JPH0422890A - Photoelectric switch circuit - Google Patents

Abstract

PURPOSE:To accurately distinguish projection light from another nearby photoelectric switch by generation a projection light pulse whose period is not fixed and periodically generating the prescribed number of projection light pulses at the time of receiving light by a light reception circuit. CONSTITUTION:When a light reception circuit 6 receives light, a control signal (o) is outputted from a control circuit 4 to fix the period of a projection light pulse (g) during the time of output of a prescribed number of pulses (g). When received light is the noise projected from another photoelectric switch, projection light pulses of projection light pulses of its own projection light pulse and that of another projection light are not synchronized with each other, and the light reception timing does not match with the read timing, and the malfunction due to the noise projected from another photoelectric switch is prevented. When received light is projected from its own light projecting circuit 5, a read clock pulse f2 supplied to a signal processing circuit 8 is synchronized with a light throwing pulse (g) supplied to the light projecting circuit 5, and therefore, the light projected from its own light projecting circuit 5 can be received even after the prescribed number of light projecting pulses (g) are periodically outputted, and accurate detection is possible.

Description

Detailed Description of the Invention fa) Industrial Application Field This invention emits pulse-modulated light from a light emitting circuit, and detects the presence or absence of an object to be detected depending on whether or not this light is received by a light receiving circuit. The present invention relates to a photoelectric switch circuit for detection, and particularly to a plurality of photoelectric switch circuits arranged in parallel.

(b) Conventional technology When detecting the presence or absence of an object to be detected, when multiple photoelectric switches are installed in parallel, one photoelectric switch receives light from other adjacent photoelectric switches. False detection may occur. Generally, in order to eliminate the influence of such noise, photoelectric switches change the phase of the drive pulse (light emitting pulse) supplied to the light emitting circuit, and also provide a gate in the light receiving section that synchronizes with its own light emitting pulse. Only the light emitted from the light emitting circuit is received. However, in such photoelectric switches, the periods of the light emitting pulses are often uneven, and the reading timing in the light receiving circuit may overlap with the light emitting timing of other photoelectric switches, so that the light emitted from other photoelectric switches is It was not possible to completely eliminate the influence of In order to improve this situation, some devices narrowed the light emitting and receiving range of the light emitter and light receiver, but in this case, the mounting accuracy of the photoelectric switch became a problem in order to align the optical axes. In addition, if a positional shift occurs due to an impact or the like, the operation becomes unstable. In addition, there are some photoelectric switches in which the light emitting timing is sequentially shifted, but such a configuration requires an external control means, which is complicated and requires wiring work between the control means and each photoelectric switch. There was a problem that required .

Therefore, in the photoelectric switch disclosed in Japanese Patent Publication No. 60-51043, when noise from other photoelectric switches is received, the pulse period of the oscillator that generates the basic clock pulse is changed to be longer or shorter. The light emitting pulses of other photoelectric switches are prevented from overlapping their own light emitting pulses many times, and erroneous detection in the light receiving circuit is prevented.

(C) Problems to be Solved by the Invention However, even in the conventional photoelectric switch described above, when multiple photoelectric switches of the same type are installed in parallel, the frequency of the light emitting pulse in the multiple photoelectric switches in the vicinity is If the power-on timings for multiple photoelectric switches are the same and the power-on timings for multiple photoelectric switches are close to each other, the phases of the emitted light pulse waveforms may also be close to each other. The purpose of this invention is to eliminate the possibility of malfunctions because the received light almost coincides with the light reception timing of the photoelectric switch and cannot detect that the received light is noise emitted from another photoelectric switch. By generating non-constant light emitting pulses and generating a predetermined number of light emitting pulses at regular intervals when the light receiving circuit receives light, the light emitted from other photoelectric switches can be adjusted to its own light receiving timing. To provide a photoelectric switch which can accurately detect that light is noise even when the light is received at a timing very similar to that of , and can reliably prevent erroneous detection.

(61) Means for Solving Problems The photoelectric switch circuit of the present invention includes an oscillation circuit that generates a basic clock pulse, and a light emitting pulse whose frequency is not constant by dividing the basic clock pulse generated by the oscillation circuit. A frequency dividing circuit that outputs a read pulse synchronized with this light emitting pulse, a light emitting circuit driven by the light emitting pulse supplied from the frequency dividing circuit, and a light receiving circuit that receives the light emitted from the light emitting circuit. a signal processing circuit that reads the light reception signal of the light reception circuit based on the reading pulse supplied from the frequency dividing circuit and outputs a detection signal when a certain number of light reception signals are read in succession; The present invention is characterized in that it includes a frequency division cycle control circuit that holds the frequency division cycle of the frequency divider circuit constant for a predetermined number of times when a number of received light signals are output.

Further, the frequency dividing circuit may alternately repeat long periods and short periods.

(81) In the present invention, a basic clock pulse is frequency-divided to generate a light emitting pulse whose frequency division period is not constant, and a light receiving signal of the light receiving circuit is read based on a read pulse synchronized with this light emitting pulse. Then, when a certain number of these received light signals are read in succession, a detection signal is output from the signal processing circuit. Light emitting pulses with a constant period are output multiple times.

For example, if a light emitting pulse of waveform A consisting of alternating short periods Ta and long periods Tb is output from a frequency dividing circuit as shown in FIG. When the long period Tb is output three times in succession at time t, the waveform A and waveform B of the fourth and subsequent pulses are significantly different.

On the other hand, since the signal processing circuit reads the light reception signal based on the read pulse synchronized with the light projection pulse, the read timing is the same as that shown in waveform B. Here, if the light received by the light receiving circuit is the light emitted from its own light emitting circuit, the signal processing circuit will synchronize with this even if the period of the light emitting pulse changes as shown in waveform B. Since the light reception signal is read at the specified timing, the light reception signal can be read even at a later time. However, if the light receiving circuit is receiving light emitted from another photoelectric switch, the light emitting pulse shown in the waveform will continue to enter the light receiving circuit even after changing the periods of the light emitting pulse and reading pulse. As a result,
The second and subsequent light emitting pulses are not shown in waveform B and have a large difference from the reading timing, and the signal processing circuit does not read the second and subsequent light reception signals. In this way, if the light receiving circuit is receiving only light emitted from other photoelectric switches, by keeping the period of the light emitting pulse and reading pulse constant for a predetermined number of times, the subsequent light receiving timing will be changed before the change. This causes a difference in the light reception timing of the photoelectric switch, and the light reception timing of that photoelectric switch causes a large error with the light emission timing of other photoelectric switches.

(f) Embodiment FIG. 2 is a block diagram showing the configuration of a photoelectric switch which is an embodiment of the present invention.

An oscillation circuit 2 driven by a power supply circuit 1 generates a basic clock pulse a. A basic clock pulse a generated in this oscillation circuit 2 is input to a frequency dividing circuit 3.

The frequency dividing circuit 3 divides the basic clock pulse a into a light emitting pulse g, a reading clock pulse f2 and a reset pulse g.
Generates 2. The light emitting pulse g is supplied to the light emitting circuit 5,
The light projection circuit 5 emits light that is pulse-modulated with the period of the light projection pulse g. The photoelectric switch 1) is a reflective photoelectric switch, and a light receiving circuit 6 receives light reflected by an object 10 located in front of a light projecting circuit 5.

The light receiving circuit 6 converts the received light into an electrical signal and outputs a light receiving pulse signal i. This light reception pulse signal l is input to the control circuit 4 and the signal holding circuit 7. Signal holding circuit 7
The light reception pulse signal l sent to is temporarily held and becomes a light reception signal having a predetermined waveform. The waveform of this light reception signal is determined by the reset pulse g2 supplied from the frequency dividing circuit 3. The received light signal is processed by the signal processing circuit 8 at the timing of the read clock pulse f2 supplied from the frequency dividing circuit 3.
is loaded into. The signal processing circuit 8 outputs a detection signal t to the output circuit 9 when it successively detects a plurality of received signals k.

FIG. 3 is a circuit diagram showing the configuration of essential parts of the photoelectric switch.

The basic clock pulse a outputted from the oscillation circuit 2 is guided and frequency-divided by D-type flip-flops 21 to 23 configured in three stages inside the frequency dividing circuit 3. The Q outputs of flip-flops 21 to 23 are exclusive OR circuit 2.
4 to 26 to an OR circuit 27. OR circuit 2
When the output e of 7 becomes the "L level", the Q output f of the flip-flop 29 becomes the "I" level, and the timer power p of the Pflo knob 32 is switched. By switching the timer input of this flip-flop 32, its Q output q is switched, and the cycle of the light projection pulse g output from the AND circuit 31 changes alternately between a long cycle and a short cycle. This light projection pulse g is supplied to the light projection circuit 5.

The control circuit 4 receives the light reception signal i of the light reception circuit 6 and the oscillation circuit 2.
A control signal 0 is output to the frequency dividing circuit 3 based on the basic clock signal and the 7 clock signal a supplied from the circuit.

Further, the control circuit 4' outputs the control signal U to the frequency dividing circuit 3 based on the intermediate detection signal of the signal processing circuit 8. The frequency dividing circuit 3 changes the frequency dividing period of the light emitting pulse g according to the control signals o and u output from the control section 4.4'. That is, when the control signal 0 is at the "H" level, the division period of the light emitting pulse g is set to a long period, and when the control signal U is at the "L" level, the division period is set to a short period. L
Under normal conditions, when the control signal U is at the Ho level, the frequency dividing circuit 3 alternately repeats long and short periods as the light emitting pulse g, but when the control signal 0 is at the Ho level, In between, long-period light emitting pulses are continuously output.

Furthermore, when the control signal U is at the "L" level, short-period light projection pulses are continuously output. A state in which the object to be detected 10 is not located in front of the switch 1), the light receiving circuit 6 is not receiving the light emitted from the light projecting circuit 5, and the noise from other photoelectric switches is not being received. Now, from the signal processing circuit 8 to the control circuit 4
There is no input signal to the control circuit 4', and the control signal U output from the control circuit 4' remains at the "L" level. Further, the light receiving pulse signal i output from the light receiving circuit 6 remains at the "L" level, and the flip-flop 41.4 of the control circuit 4
The output l1m of No. 2 also remains at the "°L" level. Therefore, the control signal 0 output from the OR circuit 48 of the control circuit 4 also remains at the "L" level, and the output f of the flip-flop 29 is inputted as is to the flip-flop 32 of the frequency dividing circuit 3, and this output f flip flop 3 by
The outputs q and r of 2 are inverted. As a result, the light emitting circuit 5
The waveform of the light emitting pulse g manually inputted is such that long periods and short periods are alternately repeated.

FIG. 5 shows a signal waveform when the object 10 to be detected is not located in front of the photoelectric switch 1) and the photoelectric switch 1) receives light projected from another photoelectric switch. As shown in the figure, when noise from another photoelectric switch is received in the vicinity of the third emitted light pulse g at time t, a received light pulse signal i is generated, and in the control circuit 4, the Q output 2 of the flip-flop 41 is H"
become the level. The output p of this flip-flop 41 is read by the flip-flop 42 at the rising edge of the projection pulse g, and its Q output becomes the "°H" level. Output m
When the control signal 0 goes to the "H" level, the control signal 0 also goes to the "H" level, the output q of the flip-flop 7 block 32 goes to the "L" level, and the output r goes to the "H" level. As a result, the fourth light projection pulse g2 also has a long period.

Noise also enters just before this fourth light emitting pulse g2, and the output q is “L” and the output r is “°H”.
level is maintained. Therefore, the fifth light emitting pulse g
3 also has a long period. Immediately before this fifth light emitting pulse g3, no noise enters the light, and the output m becomes the "°L°" level. However, the output m of the flip-flop 47 remains at the "'H" level. , the control signal 0 maintains the "H" level, and the sixth light emitting pulse g also has a long period. Here, since no noise enters the light just before the sixth light emitting pulse g4, the output m of the flip-flop 47 also becomes "L" level, and the control signal 0 also becomes "L" level.As a result, The seventh light emitting pulse g has a short period,
Thereafter, its own light projection pulse is output at a timing different from the noise light projection timing.

As described above, when the light receiving circuit 6 receives light, the control circuit 4
A control signal 0 is outputted from the control signal generator 1 to make the period of the light emitting pulse g constant for a predetermined number of times. As a result, if the received light is noise emitted from another photoelectric switch, the emitted light pulses of the self and other photoelectric switches will not be synchronized, and the light reception timing will no longer match the reading timing, causing the light emitted from other photoelectric switches to No malfunctions will occur due to noise from the projected light. In addition, when the received light is the light projected from the own light projection circuit 5, the read clock pulse f2 supplied to the signal processing circuit 8 becomes the light projection pulse g supplied to the light projection circuit 5. Because of synchronization, it is possible to receive the light projected from its own light projection circuit even after the light projection pulse g is output with a predetermined number of legs equal to 0.

In addition, in the example shown in FIG. 6, when the signal processing circuit 8 successively reads a plurality of received light signals, the signal is inputted from the signal processing circuit 8 here to the control circuit 4'. In response, the control signal U is sent from the control circuit 4' to the frequency dividing circuit 3.
It is designed to output to . Here, the number of consecutive readings of the light reception signal required until the signal is inputted from the signal processing circuit 8 to the control circuit 4' is greater than the number of consecutive readings required until the detection signal t is output from the signal processing circuit 8. It is a small value. By doing this, for example, if the control signal U is set to "L" level when six light reception signals are input to the signal processing circuit 8 in succession, the seventh light reception time after the first light reception time is set. and the 8th light emission pulse gt, g
s has a short period, and if the received light is noise emitted by another photoelectric switch, the light emitted pulses of the self and other photoelectric switches are synchronized and disappear. For this reason, the read clock pulse in the signal processing circuit 8 is no longer synchronized with the light reception timing in the light receiving circuit 6, the eight received signals i are not continuously input to the signal processing circuit 8, and the detection signal t is not output. Note that the number of light reception signals that should be input to the signal processing circuit 8 in order for the control signal U to reach the L level is greater than the number of consecutive readings required until the detection signal t is output from the signal processing circuit 8. You can select any smaller value.

On the other hand, if the light received by the light receiving circuit 6 is the reflected light on the detected object 10 of the light projected from its own light projecting circuit,
As shown in Figure 7, the 7th and 8th received light pulses g
7. As gs is output in a short period, the light receiving circuit 6 receives the seventh and eighth lights in a short period.
th and 8th light reception pulse signal 'ff+Ill
is output in short cycles. As a result, the seventh and eighth received light signals 7. 8 is a light emitting pulse g7. gs
The signal is input to the signal processing circuit 8 in synchronization with the read clock pulse f2 which is synchronized with the read clock pulse f2. Therefore, the signal processing circuit 8 reads eight received signals k continuously and outputs a detection signal t.

As explained above, by making the period of the light emitting pulse constant when the light receiving circuit 6 receives light, the light emitting timing of another nearby photoelectric switch of the same type can be adjusted to match the light emitting timing of the own light emitting circuit. It is possible to accurately detect only the light emitted from its own light emitting circuit without synchronizing with the timing.

In this embodiment, the frequency dividing circuit 3 outputs a light emitting pulse and a light receiving pulse in which a long period and a short period are alternately repeated, but a long period, a medium period, and a short period are alternately repeated. It may be one that outputs pulses,
Alternatively, a light emitting/light receiving pulse of a predetermined length may be configured with a plurality of irregularly changing periods.

(g1 Effect of the Invention According to this invention, when a certain number of light reception signals that are less than or equal to the number of light reception signals read in the signal processing circuit are output from the light reception circuit, the frequency dividing period of the frequency dividing circuit is made constant by a predetermined same number. As a result, if the light received by the light receiving circuit is light emitted from another nearby photoelectric switch, it is possible to desynchronize the light emitting timing of the self and other photoelectric switches, and the signal processing circuit A certain number of light reception signals emitted from the photoelectric switch are not read in succession, and in this case no detection signal is output.On the other hand, if the light received by the light receiving circuit is emitted from its own light emitting circuit In the case of light, the frequency division cycle of the frequency dividing circuit is set constant for a predetermined number of times, so that the cycle of the reading pulse as well as the light emission pulse becomes constant, and the signal processing circuit receives light from its own light emission circuit. The signal is continuously read and a detection signal is output.In this way, the light received by the light receiving circuit is either emitted from its own light emitting circuit or from another nearby photoelectric switch. It is possible to accurately determine whether the light has been emitted, and there is an advantage that accurate detection processing can be performed even when a plurality of photoelectric switches of the same type are installed in parallel.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the operation of the present invention. Figure 2 shows the configuration of a photoelectric switch that is an embodiment of this invention.
3 is a circuit diagram showing the configuration of the main part of the photoelectric switch, and FIGS. 4 to 7 are timing charts of signal waveforms at each point of the photoelectric switch. 2 - oscillation circuit, 3 - frequency dividing circuit, 4 - control circuit, 5 - light emitting circuit, 6 - light receiving circuit, 8 - signal processing circuit.

Claims (2)

[Claims] (1) An oscillator circuit that generates basic clock pulses, and a frequency divider that divides the basic clock pulses generated by the oscillator circuit and outputs a light emission pulse whose frequency division cycle is not constant and a read pulse that is synchronized with this light emission pulse. circuit, a light emitter circuit driven by the light emitter pulse supplied from the frequency divider circuit, a light receiver circuit that receives the light emitted from the light emitter circuit, and a read pulse supplied from the frequency divider circuit. A signal processing circuit that reads the light receiving signal of the light receiving circuit and outputs a detection signal when a certain number of light receiving signals are read in succession, and a frequency dividing circuit that outputs a detection signal when the light receiving circuit outputs the light receiving signal of the certain number or less. A photoelectric switch circuit comprising: a frequency division cycle control circuit that keeps the frequency division cycle constant for a predetermined number of times. (2) The frequency dividing circuit divides the basic clock pulse generated by the oscillation circuit and outputs a light emitting pulse in which a long period and a short period are alternately repeated, and a reading pulse synchronized with this light emitting pulse. The photoelectric switch circuit according to claim (1).