JPH0418256Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of the Invention] The present invention relates to a detection switch such as a photoelectric switch or a proximity switch, and particularly to a detection switch whose output mode can be easily switched.

[Summary of the idea]

The detection switch according to the present invention connects a series resistor circuit to two selectively connected power supply terminals, supplies power to the power supply terminal of the detection circuit through the resistor, and detects the connection direction using a comparator. are doing. The outputs of the comparator and detection circuit are then fed to an exclusive OR circuit, and the output circuit is operated by the output of the exclusive OR circuit, thereby switching the output type of the detection switch between normally closed type and normally open type. It is.

[Prior art and its problems]

As a detection switch that switches the output mode by switching the DC power supply, for example,
12430 etc. are known. As shown in FIG. 3, this detection switch has a diode D1 connected between power input terminals 2 and 3 to which the positive end of the DC power supply 1 is connected, and a resistor R1 between the input terminal and the negative power input terminal 4. is connected. A load 6 is connected to the other input terminal 5. A power source is connected to the detection circuit 7 and the output circuit 8 from one power input terminal 2. The detection circuit 7 has a light emitting diode 9 and a phototransistor 10, and detects an object based on the presence or absence of reflected light, and its output terminal and the other power input terminal 3 are connected to an exclusive NOR circuit 11.
given to. Exclusive Noah circuit 11
The output of is given to the output circuit 8, and the load 6 is driven via the output circuit 8.

In this way, the positive end of the DC power supply can be connected to the power input terminal 2.
When connected to , one input terminal of the exclusive NOR circuit 11 is pulled down by the resistor R1 and becomes the "L" level, so the output of the detection circuit 7 is inverted and applied to the output circuit 8, Since the load 6 is opened and closed, it can be used as a normally closed type detection switch. Furthermore, when a DC power source is connected to the power supply input terminal 3, an "H" level input is transmitted to the exclusive NOR circuit 11 via the diode D1, so that the output of the detection circuit 7 is directly applied to the output circuit 8. It can be a normally closed type detection switch.

However, according to such a conventional detection switch, the diode D1 is inserted into the power supply line by switching the output mode, and the voltage applied to the detection circuit 7 or the output circuit 8 drops by the forward voltage drop of the diode. do. Therefore, there was a problem in that the power supply voltage had to be increased by the amount of the power supply drop in order to compensate for the voltage drop.

[Purpose of invention]

The present invention was devised in view of the problems of conventional detection switches, and the purpose of the present invention is to provide a detection switch that can easily switch output modes without connecting a diode to the power supply terminal. shall be.

[Structure and effect of the idea]

The present invention includes a detection circuit, a pair of resistors connected in series to first and second power input terminals to which one of the power supply terminals is selectively connected, and a power supply applied from the midpoint of the pair of resistors. a comparator whose input terminals are connected to the first and second power supply input terminals, respectively, and an exclusive OR circuit which is supplied with the comparison output of the comparator and the detection output of the detection circuit and drives the output circuit. and, characterized in that, by connecting the power supply terminal to either the first or second power supply input terminal, the input given to the exclusive OR circuit can be varied and the output mode can be switched. It is.

According to the present invention having such characteristics, the comparator is operated and the output mode is switched by switching the connection of the power input terminal. Therefore, the power supply voltage can be supplied to the detection circuit with almost no drop, and it can be stably used even when the power supply voltage is low. Furthermore, since the voltage drop does not change even when the output mode is switched, a constant voltage can always be supplied to the detection circuit.

[Explanation of Examples]

FIG. 1 is a circuit diagram showing an embodiment of a detection switch according to the present invention. In this figure, the same parts as in the conventional example described above are given the same reference numerals. In this embodiment, terminals 21 and 22 are used as positive power input terminals, and both ends thereof are connected to a series connection of resistors R2 and R3. Here, it is assumed that resistors R2 and R3 have the same resistance value. The midpoint thereof is connected to the power input terminal of the detection circuit 7. The power input terminals 21 and 22 are connected to an inverting input terminal and a non-inverting input terminal of a comparator 23 via resistors R4 and R5, respectively. A comparator 23 discriminates these input voltages and sends its output to an exclusive OR circuit 24.
It is given to The other input of the exclusive OR circuit 24 is connected to the output terminal of the detection circuit 7 as in the prior art described above, and its exclusive OR output is applied to the output circuit 8. The output terminal of the output circuit 8 is connected to the load 6 via the terminal 25, and the negative end of the power supply is connected to the terminal 26.

Next, the operation of this embodiment will be explained with reference to the waveform diagram in FIG. Now the positive end of the power supply is terminal 21
, the power supply voltage is supplied to the detection circuit 7 and the output circuit 8 through the resistor R2, and the power supply voltage is applied to the comparator 23 through the resistor R5. Also, since the other inverting input terminal of the comparator 23 is supplied with power through the resistors R2, R3, and R4, the "H" level output from the comparator 23 is sent to the exclusive OR circuit as shown in FIG. 2c. 24. Now, suppose that the object 27 approaches and the light emitted from the light emitting diode 9 is reflected and transmitted to the phototransistor 10 as shown in FIG. The output is provided to an exclusive OR circuit 24 as shown in FIG. b. Therefore, the exclusive OR circuit 24 generates an output that goes to the "L" level as the object approaches, as shown in FIG. 2d, and the drive of the load 6 is stopped via the output circuit 8. Therefore, the positive end of DC power supply 1 is connected to power supply input terminal 2.
1, it can be used as a normally closed type output detection switch that drives the load 6 when an object is not close to it and stops driving when the object moves away, as shown in FIG. 2e.

Next, when the positive end of the DC power supply 1 is connected to the power supply input terminal 22, the power supply voltage is supplied to the detection circuit 7 via the resistor R3, and the input voltage is supplied to the inverting input terminal of the comparator 23 via the resistor R4. is given. Also, the non-inverting input terminal of the comparator 23 has a resistor R3 and a resistor R2.
Since the power supply voltage is applied through the resistor R5 and the voltage applied to the inverting input terminal becomes high, the comparator input 23 outputs the "L" level to the exclusive OR circuit as shown in FIG. Give to 24. Here, if the object 27 approaches, a corresponding output is given from the detection circuit 7 to the exclusive OR circuit 24 as shown in FIGS. 2a and 2b, as in the case described above. As shown in FIG. 2g, it becomes "H" level only when an object approaches, and its output is given to the output circuit 8 to drive the load 6. Therefore, by connecting the positive end of the DC power source 1 to the input terminal 22, it is possible to create a normally open type detection switch in which the load 6 is driven only when an object approaches, as shown in FIG. 2h.

As described above, according to the present invention, power is supplied to the detection circuit via the resistor no matter which terminal the power input terminal is connected to, so that the same voltage can always be applied.

Although this embodiment uses an exclusive OR circuit to take the exclusive OR of the output of the comparator and the output of the detection circuit, an exclusive OR circuit may also be used as in the conventional example described above. In this case, the output mode that is switched depending on the power supply connection can be reversed.

Although this embodiment describes a reflective photoelectric switch that detects an object using reflected light from a light emitting diode, the present invention is applicable to various types of detection such as other types of photoelectric switches, proximity switches, and ultrasonic switches. Needless to say, it can be applied to a switch.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of a detection switch according to the present invention, Fig. 2 is a time chart of various parts showing the operation of this embodiment, and Fig. 3 is a circuit diagram showing an example of a conventional detection switch. . 1...DC power supply, 2, 3, 4, 21, 22, 2
6...Power input terminal, 6...Load, 7...Detection circuit, 8...Output circuit, 23...Comparator, 24...
Exclusive OR circuit.

Claims (1)

[Claims for Utility Model Registration] (1) A first circuit to which the detection circuit and one of the power supply terminals are selectively connected;
a pair of resistors connected in series to the second power input terminal; a detection circuit to which power is supplied from the midpoint of the pair of resistors; and input terminals connected to the first and second power input terminals, respectively. a connected comparator; and an exclusive OR circuit that is supplied with a comparison output of the comparator and a detection output of the detection circuit and drives an output circuit, and the power supply terminal is connected to either the first or second one. 1. A detection switch characterized in that the detection switch is configured to vary the input given to the exclusive OR circuit and switch the output mode by being connected to the power supply input terminal. (2) The detection switch according to claim 1, wherein the pair of resistors connected to the power input terminal have the same resistance value.