, which continues for a long time, the device 26 may be damaged or cause an accident.

Alternatively, even for types that can detect ambient light, even if the lid of the device is temporarily opened for inspection or replenishment of work, etc. Every time an emergency stop or an alarm was sounded, the control was interrupted and work efficiency was reduced.

It is an object of the present invention to provide a photoelectric sensor control method and control system capable of flexibly responding to the influence of ambient light.

(Means for Solving the Problems) In order to achieve the above object, the invention according to claim 1 provides a light emitting pulse signal for intermittently emitting a light emitting element and a light receiving signal from a light receiving element corresponding to the light emitting element. And the process of determining whether the ambient light is entering the light receiving element of the photoelectric sensor depending on whether the light receiving element is receiving light when the light emitting element is not emitting light, and the ambient light entering the light receiving element. Including the process of counting the incoming time of the ambient light while the state that it is judged that the light has been emitted and the process of activating the abnormality response means when the incoming time reaches a certain length A control method for the photoelectric sensor was constructed.

According to a second aspect of the present invention, the light emitting pulse signal for intermittently emitting the light emitting element is compared with the light receiving signal from the light receiving element corresponding to the light emitting element, and the light receiving element receives the light when the light emitting element is not emitting light. In this case, the control system of the photoelectric sensor is configured to output an error, count the error output, and determine the intrusion of ambient light.

(Operation effect) Since the present invention is configured as described above, the following operation effects are achieved.

According to the control method of the photoelectric sensor of the first aspect of the present invention, it is first determined whether the ambient light enters the light receiving element of the photoelectric sensor. It goes without saying that normal operation is performed unless ambient light is incident. When the ambient light is incident, the ambient light incident time is counted. The counting is performed while the state in which it is determined that the ambient light is incident continues. If it is interrupted before the incident time of ambient light reaches a certain length, counting is also stopped. When the light incident time reaches a certain length, the easy response means is activated, for example, an alarm is activated, or an emergency stop of the controlled device is performed.

Therefore, according to the photoelectric sensor control method of the first aspect of the present invention, when the ambient light does not continue for a certain time or longer, the alarm does not activate, and therefore an accident or a device failure does not occur. Do not hypersensitively respond to the intrusion of ambient light for a short period of time due to various causes, but activate the abnormality response means for long-term intrusion of ambient light due to abnormal operation of the controlled device. Accidents and malfunctions can be prevented in advance. The length of the light incident time counted is adjusted appropriately.

According to the control system of the photoelectric sensor of the present invention, the light receiving signal is compared with the light emitting pulse signal, and if the light receiving element receives the light when the light emitting element is not emitting light, an error output is performed. Then, the number of error outputs is counted, and when it reaches a certain number, it is determined that the ambient light has entered.

Therefore, according to the control system of the photoelectric sensor according to the present invention, the disturbance light does not affect the control unless it continues for a certain period of time or more, so that the disturbance light enters for a short time so that an accident or damage to the device does not occur. However, it is determined that the ambient light is invading for a certain period of time or more, and the corresponding output is made. The reference time is set appropriately for each system.

(Example) Hereinafter, the illustrated example will be described.

FIG. 1 is a circuit block diagram embodying an embodiment of a photoelectric sensor control system according to the present invention.

In the figure, reference numeral 1 denotes an oscillation circuit, which outputs a light emission pulse signal having a constant cycle. The light emission pulse signal of the oscillation circuit 1 is input to the photodiode 3 via the amplifier 2,
It is input to the AND circuit 4 and is input to the flip-flop 6 via the inverter 5. The photodiode 3 is intermittently turned on according to this light emission pulse signal, and the optical axis of the photodiode 2 enters the phototransistor 7. The phototransistor 7 outputs according to the light incident from the photodiode 3.

The output of the phototransistor 7 is inverted by the inverter 8 and input to the set side of the flip-flop 6,
It is directly input to the reset side. Also inverted and AND
It is input to the circuit 4.

The outputs of the AND circuit 4 and the flip-flop 6 are input to the AND circuit 9, and the output of the AND circuit 9 is the mono multivibrator 10.
Entered in. The output of the AND circuit 4 becomes an N output, and the output of the mono multivibrator 10 becomes a Z output, which is input to a controller (not shown).

FIG. 2 is a timing chart showing the digital output at each point in the circuit.

In the same figure, (a) shows a waveform when there is no light entering, that is, when the optical axis L is shielded because an object is interposed between the photodiode 3 and the phototransistor 7. In this state, the photodiode intermittently emits light in accordance with the light emission pulse signal of the oscillation circuit 1, but since the optical axis L is shielded, it does not enter the phototransistor 7, and therefore the photodiode Transistor 7 is OF
It remains F and does not change. Therefore, the light reception signal output of c remains 1.

Since the received light signal is inverted and input to the AND circuit 4, the N output g remains 0.

(B) indicates that there is incident light, that is, the photodiode 3
2 shows a waveform when there is no object blocking the optical axis between the phototransistor 7 and the phototransistor 7. At this time, the phototransistor 7
Is repeatedly turned on and off by intermittent light emission of the photodiode, and the light receiving signal output d becomes a pulse signal whose phase is opposite to that of the light emitting pulse signal a of the oscillation circuit 1. When this is inverted and input to the AND circuit 4, its N output becomes a pulse signal in phase with the original pulse signal a.

Therefore, it is possible to determine whether light is incident or not depending on whether the N output g remains 0 or becomes a pulse signal.

(C) is a case of a light incident error, that is, a case where ambient light is incident. At this time, the phototransistor 7 is ON
Since the above state continues, the light reception signal c continuously shows 0. Therefore, 1 is input to the AND circuit 4, and the N output g becomes a pulse signal as in the case of (B) with light incident. Therefore, it is not possible to distinguish between the case where the light is incident and the case where the ambient light is influencing with this alone.

Therefore, in the present invention, the Z output is obtained using the flip-flop 6, the AND circuit 9 and the mono-multivibrator 10.

When ambient light enters, the continuous 0 is input to the set side and the continuous 1 is input to the reset side in the flip-flop 6. Since a pulse signal as a clock pulse is inverted and input from the oscillation circuit 1, the NG latch SETd outputs a pulse signal when a light incident error (c) occurs, and outputs 1 at other times. NG
Latch RESe is the opposite. The output f of the flip-flop 6 becomes 0 when (a) and (b) and becomes 1 when (c). When the logical sum of this output and the output of the AND circuit 4 is taken by the AND circuit 9, it becomes like h, and the output Z of the mono multivibrator 10 is the second
As shown in i in the figure, 0 for (a) and (b) and 1 for (c).
Becomes

The N output and the Z output are counted by a counter (not shown) only when the N output is a pulse signal and the Z output is 0, and the number of N output pulses is counted. ing. Further, it goes without saying that some output is made to the controlled device depending on the N output.

FIG. 3 is a flowchart showing the procedure of the control program of the control system of the above embodiment. This embodiment is applied to an automatic feeder that feeds a screw from a hopper of an automatic screw tightener to a chute, and a photoelectric sensor is provided in a rail to which the screw is fed to detect the presence or absence of the screw, and the screw must be removed. For example, the screw aligner is activated after a certain time T1, and if there is a screw, the screw aligner is stopped after a certain time T2. A signal indicating the presence or absence of received light, a signal indicating the presence or absence of ambient light, and a clock pulse are input to the sequence controller. Hereinafter, description will be made step by step.

<< Step 1 >> First, the presence or absence of ambient light is determined. According to the above example, Z
When the output is 0 and 1 is input to the N output, it is determined that there is ambient light.

<< Step 2 >> When it is determined that ambient light is present, an error counter having a predetermined value is updated and -1 is added. The value of the error counter is determined so as to be able to cope with the malfunction before the screw alignment device malfunctions due to the continuous influence of ambient light and causes a failure or an accident.

<< Step 3 >> It is determined whether or not the error counter has reached 0. If it is not 0, that is, if a fixed time has not elapsed, the process returns to the beginning.

<< Step 4 >> When the error counter reaches 0 for a certain period of time, an alarm is activated to notify that an abnormality due to ambient light has occurred.

Upon activation of the alarm, the screw aligning device makes an emergency stop, and an operator who knows that an abnormality has occurred performs maintenance on the screw aligning device to eliminate the cause of ambient light.

The procedure when it is determined that there is no ambient light is as follows.

<< Step 2 '>> When there is no ambient light, the error counter is reset,
It is set back to 0.

Therefore, if the ambient light enters for a shorter time than the time set by the error counter and then the ambient light does not enter again, the error counter is reset and the previous count is invalid. Therefore, the alarm is not triggered by the intrusion of ambient light for a time shorter than the predetermined time that does not affect the screw alignment device.

<< Step 3 '>> Next, it is determined whether or not light is received, that is, whether or not there is a screw in the middle of the rail. If there are no screws, there is a light reception and the screw aligner must be activated.
If the screw is present, there is no light reception and there is no need to activate the screw alignment device.

<Step 4 ′> When light is received, the delay time T2 for stopping the screw aligner is reset, and similarly, when there is no light, the delay time T1 for starting the screw aligner is reset. It

<< Step 5 '>> When light is received, 1 is subtracted from T1 which is the delay time for starting the screw aligning device, and updated. When no light is received, 1 is subtracted from T2 and updated.

<< Step 6 '>> It is determined whether the updated T1 or T2 is zero. If it is not 0, it returns to the beginning.

<< Step 7 '>> When T1 becomes 0, the screw aligner is activated and T2 becomes 0.
If so, the screw aligner stops.

As described above, according to the photoelectric sensor control system of the present embodiment, since the alarm does not start until the error counter reaches 0 when the disturbance light enters, the screw is attached to the shooting position due to the influence of the disturbance light for a long time. It is possible to prevent an accident in which the screw supply device continues to operate and the device is damaged because it is determined that the screw does not exist despite being sent. In addition, if there is an incident of ambient light for a time that does not cause such an accident or damage to the equipment, an alarm is activated if the ambient light is not received continuously for a certain period of time by setting an error counter. It is designed not to take measures such as letting it happen.

Therefore, it is not affected by the intrusion of ambient light for a short time that does not affect the operation of the device, and only the invasion of ambient light for a long time can be dealt with.

Although the embodiments of the present invention have been described above, it is needless to say that the present invention is not limited to the above embodiments and can be appropriately modified within the scope of the gist of the present invention.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing a hardware configuration embodying a control system of a photoelectric sensor according to the present invention, and FIG. 2 is a timing chart showing digital signals of respective portions of the circuit of FIG. FIG. 3 is a flow chart showing a control flow for an input from the circuit of FIG.
FIG. 5 is a circuit block diagram showing the configuration of a conventional photoelectric sensor device, and FIG. 5 is a diagram showing the output of the photoelectric sensor of FIG. 1 ... Oscillation circuit, 3 ... Photo diode, 4 ... AND
Circuit, 6 ... Flip-flop, 7 ... Phototransistor, 9 ... AND circuit, 10 ... Mono multivibrator.

Claims (2)

[Claims] 1. A light emitting pulse signal for intermittently emitting a light emitting element and a light receiving signal from a light receiving element corresponding to the light emitting element are compared to determine whether or not the light receiving element is receiving light when the light emitting element is not emitting light. The process of determining whether the ambient light is incident on the light receiving element of the photoelectric sensor and the state that the ambient light is incident on the light receiving element continues for a while. A method of controlling a photoelectric sensor, comprising: a step of counting time; and a step of activating an abnormality handling means when a light incident time reaches a certain length. 2. A light emitting pulse signal for intermittently emitting a light emitting element and a light receiving signal from a light receiving element corresponding to the light emitting element are compared to output an error when the light receiving element receives light when the light emitting element is not emitting light. The control system of the photoelectric sensor that determines the intrusion of ambient light by counting the number of error outputs.