JPH06164357A - Two-wire type electronic switch - Google Patents

Abstract

PURPOSE:To increase a current, supplied to a pilot lamp when the two-wire type electronic switch is turned ON, stepwise corresponding to a load current. CONSTITUTION:This two-wire type electronic switch is provided with an output circuit 14A which short-circuits terminals 1 and 2 of the switch, and an A/D converter 24 and gate circuits 21-23 which detect its output current. The gate circuits 21-23 are placed in operation with the output of the A/D converter 24 and a stable operation display output. A specific driving current is supplied to a light emitting diode D2 for stable operation display with an output of each gate circuit to vary the display current stepwise.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a two-wire photoelectric switch,
The present invention relates to an electronic switch such as a proximity switch, and more particularly to a two-wire type electronic switch characterized by its operation display.

[0002]

2. Description of the Related Art A conventional two-wire type electronic switch, for example, a direct current two-wire type proximity switch, has a pair of terminals connected in series with a load and a power source. The switch operation is performed by opening and closing the output switching element. In such a DC 2-wire proximity switch, when the output switching element is open,
Small leakage current, for example 1mA, to prevent load current
It is necessary to operate the internal circuit with a certain amount of current.
Also, when the electronic switch is on, the load is, for example, 3 mA to 100
The load current in the mA range is applied.

[0003]

In the proximity switch, as shown in FIG. 8, 100 to 80% of the rated detection distance is an unstable detection area, so that red light emission is displayed, and 80 to 0% is a stable detection area. Therefore, the green indicator light is often turned on. There is also a two-wire type electronic switch in which red is turned on as an operation indicator at any of 0 to 100% and red and green indicators are simultaneously turned on at 80 to 0%. Thus, when the display element for stable operation display is used in addition to the operation indicator lamp, the green light emitting diode is often used for stable display. However, if the minimum value of the load current is 3 mA, the indicator lamp for the operation display and the stable operation indicator can only supply a current of about 2 mA. In particular, in the case of a green light emitting diode, if the current value is small, it is dark and sufficient display cannot be performed.

As described above, in the conventional two-wire type electronic switch, the sum of the current supplied to the indicator lamp, the output current, and the current of the sensor circuit is set within the range of the minimum load current of 3 mA. Therefore, there is a drawback that the display is always dark and difficult to confirm even when the load current greatly exceeds 3 mA.
Particularly, the two-wire type electronic switch is often used in combination with a programmable controller, and the load current is often 8 to 10 mA. However, there is a drawback that the display is always dark even at this load current level.

The present invention has been made in view of the above-mentioned conventional problems, and makes it possible to light the indicator lamp even when the load current is at a minimum value, and the current flowing through the indicator lamp depends on the magnitude of the load current. The technical issue is to be able to increase the value stepwise.

[0006]

According to the invention of claim 1 of the present application, a pair of terminals connected in series to an external load and a power source, a sensor circuit connected to the pair of terminals, and an output of the sensor circuit are used. A two-wire type electronic switch comprising an output circuit for opening and closing a pair of terminals and a display circuit for displaying an output state of a sensor circuit, the output circuit comprising a switching element and a switching element which operate according to an object detection signal. And a resistance for current detection connected in series to the display circuit, and the display circuit displays the terminal voltage of the resistance for current detection as A /
An A / D converter that outputs a parallel signal that is D-converted and sequentially turns on according to the terminal voltage level, a display element for operation display that operates according to an object detection signal, and a stable operation display signal at one input terminal, A plurality of gate circuits to which the parallel outputs of the A / D converters are respectively input to the other input terminal, a plurality of current mirror circuits that respectively operate according to the output of each gate circuit, and a current output of each current mirror circuit And a display element for stable operation display, the end of which is commonly connected to the one end.

According to the second aspect of the present invention, a pair of terminals connected in series to an external load and a power source, a sensor circuit connected to the pair of terminals, and a pair of terminals opened and closed by the output of the sensor circuit. A two-wire type electronic switch comprising an output circuit for displaying an output state of a sensor circuit, the output circuit being connected in series with a switching element operated by an object detection signal and the switching element. The display circuit includes a resistance for current detection, and the display circuit A / D converts the terminal voltage of the resistance for current detection and outputs a parallel signal that is sequentially turned on according to the terminal voltage level.
D converter, a plurality of gate circuits in which an object detection signal is input to one input terminal and parallel outputs of an A / D converter are input to the other input terminal, respectively, and each operates according to the output of each gate circuit And a plurality of current mirror circuits, and a current output terminal of each current mirror circuit is commonly connected to one end of the current mirror circuit, and a display element for operation display is provided.

According to the third aspect of the present invention, a pair of terminals connected in series to an external load and a power source, a sensor circuit connected to the pair of terminals, and a pair of terminals opened and closed by the output of the sensor circuit. A two-wire type electronic switch comprising an output circuit for displaying an output state of a sensor circuit, the output circuit being connected in series with a switching element operated by an object detection signal and the switching element. The display circuit includes a resistance for current detection, and the display circuit A / D converts the terminal voltage of the resistance for current detection and outputs a parallel signal that is sequentially turned on according to the terminal voltage level.
D converter, a plurality of gate circuits to which the operation display signal is input to one input terminal and the parallel output of the A / D converter is input to the other input terminal, respectively, and operate in accordance with the output of each gate circuit And a plurality of operation display elements that operate.

According to the invention of claim 4 of the present application, a pair of terminals connected in series to an external load and a power supply, a sensor circuit connected to the pair of terminals, and a pair of terminals opened and closed by the output of the sensor circuit. A two-wire type electronic switch comprising an output circuit for displaying an output state of a sensor circuit, the output circuit being connected in series with a switching element operated by an object detection signal and the switching element. The display circuit includes a resistance for current detection, and the display circuit A / D converts the terminal voltage of the resistance for current detection and outputs a parallel signal that is sequentially turned on according to the terminal voltage level.
It is characterized by having a D converter and a numerical display circuit for decoding and displaying the output of the A / D converter.

[0010]

The operation according to claim 1 or 2 of the present application having such characteristics
According to the invention, the driving current of the output circuit is detected by the A / D converter, and the stable operation display element is detected based on the output.
Alternatively, the current flowing through the operation display element is changed stepwise. Therefore, as the drive current increases, the current flowing through these display elements also increases, so that the operating state can be clearly recognized.

Further, according to the invention of claim 3, the plurality of display elements are used to sequentially turn on the display elements in accordance with the load current. In the invention of claim 4, the A / D conversion is decoded to obtain a numerical value. Since it is displayed, the magnitude of the load current can be recognized.

[0012]

1 is a block diagram showing the overall construction of a DC two-wire photoelectric switch according to one embodiment of the present invention. In this figure, a load 3 and a DC power source 4 are connected in series to terminals 1 and 2 of the photoelectric switch. A constant voltage circuit 5 is connected to the terminal 1 and a voltage is supplied to each part of the photoelectric switch. An oscillating circuit 6 for generating a light emitting pulse at a constant cycle is provided in the photoelectric switch. The output of the oscillation circuit 6 is the light projecting circuit 7.
The light projecting element 8 is periodically driven via the. If this photoelectric switch is, for example, a diffuse reflection photoelectric switch, the light emitted from the light projecting element 8 is received by the light receiving element 9 via the object when the object approaches. A light receiving circuit 10 is connected to the light receiving element 9, and the light receiving signal is sent to the comparison circuit 11
Given to. The comparison circuit 11 discriminates the signals with a predetermined threshold value, and the output thereof is given to the signal processing circuit 12. The signal processing circuit 12 is configured to include a gate circuit, an integrating circuit, etc., and the light emitting pulse is given as a gate signal from the oscillation circuit 6 to output the object detection signal IN1 and the stable operation display signal IN2. Now signal processing circuit 1
The object detection output of No. 2 is given to the display circuit 13. The display circuit 13 conducts the output circuit 14 based on the object detection signal, and controls the display current of the display element in accordance with the current flowing through the output circuit.

Next, a detailed configuration example of the display circuit 13 and the output circuit 14 will be described with reference to FIG. FIG. 2 is a circuit diagram showing a display circuit having a red light emitting diode for operation display and a light emitting diode for stable operation display in the display circuit. In the figure, a switching transistor Q1 which is an output switching element and a current detection resistor R1 are connected in series between terminals 1 and 2 to form an output circuit 14A. In the display circuit 13A, the resistor R2, the red light emitting diode D1 for operation display, and the transistor Q2 are connected in series, and the common connection end of the resistor R2 and the light emitting diode D1 is connected to the base of the transistor Q1. The transistor Q2 has an object detection signal I for operation display.
N1 is input. Furthermore, the transistor Q3 is connected to the terminal 1.
A first current mirror circuit composed of Q4, a second current mirror circuit composed of Q5 and Q6, and a transistor Q
A third current mirror circuit consisting of Q7 and Q7 is connected. Transistors Q3, Q5 of each current mirror circuit
Control transistors Q9, Q10 and Q11 of the current mirror circuit are connected between Q7 and the terminal 2, respectively.
Gate circuits 21, 22, 23 are connected to the bases of the transistors Q9, Q10, Q11, respectively.

The resistor R1 of the output circuit 14A is a current detecting resistor for detecting the current flowing through the load 3.
The terminal voltage at the common connection end with the collector of the transistor Q1 is given to the A / D converter 24. The A / D converter 24 performs A / D conversion each time a light projecting pulse is applied, and outputs three parallel switching signals in accordance with the terminal voltage of the resistor R1. The outputs corresponding to the voltage levels of the A / D converter 24 are the gate circuits 21, 22, 2 described above, respectively.
3 to one of the input terminals. Further, the common input end of each gate circuit 21, 22, 23 is a stable operation display signal I
N2 is supplied.

The input signal IN2 is also given to the base of the transistor Q12. Transistor Q12
Is grounded and the collector is connected to the green second light emitting diode D2. The anode end of the light emitting diode D2 is connected to the current output terminals of the transistors Q4, Q6, Q8 of the first to third current mirror circuits.

Next, the operation of this embodiment will be described. First, when the load 3 and the power supply 4 are connected between the terminals 1 and 2, the constant voltage circuit 5 supplies the power to each part, and the oscillation circuit 6 periodically generates a light projection pulse. The light projecting element 8 is intermittently driven via the light projecting circuit 7. If the object is not approaching, the signal processing circuit 12 outputs the object detection signal IN1.
Is not output, the outputs of the transistor Q2 and the gate circuits 21 to 23 are all at the L level, and the light emitting diodes D1 and D2 do not light.

When an object reaches the detection area, the light from the light projecting element 8 is received by the light receiving element 9 and the light receiving circuit 1 is received.
It is given to the comparison circuit 11 via 0 as a voltage signal.
When a signal exceeding the threshold value is continuously detected, the signal processing circuit 12 outputs the object detection signal IN1 and the stable operation signal IN2 is given to the transistor Q12 and the gate circuits 21 to 23 depending on the level thereof. When the object detection signal IN1 is input to the transistor Q2, a collector current flows to the transistor Q2 via the resistor R2, and the red light emitting diode D1 lights up. At the same time, the transistor Q1 is energized and a current flows through the load 3. Here, the load current is detected as the voltage across the resistor R1, and one or more outputs are obtained from the A / D converter 24 according to the load current I _L.

When the object approaches the stable operation position, the signal processing circuit 12 outputs the stable operation display signal IN.
2 is added to each gate circuit 21-23. Therefore A
Transistors Q9 to Q depending on the output of the / D converter 24
Then, Q and Q11 are sequentially urged as shown in FIG. Therefore, when only the transistor Q9 is energized, the current I _G1 determined by the first current mirror circuit is applied to the second light emitting diode D2. Next, when the load current I _L increases and both the transistors Q9 and Q10 are turned on, the current I _G1 + I _G2 determined by the first and second current mirror circuits is added to the light emitting diode D2. When the load current further increases, the transistor Q11 also turns on, and the currents I _G1 + I _G2 + I _G3 determined by the first to third current mirror circuits are added to the light emitting diode D2. Therefore, the current flowing through the light emitting diode D2 increases stepwise in accordance with the load current. In this way, by changing the indicator light current I _G flowing through the light emitting diode D2 for stable operation display according to the load current I _L flowing through the load 3, the indicator light can be displayed sufficiently bright if the load current is large. .

FIG. 4 is a circuit diagram showing the structure of the display circuit according to the second embodiment of the present invention. In this figure, the same parts as those in the first embodiment are designated by the same reference numerals and detailed description thereof will be omitted. In the embodiment shown in FIG. 4, only the red light emitting diode is used to control the indicator lamp current according to the load current. In the figure, in the output circuit 14B between the terminals 1 and 2, the switching transistor Q1 and the resistor R1 are connected in series, and the terminal voltage is connected to the A / D converter 24, as in the first embodiment. Is. Transistor Q1
An output circuit is formed by connecting the base and collector of the transistor Q13 and the resistor R2 to the base of the transistor Q13.
In this case, the emitter area ratio of the transistors Q1 and Q13 is set to 100: 1. The display circuit 13B has a red light emitting diode D1 at the other end of the resistor R2.
Are connected. This embodiment also has first to third current mirror circuits, and the connection thereof is similar to that of the first embodiment, but the current output terminal of each current mirror circuit is the anode terminal of the red light emitting diode D1. It is connected to the transistor Q12 via. Other configurations are similar to those of the first embodiment.

Next, the operation of this embodiment will be described. When an object is detected, the transistor Q12 is turned on by the object detection signal IN1, and the transistor Q1 is also turned on via the transistor Q13. Therefore, a load current flows through the load 3, and the voltage across the resistor R1 changes according to the load current I _L. Then, either of the outputs is similarly obtained by the A / D converter 24, and the logical product of this and the input signal causes only the transistor Q9, the transistors Q9 and Q10, or the transistors Q9 to Q11 via the gate circuits 21 to 23.
All become conductive. As a result, the current flowing from each current mirror circuit is sequentially changed, whereby the drive current of the red light emitting diode D1 is changed stepwise corresponding to the load current. Although only one red light emitting diode is used in this embodiment, two red light emitting diodes and green light emitting diodes may be similarly used to drive the display current in multiple stages.

Next, a third embodiment of the present invention will be described. FIG. 5 shows a structure in which a plurality of light emitting diodes are used for lighting in accordance with a load current. In this embodiment, the same parts as the first and second parts are designated by the same reference numerals, and detailed description thereof will be omitted. In the display circuit 13C of this embodiment, the light emitting diodes D2, D3, D4 are connected between the correct ground terminals of the transistors Q4, Q6, Q8 of the plurality of current mirror circuits, respectively. Other configurations are the same as those in the second embodiment. In this embodiment, A /
Switching outputs are sequentially given to the gate circuits 21, 22, and 23 by the D converter 24. Then, the light emitting diodes D2 to D4 are sequentially turned on according to the load current. Therefore, as shown in FIG. 6A, a plurality of display elements D1 to D4 are continuously attached to the front surface of the photoelectric switch. Further, a variable resistor or the like for setting the sensitivity is attached.

Further, in the present embodiment, the plurality of light emitting diodes D2 to D4 are respectively turned on according to the output of the A / D converter, but a decoding circuit for decoding the output of the A / D converter 24, As shown in FIG. 6B, a numerical value display circuit having a numerical value display 25 such as a liquid crystal display may be used to display a numerical value corresponding to the load current. In this case, the guideline of the load current can be known.

FIG. 7 shows the A / A used in each of the above-mentioned embodiments.
It is a figure which shows an example of the D converter 24. As shown in this figure, the current detection resistor R1 is divided by a plurality of resistors to divide it into R1.
a to R1c, the base of the transistor Q14 is connected to the common connection end of R1a and R1b, and the base of the transistor Q15 is connected to the common connection end of R1b and R1c. The base of the transistor Q16 is connected to the common connection end of R1c and the collector of the transistor Q1. Transistors Q14-1
6, the emitter is grounded, and the collector is connected to the terminal 1 via a resistor. Further, the outputs are connected as parallel digital outputs to the above-mentioned gate circuits 21 to 23, respectively. This makes it possible to configure the A / D converter 24 with a relatively simple configuration.

Although the present embodiment describes the diffuse reflection type photoelectric switch, it goes without saying that the present invention can be applied to various kinds of electronic switches such as other types of photoelectric switches and proximity switches.

[0025]

As described in detail above, according to the invention of claim 1 or 2 of the present application, when used as a two-wire type electronic switch, the display current is changed stepwise as the load current increases. Can be made. Therefore, since the display current of the display circuit can be increased when the load current is increased, the display can be made clear. According to the third aspect of the invention, when the load current becomes large, the plurality of light emitting diodes are turned on so that the magnitude of the load current can be confirmed at a glance. Further, in the invention of claim 4,
By displaying the magnitude of the load current on the numerical display circuit, the load current can be accurately recognized.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram showing configurations of an output circuit and a display circuit according to a second embodiment of the present invention.

FIG. 3 is a graph showing changes in the output of the A / D converter and the indicator lamp current with respect to the load current according to the present embodiment.

FIG. 4 is a circuit diagram showing a configuration of a display circuit and an output circuit according to a second embodiment of the present invention.

FIG. 5 is a circuit diagram showing configurations of a display circuit and an output circuit according to a third embodiment of the present invention.

FIG. 6 is a front view showing a configuration example of a display unit of a third embodiment.

FIG. 7 is an A / D used in the first to third embodiments of the present invention.
It is a circuit diagram which shows an example of a structure of a converter.

FIG. 8 is a diagram showing a relationship between an electronic switch and an object and a change in output of the indicator lamp.

[Explanation of symbols]

 1, 2 terminals 3 power supply 4 load 12 signal processing circuit 13, 13A, B, 13C display circuit 14, 14A, 14B output circuit 21-23 gate circuit 24 A / D converter

Claims (4)

[Claims] 1. A pair of terminals connected in series to an external load and a power source, a sensor circuit connected to the pair of terminals, and an output circuit that opens and closes between the pair of terminals by the output of the sensor circuit. A two-wire electronic switch comprising a display circuit for displaying the output state of the sensor circuit, wherein the output circuit is a switching element operated by an object detection signal and a current detection circuit connected in series to the switching element. The display circuit A / D converts the terminal voltage of the current detection resistor and outputs a parallel signal that is sequentially turned on according to the terminal voltage level.
A D converter, a display element for operation display that operates according to the object detection signal, and a stable operation display signal are input to one input terminal and the parallel output of the A / D converter to the other input terminal, respectively. A plurality of gate circuits, a plurality of current mirror circuits that respectively operate according to the outputs of the respective gate circuits, and a display element for stable operation display in which the current output terminals of the respective current mirror circuits are commonly connected to one end thereof And a two-wire electronic switch. 2. A pair of terminals connected in series to an external load and a power supply, a sensor circuit connected to the pair of terminals, and an output circuit that opens and closes between the pair of terminals by the output of the sensor circuit. A two-wire electronic switch comprising a display circuit for displaying the output state of the sensor circuit, wherein the output circuit is a switching element operated by an object detection signal and a current detection circuit connected in series to the switching element. The display circuit A / D converts the terminal voltage of the current detection resistor and outputs a parallel signal that is sequentially turned on according to the terminal voltage level.
A D converter, a plurality of gate circuits to which an object detection signal is input to one input terminal and a parallel output of the A / D converter is input to the other input terminal, respectively. A two-wire electronic switch having a plurality of current mirror circuits that operate respectively, and a display element for operation display in which a current output terminal of each current mirror circuit is commonly connected to one end thereof. . 3. A pair of terminals connected in series to an external load and a power source, a sensor circuit connected to the pair of terminals, and an output circuit for opening and closing the pair of terminals by the output of the sensor circuit. A two-wire electronic switch comprising a display circuit for displaying the output state of the sensor circuit, wherein the output circuit is a switching element operated by an object detection signal and a current detection circuit connected in series to the switching element. The display circuit A / D converts the terminal voltage of the current detection resistor and outputs a parallel signal that is sequentially turned on according to the terminal voltage level.
A D converter, a plurality of gate circuits to which an operation display signal is input to one input terminal, and a parallel output of the A / D converter is input to the other input terminal, respectively. A two-wire electronic switch, comprising: a plurality of operation display elements each operating. 4. A pair of terminals connected in series to an external load and a power source, a sensor circuit connected to the pair of terminals, and an output circuit that opens and closes between the pair of terminals by the output of the sensor circuit. A two-wire electronic switch comprising a display circuit for displaying the output state of the sensor circuit, wherein the output circuit is a switching element operated by an object detection signal and a current detection circuit connected in series to the switching element. The display circuit A / D converts the terminal voltage of the current detection resistor and outputs a parallel signal that is sequentially turned on according to the terminal voltage level.
A two-wire electronic switch having a D converter and a numerical display circuit for decoding and displaying an output of the A / D converter.