JP2014086518A - Digital signal input circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate digital input by making the output of both an NPN-type transistor and a PNP-type transistor connectable for a photocoupler.SOLUTION: A digital signal input circuit includes a photocoupler (2) having a pair of light-emitting elements (D, D) connected in inverse-parallel, a power supply voltage (Vcc) and a ground (GND) connected with one end side (3) of a light-emitting element body (20) via first and second resistors (6, 21) of parallel arrangement, and only one input terminal (7) connected with the other end side (5) of the light-emitting element body (20). Any of an NPN-type output transistor (TR) and a PNP-type transistor (TR) can be connected for the input terminal (7).

Description

  The present invention relates to a digital signal input circuit, and in particular, outputs from either an NPN-type or PNP-type output transistor via only one common input terminal connected to one terminal of a light-emitting element body of a photocoupler. The present invention relates to a new improvement for allowing a signal to be input.

As a digital signal input circuit of this type that has been conventionally used, for example, in the programmable controller disclosed in Patent Document 1, a configuration using a pair of antiparallel light emitting elements is provided, although not shown. ing.
Moreover, although the patent document etc. are not disclosed, the structure shown by FIGS. 4-6 can be mentioned as a digital signal input circuit generally used widely.

FIG. 4 is a circuit diagram showing a conventional digital signal input circuit, in which a light receiving element 1 made of a photodiode is provided corresponding to a light emitting element D _{1 made} of LED, and the light emitting element D ₁ and the light receiving element 1 A coupler 2 is configured.

A first input terminal 4 is connected to one end side 3 of the light emitting element D _{1, and} a second input terminal 7 is connected to the other end side 5 via a first resistor 6.
When the digital signal input circuit 10 shown in FIG. 4 is used, for example, as shown in FIG. 5, a power supply voltage Vcc is connected to the first input terminal 4, and a limit switch or the like is connected to the second input terminal 7. The collector C of the output side NPN type output transistor TR ₁ is connected and the emitter E is connected to the ground GND. As shown in FIG. 6, the first input terminal 4 is connected to a PNP such as a limit switch. type output collector C of the transistor TR ₂ is connected to the second input terminal 7 is connected to the power supply voltage Vcc.

JP 7-36368 A

  In the case of the configuration of the conventional Patent Document 1, a switching element and a programmable controller are required for switching the polarity of the power supply on the input side, and it has been difficult to avoid an increase in size and cost of the device.

Further, in the case of the conventional configuration shown in FIGS. 4 to 6 described above, in the configuration of FIG. 5, the output of the NPN output transistor TR ₁ is at the GND level when the signal is on, and the photocoupler 2 is turned on. When the signal is off, the signal is in an open state and no current flows through the photocoupler 2 and it is turned off.

In the configuration of FIG. 6, when the signal is on, the output of the PNP output transistor TR ₂ is the power supply voltage Vcc, for example, 24 V, and the photocoupler 2 is turned on.
Therefore, as described above, the common digital signal input circuit 10 can be used both when the NPN output transistor TR ₁ of FIG. 5 is used and when the PNP output transistor is used as shown in FIG. In order to achieve this, a pair of input terminals is necessarily required on the input side of the digital signal input circuit 10, and the connection configuration must be changed depending on the junction type of the output transistor.

  The present invention has been made to eliminate the above-described problems. In particular, a bidirectional receiving photocoupler is used, and a power supply voltage and a ground are connected to one end side of the light emitting element body through a resistor. One input terminal is connected only to the end side, and an NPN type and PNP type output transistor can be connected to this input terminal.

  A digital signal input circuit according to the present invention is a photo of a light emitting element body composed of a pair of light emitting elements connected in reverse parallel with different polarities, and a light receiving element for receiving light from the light emitting element body. A coupler, a power supply voltage and a ground commonly connected via first and second resistors connected in parallel to one end side of each light emitting element body, and one piece connected to the other end side of each light emitting element body The NPN type output transistor or each output from the PNP type output transistor can be connected to the input terminal, and the NPN type and PNP type can be connected to the input terminal. The output transistor is provided on the output side of the limit switch.

Since the digital signal input circuit according to the present invention is configured as described above, the following effects can be obtained.
That is, a photocoupler comprising a light emitting element body composed of a pair of light emitting elements connected in reverse parallel with different polarities, a light receiving element for receiving light from the light emitting element body, and each of the light emitting elements Power supply voltage and ground commonly connected via first and second resistors connected in parallel to one end side of the body, and only one connected to the other end side of each light emitting element body via a third resistor Any of the junction type outputs can be connected to each of the output signals from the NPN type output transistor or the PNP type output transistor. Even in the case of a transistor, the photocoupler is turned on when the signal is on, and the photocoupler is turned off when the signal is off, so that only one input terminal is required. Nectar becomes inexpensive and can be miniaturized.
Further, since the NPN-type and PNP-type output transistors are provided on the output side of the limit switch, output signal processing of the limit switch or the like is facilitated.

1 is a circuit diagram showing a digital signal input circuit according to the present invention. It is a block diagram which shows the case where an NPN-type output transistor is connected to only one input terminal of FIG. It is a block diagram which shows the case where a PNP type output transistor is connected to only one input terminal of FIG. It is a circuit diagram which shows the conventional digital signal input circuit. It is a circuit diagram which shows the other prior art example of FIG. It is a circuit diagram which shows the other prior art example of FIG.

  The present invention is a digital signal which can input an output signal from either an NPN or PNP type output transistor through only one common input terminal connected to one terminal of a light emitting element body of a photocoupler. An object is to provide an input circuit.

DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a digital signal input circuit according to the present invention will be described with reference to the drawings.
Note that the same or equivalent parts as in the conventional example will be described using the same reference numerals.
In Figure 1, the light receiving element 1 consisting of photodiode provided corresponding to the light-emitting element D ₁ consisting of LED, other light emitting element D ₂ is provided in parallel to the light emitting element D _1, wherein the light-emitting elements D emitting element 20 is constituted by _{1, D 2.}

The light emitting elements D ₁ and D ₂ of the light emitting element body 20 are connected in reverse parallel with different polarities, and the one end side 3 and the other end side 5 forming both ends of the light emitting element body 20 are A pair of first resistor 6 and second resistor 21 are connected to one end side 3 so as to be connected in parallel with each other, and a power supply voltage Vcc is connected to an input end 6a of the first resistor 6. The input terminal 21a of the second resistor 21 is connected to the ground GND.
Only one input terminal 7 is provided on the other end side 5 of the light emitting element body 20.

In the configuration of FIG. 2, the collector C of an NPN output transistor TR ₁ provided on the output side of a limit switch or the like is connected to the input terminal 7 of the digital signal input circuit 10 of FIG. the emitter E of the transistor TR ₁ is connected to the ground GND.

In the configuration of FIG. 3, a collector C of a PNP output transistor TR ₂ provided on the output side of a limit switch or the like is connected to the input terminal 7 of the digital signal input circuit 10 of FIG. the emitter E of the transistor TR ₂ is connected to the power supply voltage Vcc.

In the configuration described above, in the configuration of FIG. 2, since the photocoupler 2 is a bidirectional reception type, an NPN output transistor TR ₁ is connected to the input terminal 7, so that a limit switch, etc. when the signal is on, the first resistor 6, the photocoupler 2, the photocoupler 2 because current flows in a path to ground GND via the input terminal 7 and an NPN output transistor TR ₁ is turned on from the power supply voltage Vcc .
When the signal from the limit switch or the like is off, the signal is in an open state, so that no current flows through the photocoupler 2 and it is off.

Further, when the PNP output transistor TR ₂ is used as shown in FIG. 3, when a signal such as a limit switch is ON, the path of the input terminal 7, the photocoupler 2, the one end side 3, the second resistor 21 and the ground GND is used. A current flows and the photocoupler 2 is turned on.
When the signal from the limit switch or the like is off, the signal is in an open state, so that no current flows through the photocoupler 2 and it is off.
Therefore, in both cases of FIGS. 2 and 3, the photocoupler 2 is turned on when the output signal of the limit switch or the like is on, and the photocoupler 2 is turned off when the signal is off.

  The digital signal input circuit according to the present invention can input an output signal from either an NPN-type or PNP-type output transistor to only one common input terminal connected to one terminal of a light-emitting element body of a photocoupler. is there.

1 light receiving element 2 photo-coupler 3 one end 5 the other end 6 first resistor 7 input terminal 20 light-emitting element body 21 the second resistor 21a inputs _D 1, _{D 2} emitting element Vcc power supply voltage GND Ground _TR 1 NPN-type output transistor TR ₂ PNP output transistor

Claims (2)

A light emitting element body (20) composed of a pair of light emitting elements (D ₁ , D ₂ ) connected in reverse parallel with different polarities, and a light receiving element for receiving light from the light emitting element body (20) ( 1) and a photocoupler (2) comprising a first resistor and a second resistor (6, 21) connected in parallel to one end side (3) of each light emitting element body (20). Power supply voltage (Vcc) and ground (GND), consisting of only one common input terminal (7) connected to the other end side (5) of each light emitting element body (20),
Digital signal input circuit characterized in that any of the outputs from the NPN output transistor (TR ₁ ) or the PNP output transistor (TR ₂ ) can be connected to the input terminal (7). . The digital signal input circuit according to claim ₁ , wherein the NPN type and PNP type output transistors (TR ₁ , TR ₂ ) are provided on an output side of a limit switch.

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