JPS6139623A - Indicator circuit of photoelectric switch - Google Patents

Abstract

PURPOSE:To enable to indicate optical axis coincidence and stability of operation of a photoelectric switch simply and accurately by comparing a DC signal obtained by receiving and demodulating pulse modulated projected light with a non-linear wave signal from an oscillation circuit and lighting up an indicator lamp by the output. CONSTITUTION:When pulse modulated projected light is irradiated from a projector, the light is received by a photodetecting element 3 and amplified by an amplifier circuit 4 and demodulated to a DC signal by a detecting circuit 5 and given to a waveform shaping circuit 6 and an amplifier circuit. When input is above specified level, the wave-form shaping circuit 6 controls an output switching circuit 7 and outputs on/off signals from an output terminal 8. DC voltage output A of the amplifier circuit 10 is given as input of a comparator circuit 12 and compared with a triangular wave signal B and comparison output for which duty ratio of H level is controlled proportional to the level of DC voltage output is generated. When light receiving level is low, duty ratio becomes small, and an indicator lamp 9 makes dim flickering, and when the level is high, makes continuous lighting. Thus, change of light receiving level can be indicated.

Description

[Detailed Description of the Invention] (Technical Field of the Invention) The present invention relates to a photoelectric switch that detects the presence or absence of an object to be detected by receiving pulse-modulated projected light, and particularly relates to a photoelectric switch that detects the presence or absence of an object to be detected by receiving pulse-modulated projected light, and in particular, This invention relates to a display circuit for a charging switch that displays stability, etc.

(Technical background of the invention and its problems) As a conventional photoelectric switch, there is one shown in FIG. 3, for example. FIG. 3 is a schematic diagram of a transmission type optical switch. In the figure, ■ is a light projector that projects a pulse-modulated light beam, and the projected light from the projector 1 is received by a light receiver 2. The light receiver 2 includes a light receiving element 3 such as a phototransistor or a photodiode that receives projected light and converts it into an electrical signal, an amplifier circuit 4 that amplifies the output signal of the light receiver 3 with AC, and a diode for the output of the amplifier circuit 4. A waveform shaping circuit 6 detects whether the DC voltage output of the detection circuit 5 is above a certain value -L, and a switching element etc. based on the detection signal of the waveform shaping circuit 6. It is composed of an output switching circuit 7 that turns on and off the output switching circuit 7, an output terminal 8 that connects a device such as a security alarm, and an indicator light 9 such as a light emitting diode that displays the on and off state of the output switching circuit 7.

In the above configuration, when a pulse-modulated light beam is emitted from the emitter l to the receiver 2, this pulse-modulated light is converted into an electrical signal by the light receiving element 3 on the receiver 2 side, and the amplifier circuit 4
After being amplified, the signal is modulated into a DC signal by a detection circuit 5 and sent to a waveform shaping circuit 6. The waveform shaping circuit 6 detects whether the level of the DC signal is above a certain value or not, and uses this detection signal to control the output switching circuit 7 to output an on/off signal from the output terminal 8. A device such as a security alarm connected to the output terminal 8 is activated by this on/off signal, and the presence or absence of a detected object between the light emitter 1 and the light receiver 2 is notified. The indicator light 9 blinks according to the on/off operation of the output switching circuit 7, thereby allowing the operating state of the photoelectric switch to be confirmed.

A photoelectric switch like the one described in -I- needs to be operated with sufficient stability to ensure its functionality, and for this purpose alignment of the optical axes of the emitter 1 and the receiver 2 is a very important task. . When the light projected from the emitter 1 is visible light and the distance between the emitter 1 and the receiver 2 is short in the transmission type photoelectric switch as described above, or when the emitter 1 and the receiver 2 are integrated Reflective type photodenkyu.

In a switch, if the distance between the photoelectric switch and the object to be detected is short, it is possible to align the optical axes relatively easily by visually following the projected light. However, when an infrared light emitting diode or the like is used as the light source of the floodlight l,
Since the projected light becomes invisible light, alignment of the optical axes becomes extremely difficult. In particular, in photoelectric switches for security alarms, etc., the installation distance between the emitter 1 and the receiver 2 is long, and at the same time,
Since a large sensitivity margin is provided in consideration of the usage environment, even if the center of the projected light from the emitter 1 is considerably shifted from the light receiving surface of the receiver 2, it will operate as a photoelectric switch, ensuring accurate optical axis alignment. It becomes even more difficult to check the status. In the conventional photoelectric switch described in -I-, an indicator light 9 is connected to the final stage of the output switching circuit 7, and this indicator light 9 indicates the on/off operating status of the photoelectric switch. However, it was not possible to check the alignment of the optical axes of the photoelectric switch and the stability of its operation, which was disadvantageous and inconvenient.

(Purpose of the Invention) The present invention has been made to solve the problems of the conventional photoelectric switch as described above. The purpose is to provide display circuits.

(Summary of the Invention) In order to achieve the above object, the present invention provides a method in which, after pulse-modulated projected light is received by a light-receiving element and demodulated into a DC signal by a detection circuit, the level of the DC signal is higher than a certain value. In a photoelectric switch that outputs an on/off signal depending on whether the It is characterized by being made to light up.

(Embodiments of the Invention) The present invention will be described in detail below with reference to FIGS. 1 and 2.

Figure i1 shows a display circuit of a photoelectric switch, and the same elements as those in the middle part of Figure 3 are given the same reference numerals. In this circuit, an amplifier circuit 10 is provided on the photoreceiver 2 side to amplify the DC voltage output of the detection circuit 5 and obtain a DC voltage output A that shows a larger potential fluctuation in response to changes in the received light level.
, an oscillation circuit 11 that oscillates a triangular wave signal B, DC voltage output A is applied to (+) input terminals, triangular wave signal B is applied to (-) input terminals, and the re-input signals are compared to determine a predetermined duty. a comparison circuit 12 that outputs a signal having a ratio;
A lighting circuit 13 that lights up the indicator lamp 9 based on the output signal of the comparison circuit 12 is provided. Here, the lighting circuit 13 is
Resistor 209 connected in series between DC power supply Vcc and ground
It is composed of an indicator light 9, a switching transistor 21, and a resistor 22 connected between the output side of the comparison circuit 12 and the base of the switching transistor 21.

FIG. 2 shows signal waveforms of various parts of the circuit in FIG. 1, and the operation of the circuit in FIG. 1 will be explained with reference to this diagram. When a pulse-modulated light beam is emitted from the emitter l to the receiver 2, this pulse-modulated light is converted into an electrical signal by the light-receiving element 3, amplified by the amplifier circuit 4, and then modulated into a DC signal by the detector circuit 5. , are applied to the waveform shaping circuit 6 and the amplifier circuit 10. As described above, the waveform shaping circuit 6 detects whether the level of the DC signal is equal to or higher than a certain value, and controls the output switching circuit 7 based on this detection signal to turn the output terminal 8 on or off. Output a signal. On the other hand, the amplifier circuit 10 amplifies the DC voltage output of the detection circuit 5 and provides the DC voltage output A to (+) input terminals of the comparison circuit 12 . Then, the comparator circuit 12 compares the triangular wave signal B of the oscillation circuit 11 applied to the (-) input terminals with the DC voltage output A, and increases °°H in proportion to the potential of the DC voltage output A.
Outputs a waveform signal with a controlled duty ratio of '° level. In other words, when the received light level is low and the potential of the DC voltage output A is low, the output of the comparator circuit 12 becomes a signal waveform with a small duty ratio of ``H'' level. Given. Then, the transistor 21 is turned on when the output signal of the comparator circuit 12 is at "H" level, and the DC power supply v
Since CC is applied to the indicator light 9 through the resistor 20, the lighting state of the indicator light 9 becomes dark and blinking. Furthermore, when the received light level becomes low and the potential of the DC voltage output A becomes lower than the lowest potential of the amplitude of the triangular wave signal B, the output of the comparator circuit 12 becomes zero and the switching transistor 21 is turned off, so that the indicator light 9 is turned off. Lights out. On the other hand, when the received light level increases and the potential of the DC voltage output A increases accordingly, the output signal waveform of the comparator circuit 12 has a large duty ratio of the II H11 level, and the indicator lamp 9 correspondingly increases. It flashes brightly. When the light reception level further increases and the potential of the DC voltage output A becomes equal to or higher than the highest potential of the amplitude of the triangular wave signal B, the switching transistor 21 is turned on and the indicator lamp 9 is lit continuously. According to Honjitsu Iku, the level of light received by the light receiver 2 can be known as a continuous change by the indicator light 9, so the optical axis alignment and operation stability of the photoelectric switch, regardless of whether it is a reflective type or a transmissive type, can be determined. This has the effect of making it easy to confirm the following, and greatly simplifying maintenance and inspections.

Note that, of course, the present invention is not limited to the above embodiments. For example, in the above embodiment, the oscillation circuit 11
Although a triangular wave oscillation circuit is used as the embodiment, similar effects can be obtained by using other non-linear wave oscillation circuits such as a sawtooth wave oscillation circuit and a nine-step waveform oscillation circuit. In addition, the DC voltage output A is applied to the (-) input terminals of the comparator circuit 12, and the triangular wave signal B is applied to the (+) input terminals of the comparator circuit 12, respectively, to reverse the lighting, blinking, and extinguishing operations of the indicator light 9. However, the same effect as in the above embodiment can be obtained.

(Effects of the Invention) As explained above, according to the present invention, the nonlinear wave signal oscillated from the oscillation circuit and the DC output signal of the detection circuit are compared by the comparison circuit, and the Since the indicator light is turned on, it is possible to easily check whether the optical axes of the photoelectric switch match or the operating stability of the photoelectric switch is consistent based on the lighting state of the indicator light.

[Brief explanation of drawings]

FIG. 1 is a display circuit diagram of a photoelectric switch showing an embodiment of the present invention, FIG. 2 is a signal waveform diagram of each part of the circuit in FIG. 1, and FIG.
FIG. 1 is a schematic configuration diagram of a conventional photoelectric switch. ■... Emitter, 2... Light receiver. 3... Light receiving element, 4... Amplification circuit. 5...Detection circuit, 6...Waveform shaping circuit. 7... Output switching circuit, 8... Output terminal. 9... Indicator light, 10... Amplification circuit. 11...Oscillation circuit, 12...Comparison circuit. 13...Lighting circuit.

Claims (1)

[Claims] A light-receiving element that receives pulse-modulated projected light and converts it into an electrical signal, a detection circuit that demodulates the output signal of this light-receiving element into a DC signal, and whether or not the DC signal level of this detection circuit is above a certain value. An oscillation circuit that oscillates a non-linear wave signal, a comparison circuit that compares the non-linear wave signal of this oscillation circuit with the DC signal, and a photoelectric switch that outputs an on/off signal depending on the direction. 1. A display circuit for a photoelectric switch, comprising a circuit for lighting an indicator light according to the output of the circuit.