JPH0425728A - Control method and control system for photoelectronic sensor - Google Patents

Abstract

PURPOSE:To flexibly cope with the influence of disturbing light by counting the incidence time of the disturbing light and actuating an abnormality correspondence means when the light incidence time reaches certain length. CONSTITUTION:The light emission pulse signal of an oscillation circuit 1 is inputted to an FF 6 through an amplifier 2, and a photodiode 3, an AND circuit 4, and further an inverter 5. The photodiode 3 illuminates intermittently accord ing to the light emission pulse signal and the optical axis of the photodiode 2 enters the phototransistor (FTR) 7. The output of the FTR 7 is inverted by an inverter 8 and inputted to the set side of the FF 6, and inputted to the reset side as it is. Further, the output is inverted and inputted to the AND circuit 4. Then the outputs of the AND circuit 4 and FF 6 are inputted to an AND circuit 9, whose output is inputted to a monostable multivibrator 10. The output of the AND circuit 4 and the output of the vibrator 10 are inputted to a controller. Consequently, the influence of the disturbing light is handled flexibly.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a control system for a photoelectric sensor comprising a light emitting element and a light receiving element.

(Prior Art) Photoelectric sensors are used as one of the switches in various sequence control processes.

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

In the same figure, a photoelectric sensor 21 consists of a light emitting element 22 and a light receiving element 23, and the light emitting element 22 has an optical axis that is aligned with the light receiving element 2.
It is emitted towards 3. 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 an object exists 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,
Controller section 25 controls equipment 26 .

Generally, a pulse wave is input to the light emitting element 22 of the photoelectric sensor 21, and the light is turned on intermittently at a certain period, and the amplifier section 24 detects the object by comparing it with a pulse signal synchronized with this pulse wave. I was deciding whether or not it existed.

(Problems to be Solved by the Invention) The configuration described above is susceptible to the influence of ambient light. That is, as shown in FIG.
The output signal of can take three types of waveforms. Figure 5 (a) (
(b) and (c) are respectively (a) when no light from the light-emitting element 22 is received, (b) when light from the light-emitting element 22 is received, and (c) when ambient light is received. This shows the waveform when Of these, (a) and (b) are in a normal operating state, and the amplifier section 24 can transmit the presence or absence of an object to the controller section 25 in response to the inputs of (a) and (b).

However, when disturbance light is incident, the amplifier section 24
Since it is not possible to process detailed data, it judges that (a) is being input and sends the same signal to the controller unit 25, indicating that the cause of the disturbance light is the setting sun or light entering the equipment. If the leakage continues for a long time, it may result in damage to the equipment 26 or an accident.

Alternatively, even for types that can detect ambient light, even if the lid of the equipment is temporarily opened for inspection or replenishment of workpieces, the effects of slight ambient light will be sensitively detected and the equipment will be shut down immediately. Control was interrupted each time by making an emergency stop or sounding an alarm, reducing work efficiency.

An object of the present invention is to provide a photoelectric sensor control method and control system that can flexibly respond 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 process for determining whether or not disturbance light is incident on the light receiving element of a photoelectric sensor, and A process of counting the incident time of the disturbance light while the state in which it is determined that the disturbance light has entered the light continues, and a process of activating the abnormality response means when the large light time reaches a certain length. A control method for a photoelectric sensor was constructed including the following.

The invention according to claim 2 compares a light emission pulse signal that causes a light emitting element to emit light intermittently and a light reception signal from a light receiving element corresponding to the light emitting element, and determines whether light is received by the light receiving element when the light emitting element is not emitting light. The control system for the photoelectric sensor was configured to output an error in the event of an error, count the number of error outputs, and determine the intrusion of disturbance light.

(Effects) Since the present invention has the above-described configuration, the following effects are achieved.

According to the method for controlling a photoelectric sensor according to the first aspect of the invention, first, it is determined whether or not disturbance light is entering the light receiving element of the photoelectric sensor. Needless to say, normal operation is performed if no disturbance light is received. If disturbance light is incident, the incident time of the disturbance light is counted. Counting is performed while the state in which it is determined that disturbance light has entered continues. If the counting is interrupted before the incident time of the disturbance light reaches a certain length, the counting is also stopped. When the light incident time reaches a certain length, the abnormality response means is activated, for example, an alarm is activated or the controlled equipment is brought to an emergency stop.

Therefore, according to the method for controlling a photoelectric sensor according to the invention set forth in claim 1, if the disturbance light does not continue for a certain period of time or more, the alarm will not be activated, and therefore an accident or equipment failure will not occur. Rather than reacting too sensitively to the intrusion of disturbance light for a short period of time due to minor causes, it is necessary to take abnormal response measures against the intrusion of disturbance light that continues for a long time due to abnormal operation of controlled equipment. By starting the system, you can prevent accidents and malfunctions. The length of the great light time to be counted is adjusted appropriately.

According to the control system for a photoelectric sensor according to the present invention, a light reception signal is compared with a light emission pulse signal, and if the light reception element receives 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 a certain number is reached, it is determined that disturbance light is intruding.

Therefore, according to the control system for a photoelectric sensor according to the present invention, since the control is not affected unless the intrusion of ambient light continues for a certain period of time, the intrusion of ambient light for a short period of time that does not cause accidents or damage to equipment can be avoided. It is not affected by this, and only after a certain period of time has elapsed, it is determined that disturbance light is intruding, and a corresponding output is made. The reference time is set appropriately for each system.

(Example) The illustrated embodiment will be described below.

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

In the figure, 1 is an oscillation circuit which outputs a light emission pulse signal of a constant period. The light emission pulse signal of the oscillation circuit 1 is inputted to the photodiode 3 via the amplifier 2,
The signal is input to an AND circuit 4 and then to a flip-flop 6 via an inverter 5. The photodiode 3 is intermittently lit according to this light emission pulse signal, and the optical axis of the photodiode 2 enters the phototransistor 7 .

The phototransistor 7 outputs an output according to the incident light from the photodiode 3.

The output of the phototransistor 7 is inverted and inputted to the set side of the flip-flop 6 by an inverter 8.
It is input as is to the reset side. It is also reversed AN
It is input to the D circuit 4.

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

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

In the figure, (a) shows a waveform when no light is incident, that is, when an object is interposed between the photodiode 3 and the phototransistor 7, so that the optical axis is blocked. In this state, the photodiode emits light intermittently according to the light emission pulse signal of the oscillation circuit 1;
Since the optical axis is blocked, no light enters the phototransistor 7, so the phototransistor 7 is turned off.
It remains unchanged. Therefore, the light reception signal output of C remains at l.

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

(b) is when there is incident light, that is, photodiode 3
The waveform is shown when there is nothing blocking the optical axis between the phototransistor 7 and the phototransistor 7. At this time, phototransistor 7
is turned on and off by intermittent light emission from the photodiode.
is repeated, and the light reception signal output d becomes a pulse signal whose phase is reversed from that of the light emission 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 that is in phase with the original pulse signal a.

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

(C) is a case of a light entry error, that is, a case where disturbance light is incident. At this time, the phototransistor 7 is
Since the N state continues, the light reception signal C continues to indicate O.

Therefore, l is input to the AND circuit 4, and the N output g becomes a pulse signal as in the case (b) when light is incident. Therefore,
With this alone, it is not possible to distinguish between cases where light is incident and cases where disturbance light is affecting.

Therefore, in the present invention, a flip-flop 6, an AND circuit 9, and a mono multi-by-break 10 are used to obtain two outputs.

When disturbance light enters, a continuous O is applied to the set side of the flip-flop 6, and a continuous 1 is applied to the reset side of the flip-flop 6. Since a pulse signal is inverted and input from the oscillation circuit 1 as a clock pulse, the NG clutch ETd outputs a pulse signal when there is a light input error (c), and outputs 1 at other times.

The NG latch RESe is the opposite. The pressure f of the flip-flop 6 is 0 in (a) and (b), and 1 in (c).

When the AND circuit 9 takes the logical sum of this pressure and the output of the AND circuit 4, it becomes h, and the mono multi-by-break 1
As shown at i in FIG. 2, the output 2 of 0 becomes 1 when O1 is (A) and (B) (C).

A counter (not shown) for the N output and 2 output counts the number of pulses of the N output only when the N output is a pulse signal and the 2 output is 0, and when a certain number is reached, it is determined that there is a light input error. ing. Furthermore, it goes without saying that some kind of 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 example is applied to an automatic screw feeding device that feeds screws from the hopper to the chute of an automatic screw tightening machine.A photoelectric sensor is installed in the middle of the rail where screws are fed to detect the presence or absence of screws. For example, the screw alignment device is activated after a certain period of time Tl, and if there are screws, the screw alignment device is stopped after a certain period of time Tl. A signal indicating the presence or absence of light reception, a signal indicating the presence or absence of disturbance light, and a clock pulse are input to the sequence controller. The following is a step-by-step explanation.

(Step 1) First, the presence or absence of disturbance light is determined. Following the example above, 2
When the output is O and the N output is manually set to 1, it is determined that there is ambient light.

(Step 2) When it is determined that there is ambient light, an error counter with a predetermined value is updated and -1 is added. The value of the error counter is determined so that a malfunction can be dealt with before the screw alignment device malfunctions due to the influence of continuous ambient light and causes a failure or accident.

(Step 3) Determine whether the error counter has reached O. If it is not 0, that is, if a certain period of time has not elapsed, the process returns to the beginning.

(Step 4) When a certain period of time has elapsed and the error counter reaches O, an alarm is activated to notify that an abnormality has occurred due to ambient light.

When the alarm is activated, the screw alignment device makes an emergency stop, and the operator who knows that an abnormality has occurred performs maintenance on the screw alignment device to eliminate the cause of the disturbance light.

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

(Step 2') When there is no disturbance light, the error counter is reset,
Returned to 0.

Therefore, the disturbance light enters for a shorter time than the time set by the error counter, and then the disturbance light stops entering (
If this occurs, the error counter will be reset and the previous count will become invalid. Therefore, an alarm will not be activated due to the intrusion of ambient light for a period shorter than a predetermined time period 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 is no screw present, there is light reception and the screw alignment device must be activated.

If a screw is present, no light is received and there is no need to activate the screw alignment device.

(Step 4') If light is received, T2, which is the delay time for stopping the screw alignment device, is reset.

Similarly, when no light is received, T1, which is the delay time for starting the screw alignment device, is reset.

(Step 5') If light is received, then 1 is subtracted from T1, which is the delay time for starting the screw alignment device, and the delay time is updated. If no light is received, 1 is subtracted from T2 and updated.

(Step 6') It is determined whether the updated T1 or T2 is O. If it is not O, return to the beginning.

(Step 7') If T1 becomes 0, the screw alignment device is activated and T2
When becomes 0, the screw alignment device stops.

As described above, according to the photoelectric sensor control system of this embodiment, the alarm is not activated until the error counter reaches 0 due to the intrusion of ambient light. It is possible to prevent an accident in which the screw feeding device continues to operate because it is determined that the screw is not present even though the screw is being fed, and the device is damaged. In addition, if disturbance light enters for a period of time that does not cause such an accident or damage to equipment, an error counter is set to activate an alarm if disturbance light is not continuously received for a certain period of time. The system does not take any measures such as forcing the user to do so.

Therefore, it is not affected by the intrusion of disturbance light for a short period of time that does not affect the operation of the equipment, and can only deal with the intrusion of disturbance light for a long time.

The embodiments of the present invention have been described above.

It goes without saying that the present invention is not limited to the above-mentioned embodiments, and can be modified as appropriate within the scope of the gist of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram showing a hardware configuration embodying a photoelectric sensor control system according to the present invention, and FIG. 2 is a timing chart showing digital signals of each part of the circuit in FIG. FIG. 3 is a flowchart showing the flow of control for the input from the circuit in FIG.
This figure 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 shown in FIG. 4. 1...Oscillation circuit, 3...Photodiode, 4...
・AND circuit, 6...Flip-flop, 7...Phototransistor, ・AND circuit, ・Mono multi-by-break.

Claims (2)

[Claims] (1) During the process of determining whether or not ambient light has entered the light-receiving element of the photoelectric sensor, and while the state in which it is determined that ambient light has entered the light-receiving element continues, 1. A method of controlling a photoelectric sensor, comprising the steps of counting the light incident time and activating an abnormality response means when the light incident time reaches a certain length. (2) Compares the light emitting pulse signal that causes the light emitting element to emit light intermittently and the light reception signal from the light receiving element corresponding to the light emitting element, and outputs an error if the light receiving element receives light while the light emitting element is not emitting light. , a photoelectric sensor control system that counts the number of error outputs and determines the intrusion of disturbance light.