JPH0248819A - Input device for control instrument - Google Patents

Abstract

PURPOSE:To reduce the manufacturing cost by making the device correspondent to an input signal from a low level to a high level. CONSTITUTION:When an external input contact 3 is closed and an input signal E at a low level is supplied, a transistor(TR) 11 is turned on, a resistance control switch 13 is closed by a potential difference across a resistor 12, a current limiting resistor 4B is short-circuited, a proper current flows to an input side LED 6A and an internal arithmetic processing section signal is outputted from an output side photo TR 6B. Moreover, when a signal E at a high level is supplied, the TR 11 is not turned on, no potential difference is generated across the resistor 12, the switch 13 is turned off and the resistor 4B is not short- circuited. Thus, the current from the LED 6A is adjusted by the resistors 4A, 4B and the processing section signal is outputted from the TR 6B.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to an input device, and particularly to an input device for a control device.

(Summary of the Invention) The present invention provides a signal input device for control equipment such as a programmable controller, by making the input device compatible with input signals ranging from low-level voltage to high-level voltage. This is intended to reduce the manufacturing cost by having only one type of input device, and by reducing the number of input devices to one type as described above, the number of input devices in stock is reduced and the cost of inventory management is reduced.

(Prior art and its problems) Programmable controller (hereinafter referred to as rPCJ)
Since the voltage level of the input signal input from the sensor, limit switch, etc. and the voltage level of the internal arithmetic processing unit are different for control equipment such as This converts the input signal into a voltage level for the internal arithmetic processing section. In FIG. 3, 2 is an external signal power supply, E is its voltage, and 3 is an external input contact.

After the input signal is input to the input terminals LA and IB, it is input to the input side light emitting diode 6A of the isolation photocoupler 6 via the current limiting resistor 4, and from the output side phototransistor 6B to the internal arithmetic processing section. Output to. The resistor 5 is used together with the resistor 4 to adjust the voltage applied to the input side light emitting diode 6A of the photocoupler 6 to an appropriate value. If the voltage is lower than that, the input device is turned off. Here, the input side light emitting diode 6
Since A normally has a current value suitable for its operation, the current limiting resistor 4 is selected to have an appropriate resistance value.

However, the input signal voltage E is 5V, 12V, 24V,
Since there are various types of input signals such as V, conventional control equipment is prepared in advance with multiple types of input devices in which the values of the current limiting resistor 4 and the resistor 5 are changed in accordance with the respective input signals. Among these, the one that matches the input signal is set. In other words, as mentioned above, it was necessary to prepare multiple input devices according to the voltage level of the input signal, which increased the manufacturing cost of the input devices and the need to store them until they were installed in the control equipment. Since the number of input devices to be stored increases, there is a problem in that the cost of inventory management increases.

(Object of the Invention) The present invention has been made to solve the above problems, and by configuring the input signal level conversion function of the input device to be able to handle multiple types of input signals with different voltages, The purpose is to reduce manufacturing costs by unifying input devices into one type, and to reduce inventory management costs by reducing the number of inventories to be kept.

(Structure and Effects of the Invention) In order to achieve the above object, the present invention includes a photocoupler that transmits an input signal to an internal arithmetic processing unit, and a current limiting resistor connected in series to the input side light emitting diode of this photocoupler. an input signal voltage level determination circuit for determining the voltage level of the input signal; and an input signal voltage level determination circuit that is turned ON at the output of the input signal voltage level determination circuit.

The present invention is characterized by comprising a resistance control switch that is turned off to control the current limiting resistor.

Since the input device of the present invention is configured as described above, when a low voltage level input signal is input, the resistance control switch is turned ON or OFF to reduce the resistance value of the current limiting resistor. , on the other hand, when a high voltage level input signal is input, the resistance control switch is OFF,
Alternatively, it turns on and increases the resistance value of the current-limiting resistor, so that a suitable, almost constant current always flows to the light emitting diode on the input side of the photocoupler, so the manufacturing cost can be reduced by unifying input devices to one type. It also has the effect of reducing the number of inventories to be kept and reducing inventory management costs.

(Explanation of Examples) Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 1 is an electrical circuit diagram showing a first embodiment of an input device according to the present invention. Note that the same reference numerals are given to the same components as in the prior art in the explanation.

The input device Cin of a control device such as a PC in this embodiment is a first
As shown in the figure, the current limiting resistor 4 consists of two current limiting resistors 4A and 4B, which are connected to a photocoupler 6.
It is connected in series to the input side light emitting diode 6A.

Reference numeral 7 denotes an input signal voltage level determination circuit (hereinafter simply referred to as "determination circuit"), which is provided between input terminal IA and input terminal IB, and is configured to determine whether the voltage level of input signal voltage E is low level voltage EL (for example, 5V). ) or high level voltage EH
(for example, 12 to 24 ■).

The determination circuit 7 of this embodiment includes a resistor 8.9, a Zener diode 10, a PNP transistor 11, and a resistor 12.
As shown in FIG. 1, the resistor 8 and the resistor 9 are connected in series, and one end of the resistor 9 is connected to the input terminal IA, and one end of the resistor 8A is connected to the input terminal IB. .

The connection portion between resistor 8 and resistor 9 is connected to the base of transistor 11 via Zener diode 10. The emitter of the transistor 11 is the input terminal 1A,
It is connected to the resistor 9, the emitter of a resistance control switch 13, and a current limiting resistor 4B, which will be described later.

The collector of the transistor 11 is connected to the resistance control switch 13
is also connected to the base of resistor 8 through resistor 12.
, are connected to the input terminal IB and the input side light emitting diode 6A of the photocoupler 6. The resistance control switch 13 is made of a PNP transistor, and the base is connected to the transistor 1.
1 and one end of the resistor 12, its emitter is connected to one end of the current limiting resistor 4B, and its collector is connected to a different end of the current limiting resistor 4B and one end of the current limiting resistor 4A. ing.

A different end of the current limiting resistor 4A is connected to a light emitting diode 6A on the input side of the photocoupler 6. The resistance control switch 13 is turned on and off by an output signal taken out between the transistor 11 and the resistor 12 of the judgment circuit 7.
When the input signal voltage E is a low level voltage EL, the current limiting resistor 4B is short-circuited, and when the input signal voltage E is a high level voltage EH, the current limiting resistor 4B is controlled not to be short-circuited. Therefore, the resistance value of the current control resistor 4 consisting of the current limit resistor 4A and the current limit resistor 4B is reduced by short-circuiting the current limit resistor 4B with the resistance control switch 13, and the current limit resistor 4 is When 4B is not shorted, it has a large resistance value.

When the resistance control switch 13 is turned on, the current limiting resistor 4
When B is short-circuited, the current value supplied to the light emitting diode 6A is determined by the resistance value of the current limiting resistor 4A, so the current limiting resistor 4A is , a light emitting diode 6A that can flow an appropriate current is used. On the other hand, high level voltage EH
The input signal E is input and the resistance control switch 13 is turned OFF.
When set to F, the current limiting resistor 4B is not short-circuited and the current supplied to the light emitting diode 6A is supplied to the current limiting resistor 4.
Since it is determined by the sum of the resistance values of A and the current limiting resistor 4B, the current limiting resistor 4B emits light when the sum of the current limiting resistor 4A and the high level voltage EH input signal is input. A diode capable of passing a suitable current through the diode 6A is used.

The resistance value of the resistor 8.9 is such that when the input signal E of the low level voltage EL is input, the potential drop across the resistor 9 is equal to the Zener voltage Vz of the Zener diode 10 and the transistor 1.
1 becomes larger than the sum of the emitter-to-emitter voltages, the base-emitter voltage becomes forward biased, turning on the transistor 11, and when the input signal E of the high-level voltage E+ is input, the potential drop across the resistor 9 The voltage becomes smaller than the sum of the Zener voltage Vz and the voltage between the pace emitters, and the voltage between the pace emitters becomes reverse biased, turning off the transistor 11.
It is set to

Next, the resistance value of the resistor 12 is set to be able to supply sufficient base current to the resistance control switch 13 at that time, since it is operated in the saturation operating region when the resistance control switch 13 is ON. ing.

Next, a description will be given of the circuit operation of the input device Cin when the input signal E of the low level voltage EL is input.

When the external input contact 3 is closed and the input signal E of the low level voltage EL is input, the potential at the connection point between the resistors 8 and 9 turns on the transistor 11 via the Zener diode 10. Therefore, the transistor 11 is turned on. Then, a potential difference sufficient to turn on the resistance control switch 13 is generated across the resistor 12, so that the turned on resistance control switch 13 short-circuits the current limiting resistor 4B, allowing an appropriate current to flow through the input side light emitting diode 6A. flows, and the output side phototransistor 6
An output signal of the signal level of the internal arithmetic processing section is output from B.

Next, the circuit operation when input signal voltage E of high level voltage EH is input will be described.

When the external connection point 3 is closed and an input signal of high level voltage EH is input, the potential at the connection point between the resistors 8 and 9 is high, and the transistor 11 does not become forward biased between the pace emitters and is not turned on. Therefore, no potential difference occurs between both ends of the resistor 12.

For this reason, the base of the resistance control switch 13 does not have a potential for turning the switch 13 ON, so the resistance control switch 13 is turned OFF and the current limiting resistor 4B is not short-circuited. Therefore, the current flowing through the input light emitting diode 6A is properly adjusted by the current limiting resistors 4A and 4B, and the output phototransistor 6B outputs an output signal that matches the signal level of the internal arithmetic processing section.

As is clear from the above description, according to the configuration of the input device of the first embodiment of the present invention, the input device set in a control device such as a PC can be switched from an input signal E of a low level voltage EL to a high level. Since it can be made wide enough to accommodate input signals E of voltage EH, it is sufficient to manufacture one type of input device. Therefore, manufacturing costs can be reduced compared to manufacturing multiple types of input devices, and since there is only one type of input device as described above, the number of input devices to be kept in stock can be reduced. Therefore, the cost of inventory management can be reduced.

Next, a second embodiment of the present invention will be described using FIG. 2.

In this embodiment, NPN transistors are used for each of the transistor 11 and the resistance control switch 13 of the determination circuit 7. The base of the transistor 11 is connected from the Zener diode 10 to the input terminal IA via the resistor 8, and is also connected to the input terminal IB via the resistor 9. The collector of the transistor 11 is connected to the base of the resistance control switch 13, and is also connected via the resistor 12 to the input terminal IA, the resistor 8, and the current limiting resistor 4A. The emitter of the transistor 11 is connected to the input terminal IB, the resistor 9, the emitter of the resistance control switch 13, and the current limiting resistor 4B. The collector of the resistance control switch 13 is connected to the input side light emitting diode 6A of the photocoupler 6 and the current limiting resistor 4B.

The resistance values of the resistors 8 and 9 are such that when the input signal E of the low level voltage EL is input, the transistor 11 is turned off.
The transistor 11 is set to be turned on when the input signal E of the high level voltage EH is input. The resistor 12 is set so that a sufficient base current can flow through the resistance control switch 13 when it is turned on.

Next, the circuit operation when input signal E of low level voltage EL is input will be described.

When the input signal E is a low level voltage EL, the potential drop across the resistor 9 is small (that is, the base potential of the transistor 11 is low), and the transistor 11 is turned off. When a sufficiently large voltage is applied to the base of 13, the resistance control switch 1
Turn on 3. Therefore, the current limiting resistor 4B is short-circuited, and an appropriate current is supplied to the input side light emitting diode 6A.

Next, the circuit operation when input signal voltage E of high level voltage EH is input will be described.

When the input signal E is a high level voltage EH, the potential drop across the resistor 9 is large (that is, the base potential of the transistor 11 is sufficiently high), and the transistor 11 is turned on, so the base potential of the resistance control switch 13 is small. Therefore, the resistance control switch 13 is turned off. Therefore, the current limiting resistor 4B is not short-circuited, and the current limiting resistor 4B is not short-circuited.
An appropriate current is supplied to the input side light emitting diode 6A by A and 4B.

With the configuration of the input device Cin of the second embodiment described above, the input signal E of the low level voltage EL is changed from the input signal E of the low level voltage EL to the high level voltage E.
Since it is possible to obtain an input device that can handle up to input signals E of By using only one type of input device,
Since the number of input devices to be kept in stock can be reduced, inventory management costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is an electrical circuit diagram showing a first embodiment of an input device according to the present invention, FIG. 2 is an electrical circuit diagram of an input device showing a second embodiment of the invention, and FIG. 3 is a conventional input device. FIG. 3 is an electrical circuit diagram of the device. Cin...Input device 4A, 4B...Current limiting resistor 6...Photocoupler 7...Judgment circuit 13...Resistance control switch

Claims (1)

[Claims] 1. In an input device for a control device, comprising a photocoupler that transmits an input signal to an internal arithmetic processing unit, and a current limiting resistor connected in series to a light emitting diode on the input side of the photocoupler. , an input signal voltage level determination circuit that determines the voltage level of the input signal;
An input device for a control device, comprising: a resistance control switch that is turned FF to control the resistance value of the current limiting resistor.