JPH05175817A - Signal discriminating method for photoelectric switch - Google Patents

Abstract

PURPOSE:To eliminate the malfunction due to an influence of another photoelectric switch or the malfunction due to noise light by operating AND between a delay detection signal and a detection signal. CONSTITUTION:Since not only the thrown light pulse of a thrown light signal (b) but also the thrown light signal of another photoelectric switch and noise light are included in a light reception signal C as the output of a light reception circuit 6, not only the thrown light pulse but also the pulse component of the noise component other than the signal component is included in a detection signal (d). The detection signal (d) is delayed in a delay circuit 10 by a time equal to a period T of the thrown light pulse to obtain a delay detection signal (e), and AND between the delay signal (e) and the detection signal (d) is operated by an AND circuit 11, thereby eliminating the pulse component of the noise component from a discrimination signal (f). Therefore, only an effective pulse train is obtained as the discrimination signal, and pulse trains whose periods are different from the period T of light throwing are completely eliminated. A light receiving device B integrates the discrimination signal (f) to discriminate only the state of signal light from a light throwing device A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal discriminating method for a photoelectric switch suitable for a transmission type photoelectric switch.

[0002]

2. Description of the Related Art In a transmission type photoelectric switch, a light emitting section and a light receiving section are housed in different devices. Therefore, when a plurality of photoelectric switches are used, the signal light of other photoelectric switches is received. There was a drawback that it caused a malfunction.

For this reason, there has been provided a device in which a light emitting device and a light receiving device are connected by a synchronizing signal line to reliably discriminate a predetermined signal, but there is a drawback that the wiring cost is high.

In particular, in an apparatus using a plurality of light emitters and light receivers, the operating angles of the light emitters and light receivers are narrowed so that they do not affect each other to prevent malfunctions. But especially when installing the photoelectric switch,
There is a drawback that it is difficult to adjust the optical axis.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to provide a photoelectric switch in which malfunction due to influence between photoelectric switches or malfunction due to noise light is eliminated. It is to provide a signal discrimination method.

[0006]

According to a signal discriminating method for a photoelectric switch of the present invention, a pulsed light is periodically projected from a light projecting element, the pulsed light is received, and the received optical signal is converted into an electric signal. In a photoelectric switch configured to detect after conversion, delay the detected signal by the projection period time of the pulsed light, and take a logical product of the delayed signal and the detected signal before delaying. Is used to discriminate signals.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a signal discrimination method for a photoelectric switch according to the present invention will be described with reference to FIGS.

FIG. 1 is a block diagram of a transmission type photoelectric switch of the present invention, and FIG. 2 is a diagram showing signal waveforms of essential parts.

In the figure, A is a projector, B is a light receiver, 1 is an oscillation circuit of the projector A for generating a pulse signal, and 2 is an oscillation circuit 1.
A frequency dividing circuit for dividing the signal of 3 is a light projecting circuit for guiding a pulse signal a having a period T divided by the frequency dividing circuit 2 to a light projecting element 4, and 5 is an oscillating circuit 1 and a frequency dividing circuit 2. And 6 is a power supply circuit for the light projecting circuit 3, 6 is a light receiving circuit of a light receiver B including a light receiving element 7 for receiving a light projecting signal b, and 8 is a light receiving signal c output from the light receiving circuit 6 at a predetermined level. An amplifier for amplification, 9 is a detection circuit for obtaining the detection signal d, 10 is a delay circuit for delaying the detection signal d by a period T, and 11 is a detection signal d of the detection circuit 9 and an output of the delay circuit 10. AND circuit for obtaining a logical product with the differential detection signal e
An integrating circuit for integrating the discrimination signal f obtained by the D circuit 11,
Reference numeral 13 is an output circuit that outputs a predetermined signal based on the output of the integration circuit 12, and 14 is power supply to each circuit of the light receiving circuit 6, the amplification circuit 8, the detection circuit 9, the delay circuit 10, the integration circuit 12, and the output circuit 13. Power supply circuit.

In the transmission type photoelectric switch constructed as described above, the received light signal c output from the light receiving circuit 6 includes other light emitting pulses other than the light emitting pulses P1, P2, P3, P4 and P5 of the light emitting signal b. Since the light projection signal of the switch and the noise light g are included, the detection signal d includes pulse components of noise components N1, N2, and N3 that are not signal components in addition to the light projection pulses P1 to P5.

Therefore, a noise component N1 which is not a signal component,
In order to remove the pulse components such as N2 and N3, the detection signal d is delayed by the delay circuit 10 for a time equal to the period T to obtain the delay detection signal e, and the logical product of the delay detection signal e and the detection signal d. By the AND circuit 11, the pulse components of the noise components N1, N2, and N3 are removed from the discrimination signal f. Therefore, only the effective pulse trains PA, PB, PC, and PD are obtained as the discrimination signal f, and the pulse train having a period T1 other than the light projecting period T is completely removed.

Then, the light receiver B determines only the state of the signal light from the light projector A by integrating the discrimination signal f.

[0013]

According to the signal discriminating method of the photoelectric switch of the present invention, since it is configured as described above, it is possible to eliminate the influence of the pulsed light of another photoelectric switch having a different light emitting period. Disappear. Further, it has an effect that it operates stably against noise light from an illuminating device and electrical noise.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a signal discrimination method for a photoelectric switch according to the present invention.

FIG. 2 is a signal waveform diagram showing the signal waveform of each part of FIG.

[Explanation of symbols]

 A Light emitter B Light receiver 4 Light emitting element 7 Light receiving element 6 Light receiving circuit 8 Amplifying circuit 9 Detection circuit 10 Delay circuit 11 AND circuit 12 Integration circuit 13 Output circuit 14 Power supply circuit

Claims (1)

[Claims] 1. A photoelectric switch configured to project pulsed light periodically from a light projecting element, receive the pulsed light, convert the received optical signal into an electric signal, and then detect the electric signal. A photoelectric signal characterized in that the detected signal is delayed by the projection period time of the pulsed light, and the signal is discriminated by taking a logical product of the delayed signal and the detected signal before delaying. Switch signal discrimination method.