CN104991471A - 4-20 mA current loop circuit controlled by digital potentiometer - Google Patents
4-20 mA current loop circuit controlled by digital potentiometer Download PDFInfo
- Publication number
- CN104991471A CN104991471A CN201510264169.2A CN201510264169A CN104991471A CN 104991471 A CN104991471 A CN 104991471A CN 201510264169 A CN201510264169 A CN 201510264169A CN 104991471 A CN104991471 A CN 104991471A
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- Prior art keywords
- resistance
- photoelectrical coupler
- operational amplifier
- digital regulation
- circuit
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B19/00—Programme-control systems
- G05B19/02—Programme-control systems electric
- G05B19/04—Programme control other than numerical control, i.e. in sequence controllers or logic controllers
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B2219/00—Program-control systems
- G05B2219/20—Pc systems
- G05B2219/25—Pc structure of the system
- G05B2219/25338—Microprocessor
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Automation & Control Theory (AREA)
- Control Of Electrical Variables (AREA)
- Control Of Voltage And Current In General (AREA)
Abstract
The invention provides a 4-20 mA current loop circuit controlled by a digital potentiometer. Input ends of photoelectric couplers U1, U2 and U3 respectively receive chip selection signals, clock signals and data input signals of the digital potentiometer, all of which are sent by a microprocessor. Output ends of the photoelectric couplers U1, U2 and U3 are directly connected with a control end of the digital potentiometer U4 and a reference voltage circuit, electric isolation between the digital potentiometer U4 and the microprocessor is realized, and the microprocessor is prevented from being damaged. According to the invention, problems in the prior art are solved, the circuit is optimized, the linearity and the precision of the circuit are improved, the area of the circuit board is reduced, the power consumption of the circuit is lowered, the interference resistance is improved, electric isolation is easy, the production cost is saved, and the 4-20 mA current loop circuit can be widely applied to various kinds of industrial apparatuses and instruments.
Description
Technical field
The invention belongs to new-type circuit technical field, relate to a kind of use digital regulation resistance control 4-20mA current loop circuit.
Background technology
Existing many industrial instruments all contain 4-20mA electric current output function, and 4-20mA electric current exports can carry out long-distance transmissions by measured physical quantity, and has very strong antijamming capability, is convenient to monitor in real time the duty of instrument.
At present, the 4-20mA current loop circuit that microprocessor digital controls mainly contains two kinds of implementations: D/A conversion regime and PWM conversion regime.But current many microprocessors do not comprise DAC, even if some microprocessor internal is integrated with DAC, its precision usually can not practical requirement, and cannot realize electrical isolation, if DAC chip external again, not only can increase cost widely, and when parallel data exports, need to take a large amount of I/O port of microprocessor, when carrying out electrical isolation, circuit structure can be caused complicated, and circuit area is larger; And in the application of reality, the linearity of PWM conversion regime is not very desirable yet.
For above-mentioned background content, study the 4-20mA current loop circuit that a kind of stable performance, structure are simple and cheap, thus be applied in industrial instruments, have great importance.
Summary of the invention
In order to solve above problem better, present invention employs a kind of digital regulation resistance and digital quantity is converted to resistance value, and then the output of control 4-20mA current signal.
The technical solution adopted in the present invention is:
The 4-20mA current loop circuit that a kind of digital regulation resistance device controls, the input end of photoelectrical coupler U1, U2 and U3 receives the chip selection signal of the digital regulation resistance that microprocessor sends, clock signal and data input signal respectively, and photoelectrical coupler U1, U2 are directly connected with reference voltage circuit with the control end of digital regulation resistance U4 with the output terminal of U3, realize the electrical isolation of digital regulation resistance U4 and microprocessor, ensure that microprocessor can not be damaged.
In described reference voltage circuit, industrial DC power supply+24V is connected with voltage stabilizing diode Q1 negative electrode through diode D1 with R4, and diode D1 prevents the reverse access of power supply, ensures circuit safety.The 2.5V that voltage stabilizing diode Q1 negative electrode exports amplifies twice via the in-phase proportion computing circuit that operational amplifier U5A, R5 and R6 are formed and obtains 5V, emitter follower again through being made up of U5B and R10, which enhance the carrying load ability of whole reference voltage circuit, to provide stable 5V voltage source for other functional circuits.
The positive pin of power supply of described digital regulation resistance U4 is all connected reference voltage circuit with hot end, and the cold end of digital regulation resistance U4, through resistance R11 ground connection, ensures that minimum output current is 4mA.The emitter follower that the tap outputs of digital regulation resistance U4 is formed via operational amplifier U5C and resistance R12 is connected with 4-20mA current loop circuit control end.Wherein, the inverting input of operational amplifier U5D is as the negative output terminal of 4-20mA current loop circuit, and the emitter of triode Q2 is as the positive output end of 4-20mA current loop circuit.
Structure of the present invention is simple, and digital control output I/O mouth line is easy to realize electrical isolation less, and the linearity is good, precision is high, cheap, reliability is high, can be widely used in various industrial instruments.
Accompanying drawing explanation
Accompanying drawing is the 4-20mA current loop circuit structural representation that a kind of digital regulation resistance controls.
Embodiment
The present invention is elaborated below in conjunction with the drawings and specific embodiments.
Embodiment, as shown in drawings, the 4-20mA current loop circuit that digital regulation resistance controls comprises: 3 photoelectrical couplers U1, U2 and U3, digital regulation resistance U4, four-operational amplifier integrated circuit U5, diode D1, voltage stabilizing diode Q1, triode Q2, electrochemical capacitor C1, resistance R1, resistance R2, resistance R3, resistance R4, resistance R5, resistance R6, resistance R7, resistance R8, resistance R9, resistance R10, resistance R11, resistance R12, resistance R13 and resistance R14.Wherein, the model of photoelectrical coupler U1 and photoelectrical coupler U3 is TLP112, and the model of photoelectrical coupler U3 is TLP181, and the model of digital regulation resistance U4 is MCP41010, the model of four-operational amplifier integrated circuit U5 is LM2902, and it comprises four operational amplifiers U5A, U5B, U5C and U5D.
Photoelectrical coupler U1, U2 and the input negative electrode of U3 are connected the chip selection signal of control figure potentiometer, clock signal and the data input signal that microprocessor exports respectively, the input anode of photoelectrical coupler U1 is connected with 3.3V power supply through resistance R1, the output collector of photoelectrical coupler U1 is connected with digital regulation resistance with reference voltage circuit through resistance R7, the output grounded emitter of photoelectrical coupler U1, the input anode of photoelectrical coupler U2 is connected with 3.3V power supply through resistance R2, and the output collector of photoelectrical coupler U2 is connected with digital regulation resistance with reference voltage circuit through resistance R8, the output grounded emitter of photoelectrical coupler U2, the input anode of photoelectrical coupler U3 is also connected with 3.3V power supply through resistance R3, and the output collector of photoelectrical coupler U3 is connected with digital regulation resistance with reference voltage circuit through resistance R9, the output grounded emitter of photoelectrical coupler U3, digital regulation resistance U4 is connected with the normal phase input end of operational amplifier U5C, between the inverting input that resistance R12 is connected across operational amplifier U5C and output terminal, the output terminal of operational amplifier U5C is connected with the normal phase input end of operational amplifier U5D, one end of the inverting input contact resistance R14 of operational amplifier U5D, and as the negative output terminal of 4-20mA current loop circuit, the other end ground connection of resistance R14, one end of the output terminal contact resistance R13 of operational amplifier U5D, the base stage of the other end access triode Q2 of resistance R13, the collector of triode Q2 is connected with the negative electrode of diode D1, the emitter of triode Q2 is as the positive output end of 4-20mA current loop circuit.
Anode connection+the 24V of the diode D1 of reference voltage circuit, its negative electrode is through electrochemical capacitor C1 ground connection, and be connected to one end of R4, the other end of resistance R4 and the negative electrode of voltage stabilizing diode Q1, the normal phase input end of operational amplifier U5A is connected with the hot end of digital regulation resistance, the plus earth of voltage stabilizing diode Q1, one end of the inverting input contact resistance R6 of operational amplifier U5A, and through resistance R5 ground connection, the output terminal of operational amplifier U5A connects the other end of R6 and the normal phase input end of operational amplifier U5B, and respectively through resistance R7, R8 and R9 and photoelectrical coupler U1, the output collector of U2 with U3 is connected, between the inverting input that resistance R10 is connected across operational amplifier U5B and output terminal, the output terminal of operational amplifier U5B is connected with the energization pins of digital regulation resistance.
The sheet of digital regulation resistance U4 selects pin, clock pins and data-out pin to be connected with the output collector of photoelectrical coupler U1, U2 and U3 respectively, the positive pin of power supply of digital regulation resistance U4 connects the output terminal of the operational amplifier U5A in reference voltage circuit, the hot end of digital regulation resistance U4 is connected with the negative electrode of voltage stabilizing diode Q1, and the cold end of digital regulation resistance U4 is through resistance R11 ground connection.
The front end of this specific embodiments adopts digital data transmission Model Design, and the digital signal representing physical quantity has stronger antijamming capability, and is easy to realize photoelectric coupling; Photoelectrical coupler makes signal scene realize isolating on electrically with main control end, avoids master control system and is damaged, and the present invention can be made into the circuit board independent of main control end, easy to use; Reference voltage circuit is the power supply that the modules of system provides high stability; Control because 4-20mA current loop circuit have employed digital regulation resistance, instead of adopt traditional DAC or PWM conversion regime, and then improve degree of simplifying and the high efficiency of whole system circuit.The present invention can be applied in the industrial instruments with Microprocessor S3C44B0X 4-20mA electric current output function.
Claims (2)
1. the 4-20mA current loop circuit of a digital regulation resistance control, comprise photoelectrical coupler U1, photoelectrical coupler U2, photoelectrical coupler U3, digital regulation resistance U4, four-operational amplifier integrated circuit U5A, U5B, U5C and U5DU5, diode D1, voltage stabilizing diode Q1, triode Q2, electrochemical capacitor C1, resistance R1-R14; It is characterized in that,
The input end of photoelectrical coupler U1, photoelectrical coupler U2 and photoelectrical coupler U3 receives the chip selection signal of the digital regulation resistance that microprocessor sends, clock signal and data input signal respectively, and photoelectrical coupler U1, U2 are directly connected with reference voltage circuit with the control end of digital regulation resistance U4 with the output terminal of U3, realize the electrical isolation of digital regulation resistance U4 and microprocessor; The input anode of photoelectrical coupler U1 is connected with 3.3V power supply through resistance R1, and the output collector of photoelectrical coupler U1 is connected with digital regulation resistance with reference voltage circuit through resistance R7, the output grounded emitter of photoelectrical coupler U1; The input anode of photoelectrical coupler U2 is connected with 3.3V power supply through resistance R2, and the output collector of photoelectrical coupler U2 is connected with digital regulation resistance with reference voltage circuit through resistance R8, the output grounded emitter of photoelectrical coupler U2; The input anode of photoelectrical coupler U3 is also connected with 3.3V power supply through resistance R3, and the output collector of photoelectrical coupler U3 is connected with digital regulation resistance with reference voltage circuit through resistance R9, the output grounded emitter of photoelectrical coupler U3;
Digital regulation resistance U4 is connected with the normal phase input end of operational amplifier U5C, between the inverting input that resistance R12 is connected across operational amplifier U5C and output terminal, the output terminal of operational amplifier U5C is connected with the normal phase input end of operational amplifier U5D, one end of the inverting input contact resistance R14 of operational amplifier U5D, and as the negative output terminal of 4-20mA current loop circuit, the other end ground connection of resistance R14, one end of the output terminal contact resistance R13 of operational amplifier U5D, the base stage of the other end access triode Q2 of resistance R13, the collector of triode Q2 is connected with the negative electrode of diode D1, the emitter of triode Q2 is as the positive output end of 4-20mA current loop circuit,
Anode connection+the 24V of the diode D1 of reference voltage circuit, its negative electrode is through electrochemical capacitor C1 ground connection, and be connected to one end of R4, the other end of resistance R4 and the negative electrode of voltage stabilizing diode Q1, the normal phase input end of operational amplifier U5A is connected with the hot end of digital regulation resistance, the plus earth of voltage stabilizing diode Q1, one end of the inverting input contact resistance R6 of operational amplifier U5A, and through resistance R5 ground connection, the output terminal of operational amplifier U5A connects the other end of R6 and the normal phase input end of operational amplifier U5B, and respectively through resistance R7, R8 and R9 and photoelectrical coupler U1, the output collector of U2 with U3 is connected, between the inverting input that resistance R10 is connected across operational amplifier U5B and output terminal, the output terminal of operational amplifier U5B is connected with the energization pins of digital regulation resistance.
2. 4-20mA current loop circuit according to claim 1, is characterized in that, the chip selection signal of described control figure potentiometer, clock signal and data input signal produce by microprocessor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510264169.2A CN104991471A (en) | 2015-05-21 | 2015-05-21 | 4-20 mA current loop circuit controlled by digital potentiometer |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510264169.2A CN104991471A (en) | 2015-05-21 | 2015-05-21 | 4-20 mA current loop circuit controlled by digital potentiometer |
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| CN104991471A true CN104991471A (en) | 2015-10-21 |
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| CN201510264169.2A Pending CN104991471A (en) | 2015-05-21 | 2015-05-21 | 4-20 mA current loop circuit controlled by digital potentiometer |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106603023A (en) * | 2016-12-15 | 2017-04-26 | 中国电子科技集团公司第四十研究所 | Dual-power power amplifier circuit |
| CN108414825A (en) * | 2018-02-07 | 2018-08-17 | 大连理工大学 | A kind of input and output scaling method of 4-20mA electric current loops |
| CN111198512A (en) * | 2020-03-12 | 2020-05-26 | 辽宁众联石油天然气有限公司 | Parameter simulator |
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| CN1707936A (en) * | 2004-06-05 | 2005-12-14 | 比亚迪股份有限公司 | Motor controller and controlling method thereof |
| CN2796234Y (en) * | 2005-04-21 | 2006-07-12 | 泰豪科技股份有限公司 | Cut-in digital potentioment without distubance |
| EP2407855A1 (en) * | 2009-03-09 | 2012-01-18 | Huawei Technologies Co., Ltd. | Single board energy-saving device, method thereof, and single board |
| CN203193985U (en) * | 2013-04-25 | 2013-09-11 | 南京瑞宝特电子设备有限公司 | Intelligent illumination voltage-regulation control device |
| CN104035047A (en) * | 2014-06-19 | 2014-09-10 | 上海科梁信息工程有限公司 | Aerospace power single cell simulator and simulation method |
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2015
- 2015-05-21 CN CN201510264169.2A patent/CN104991471A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1707936A (en) * | 2004-06-05 | 2005-12-14 | 比亚迪股份有限公司 | Motor controller and controlling method thereof |
| CN2796234Y (en) * | 2005-04-21 | 2006-07-12 | 泰豪科技股份有限公司 | Cut-in digital potentioment without distubance |
| EP2407855A1 (en) * | 2009-03-09 | 2012-01-18 | Huawei Technologies Co., Ltd. | Single board energy-saving device, method thereof, and single board |
| CN203193985U (en) * | 2013-04-25 | 2013-09-11 | 南京瑞宝特电子设备有限公司 | Intelligent illumination voltage-regulation control device |
| CN104035047A (en) * | 2014-06-19 | 2014-09-10 | 上海科梁信息工程有限公司 | Aerospace power single cell simulator and simulation method |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106603023A (en) * | 2016-12-15 | 2017-04-26 | 中国电子科技集团公司第四十研究所 | Dual-power power amplifier circuit |
| CN106603023B (en) * | 2016-12-15 | 2020-01-21 | 中国电子科技集团公司第四十一研究所 | Dual-power amplifier circuit |
| CN108414825A (en) * | 2018-02-07 | 2018-08-17 | 大连理工大学 | A kind of input and output scaling method of 4-20mA electric current loops |
| CN111198512A (en) * | 2020-03-12 | 2020-05-26 | 辽宁众联石油天然气有限公司 | Parameter simulator |
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