KR20200058942A - Digital input apparatus with programmable input voltage level - Google Patents

Abstract

The present invention relates to a digital input device having an isolated digital input circuit free to set binary input levels by applying a digital-to-analog converter (DAC) for programmatically adjusting the voltage level of a binary input circuit, a comparator for comparing voltage levels, a resistor for current regulation, and a photo coupler for insulation. According to the present invention, the digital input device with a programmable input voltage level includes: a power supply unit that receives AC power and converts and supplies AC power to DC power; an isolation digital input unit that recognizes a voltage applied from the power supply unit and compares a reference voltage set based on the recognized voltage level with the recognized voltage to insulate input/output and output signals according to on and off states; and an MCU that reads a state of a control target controlled through the isolation digital input unit, performs internal calculation, and outputs a control signal through an output unit.

Description

Digital input apparatus with programmable input voltage level

The present invention relates to a digital input device of a PLC, specifically, a digital input device of a PLC having an isolated digital input circuit free to set the binary input level by allowing the voltage level of the binary input circuit to be programmable. It is about.

In general, a programmable logic controller (PLC) is a digital electronic device that uses programmable memory and controls various types of machines or processors to perform special functions such as sequencing, counting, and calculation through digital or analog input / output devices.

On the other hand, the digital input device of the PLC is a device that receives various signals of AC or DC input from the outside and converts them into signals that can be processed by the Micro Processor Unit (MPU) through an internal interface and transmits them.

Conventional PLC digital input devices include signal conversion circuits, isolated digital input circuits, interface circuits, and the like.

The signal conversion circuit is a circuit that converts a signal input from an external device into a digital signal. The input signal is compared with the reference value, and if the size of the input signal is greater than the reference value, it is converted into a digital signal of "H" (high, high) and "L" (low, low) if it is smaller than the reference value.

The isolated digital input circuit is a means to insulate the output signal of the signal conversion circuit and the circuit inside the PLC device to prevent the occurrence of noise or mutual interference. In general, the isolated digital input circuit includes a photo coupler.

The interface circuit functions as an internal interface for transmitting the signal input from the isolated digital input circuit to the PLC's MPU.

However, in the conventional digital input device, the isolated digital input circuit must know the voltage level in order to receive the binary input converted to the digital signal from the signal conversion circuit, and the isolated digital input circuit must be designed accordingly. Therefore, when the input voltage level is changed, there is a problem that the insulating digital input circuit must be changed accordingly.

In order to solve this problem, the present invention, a digital-to-analog converter (DAC) that allows programmatically adjusting the voltage level of a binary input circuit, a comparator for comparing voltage levels, and current adjustment An object of the present invention is to provide a digital input device having an isolated digital input circuit free to set a binary input level by applying a photo coupler for resistance and isolation.

The objects of the present invention are not limited to the above-mentioned objects, and other objects and advantages of the present invention not mentioned can be understood by the following description, and will be more clearly understood by embodiments of the present invention. In addition, it will be readily appreciated that the objects and advantages of the present invention can be realized by means of the appended claims and combinations thereof.

In order to achieve the above object, a digital input device having a programmable input voltage level of the present invention includes: a power supply unit that receives AC power (AC) and converts and supplies DC power (DC); An isolated digital input unit that recognizes a voltage applied from the power supply unit and compares a reference voltage set based on the recognized voltage level with the recognized voltage to insulate input / output and output signals according to on and off states; And an MCU that reads a state of a control target to be controlled through the isolated digital input unit, performs internal calculation, and outputs a control signal through the output unit.

In addition, the isolated digital input unit divides the external signal input to the external signal input terminal into first and second resistors by connecting the first and second resistors R1 and R2 in series between the external signal input terminals, and the second A photo-coupler (PC) consisting of a signal input unit for outputting the voltage across the resistor R2, a light-emitting element for receiving and transmitting an external signal output from the signal input unit, and a light-receiving transistor, and the light reception of the photocoupler Connected to the emitter of the transistor, the third resistor R3 stably outputs the power supply voltage transmitted through the light-receiving transistor of the photocoupler, and the preset reference voltage and the level of the voltage induced by the third resistor R3. And a comparator that compares and converts to a digital signal.

In addition, the reference voltage is characterized in that the program is set through the MCU.

In addition, the MCU is characterized in that to set the reference voltage based on the voltage level induced by the third resistor (R3).

In addition, it further comprises a digital to analog converter (DAC) that converts the output value set by the MCU into a digital signal and outputs it as a reference voltage to the (+) input terminal of the comparator.

In addition, when the voltage level induced by the third resistor R3 input to the (-) input terminal is greater than the reference voltage level input to the (+) input terminal, the output is grounded (GND), and the (-) input terminal When the voltage level induced by the third resistor R3 input to the input voltage is smaller than the reference voltage level input to the (+) input terminal, the output is opened.

In order to achieve this object, the digital input device having a programmable input voltage level of the present invention, the first and second resistors (R1, R2) are connected in series between the external signal input terminals and input to the external signal input terminals. A signal input unit for dividing the external signal into first and second resistors and outputting voltages across the second resistor R2; A photo coupler (PC) consisting of a light emitting element and a light receiving transistor that insulates and transmits an external signal output from the signal input unit; A third resistor (R3) connected to the emitter of the light-receiving transistor of the photocoupler and stably outputting a power voltage transmitted through the light-receiving transistor of the photocoupler; A comparator that compares a predetermined reference voltage with a level of the voltage induced by the third resistor R3 and converts the digital signal into a digital signal; And a digital to analog converter (DAC) that converts the output value set by the program to a digital signal and outputs it to the (+) input terminal of the comparator as a reference voltage.

According to the present invention as described above, a digital input device having a programmable input voltage level of the present invention, a digital to analog converter (DAC) and a voltage to programmatically adjust the voltage level of a binary input circuit By applying a comparator for comparing levels, a resistor for adjusting current, and a photo coupler for isolation, it is possible to determine the binary input level freely.

In addition to the above-described effects, the concrete effects of the present invention will be described together while describing the specific matters for carrying out the invention.

1 is a block diagram showing the configuration of a digital input device having a programmable input voltage level according to an embodiment of the present invention
Figure 2 is a circuit diagram showing the configuration of the isolated digital input unit in Figure 1 in detail
3 is a view for explaining the operation of the circuit diagram of the isolated digital input unit in FIG.

The above-described objects, features, and advantages will be described in detail below with reference to the accompanying drawings, and accordingly, a person skilled in the art to which the present invention pertains can easily implement the technical spirit of the present invention. In the description of the present invention, when it is determined that detailed descriptions of known technologies related to the present invention may unnecessarily obscure the subject matter of the present invention, detailed descriptions will be omitted. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The same reference numerals in the drawings are used to indicate the same or similar components.

Hereinafter, a digital input device having a programmable input voltage level according to a preferred embodiment of the present invention will be described in detail with reference to the drawings.

1 is a block diagram showing the configuration of a digital input device having a programmable input voltage level according to an embodiment of the present invention. The digital input device illustrated in FIG. 1 is according to an embodiment, and its components are not limited to the embodiment illustrated in FIG. 1, and some components may be added, changed, or deleted as necessary.

As shown in FIG. 1, the digital input device receives an AC power (AC), converts it into DC power (DC), and supplies power to each unit 100,

An isolated digital input unit that recognizes a voltage applied from the power supply unit 100 and compares a reference voltage set based on the recognized voltage level with the recognized voltage to insulate input / output and output signals according to on / off states ( 200) and an MCU 300 that reads a state of a control target to be controlled through the insulating digital input unit 200, performs internal calculation, and outputs a control signal through the output unit 400.

FIG. 2 is a circuit diagram showing the configuration of the isolated digital input unit in FIG. 1 in detail.

As shown in FIG. 2, the isolated digital input unit 200 is connected to the first and second resistors R1 and R2 in series between the external signal input terminals IN + and IN- to be input to the external signal input terminal. The external signal is divided into the first and second resistors R1 and R2, and the signal input unit 210 for outputting the voltage across the second resistor R2 and the external signal output from the signal input unit 210 are insulated and transmitted. The photo-coupler (PC) 220 made of a light-emitting element and a light-receiving transistor is connected to the emitter of the light-receiving transistor of the photo coupler 220 and the power voltage transmitted through the light-receiving transistor of the photo coupler 220 Comparator 230 that compares the level of the voltage induced by the third resistor R3 with the third resistor R3 stably outputting, and the reference voltage set by the MCU 300 as a program, and converts it into a digital signal 230 And a digital to analog convertor (DAC) 240 which converts the output value set by the program to a digital signal and outputs it to the (+) input terminal of the comparator 230 as a reference voltage.

Accordingly, when the voltage level induced by the third resistor R3 input to the (-) input terminal is greater than the reference voltage level output from the DAC 240 input to the (+) input terminal, the comparator 230 outputs the ground ( The light receiving transistor is turned on). Conversely, when the voltage level induced by the third resistor R3 input to the (-) input terminal is smaller than the reference voltage level output from the DAC 240 input to the (+) input terminal, the comparator 230 opens (received) Transistor off).

To this end, the MCU 300 sets a reference voltage based on the voltage level induced by the third resistor R3. Therefore, even when the voltage level of the input signal is changed, the input circuit can be adjusted by the MCU 300 without changing the input circuit accordingly.

The operation according to the digital input device having the programmable input voltage level of the present invention configured as described above will be described in detail with reference to the accompanying drawings. The same reference numerals as those in Fig. 1 or 2 refer to the same members performing the same functions.

Referring to Figure 1, first, the power supply 100 receives the AC power (AC) through the external signal input terminal (IN +, IN-) DC power (DC) such as 5 [V], 24 [V] Convert to

The isolated digital input unit 200 recognizes the voltage applied from the power supply unit 100 and outputs signals according to on and off states.

In more detail, the operation of the isolated digital input unit 200 is divided into first and second resistors R1 and R2 connected in series between the input terminals IN + and IN-, and the second resistor R2 Output voltage across both ends.

At this time, the first resistor R1 is a current limiting resistor according to the input voltage, and the second resistor R2 serves to prevent the light emitting element on the input side of the photocoupler 220 from turning on even when a leakage current flows. Therefore, the isolated digital input unit 200 requires a current greater than or equal to a certain current to operate the light emitting device.

The photocoupler 220 insulates and transmits the output of the voltage across the second resistor R2. At this time, the photocoupler 220 flows in proportion to the magnitude of the input current and the output current at a constant amplification ratio.

In addition, the output value to the photocoupler 220 stably outputs the power supply voltage transmitted through the third resistor R3 connected to the emitter of the light receiving transistor. At this time, while the third resistor R3 proposes the current of the output terminal, the voltage induced by the third resistor R3 is input to the (-) input terminal of the comparator 230.

The output value of the DAC 240 set as a program by the MCU 300 is input to the (+) input terminal which is the other input of the comparator 230. At this time, the MCU 300 converts the output value set by the program into a digital signal through the DAC 240 and outputs it to the (+) input terminal of the comparator 230 as a reference voltage.

Accordingly, the comparator 230 compares the level of the voltage induced by the third resistor R3 with the reference voltage set by the MCU 300 as a program and converts it into a digital signal. Accordingly, when the voltage level induced by the third resistor R3 input to the (-) input terminal is greater than the reference voltage level output from the DAC 240 input to the (+) input terminal, the comparator 230 outputs the ground ( 0V). Conversely, when the voltage level induced by the third resistor R3 input to the (-) input terminal is smaller than the reference voltage level output from the DAC 240 input to the (+) input terminal, the comparator 230 opens (VCC ) do.

To this end, the MCU 300 sets a reference voltage based on the voltage level induced by the third resistor R3. Therefore, even when the voltage level of the input signal is changed, the input circuit can be adjusted by the MCU 300 without changing the input circuit accordingly.

The comparator 230 compares the voltage value of the third resistor R3 with the output value of the DAC 240 and inputs the result value to the input port of the MCU 300.

The MCU 300 reads the state of the control target through the insulating digital input unit 200, performs internal calculation, and outputs a control signal through the output unit 400.

3 is a view for explaining the operation of the circuit diagram of the isolated digital input unit in FIG.

)에 의하여 제1 저항(R1)에 흐르는 전류(

)는 다음 수학식 1과 같고, 제2 저항(R2)에 흐르는 전류(

)는 다음 수학식 2와 같다.Referring to Figure 3, the external input from the power supply unit 100 (

), The current flowing through the first resistor (R1) (

) Is equal to Equation 1 below, and the current flowing through the second resistor R2 (

) Is as shown in Equation 2 below.

는 포토커플러(220)의 입력측 다이오드의 순방향 전압이다.At this time,

Is a forward voltage of the diode on the input side of the photocoupler 220.

)는 다음 수학식 3과 같다.Therefore, the current flowing through the input of the photocoupler 220 (

) Is as in Equation 3 below.

)는 외부 입력(

)에 비례함을 알 수 있다.The current of the input terminal of the photocoupler 220 through Equation (3)

) Is an external input (

).

)는 포토커플러(220)의 전류 전달비(Current Transfer Ratio: CTR)(

)에 의해 다음 수학식 4로 결정된다.And the current induced in the third resistor (R3) (

) Is the current transfer ratio (CTR) of the photocoupler 220 (

) Is determined by the following equation (4).

)은 다음 수학식 5와 같다.Therefore, the voltage applied by the third resistor R3 (

) Is as in Equation 5 below.

)을 제외하고는 모두 상수로 가정할 수 있기 때문에 제3 저항(R3)에 의해 인가되는 전압(

)은 외부 입력(

)에 비례하는 것을 알 수 있다.At this time, as in Equation 5 above, an external input (

Since all can be assumed to be constant except for), the voltage applied by the third resistor R3 (

) Is an external input (

).

이라 가정하고, 상기

이 입력되었을 때에 제3 저항(R3)에 인가되는 전압을

라고 가정한다.Therefore, the minimum voltage value that the input is recognized as

Assuming,

The voltage applied to the third resistor (R3) when is input

Is assumed.

)이

이 되도록 설정하면,

값보다 큰 전압이 입력에 인가되었을 경우에는, 비교기(230)의 출력(

)은 0V가 될 것이고,

보다 작은 전압이 입력에 인가되었을 경우에는 비교기(230)의 출력(

)은 VCC(회로전원)가 될 것이다.At this time, the voltage output value of the DAC 240 (

)this

If you set it to be

When a voltage greater than the value is applied to the input, the output of the comparator 230 (

) Will be 0V,

When a smaller voltage is applied to the input, the output of the comparator 230 (

) Will be VCC (Circuit Power).

)의 출력을 조절함으로써 입력 기준값

을 조절할 수 있다.Therefore, the voltage output value of the DAC 240 (

) By adjusting the output of the input reference value

Can be adjusted.

= 60V 인 경우,

=

= 3V 이라고 가정한다.As an embodiment,

= 60V,

=

= 3V.

의 출력값을 3V 보다 크게 한다면, 입력 전압이 60V 보다 더 큰 값이 입력되어야 인식할 것이고,

의 출력값을 3V보다 작게 한다면, 입력 전압이 60V 보다 작은 값이 인가되어도 인식할 것이다.At this time,

If the output value of is greater than 3V, an input voltage greater than 60V must be input to recognize it.

If the output value of is less than 3V, the input voltage will be recognized even if a value less than 60V is applied.

The above-described present invention, the above-described embodiments and the accompanying drawings because it is possible for a person having ordinary knowledge in the technical field to which the present invention pertains to various substitutions, modifications and changes without departing from the technical spirit of the present invention It is not limited by.

100: power supply 200: isolated digital input
210: signal input unit 220: photo coupler
230: comparator 240: DAC
300: MCU 400: output

Claims (7)

A power supply unit that receives AC power (AC) and converts and supplies AC power (DC);
An isolated digital input unit that recognizes a voltage applied from the power supply unit and compares a reference voltage set based on the recognized voltage level with the recognized voltage to insulate input / output and output signals according to on and off states; And
A digital input device including an MCU that reads a state of a control target to be controlled through the isolated digital input unit, performs an internal operation, and outputs a control signal through the output unit.
According to claim 1,
The isolated digital input
The first and second resistors R1 and R2 are connected in series between the external signal input terminals to divide the external signal input to the external signal input terminals into first and second resistors, and the voltage across the second resistor R2. A signal input unit for outputting,
A photo coupler (PC) consisting of a light emitting element and a light receiving transistor that insulates and transmits an external signal output from the signal input unit,
A third resistor (R3) connected to the emitter of the light-receiving transistor of the photocoupler and stably outputting a power supply voltage transmitted through the light-receiving transistor of the photocoupler;
And a comparator that compares a predetermined reference voltage and a level of the voltage induced by the third resistor (R3) and converts it into a digital signal.
According to claim 2,
The reference voltage is a digital input device, characterized in that is set by the program through the MCU.
According to claim 3,
The MCU sets a reference voltage based on a voltage level induced by the third resistor (R3).
According to claim 3,
And a digital to analog converter (DAC) that converts the output value set by the MCU into a digital signal and outputs it to a (+) input terminal of the comparator as a reference voltage.
According to claim 2,
When the voltage level induced by the third resistor R3 input to the (-) input terminal is greater than the reference voltage level input to the (+) input terminal, the output is grounded.
When the voltage level induced by the third resistor (R3) input to the (-) input terminal is smaller than the reference voltage level input to the (+) input terminal, the output is opened.
The first and second resistors R1 and R2 are connected in series between the external signal input terminals to divide the external signal input to the external signal input terminals into first and second resistors, and the voltage across the second resistor R2. A signal input unit for outputting;
A photo coupler (PC) consisting of a light emitting element and a light receiving transistor that insulates and transmits an external signal output from the signal input unit;
A third resistor (R3) connected to the emitter of the light-receiving transistor of the photocoupler and stably outputting a power supply voltage transmitted through the light-receiving transistor of the photocoupler;
A comparator that compares a predetermined reference voltage with a level of the voltage induced by the third resistor R3 and converts it into a digital signal; And
A digital input device including a digital to analog converter (DAC) that converts the output value set by the MCU to a digital signal and outputs it to the (+) input terminal of the comparator as a reference voltage.

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