JPH06224726A - Photoelectric switch - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a photoelectric switch resistant to noise. This photoelectric switch is a photoelectric switch for controlling energization of a load connected to a commercial power source, and has a light source that irradiates an object with pulsed light and a photodetector that detects light reflected by the object. The photo IC, a circuit for generating a pulse signal for driving the light source synchronized with the commercial power source at a predetermined timing, and a circuit for controlling the energization based on the detection output of the photodetector.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric switch for controlling energization of a load connected to a commercial power source by light.

[0002]

2. Description of the Related Art In recent years, semiconductor photodetectors have become available at low cost, and various devices applying them have been developed. The photoelectric switch detects the presence of people or objects in the room by the light that is reflected and returned, and detects the load of a load connected to a commercial power source such as a motor for automatic door drive, indoor lighting, air conditioning equipment, and power source for locking actuators. It controls energization and operates in accordance with the presence of people or objects. Generally, a photoelectric switch is disclosed in, for example, “Japanese Patent Laid-Open No. 61-26952”.
As described in "2", the light emission of the built-in light source (LED or the like) is driven by the internal oscillation circuit, and the light reflected and returned is detected. When the reflected light is detected, it is determined that a person or an object is present, and a mechanical relay, a photo MOS relay, a photothyristor, etc. are turned on to energize the load. Since the on / off control of the commercial power source is performed, the power source of the photoelectric switch is directly taken from the commercial power source for simplification of the device.

[0003]

The operation of detecting the reflected light of the photoelectric switch is performed asynchronously with the commercial power source. Of the noise synchronized with the commercial power source, the line noise coming from the power source of the photoelectric switch can be considerably removed by a capacitor or a commercially available noise filter. It was not possible to reduce inductive or electrostatic disturbance noise, and it was not possible to reduce the influence of disturbance light. There is a risk that the photoelectric switch malfunctions due to noise or the like that is synchronized with the commercial power supply, and the reliability of the operation of the device is reduced.

[0004]

A photoelectric switch for controlling the energization of a load connected to a commercial power supply, the first switch generating a pulse signal at a predetermined timing in synchronization with the commercial power supply, A light source that illuminates an object with pulsed light for a lighting period that is determined by a pulse signal, a photodetector that detects light from the light source reflected by the object, and an energization control based on the detection output of the photodetector. A photoelectric switch having the means of 2.

The first means may be characterized by delaying a pulse synchronized with a commercial power source to generate the pulse signal at a predetermined timing.

The second means may be characterized by energizing while the light from the light source reflected by the object is detected in synchronization with the periodic lighting of the light source.

The light source may be turned on intermittently during the lighting period.

The pulse signal may be set at a timing at which noise generated by the commercial power source is small.

[0009]

In the photoelectric switch of the present invention, the pulse signal for driving the light source is generated at the predetermined timing synchronized with the commercial power source by the first means, and the output timing of the pulsed light from the light source is controlled by this. When there is an object that reflects this pulsed light, the light reflected by the object is detected by the photodetector. Then, the energization of the load is controlled based on the detection output of the photodetector. The light reflected by the object is detected when the pulse signal is output from the first means. When the reflected light is detected, the energization of the load is controlled, and when it is not detected, the energization of the load is not controlled. Therefore, even if there is noise synchronized with the commercial power source, noise does not cause malfunctions when the energization is not controlled. Therefore, there are few malfunctions.

[0010]

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a main part of a circuit according to an embodiment of the present invention. This photoelectric switch generates a pulse synchronized with the commercial power supply AC, and drives the photo IC by this pulse to control the energization of a load (fluorescent lamp, actuator of automatic door) not shown. Each component of this photoelectric switch will be described below.

The power supply circuit 110 is a commercial power supply AC (100
V) is rectified and predetermined DC voltages V _CC and V _DD determined by the built-in Zener diode are applied to each part. The synchronization pulse generation circuit 120 generates a square wave (60 or 50 Hz) from the commercial power supply AC. The frequency dividing circuit 122 divides this square wave (for example, divides by 10) and generates a square wave of a predetermined cycle (for example, about 200 ms). Delay circuit 12
4 is to shift the timing determined by the square wave from the frequency dividing circuit 122 according to the setting from the outside.
The monostable multivibrator delays the rising timing of the square wave by generating a pulse at the rising edge of the output of the frequency dividing circuit 122. The pulse width of this pulse is determined according to the setting from the outside.

The intermittent pulse power supply generation circuit 126 generates a timing pulse for determining the time at which the intermittent pulse is output according to the pulse from the delay circuit 124. Here, a predetermined pulse starts from the falling edge of the pulse. Timing pulses are generated at intervals (here, about 1 ms). The photo IC 128 outputs an intermittent pulse to the light emitting element drive circuit 130 for a time determined by the timing pulse, and detects light reflected from the LED of the light emitting element drive circuit 130. Light emitting element drive circuit 13
0 drives the LED to emit light by intermittent pulses from the photo IC 128.

The delay circuit 132 delays the timing pulse from the intermittent pulse power supply generation circuit 126 for a predetermined time (here, the inverted output is delayed by 0.5 ms). The gate circuit 134 is the intermittent pulse power supply generation circuit 1
26 and the timing pulse delayed by the delay circuit 132 at a predetermined time interval (here,
A window of 0.5 ms) is created, and the output of the photo IC 128 is output to the switching time processing circuit 136. The switching time processing circuit 136 includes a mute circuit 136.
c, a monostable multivibrator 136a, and a flip-flop 136b. This circuit is a switching time processing circuit 1 when there is an output of the photo IC 128 (when there is an object that reflects the light from the LED).
The output of the photo IC 128 after passing through 36 is output as a square wave. The mute circuit 136c is for preventing the output of the switching time processing circuit 136 when the level becomes lower than a predetermined level. A relay (including a mechanical relay, a photothyristor, a photoMOS switch, etc.) is connected to the output of the switching time processing circuit 136, and this controls the energization of a load (not shown).

FIG. 2 shows an example in which the circuit shown in the block diagram of FIG. 1 is specifically configured by using a CMOS IC or the like. In this figure, the same reference numerals are assigned to the ICs that realize their functions corresponding to the blocks of FIG. The synchronization pulse generating circuit 120 is simplified by utilizing that both ends of the Zener diode of the power supply circuit 110 become zero volts at the zero cross point of the commercial power supply AC. In addition, the intermittent pulse power supply generation circuit 126 is
By turning on and off the power supply to C128 for a predetermined time, timing pulses at predetermined intervals are generated. And
A mechanical relay is connected to the output of the switching time processing circuit 136, and this mechanical relay turns the load on and off. In this embodiment, the first means is composed of a synchronous pulse generating circuit, a frequency dividing circuit, a delay circuit, an intermittent pulse power supply generating circuit and a photo IC, and the second means is a light emitting element drive circuit, a delay circuit and a gate. It is composed of a circuit and a switching time processing circuit.

FIG. 3 shows the waveform of each part of FIG. (A) is the waveform of the commercial power supply AC, (b) is the output waveform of the synchronization pulse generating circuit 120 (in the circuit of FIG. 2, the rectified waveform of the commercial power supply AC), (c) is the frequency dividing circuit 122.
Of the output waveform of the delay circuit 124,
(E) shows the output waveform (positive output) of the intermittent pulse power supply generation circuit 126. In this way, the timing pulse at the predetermined phase position in synchronization with the commercial power supply AC is output from the intermittent pulse power supply generation circuit 126 (FIG. 3 (e)).

FIG. 3 (f) shows an intermittent pulse power supply generation circuit 1
The output of FIG. 26 (FIG. 3 (e)) is a high-enlarged portion. (G) is the light output of the LED, (h)
Shows the output waveform (inverted output) of the intermittent pulse power supply generation circuit 126, and (i) shows the waveform of the timing pulse delayed by the delay circuit 132.

When there is an object that reflects the light from the LED, the output of the photo IC 128 passes through the window formed by the timing pulse from the intermittent pulse power supply generation circuit 126 and the delayed timing pulse (FIG. 3).
(J)). The monostable multivibrator 136a of the switching time processing circuit 136 holds the output of the photo IC 128 as long as the flip-flop 136b has the output shown in FIG. Then, the relay is turned on and the load is energized. If there is no object that reflects the light from the LED, there is no output from the photo IC 128 (see FIG.
(J remains low), the relay turns off.

Since the delay time of the delay circuit 124 is variable according to the setting, the phase relationship between the commercial power supply AC (FIG. 3A) and the output of the intermittent pulse power supply generation circuit 126 (FIG. 3E) is. It changes according to the setting. Noise and disturbance light synchronized with the commercial power supply (for example, commercial power synchronized fluorescent lamp, incandescent lamp disturbance light, disturbance noise, noise generated from thyristor, germicidal lamp noise, motor noise, mercury lamp noise, etc.) It occurs at a predetermined fixed point in 3. Therefore, by appropriately setting the delay time of the delay circuit 124, it is possible to detect the reflected light of the LED in a place not affected by these noises. That is, it becomes possible to detect the presence of a person or an object by making the influence of noise extremely small. Therefore, the photoelectric switch is resistant to noise and highly reliable, and the malfunction of the existing photoelectric switch can be reduced.

The present invention is not limited to the circuit example of FIG. 2 and can be variously modified. For example, although the one in which the synchronization pulse generation circuit 120 is omitted is shown, a pulse synchronized with the commercial power supply AC may be generated by a hysteresis comparator or the like. At this time, if the hysteresis characteristic can be changed, it becomes possible to adjust the phase relationship between the commercial power supply AC and the output of the intermittent pulse power supply generation circuit 126.

[0020]

As described above, according to the photoelectric switch of the present invention, the pulse signal is output at a predetermined timing of the commercial power supply, and the pulse signal can be prevented from being output when there is noise. There are few malfunctions. Therefore, the malfunction of the energization control of the load can be reduced.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a circuit diagram of an embodiment of the present invention.

FIG. 3 is a timing chart for the configuration of the marrow.

[Explanation of symbols]

110 ... Power supply circuit, 120 ... Synchronous pulse generation circuit, 12
2 ... Frequency divider circuit, 124 ... Delay circuit, 126 ... Intermittent pulse power supply generation circuit, 128 ... Photo IC, 130 ... Light emitting element drive circuit, 132 ... Delay circuit, 134 ... Gate circuit, 13
6 ... Switching time processing circuit, AC ... Commercial power supply.

Claims (5)

[Claims] 1. A photoelectric switch for controlling energization of a load connected to a commercial power supply, comprising: first means for generating a pulse signal at a predetermined timing in synchronization with the commercial power supply; and the pulse signal. A light source that illuminates the object with pulsed light by lighting in a lighting period determined by, a photodetector that detects light from the light source reflected by the object, and controls the energization based on the detection output of the photodetector. And a second means for controlling the photoelectric switch. 2. The photoelectric switch according to claim 1, wherein the first means delays a pulse synchronized with the commercial power source to generate the pulse signal at a predetermined timing. 3. The second means energizes while the light from the light source reflected by the object is detected in synchronization with the periodic lighting of the light source. Item 1. The photoelectric switch according to Item 1. 4. The photoelectric switch according to claim 1, wherein the light source lights up intermittently during the lighting period. 5. The photoelectric switch according to claim 1, wherein the timing of the pulse signal can be set in accordance with the timing in which noise generated in the commercial power source is small.