JPS62261982A - Photoelectric switch - Google Patents

Abstract

PURPOSE:To prevent wrong detection from occurring owing to the repetition of synchronizing pulses by nullifying light projection pulses and synchronizing pulses and outputting new projection pulses which are out of phase when a photodetecting element photodetects pulse modulated light which does not correspond to the element. CONSTITUTION:When the photodetecting element 3 receives reflected pulse modulated light in the absence of projection pulses P14a (synchronizing pulse), an amplifier 7 outputs a photodetection signal S7 to nullify pulses P13 of a pulse oscillator 13 for outputting the pulses P14a for a certain time by a monostable multivibrator 10, and new projection pulses P14b which are a 1/2 period out of phase with the pulses P14a are outputted through the operation of a monostable multivibrator 9. Consequently, if the element 3 photodetects the reflected pulse modulated light from another detection body where the starting synchronizing pulses overlap with synchronizing pulses of another photoelectric switch, an amplifier 5 outputs no wrong photodetection signal and wrong detection is securely eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a photoelectric switch that outputs a light reception signal based on light received by a light receiving element in synchronization with a synchronization pulse based on a light projection pulse.

(Prior art) A reflective photoelectric switch generates pulse modulated light from a light emitting element using a light emitting pulse, and when this pulse modulated light is reflected from an object to be detected, the reflected pulse light is modulated to a light receiving element. A common configuration is to receive light and output the received light signal in synchronization with a synchronizing pulse that is the same as the light emitting pulse and is delayed by one phase. and,
In various types of automated equipment, such as unmanned automatic trolleys, it is normal to install one photoelectric switch of this type.

(Problem to be Solved by the Invention) When a plurality of photoelectric switches are installed, the timing of the light emission pulse of each photoelectric switch, that is, the timing of the synchronization pulse, is generally very similar. It is often the case that synchronizing pulses are output in duplicate between switches.

Therefore, even though there is no detected object for one photoelectric switch, if the reflected pulse modulated light from the detected object corresponding to another photoelectric switch enters the light receiving element of that photoelectric switch, In photoelectric switches, there has been a problem in that a light reception signal based on light reception by a light receiving element is output in synchronization with a synchronization pulse, resulting in erroneous detection.

Therefore, a fourteenth object of the present invention is to provide a photoelectric switch that does not cause false detection even when a light receiving element receives pulse modulated light other than that corresponding to itself.

[Structure of the Invention] (Means for Solving the Problems) The photoelectric switch of the present invention includes a drive circuit that causes a light emitting element to emit light by a light emitting pulse based on a pulse from a pulse oscillator, and the light emitting element of this drive circuit A light receiving circuit is provided that outputs a light reception signal based on light reception by a light receiving element in synchronization with a synchronization pulse based on a pulse, and when the light reception element receives light when the synchronization pulse is not present, the pulse is output for a predetermined period of time each time the light reception signal is present. The present invention is characterized in that it includes a correction circuit that nullifies the pulse from the oscillator and causes the drive circuit to output a light projection pulse whose phase is shifted from the light projection pulse based on the light reception signal.

(Function) In the photoelectric switch of the present invention, when the light receiving element receives pulsed light other than that corresponding to itself, the light emitting pulse and synchronization pulse that have been output based on the pulse of the pulse oscillator are invalidated. and instead, a new light emitting pulse whose phase is shifted from the light emitting pulse is outputted from the drive circuit in response to a light reception signal based on light reception of a pulse eclipse dimming other than that corresponding to the self of the light receiving element. Therefore, a new synchronization pulse is output based on this new light projection pulse, and erroneous detection due to partial overlapping of synchronization pulses is prevented.

(Example) An example of the present invention will be described below with reference to the drawings.

First, the overall electrical configuration will be explained based on FIG. 1.

1 is a power supply line to which a DC constant voltage +Vec is applied, and this is grounded through a resistor 2 and a photodiode 3 which is a light receiving element in series, and the common connection point of the resistor 2 and photodiode 3 is a capacitor 4. is connected to an input terminal of an amplifier 5 with a gate terminal, which is a light receiving circuit. In this case, the amplifier 5 outputs an output signal based on a human input signal when a high-level synchronization signal is applied, as will be described later.

6 is a modification IE circuit, which will be described below.

Reference numeral 7 denotes an amplifier with a gate terminal, whose input terminal is connected to the input terminal of the amplifier 5, and whose output terminal is connected to the inverting input terminal (-) of the comparator 8. in this case,
Similarly to the amplifier 5, the amplifier 7 outputs an output signal based on a human input signal when a high level signal is applied to the tegate terminal. In the comparator 8, the reference voltage v8 is applied to the non-inverting input terminal (+), and the output terminal is connected to each input terminal B of the monostable multi-bibreaks 9 and 10. These monostable multivibrators 9 and 10 have their input terminals A grounded and are triggered by the fall of the human input signal at their input terminal B from high level rHJ to low level rLJ. Note that the j-do stable multi-bye break 10 is of a retrigger type. The output terminal 0 of the monostable multi-bi break 9 is connected to one input terminal of the AND gate 11, and the output terminal 0 of the qt-stable multi-bi break 10 is connected to one input terminal of the Nant gate 12. The output terminal of the gate 12 is connected to the other input terminal of the AND gate 11.

Now, 13 is a pulse oscillator, the output terminal of which is connected to the other input terminal of the Nandt gate 12.

14 is a monostable multivibrator comprising a drive circuit 16 (-4) together with an inverter 15, whose input terminal A is connected to the output terminal of the AND gate 11, and whose input terminal B is connected to the power supply line 1. and input terminal A
It is triggered by the rise of the human input signal from the low level rLJ to the high level "H". The output terminal Q of this lit stable multivibrator 14 is branched into two, the first branch end being connected to the input terminal of the inverter 15, and the second branch end being connected to the gate terminal of the amplifier 5. Inverter 1
It is connected to the gate terminal of the amplifier 7 via 7. Reference numeral 18 denotes a light emitting diode which is a light projecting element, and its anode is connected to the power supply line 1 via a resistor 19, and its cathode is connected to the output terminal of the inverter 15.

Next, the operation of this embodiment will be explained with reference to FIG. 2.

Now, as shown by the X section in Fig. 2, the photodiode 3
If it does not receive the reflected pulse modulated light from the object to be detected, the amplifier 7 does not output the light reception signal S, as shown in FIG. 2(a), and as shown in FIG. 2(b). The output signal S8 of the comparator 8 is at a high level rHJ. Therefore, the output signal S! of the monostable multivibrator 9.10! +StO is / as shown in Figure 2 (c) and (d)
1 level rHJ. Since the pulse oscillator 13 outputs the pulse PL3 as shown in FIG. 2(e), the Nantes gate 12 outputs an output signal S12 with the phase of the pulse P13 inverted as shown in FIG. 2(f). Therefore, the AND gate 11 outputs a pulse p having the same phase as the output signal S12, as shown in FIG. 2(g).
Output Ha. As a result, the multi-bye break 14 stabilizes +1 as shown in FIG.
"a's rise from low level rLJ to high level rHJ"
Light emitting pulse P triggered by the lily and having a pulse width t14
laa will be output. That is, the light projection pulse Pla
a is output based on the pulse P13 of the pulse oscillator 13. And monostable multivibrator 14
Every time the output pulse p14a is output, the inverter 15
Since the output signal becomes low level rLJ, the light emitting diode 18 is energized and emits light every time the light projection pulse pt a a is output, and thus pulse modulated light is projected onto the detection target site. Moreover, since this light emitting pulse P14a is given to the gate terminal of the amplifier 5 as a synchronization pulse, the amplifier 5
When the photodiode 3 receives reflected pulse modulated light from the object to be detected at the corresponding detection site when a synchronization pulse is applied, it outputs a light reception signal based on the received light. The level of the light reception signal from the amplifier 5 is detected and converted into a pulse, and then applied to, for example, a digital integration circuit, and when the digital integration circuit counts up to a predetermined value, it outputs a detection signal. Incidentally, when the light emitting pulse P1aa is applied to the gate terminal of the amplifier 5 as a synchronizing pulse, the output signal of the inverter 17 becomes low level rLJ at this time, so when the amplifier 5 is outputting the light reception signal, the amplifier 7 is It does not output a light reception signal.

Now, as shown in the Y part of FIG. 2, the reflected pulse from a detected object other than the detected object to which the photodiode 3 corresponds is 1! Let us consider the case where l light is received.

In this case, if the light emitting pulse p14a, which is a synchronizing signal, and the light received by the photodiode 3 are partially overlapped, there is a time when the photodiode 3 receives light even when the light emitting pulse pL4H is not present (1 mi). Therefore, due to the absence of the light emitting pulse P14a, the output signal of the inverter 17 becomes high level "H" as shown in FIG.
As shown in a), the amplifier 7 comes to output the light reception signal ST. When the light reception signal S7 is output, the comparator 8 compares the level of the light reception signal S7 with the reference voltage V8.
(See FIG. 2(a)), as shown in FIG. 2(b), the output signal S8 is set to low level "L" only during the period when the light reception signal S is higher than the reference voltage V8. .

Furthermore, monostable multi-by breaks 9 and 10 are triggered by the fall of this output signal S8 from high level rHJ to low level rLJ, and monostable multi-by breaks 9 and 10 are triggered.
As shown in FIG. 2(C), the output signal S, is set to low level rLJ for a time t9 (e.g., equal to the pulse width of pulse P13), and the stable multi-vibration break 10 is set at a low level rLJ as shown in FIG. 2(d). The output signal SIG is set to the low level rLJ (for example, 2 to 3 times the period of the pulse P13, which is a predetermined period of time). Therefore,
When the output signal Sio of the stable multivibrator 10 becomes low level rLJ, the NAND gate 1/12 changes the output signal S12 to high level rHJ in order to nullify the pulse P13 of the pulse oscillator 13, as shown in FIG. 2(f). I come to do it. As a result, the AND gate 11 is activated as shown in FIG.
As shown in g), the output signal S! of the monostable multi-bi break 9! The monostable multi-vibration brake 14 outputs a pulse pHb corresponding to the change in the high level rHJ and low level rLJ of I, and as shown in FIG. A new light emitting pulse p14b with a pulse width t14 shifted by two cycles is output. That is, this new light emission pulse Px
ab is output based on the light reception signal S8. Incidentally, the monostable multivibrator 1o receives the output fn of the comparator 8 every time the amplifier 7 outputs the light reception signal ST.
8 falls from the high level rHJ to the low level rLJ, so its output signal SIG is as shown in Figure 2 (
d), the output signal S12 of the Nantes gate 12 remains at the low level rLJ as shown in FIG. 2(f).
As shown, the rHJ remains at a high level. Then,
Since the new light emitting pulse p14b is also given to the inverter 15, the light emitting diode 18 is now energized and emits light every time the light emitting pulse p14b is output.
A new pulse change, 'J3 light, will be emitted. Since this light emitting pulse p14b is given to the gate terminal of the amplifier 5 as a synchronizing pulse, the light emitting diode 1
When the photodiode 3 receives the reflected pulse modulated light from the object to be detected based on the pulse modulated light of 8, the amplifier 5 outputs a light reception signal. Thereafter, the photodiode 3 no longer receives the reflected pulse modulated light from the detected object other than the one corresponding to itself, and the amplifier 7 outputs the light reception signal S7.
When the output signal S6 of the comparator 8 falls from the high level rHJ to the low level rLJ based on the last light reception signal s7, when a time t3 has elapsed, the output signal S3 of the monostable multi-bi break 9 first changes.
becomes a high level rHJ, and when time tlG has elapsed, the output signal SIO of the monostable multivibrator 10 becomes a high level rHJ. Therefore, as shown in the Z section of FIG. 2, the pulse P13 of the pulse oscillator 13 is energized as in the X section of FIG. 2, and the rJg and light projection pulses P14a are output.

As described above, according to this embodiment, when the photodiode 3 receives reflected pulse modulated light when there is no synchronization pulse (emission pulse Pxaa), the amplifier 7 outputs a light reception signal based on the light reception of the photodiode 3. S7 is output, and the light emitting pulse Pl is output based on the output of this light reception signal ST.
Pulse P1 of the pulse oscillator 13 to output aa
3 is invalidated for a predetermined time by the monostable multi-by break 10, and based on the output of the light reception signal s7, the monostable multi-by break 9 generates a new signal whose phase is shifted by approximately 1/2 cycle from the target pulse Pica. Since the light emitting pulse Pxab (synchronizing pulse) is outputted, the original synchronizing pulse (light emitting pulse P4 a
) is partially in line with the synchronous pulse of another photoelectric switch, and even if the photodiode 3 receives the reflected pulse change light from the object to be detected corresponding to the grounded photoelectric switch, the amplifier 5 may erroneously Since no light reception signal is output, erroneous detection can be reliably prevented.

In the above embodiment, the light emitting pulse Ptta+ p14b
is used as a synchronization pulse as it is, but instead, a synchronization pulse may be obtained by slightly shifting the phase of the light emitting pulse PIAa, PI31).

In addition, it goes without saying that the present invention is not limited to the embodiments shown in the drawings, but can be implemented with appropriate modifications within the scope of the invention.

[Effects of the Invention] As explained above, the photoelectric switch of the present invention has a mechanism for outputting the light emitting pulse every time there is a light reception signal when the light receiving element receives light when there is no synchronization pulse based on the light emitting pulse. The pulse of the pulse oscillator is disabled for a predetermined period of time, and a new light emitting pulse whose phase is shifted from the light emitting pulse is output based on the received light signal, so that the original synchronizing pulse can be used for other photoelectric switches. This has the excellent effect of preventing erroneous detection even when the light-receiving element receives reflected pulse-modulated light from an object to be detected, which corresponds to a photoelectric switch that is partially reciprocated with the synchronization pulse and is grounded.

[Brief explanation of drawings]

FIG. 1 is an electrical configuration diagram showing an embodiment of the present invention, and FIG. 2 is a signal waveform diagram of each part of the embodiment. In the drawing, 3 is a photodiode (light receiving element), 5 is an amplifier (light receiving circuit), 6 is a correction circuit, 13 is a pulse oscillator,
16 is a drive circuit, and 18 is a light emitting diode (light projecting element). Applicant Sanris Co., Ltd. Figure 1

Claims (1)

[Claims] 1. A light emitting element, a light receiving element, a pulse oscillator, a drive circuit that causes the light emitting element to emit light with a light emitting pulse based on a pulse from the pulse oscillator, and synchronization with a synchronization pulse based on the light emitting pulse of this drive circuit. a light receiving circuit that outputs a light receiving signal based on the light received by the light receiving element; and a light receiving circuit that outputs a light receiving signal based on the light received by the light receiving element, and when the light receiving element receives light when the synchronizing pulse is not present, the pulse from the pulse oscillator is disabled for a predetermined time every time the light receiving signal is received. and a correction circuit that causes the driving circuit to output a new light emitting pulse whose phase is shifted from the light emitting pulse based on the light reception signal.