JP3341025B2 - 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, and more particularly to a photoelectric switch having a feature of preventing mutual interference.

[0002]

2. Description of the Related Art Conventionally, a photoelectric switch drives a light emitting element in a pulsed manner, and detects an object by the presence or absence of a light receiving signal in accordance with the lighting thereof. However, there is a disadvantage that when light enters from another photoelectric switch in synchronization with the light projection timing, mutual interference occurs and a malfunction occurs.

In order to solve such a problem, a photoelectric switch having a mutual interference preventing function has been conventionally proposed. Such a prevention function is configured, for example, to stop oscillation when mutual interference occurs, or to change the oscillation frequency when mutual interference is detected. For example, in Japanese Patent Application Laid-Open No. 577-14718, the light emitting element is turned on with a pulse, and the oscillation frequency of the pulse oscillator is changed when a light receiving signal is obtained while no pulse is generated. A photoelectric switch that determines whether or not light is received immediately before or immediately after a light emitting pulse is generated, and changes the oscillation frequency to prevent mutual interference, instead of the entire time when no pulse is generated, Proposed.

[0004]

However, such a conventional mutual interference preventing circuit requires a large number of components because the oscillation frequency is changed, and it is difficult to realize the circuit without using an IC. When such processing is performed using a microprocessor, it is necessary to increase the response speed, and there is a drawback that realization is difficult.

The present invention has been made in view of such a conventional problem, and has as its technical object to prevent mutual interference easily without increasing the number of parts.

[0006]

According to a first aspect of the present invention, there is provided a light emitting section having a light emitting element, a light receiving section having a light receiving element, receiving light from the light emitting element, and a light receiving section. Level discriminating means for judging the presence or absence of an object based on the obtained light receiving level, light emitting pattern storing means for storing a plurality of light emitting patterns for pulse driving the light emitting element, and an input unit for inputting selection of a light emitting pattern And a light-projection-pattern selecting means for selecting one of the light-projection patterns stored by the light-projection-pattern storage means and giving the selected light to the light-projecting element.

According to a second aspect of the present invention, there is provided a light emitting section having a light emitting element, a light receiving section having a light receiving element and receiving light from the light emitting element, and a light receiving level obtained by the light receiving section. Level discriminating means for judging the presence or absence of an object, light emitting pattern storing means for storing a plurality of light emitting patterns for pulse driving the light emitting element, and light emitting pattern selecting means for randomly selecting the light emitting pattern when power is turned on And characterized in that:

[0008]

[0009]

According to the first aspect of the present invention having such features, when mutual interference occurs, a light projection pattern is arbitrarily selected from the input unit. By driving the light projecting element with the selected light projecting pattern, mutual interference can be prevented. In the present invention of claim 2 also has a light projection pulse given to the light emitting element by setting the projected pattern at random when the power is turned on.

[0010]

FIG. 1 is a diagram showing the overall configuration of a photoelectric switch according to a first embodiment of the present invention. In this figure, a light emitting element driving circuit 1 intermittently drives a light emitting element 3 according to a light emitting pattern provided from a microcomputer 2. The light projecting element 3 is driven by a light projecting pulse and emits a light beam to an object detection area. The light or the reflected light is received by the light receiving element 4. The output of the light receiving element 4 is sampled and held by an amplifier 5 (S / H circuit).
6 given. The sample hold circuit 6 temporarily holds the light receiving level in response to a hold signal from the microcomputer 2.

An A / D converter 7 for converting the hold level of the sample and hold circuit into a digital signal is provided in the microcomputer 2 as shown in FIG. Then, the digital signal converted by the A / D converter 7 is processed in the microprocessor. The microcomputer 2 has a microprocessor, a memory, and an input / output interface, executes arithmetic processing described later, discriminates a digital signal with a predetermined threshold, and detects an object when the signal is continuously obtained. The function of the level discriminating means 2a for providing a signal to the output circuit 8 is achieved.
The memory in the microcomputer 2 has an area for storing a plurality of light emitting patterns as light emitting pattern storage means 2b. The display unit 9 displays the operation state of the photoelectric switch, and is composed of, for example, a pair of indicator lights as shown in FIG. As shown in FIG. 2, the input unit 10 has a slide switch 10a and a push button switch 10b used to switch the light projection pattern. The slide switch 10a selects "SET1" which is set when changing the light projection pattern, "SET2" which is set when adjusting the sensitivity, and the normal operation mode "RUN".

Here, the light projecting pattern has, for example, a constant light projecting pulse width and may have a constant period, or may constitute a light projecting pattern by combining a number of different periods. For example, the period may be a fixed period of 10 μS, 20 μS, or 30 μS, or these may be appropriately combined to form a light projection pattern. Alternatively, a light emitting pattern may be obtained by setting one of the bits of several bytes of the memory to 1 and setting the other bits to 0, and continuously reading out this data and converting it into a serial signal. It is assumed that these projection patterns are switched by storing a large number of these projection patterns.

Next, the operation of this embodiment will be described. FIG. 3 is a flowchart showing the operation of this embodiment. When the operation is started in the figure, first, the processing routine 21 of the main program is executed. In this routine 21, "R
This includes an object detection operation when “UN” is set and a sensitivity adjustment operation in “SET2”. When these processes are completed, the process proceeds to step 22, where the slide switch 10a is set to “S
Check if it is set to "ET1". If not, the process returns to the routine 21 to repeat the same processing.

If "SET1" has been set, the flow advances to step 23 to check whether the push button 10b has been input. If there is no input from the push button 10b, the process returns to step 22, and if it has been pressed, the process goes to step 24 to switch the light projection pattern. This is performed by randomly selecting one of the projection patterns in the memory which is the projection pattern storage means 2b. Then, the selected light emitting pattern is displayed based on the number of times the indicator lamp blinks. Then, the process returns to step 22 to repeat the same processing. Thereafter, the data of the selected light emitting pattern is read out and a signal is supplied to the light emitting element driving circuit 1. In this case, the light emitting element 3 is selected according to the selected pattern.
Is driven. Here, in steps 23 to 25, the microcomputer 2 arbitrarily selects and switches the light emission pattern stored in the light emission pattern storage means 2b in accordance with the input from the input unit 10, and the function of the light emission pattern selection means 2c. Have achieved.

Accordingly, when a plurality of photoelectric switches are arranged close to each other and mutual interference is recognized, the slide switch 10a is set to "SET1" and the light emission pattern is automatically changed by appropriately pressing the push button 10b. Switching can be performed, and mutual interference can be prevented.

Next, a second embodiment of the present invention will be described. FIG. 4 is a block diagram showing the configuration of a photoelectric switch according to a second embodiment of the present invention, and FIG. 5 is a flowchart showing the operation thereof. In FIG. 5, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted. In this embodiment, the light emission pattern is automatically selected when the power is turned on, without switching the light emission pattern by the operation from the input unit 10. Therefore, the microcomputer 32 does not have the input unit 10 and the A / D converter 31
In addition, a CPU and a memory are provided. Other configurations are the same as those of the first embodiment.

In this embodiment, in the flowchart of FIG. 5, when the operation is started when the power is turned on, first, in step 41, the CPU is initialized. Then, the process proceeds to step 42, where a random number is generated. Then, based on the random number generated in step 43, one of the light emission patterns stored in advance in the light emission pattern storage means 32b of the memory is selected and set. Then, the main program processing of the routine 44 is performed. Here, the microcomputer 31 of the second embodiment at Steps 42 and 43 achieves the function of the light emitting pattern selecting means 32c for selecting the light emitting pattern when the power is turned on. In this case, a different light projection pattern is selected each time the power is turned on, and even if a plurality of photoelectric switches are arranged close to each other, the probability of mutual interference being extremely reduced. In a normal operation, the function of the level discriminating means 32a for obtaining the object detection signal by discriminating the output of the A / D converter 31 with a predetermined threshold value is achieved.

Next, a third embodiment of the present invention will be described. FIG. 6 is a block diagram showing the configuration of a photoelectric switch according to the third embodiment of the present invention. The same parts as those in the above-described first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. This embodiment has substantially the same configuration as that of the first embodiment, and differs only in the processing in the microcomputer 52. The microcomputer 52 includes an A / D converter 51 and a level discriminating means 52a for discriminating a level according to the output thereof.
Light emitting pulse generating means 52b, light incident monitoring means 5
2c and the light projection pulse changing means 52d.

FIG. 7 is a flowchart showing the operation of the present embodiment, and FIG. 8 is a waveform chart showing the operation. FIG. 8A shows a light emitting clock of the photoelectric switch, and FIG. 8C shows a light receiving signal obtained corresponding to the light emitting clock.
Now, consider a case where there is a light emission clock of another photoelectric switch in synchronization with the light emission clock as shown in FIG. 8B, and this signal enters the light receiving element and causes mutual interference.

When the operation is started as shown in FIG.
In step 61, a time-up is awaited, and a light emission pulse is generated every time-up (step 62). Then, in step 63, the number of pulses is counted, and it is checked whether the counted value has reached a predetermined value, for example, 7 (step 64). If it is 7 or less, the process returns to step 61 to repeat the same processing, and periodically outputs a light emitting pulse as shown in FIG.

When the count value becomes 7 in step 64, the flow advances to step 65 to stop the light projection. That is, in step 65, the time is awaited. If the time is up, the process proceeds to step 66 without generating a light emission pulse, and the light input is monitored. 8 time t ₁ of the (a) shows a state of stopping the light projection. In this case as well, the other photoelectric switches repeatedly emit light in the same cycle. Therefore, if there is mutual interference, light is received by a light emission signal from another sensor as shown by a broken line in FIG. 8C. The light receiving signal is converted into a digital signal via the A / D converter 51. Therefore, the microcomputer 52 checks in this state whether or not a predetermined level of light is received (step 67). If there is no incoming light, the process proceeds to step 69, K is reset, and light emission is restarted at the same cycle. If the light input level exceeds the predetermined value, the routine proceeds to step 68, where the light projection time is changed. This to slow the projected pulse at time t ₃ when indicated by the arrow from the time the time t ₂ as shown in FIG. 8, for example (a). Here, the microcomputer 52 performs steps 61 to
At 64, the function of the light emitting pulse generating means 52b for generating a light emitting pulse is achieved, and at the steps 65 to 67, the function of the light incoming monitoring means 52c for judging the presence or absence of light at the timing when the light emission is stopped is achieved. are doing. The microcomputer 52 constitutes a light emission timing changing means 52d for changing the light emission timing when an input signal is obtained in the routine 68 and step 69.

As described above, in this embodiment, the presence or absence of mutual interference is determined by periodically stopping the light emission pulse. Then, as shown by a broken line in FIG. 8C, even if light is received by the light receiving unit due to mutual interference from another photoelectric switch, signal processing is performed using the light emission clock as a gate signal. The effect can be eliminated. When changing the light projection time, the light projection period itself may be changed, or the period may be the same, and the position of the light emission pulse may be shifted by delaying or advancing from the original time. In this embodiment, the generation of the light emission pulse is periodically stopped, but it is needless to say that the light emission pulse may be stopped at random.

[0023]

As described above in detail, according to the first aspect of the present invention, a plurality of light emitting patterns are stored, and the light emitting pattern is changed by arbitrarily selecting the pattern. . Therefore, mutual interference can be easily prevented without adding special hardware or using a high-speed microprocessor.

According to the second aspect of the present invention, since the light emitting pattern is selected by a random number when the power is turned on, the possibility of mutual interference can be extremely reduced without performing a process of changing the light emitting pattern every time. it can.

[0025]

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a photoelectric switch according to a first embodiment of the present invention.

FIG. 2 is a front view of the photoelectric switch according to the first embodiment.

FIG. 3 is a flowchart showing the operation of the first embodiment.

FIG. 4 is a block diagram illustrating a configuration of a photoelectric switch according to a second embodiment of the present invention.

FIG. 5 is a flowchart showing the operation of the second embodiment.

FIG. 6 is a block diagram illustrating a configuration of a photoelectric switch according to a third embodiment of the present invention.

FIG. 7 is a flowchart showing the operation of the third embodiment.

FIG. 8 is a time chart showing the operation of the third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Projection element drive circuit 2, 42, 52 Microcomputer 2a, 42a, 52a Level discrimination means 2b, 42b Projection pattern storage means 2c, 42c Projection pattern selection means 3 Projection element 4 Light receiving element 6 Sample hold circuit 7, 41, 51 A / D conversion section 9 Display section 10 Input section 52b Light emitting pulse generating means 52c Light incoming monitoring means 52d Light emitting pulse changing means

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H03K 17/78

Claims (2)

(57) [Claims] A light-emitting unit having a light-emitting element, a light-receiving unit having a light-receiving element, receiving light from the light-emitting element, and determining the presence or absence of an object based on a light-receiving level obtained by the light-receiving element. Level discriminating means for discriminating; light emitting pattern storing means for storing a plurality of light emitting patterns for pulse driving the light emitting element; an input unit for inputting selection of a light emitting pattern; and storing from the light emitting pattern storing means. A light-projection pattern selecting means for selecting any one of the light-projection patterns and giving the selected light-projection pattern to the light-projection element. 2. A light projecting section having a light projecting element, a light receiving section having a light receiving element, receiving light from the light projecting element, and detecting the presence or absence of an object based on a light receiving level obtained by the light receiving section. Level discriminating means for discriminating; light emitting pattern storing means for storing a plurality of light emitting patterns for pulse-driving the light emitting element; and light emitting pattern selecting means for randomly selecting a light emitting pattern when power is turned on. A photoelectric switch.