CN105067892A - Cable impedance detection circuit - Google Patents
Cable impedance detection circuit Download PDFInfo
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- CN105067892A CN105067892A CN201510608793.XA CN201510608793A CN105067892A CN 105067892 A CN105067892 A CN 105067892A CN 201510608793 A CN201510608793 A CN 201510608793A CN 105067892 A CN105067892 A CN 105067892A
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Abstract
The invention discloses a cable impedance detection circuit comprising an impedance detection circuit and an alternating current judgment protection circuit. The alternating current judgment protection circuit is provided with a protection relay. When there is alternating current in a cable, the protection relay is switched off; and when there is no alternating current in the cable, the protection relay is switched on. One end of the impedance detection circuit is electrically connected with a direct current detection voltage end and is electrically connected with the cable through the cable through the protection relay, and the other end is electrically connected with a control module. When there is no alternating current in the cable, the protection relay is switched on, and the impedance change of the cable is detected through the impedance detection circuit. First, whether power supply is direct power supply or alternating power supply is judged; and in the direct-current state, whether the impedance state at the tail end of the cable is normal is detected. A circuit structure for cable theft alarming under the state without alternating power supply is realized.
Description
Technical field
The invention belongs to on-line monitoring of cable technical field, be specifically related to a kind of cable resistance testing circuit.
Background technology
Owing to there being a large amount of precious metal materials in cable, often there is the stolen event of cable.Now commercially occur there is much cable theft-prevention equipment, such as video is antitheft, wireless telecommunications are antitheft, surveyed antitheft etc. a series of burglary-resisting installation of antitheft, the power carrier (PowerLineCarrier, PLC) of electric current.
Adopt wireless anti-theft pattern to have certain defect in distance, existing wireless anti-theft circuit maximum distance can only reach within the scope of 500m, and receives the mutual interference of on-air radio signal, shines into Signal transmissions not smooth, very easily occurs wrong report phenomenon.And when there is no Alternating Current Power Supply module, terminal needs from power distribution cabinet, to export a direct current for wireless anti-theft terminal, this method between the lights street lamp is turned on light moment, very easily scurry in DC power-supply circuit according to one-tenth alternating voltage, DC power-supply circuit is burnt, and destroys theft-proof terminal.
Some producers have employed the large inductance short circuit of terminal or bulky capacitor short circuit, the unexpected change of electric current on test cable, and wrong report easily appears in this scheme in the road lighting cable of road is antitheft.But this mode is applicable to the situation of Alternating Current Power Supply always, if original AC dump, just cannot judge that whether cable is stolen.
Summary of the invention
For the above-mentioned technological deficiency existing for prior art, the invention provides a kind of cable resistance testing circuit, first judge direct current supply or Alternating Current Power Supply; Under DC state, whether detection streamer terminating impedance state is normal, realizes a kind of without under Alternating Current Power Supply state, the circuit structure of the stolen warning of cable.
A kind of cable resistance testing circuit, comprising: impedance detection circuit judges protection circuit with exchanging,
Described interchange judges that protection circuit has protective relay, when cable has alternating current, disconnects protective relay, when cable does not have alternating current, and closed protective relay;
One end of described impedance detection circuit is electrically connected with direct current detection voltage back end; and be electrically connected with cable by protective relay, the other end is electrically connected with control module, when cable does not have alternating current; closed protective relay, utilizes the impedance variation of impedance detection circuit to cable to detect.
Optionally, also comprise direct current output protection circuit, one end of described direct current output protection circuit is electrically connected with impedance detection circuit, direct current detection voltage back end, and the other end is electrically connected with protective relay.
Optionally; described direct current output protection circuit comprises DC output circuit and differential amplifier circuit; described differential amplifier circuit ensures that the field effect transistor of DC amplification circuit is always for conducting state, protects field effect transistor to cause because of short circuit burning circuit simultaneously.
Optionally, described DC output circuit comprises: direct current detection voltage back end is through the first resistance R3B4 in parallel, second resistance R3B5 connects the drain electrode of field effect transistor Q3B1 and the input end of impedance detection circuit, the source electrode of field effect transistor Q3B1 connects the input end of the first diode D3B3, and the normally closed contact of relay is connected to through resistance the one R3B7, the grid of field effect transistor Q3B1 is connected with the output terminal of the first diode D3B3, the other end be connected grid by resistance the 2nd R3B6 and control power supply, the input end of described first diode D3B3 is connected with the source electrode of field effect transistor Q3B1.
Optionally, described differential amplifier circuit comprises: the first triode Q2B3, second triode Q3B2, first peripheral resistance R3B8, second peripheral resistance R3B9, 3rd peripheral resistance R3B10, described first peripheral one end of resistance R3B8 is connected with the source electrode of field effect transistor Q3B1, the other end of described first peripheral resistance R3B8 is connected with the base stage of the first triode Q3B2, the collector of the second triode Q3B2 is respectively at the collector of the first triode Q2B3, the grid of field effect transistor Q3B1 is connected, the emitter of described second triode Q3B2 is respectively at the emitter of the first triode Q2B3, the normally closed contact of relay, one end of second peripheral resistance R3B9 is connected, the base stage of described first triode Q2B3 is the other end of peripheral resistance R3B9 with second respectively, one end of 3rd peripheral resistance R3B10 is connected, one end ground connection of described 3rd peripheral resistance R3B10.
Optionally; described interchange judges that protection circuit comprises: cable is electrically connected with the input end of two-stage reverse swing door circuit; the output terminal of two-stage reverse swing door circuit is connected with the first photoelectric coupled circuit U3A1, utilizes optocoupler signal to output in control module, judges whether present cable has Alternating Current Power Supply.
Optionally, also comprise: the series circuit that cable is formed with mu balanced circuit with the second diode D3B1, bleeder circuit with inductance L 3B1, half-wave rectifying circuit is connected, the other end of described mu balanced circuit is electrically connected with the input end of two-stage reverse swing door circuit.
Optionally; also comprise: relay driving chip UB2C and protective relay RY3B1; the input end of described relay driving chip UB2C connects the output terminal of two-stage reverse swing door resistance, and the output terminal of relay driving chip UB2C connects the control end of protective relay RY3B1.
Optionally, described impedance detection circuit comprises the first amplifier UA9A, the second amplifier UA10A, the second optocoupler, described first amplifier UA9A one end connect the first divider resistance R3A1, second divider resistance R3A1 form bleeder circuit, described amplifier UA9A the other end connect one end of the second optocoupler, the other end of described second optocoupler connects the input end of amplifier UA10A, and the output terminal of described amplifier UA10A is connected with control module.
Optionally, described second optocoupler is linear optical coupling, the voltage of the light emitting diode of linear optical coupling can according to the difference of branch pressure voltage, there is different brightness, feed back to the photosensitive output terminal of linear optical coupling, the resistance of photosensitive output terminal can will change according to DC partial voltage voltage, and the voltage of change is input to control module after amplifier UA10A amplifies.
Compared with prior art, the present invention at least has following technique effect:
Whole circuit application, in cable theft-prevention circuit, first judges direct current supply or Alternating Current Power Supply; Under DC state, whether detection streamer terminating impedance state is normal, can realize a kind of without under Alternating Current Power Supply state, the circuit structure of the stolen warning of cable.
Accompanying drawing explanation
Fig. 1 be the cable resistance testing circuit of the embodiment of the present invention direct current output protection circuit with exchange the electrical block diagram judging protection circuit;
Fig. 2 is the electrical block diagram of the impedance detection circuit of the cable resistance testing circuit of the embodiment of the present invention;
Fig. 3 is the first photoelectric coupled circuit structural representation that the alternating current-direct current of the embodiment of the present invention judges protection circuit;
Fig. 4 is the structural representation of a kind of cable anti-theft system application of the cable resistance testing circuit of the embodiment of the present invention.
Embodiment
In order to more specifically describe the present invention, below in conjunction with the drawings and the specific embodiments, technical scheme of the present invention and principle of work thereof are described in detail.
Please refer to Fig. 1 Fig. 2 and Fig. 3, the cable resistance testing circuit of the embodiment of the present invention comprises: direct current output protection circuit, exchange and judge protection circuit and impedance detection circuit impedance detection circuit, described interchange judges that protection circuit has protective relay, when cable has alternating current, disconnect protective relay, when cable does not have alternating current, closed protective relay; One end of described impedance detection circuit is electrically connected with direct current detection voltage back end; and be electrically connected with cable by direct current output protection circuit, protective relay; the other end is electrically connected with control module; when cable does not have alternating current; closed protective relay, utilizes the impedance variation of impedance detection circuit to cable to detect.
Due to damage may be caused to impedance detection circuit, direct current detection voltage back end when existing and exchange in cable, therefore in the present embodiment, at impedance detection circuit, between direct current detection voltage back end and cable, add a direct current output protection circuit.In other embodiments, also can one end of impedance detection circuit be directly electrically connected with cable by protective relay.
Described direct current output protection circuit comprises DC output circuit and differential amplifier circuit, DC output circuit comprises: direct current detection voltage back end is through the first resistance R3B4 in parallel, second resistance R3B5 connects the drain electrode of field effect transistor Q3B1, the source electrode of field effect transistor Q3B1 connects the input end of the first diode D3B3, and the normally closed contact of relay is connected to through resistance the one R3B7, the grid of field effect transistor Q3B1 is connected with the output terminal of the first diode D3B3, the other end be connected grid by resistance the 2nd R3B6 and control power supply, the input end of described first diode D3B3 is connected with the source electrode of field effect transistor Q3B1.Described differential amplifier circuit comprises: the first triode Q2B3, second triode Q3B2, first peripheral resistance R3B8, second peripheral resistance R3B9, 3rd peripheral resistance R3B10, described first peripheral one end of resistance R3B8 is connected with the source electrode of field effect transistor Q3B1, the other end of described first peripheral resistance R3B8 is connected with the base stage of the first triode Q3B2, the collector of the second triode Q3B2 is respectively at the collector of the first triode Q2B3, the grid of field effect transistor Q3B1 is connected, the emitter of described second triode Q3B2 is respectively at the emitter of the first triode Q2B3, the normally closed contact of relay, one end of second peripheral resistance R3B9 is connected, the base stage of described first triode Q2B3 is the other end of peripheral resistance R3B9 with second respectively, one end of 3rd peripheral resistance R3B10 is connected, one end ground connection of described 3rd peripheral resistance R3B10.
Described differential amplifier circuit ensures that the field effect transistor of DC amplification circuit is always for conducting state; protecting field effect transistor to cause because of short circuit burning circuit simultaneously, making the DC voltage of direct current detection voltage back end all can be in conducting state when detecting always.
In embodiments of the present invention, the voltage of direct current detection voltage back end is 13.5V, is the operating voltage of chip, and the power supply that grid controls power supply is 18.5V.In other embodiments, these two voltages also can be other suitable values.
Please refer to Fig. 1; the interchange of the present embodiment judges that protection circuit comprises: the series circuit that cable is formed with mu balanced circuit with the second diode D3B1, bleeder circuit with inductance L 3B1, half-wave rectifying circuit is connected; the other end of described mu balanced circuit is electrically connected with the input end of two-stage reverse swing door circuit; the output terminal of two-stage reverse swing door resistance is electrically connected with the first photoelectric coupled circuit U3A1; utilize optocoupler signal to output in control module, judge whether present cable has Alternating Current Power Supply.
In other embodiments, also can directly be electrically connected with the input end of two-stage reverse swing door circuit by cable, the output terminal of two-stage reverse swing door circuit is connected with the first photoelectric coupled circuit U3A1, utilizes optocoupler signal to output in control module, judges whether present cable has Alternating Current Power Supply.Because alternating current is by transforming digital signal after two-stage reverse swing door circuit, can directly outputs to control module and judge.
In the present embodiment, the output terminal of described two-stage reverse swing door resistance also connects the input end of relay driving chip UB2C, and the output terminal of relay driving chip UB2C connects protective relay RY3B1.After relay driving chip UB2C obtains the signal of the output terminal of two-stage reverse swing door resistance, can directly disconnect or close by Control protection relay R Y3B1.
In the present embodiment; during Alternating Current Power Supply; first diode D3B1 ends; second diode D3B2 conducting; carry out half-wave rectification simultaneously; dividing potential drop is carried out through the 3rd resistance R3B1 and the 4th resistance R3B2; after voltage stabilizing diode DZ3B1 voltage stabilizing, obtain 10V voltage, after two-stage reverse swing door circuit; through relay driving chip; make relay coil both end voltage be 13V, the electric shock state of relay overturns, and disconnects the output channel of direct current 13.5V; the path of protection 13.5V direct current and ac cable, protection direct current.Simultaneously after two-stage gate circuit, the T3_P signal of output is input on the first photoelectric coupled circuit U3A1, makes optocoupler work, and it is low level that optocoupler exports T3_STAT signal, is input in control module, namely can judges whether present cable has Alternating Current Power Supply by this signal.
In the present embodiment, described impedance detection circuit comprises the first amplifier UA9A, the second amplifier UA10A, the second optocoupler, described first amplifier UA9A one end connect the first divider resistance R3A1, second divider resistance R3A1 form bleeder circuit, described amplifier UA9A the other end connect one end of the second optocoupler, the other end of described second optocoupler connects the input end of amplifier UA10A, and the output terminal of described amplifier UA10A is connected with control module.
Described second optocoupler is linear optical coupling, the voltage of the light emitting diode of linear optical coupling can according to the difference of branch pressure voltage, there is different brightness, feed back to the photosensitive output terminal of linear optical coupling, the resistance of photosensitive output terminal can will change according to DC partial voltage voltage, and the voltage of change is input to single-chip microcomputer after amplifier UA10A amplifies.
Please refer to Fig. 4, be an Application Example---a kind of cable anti-theft system of cable resistance testing circuit of the present invention, described cable anti-theft system comprises: anti-theft control unit 10, theft-proof terminal unit 20, central control unit 30,
Central control unit 30 comprises centralized control module 31, concentrates communication module 32, communication module 32 is concentrated to be connected with centralized control module 31, and utilize communication interface to carry out communication between described concentrated communication module 32 and the main communication module 12 of anti-theft control unit 10, pass through power carrier communication with theft-proof terminal unit 20.
Described anti-theft control unit 10, comprising: main control module, main communication module 12, and main communication module 12 is connected with main control module; Exchange and judge protection circuit 13, be connected with cable 13 with main control module 11 respectively, in detection streamer, whether have alternating current; Impedance detection module, comprise the impedance detection circuit of sample circuit 14 and the embodiment of the present invention, sample circuit 14 is connected with cable with main control module respectively, gather the impedance on cable and information of voltage, and utilize impedance detection circuit to obtain the change of cable resistance, in the present embodiment, described main control module and impedance detection circuit are integrated in same MCU, in other embodiments, also can be provided separately.
Described theft-proof terminal unit 20, comprise: terminal control module 21, terminal communication module 22, voltage detecting control module 23, terminal communication module 22 is connected with terminal control module 21, and passes through power carrier communication between terminal communication module 21 and concentrated communication module 32; Voltage detecting control module 23 comprises a relay and a resistance of series connection, and the two ends of a described relay and a resistance are connected respectively on live wire and zero line, and relay is controlled by terminal control module 21.When detect cable there is no alternating current time, terminal control module 21 is by relay closes, live wire and zero line conducting, allow anti-theft control unit 10 impedance detection module testing circuit in whether whether impedance is preset value, if cable is stolen, the impedance of cable becomes large instantaneously, and the luminous moment of corresponding linear optical coupling is dimmed, thus can notify that whether control module cable is stolen very easily.
The above embodiment only in order to technical scheme of the present invention to be described, is not intended to limit; Although with reference to previous embodiment to invention has been detailed description, those of ordinary skill in the art is to be understood that: it still can be modified to the technical scheme described in foregoing embodiments, or carries out equivalent replacement to wherein portion of techniques feature; And these amendments or replacement, do not make the essence of appropriate technical solution depart from the spirit and scope of each embodiment technical scheme of the embodiment of the present invention.
Claims (10)
1. a cable resistance testing circuit, is characterized in that, comprising: impedance detection circuit judges protection circuit with exchanging,
Described interchange judges that protection circuit has protective relay, when cable has alternating current, disconnects protective relay, when cable does not have alternating current, and closed protective relay;
One end of described impedance detection circuit is electrically connected with direct current detection voltage back end; and be electrically connected with cable by protective relay, the other end is electrically connected with control module, when cable does not have alternating current; closed protective relay, utilizes the impedance variation of impedance detection circuit to cable to detect.
2. cable resistance testing circuit according to claim 1; it is characterized in that; also comprise direct current output protection circuit, one end of described direct current output protection circuit is electrically connected with impedance detection circuit, direct current detection voltage back end, and the other end is electrically connected with protective relay.
3. cable resistance testing circuit according to claim 2; it is characterized in that; described direct current output protection circuit comprises DC output circuit and differential amplifier circuit; described differential amplifier circuit ensures that the field effect transistor of DC amplification circuit is always for conducting state, protects field effect transistor to cause because of short circuit burning circuit simultaneously.
4. cable resistance testing circuit according to claim 3, it is characterized in that, described DC output circuit comprises: direct current detection voltage back end is through the first resistance R3B4 in parallel, second resistance R3B5 connects the drain electrode of field effect transistor Q3B1 and the input end of impedance detection circuit, the source electrode of field effect transistor Q3B1 connects the input end of the first diode D3B3, and the normally closed contact of relay is connected to through resistance the one R3B7, the grid of field effect transistor Q3B1 is connected with the output terminal of the first diode D3B3, the other end be connected grid by resistance the 2nd R3B6 and control power supply, the input end of described first diode D3B3 is connected with the source electrode of field effect transistor Q3B1.
5. cable resistance testing circuit according to claim 3, it is characterized in that, described differential amplifier circuit comprises: the first triode Q2B3, second triode Q3B2, first peripheral resistance R3B8, second peripheral resistance R3B9, 3rd peripheral resistance R3B10, described first peripheral one end of resistance R3B8 is connected with the source electrode of field effect transistor Q3B1, the other end of described first peripheral resistance R3B8 is connected with the base stage of the first triode Q3B2, the collector of the second triode Q3B2 is respectively at the collector of the first triode Q2B3, the grid of field effect transistor Q3B1 is connected, the emitter of described second triode Q3B2 is respectively at the emitter of the first triode Q2B3, the normally closed contact of relay, one end of second peripheral resistance R3B9 is connected, the base stage of described first triode Q2B3 is the other end of peripheral resistance R3B9 with second respectively, one end of 3rd peripheral resistance R3B10 is connected, one end ground connection of described 3rd peripheral resistance R3B10.
6. cable resistance testing circuit according to claim 1; it is characterized in that; described interchange judges that protection circuit comprises: cable is electrically connected with the input end of two-stage reverse swing door circuit; the output terminal of two-stage reverse swing door circuit is connected with the first photoelectric coupled circuit U3A1; utilize optocoupler signal to output in control module, judge whether present cable has Alternating Current Power Supply.
7. cable resistance testing circuit according to claim 6, it is characterized in that, also comprise: the series circuit that cable is formed with mu balanced circuit with the second diode D3B1, bleeder circuit with inductance L 3B1, half-wave rectifying circuit is connected, the other end of described mu balanced circuit is electrically connected with the input end of two-stage reverse swing door circuit.
8. cable resistance testing circuit according to claim 6; it is characterized in that; also comprise: relay driving chip UB2C and protective relay RY3B1; the input end of described relay driving chip UB2C connects the output terminal of two-stage reverse swing door resistance, and the output terminal of relay driving chip UB2C connects the control end of protective relay RY3B1.
9. cable resistance testing circuit according to claim 1, it is characterized in that, described impedance detection circuit comprises the first amplifier UA9A, the second amplifier UA10A, the second optocoupler, described first amplifier UA9A one end connect the first divider resistance R3A1, second divider resistance R3A1 form bleeder circuit, described amplifier UA9A the other end connect one end of the second optocoupler, the other end of described second optocoupler connects the input end of amplifier UA10A, and the output terminal of described amplifier UA10A is connected with control module.
10. cable resistance testing circuit according to claim 9, it is characterized in that, described second optocoupler is linear optical coupling, the voltage of the light emitting diode of linear optical coupling can according to the difference of branch pressure voltage, there is different brightness, feed back to the photosensitive output terminal of linear optical coupling, the resistance of photosensitive output terminal can will change according to DC partial voltage voltage, and the voltage of change is input to control module after amplifier UA10A amplifies.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201510608793.XA CN105067892B (en) | 2015-09-22 | 2015-09-22 | A kind of cable resistance detection circuit |
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| CN201510608793.XA CN105067892B (en) | 2015-09-22 | 2015-09-22 | A kind of cable resistance detection circuit |
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| CN105067892A true CN105067892A (en) | 2015-11-18 |
| CN105067892B CN105067892B (en) | 2018-09-25 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN107688133A (en) * | 2017-10-26 | 2018-02-13 | 绵阳高新区探索科技有限责任公司 | Control box has access to electricity short-circuit detecting circuit on charging gun cable |
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| CN107688133A (en) * | 2017-10-26 | 2018-02-13 | 绵阳高新区探索科技有限责任公司 | Control box has access to electricity short-circuit detecting circuit on charging gun cable |
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| CN105067892B (en) | 2018-09-25 |
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