JP2557137Y2 - DC 2-wire photoelectric switch - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC two-wire type photoelectric switch, and more particularly to a DC two-wire type photoelectric switch having a display characteristic when the optical axis is adjusted.
The present invention relates to a linear photoelectric switch.

[0002]

2. Description of the Related Art Conventional DC two-wire switches, for example, photoelectric switches, have a pair of terminals connected in series to a load and a power supply, and open and close output switching elements at both ends based on the switch state. Is working. In such a DC two-wire type photoelectric switch, when the output switching element is open, it is necessary to operate the internal circuit with a very small leakage current, for example, about 1 mA in order to prevent a load current from flowing. However, in the case of a photoelectric switch, it is necessary to light the light emitting element periodically and supply an operating current to an internal circuit. Therefore, within the range of leakage current,
It is difficult to turn on a display lamp such as a stable display or a light-indicating display, which is used in a normal three-wire electronic switch.
Therefore, in the conventional two-wire photoelectric switch, only the operation indicator light is provided as the indicator light.

[0003]

As described above, in the conventional DC two-wire type photoelectric switch, since only the operation indicator is provided, the optical axis is adjusted at the time of adjusting the optical axis so that the optical axis of the projector and the optical receiver coincide with each other. There is a drawback that it is extremely difficult to check whether they match.

The present invention has been made in view of such a problem of the conventional DC two-wire type photoelectric switch, and performs light-in display and stable display when adjusting the optical axis of the photoelectric switch.
A technical problem is to make it easy to adjust the optical axis.

[0005]

The present invention includes a pair of terminals connected in series to an external load and a DC power supply, and an oscillating circuit for generating a clock signal. The light emitting element is driven by the output of the oscillating circuit. A light-emitting unit, a light-receiving unit that receives light from the light-emitting unit, a signal processing unit that discriminates a light-receiving level of the light-receiving unit to obtain an output for stable operation and a switch operation, and an output that opens and closes a pair of terminals. A DC two-wire type photoelectric switch, comprising: a power supply to each unit, and a short circuit between a pair of terminals based on an output of the signal processing unit.
Changeover switch means for selecting one of a setting mode for performing optical axis adjustment and an operation mode for performing an operation at the time of normal detection,
When the changeover switch is switched to the setting mode, the difference between the average driving current during one cycle of the clock signal in the operation mode of the light emitting section and the average driving current during one cycle of the clock signal in the setting mode is equal to or less than the difference. It has a current source for generating a current, a stable display for a display device及<br/> beauty incident displayed for a display device that is connected to a current source between a pair of terminals, respectively stabilized display by the output of the signal processing unit A clock signal having a long period when the mode is switched to the setting mode by the changeover switch, and a short period when the mode is switched to the operation mode. Is oscillated.

[0006]

According to the present invention having the above-described features, the changeover switch is switched to the setting mode when adjusting the optical axis. By doing so, the clock cycle of the oscillation frequency of the oscillator becomes longer, and the current consumed by the light emitting unit decreases. Therefore, the difference between the normal drive current required in the light emitting section and the drive current in the setting mode is generated by the current source, and the current of the current source is used to operate based on the signal obtained from the signal processing section at the time of optical axis adjustment. The display and the stable display are performed.

[0007]

FIG. 1 is a block diagram showing the overall configuration of a DC two-point photoelectric switch according to an embodiment of the present invention. In this figure, an oscillation circuit 1 has a short period during normal operation and a long period during optical axis adjustment and generates a clock signal with a small duty ratio. Can be The light projecting circuit 2 drives a light projecting element 3 such as an LED to emit light to an object detection area, and these constitute a light projecting unit. In addition, a light receiving element 4 that receives light from the light emitting element 3 facing the light emitting element 3 or from the object detection area is provided. The output of the light receiving element 4 is an amplifier 5
And amplified. The light receiving element 4 and the amplifier 5 constitute a light receiving unit, and the output is supplied to comparators 6 and 7. Comparators 6 and 7 discriminate whether or not a signal of a stable light input level and a signal of a light input / switch operation level can be obtained, and their outputs are supplied to a signal processing circuit 8 together with the oscillation output of the oscillation circuit 1. Can be The signal processing circuit 8 performs a signal processing by applying a gate based on the oscillating output based on these inputs, and supplies the output to the integrating circuit 9. The integrator circuit 9 supplies each output to the output mode setting circuit 10 when the outputs coincide with each other for a predetermined period. Here, the comparators 6 and 7, the signal processing circuit 8, and the integrating circuit 9 constitute a signal processing unit that discriminates a light receiving level of the light receiving unit and obtains an output for a stable operation and a switch operation.

The output mode setting circuit 10 is connected to a changeover switch 11 for switching between the optical axis adjustment and the operation mode. The changeover switch 11 is a changeover switch means for changing a setting mode (Set) for adjusting the optical axis and an output state when light is received by the light receiving section. The output mode setting circuit 10 drives a display that switches between stable display, operation display, and light input display based on the integrated output,
It drives the output circuit. Output mode setting circuit 1
The output of 0 is connected to switches 12 and 13, respectively. Switches 12, 13 are indicators, for example light emitting diodes 14,
15 and each is connected in parallel. Light emitting diode 14
Is a display for stable display, the light emitting diode 15 is a display for light input display in the setting mode, and an operation display in the operation mode. As shown in FIG. Connected. The output of output mode setting circuit 10 is also provided to output circuit 19.
The output circuit 19 includes an output switching element.
The pair of terminals 18a and 18b are short-circuited according to a control signal. Here, the switch circuit 17 is for closing a switch at least in a setting mode by a light incoming signal , and the switch circuit of this embodiment additionally has a switch for closing the switch when the output is turned on in the operation mode. Circuit. The output mode setting circuit 10 opens the switch 12 according to the stable display output when the changeover switch 11 is set to the setting mode. In the setting mode, the switch 13 is opened when light enters. In the operation mode, a light incident signal is supplied to the switch 13 according to the mode.

Next, a detailed configuration example of the light projecting section according to this embodiment will be described with reference to FIG. In this figure, an oscillation circuit 1 of a light projecting unit includes an oscillator 21 that oscillates at a fixed period as shown in the figure, a frequency dividing circuit 22, an AND circuit 23, and an OR circuit 2 to which outputs of the frequency dividing circuit are supplied.
4. The other input of the OR circuit 24 is intended to switch is connected to the set terminal of the change-over switch 11, the AND circuit 23 the output of the oscillator 21 and frequency divider 22 on the basis of this signal. This oscillation circuit 1
Is given to a transistor 2a which is a light emitting circuit,
The light emitting diode 3a as a light emitting element is driven.

FIG. 3 is a circuit diagram showing a detailed configuration of the output mode setting circuit and its peripheral circuits. In the figure, the X output of the integration circuit 9 obtained at the time of stable input and the Y output of the integration circuit 9 obtained at the time of light input are output mode setting circuit 1 respectively.
OR circuit 25 of 0, exclusive OR circuit (EOR circuit) 2
6 given. The OR circuit 25 supplies the logical sum with the set input terminal to the switching transistor 12a. The changeover switch 11 is set in the setting mode (Set) /
In addition to the switching of the operation mode, the switch is a switch for switching between turning on the output during light blocking (Dark On; Don) and turning on the output during extinction (Light On; Lon) in the operation mode. Changeover switch L
The on terminal is supplied to the EOR circuit 26, and its exclusive OR output is supplied to the EOR circuit 27. A set terminal is connected to the other input terminal of the EOR circuit 27, and an exclusive OR output thereof is supplied to a switching transistor 13a.
Given to. The set terminal and the output terminal of the EOR circuit 26 are connected to a NAND circuit 28, and the logical product output is given to the output circuit 19. The output circuit 19 has a pair of terminals 1
It is composed of a switching transistor connected between 8a and 18b. A DC power supply and a load are connected in series to the terminals 18a and 18b.

On the other hand, the output of EOR circuit 27 is also applied to the base of transistor 30 via inverter 29 of switch circuit 17. Base of transistor 30 and terminal 1
8a is connected to the constant current source 31. Terminal 18a
Is connected to a constant current source 16 via a PNP transistor 32.
Is connected. The base of transistor 32 is connected to the collector of transistor 30. When the output of the inverter 29 is at the H level, the switching circuit 17
0 and 32 are made conductive to supply power to the constant current source 16. Thus, the transistor 1 is supplied from the constant current source 16.
The light-emitting diodes 2a and 13a or the light-emitting diodes 14 and 15 for stable display and light-incident display are turned on.

Next, the operation of this embodiment will be described. The oscillator 21 of the oscillating circuit 1 generates a clock signal having a constant period T as shown in FIG. 4A, and the frequency dividing circuit 22 divides the frequency of the signal to obtain, for example, as shown in FIG. A high frequency division output can be obtained. In the setting mode in which the signal of the set terminal of the changeover switch 11 is at the L level as shown in FIG. 4C, the output of the frequency dividing circuit 22 is selected by the AND circuit 23, and the oscillator 21 is set when the set input terminal is at the H level. Is selected, and the light emitting diode 3a which is a light emitting element is driven. Therefore, FIGS. 4 (f) and (g)
If the outputs of the oscillator 21 and the frequency divider 22 are shown on an enlarged time axis, the period of the oscillator 21 is represented by T, and the period of the H level period is represented by t.
The average current I _L for driving a is expressed by the following equation. I _L = (t / T) I _{P In the} setting mode, the period is x · T as shown in FIG.
Then, the average current in the setting mode is expressed by the following equation. _{I L (SET) = {t} / (x · T)} I P Therefore the difference _{I H (= I L -I L} (SET)) is the extra current in the setting mode. In this embodiment, the constant current source 16 supplies the constant current to the light emitting diode 14 when the current is supplied from the switch circuit 17. Thus, the adjustment of the optical axis is facilitated by using the extra current for stable display or light-incident display. Here, it is sufficient that the constant current source 16 supplies an arbitrary current value equal to or less than the difference I _H between the drive currents.

FIG. 5 is a time chart showing waveforms at various parts of the output mode setting circuit 10. In this figure, when the operation mode is first selected to be dark on (Don),
As shown in FIGS. 5C and 5D, the set terminal and the Lon terminal are at the H level. And in between times t ₀ ~t _2, stable incident signal X obtained from the integrating circuit 9, it is assumed that the output of the incident signal Y rises at time t _1. Set terminal is H
During the level, the output of the OR circuit 25 is always at the H level, and the transistor 12a is turned on, so that the light emitting diode 14 for stable display is not turned on. On the other hand, the EOR circuit 26,
The switch 27 operates by the output of the EOR circuit 27. Therefore, at time t ₀
constant current source 16 of the constant current I _H between t ₁ is driven, EOR
The light emitting diode 15 for operation display is turned on by the output of the circuit 27 as shown in FIG. In this case, since the operation mode is set, the light emitting diode 15 operates as an operation indicator. Also, since the set terminal is at H level,
The inverted output of the EOR circuit 26 is applied to the output circuit 19 via the NAND circuit 28 as shown in FIGS. 5E and 5L, and the pair of terminals 18a and 18b are short-circuited.

[0014] Referring now switches the changeover switch 11 at time t ₂ to the setting mode as a set terminal, the output of FIG. 5 set terminal as shown in (c) is L level and turned to the frequency dividing circuit 22 as described above is The driving cycle of the selected light emitting element 3 is increased. At this time, the terminal on the set side of the EOR circuit 26 is always at the H level, and one terminal of the EOR circuit 27 is always at the L level.
Of the switch circuit 17
Given to. Therefore, the constant current source 16 is driven as shown in FIG. In the state shown in FIG. 5B, a signal higher than the light incident level is always obtained at the time of setting, and therefore, as shown in FIG.
Lights up. The input X for stable display is the OR circuit 25.
5 is provided to the transistor 12a through
As shown in (k), the light emitting diode 14 for stable display is turned on only when the integrated output X is at the H level.
Here, since the driving currents of the light emitting diodes 14 and 15 are supplied from the constant current source 16 of I _H , the optical axis can be accurately adjusted using the two indicator lamps without increasing the current consumption when adjusting the optical axis. can do.

When the changeover switch 11 is switched to the dark on (Don) state as the operation mode, the time t ₁
To return to the operation of the ~t _2. It is switched over switch 11 to the write-one (Lon) mode further time t ₄ after, EOR
The circuits 26 and 27 and the inverter 29 are inverted, and the operation as shown in FIG. 5 is performed.

In this embodiment, the operation display and the light-incident display are distinguished from each other. In the setting mode, a pair of terminals is not short-circuited, and a level at which a switch operation is performed when the mode is simply switched to the operation mode is displayed. And the signals are substantially the same level. Although the present embodiment uses two light emitting diodes for stable display and operation display / light-indicating display, three light-emitting diodes are used independently for light-indicating display and operation-indicating display. You may comprise. In this case, the outputs X and Y of the integrator 9 are directly led to the switches 12 and 13 in the setting mode to operate the constant current source 16 in the setting mode. In the operation mode, an independent display for operation display is driven. With this configuration, the configuration of the output mode setting circuit 10 can be extremely simplified. Further, as in this embodiment, it is also possible to use two light emitting diodes and to use a two-color LED.

[0017]

As described above in detail, according to the present invention, when the changeover switch is set to the setting mode, the oscillation cycle of the oscillation circuit is lengthened, and the driving current of the light emitting element obtained by this can be stably displayed and displayed. It is used for light display. Therefore, by turning on the display lamp based on the output of the light incident display and the stable display during the optical axis adjustment, the optical axis adjustment can be performed extremely easily. Also in this case, the same function as the conventional one can be obtained without increasing the leakage current.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of a DC two-wire photoelectric switch according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration of a light projecting unit of the DC two-wire electronic switch according to the embodiment.

FIG. 3 is a circuit diagram showing a configuration of an output mode setting circuit of the DC two-wire electronic switch according to the embodiment.

FIG. 4 is a time chart illustrating operations of the oscillation circuit and the light projecting unit according to the present embodiment.

FIG. 5 is a time chart illustrating the operation of the output mode switching circuit and the switch circuit of the present embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Oscillation circuit 2, 2a Light emitting circuit 3, 3a Light emitting element 4 Light receiving element 6, 7 Comparator 8 Signal processing circuit 9 Integrating circuit 10 Output mode setting circuit 11 Changeover switch 12, 13 Switch 12a, 13a, 30, 32 Switching transistor 14 Light Emitting Diode for Stability Display 15 Light Emitting Diode for Operation Display / Light Indication 16, 31 Constant Current Source 17 Switch Circuit 18a, 18b Terminal 19 Output Circuit 21 Oscillator 22 Divider Circuit 23 AND Circuit 24, 25 OR Circuit 26, 27 EOR Circuit 28 NAND circuit

Claims (1)

(57) [Scope of request for utility model registration] A light emitting unit including a pair of terminals connected in series to an external load and a DC power supply, an oscillation circuit for generating a clock signal, and driving a light emitting element by an output of the oscillation circuit; A light receiving unit that receives light from the light emitting unit; a signal processing unit that discriminates a light receiving level of the light receiving unit to obtain an output for a stable operation and a switch operation; and an output circuit that opens and closes the pair of terminals. In a DC two-wire photoelectric switch in which power is supplied to each unit and the pair of terminals is short-circuited based on the output of the signal processing unit, a setting mode for adjusting an optical axis and an operation at the time of normal detection Switch means for selecting any one of an operation mode for performing light emission, and one of clock signals in the operation mode of the light emitting section when the changeover switch means is switched to a setting mode.
A current source for generating a difference following the current average driving current for one period of the clock signal at the average driving current and setting mode circumferential period, for stable display which is connected to the current source between the pair of terminals
A display element and a light input display for a display device, anda display circuit for performing each stable display and incident indicated by the output of the signal processing unit, wherein the oscillation circuit is switched to the setting mode by the changeover switch means A DC two-wire photoelectric switch characterized in that it oscillates a clock signal having a long period when it is turned on and a short period when it is switched to an operation mode.