SE459948B

SE459948B - PROCEDURE AND ESTABLISHMENT FOR DATA COMMUNICATION THROUGH TWO WIRING THROUGH SIGNAL TRANSFER IN ONE DIRECTION THROUGH GENERATION OF VOLTAGE VARIATIONS AND IN THE OTHER THROUGH CURRENT VARIABLES

Info

Publication number: SE459948B
Application number: SE8704629A
Authority: SE
Inventors: J Ruus
Original assignee: Diantek Ab
Priority date: 1987-11-23
Filing date: 1987-11-23
Publication date: 1989-08-21
Also published as: SE8704629L; SE8704629D0; WO1989005074A1

Description

459 948 10 15 20 25 30 35 2 långa avstånd (åtminstone 3 km) med hög överföringshastighet (ungefär 19,2 kbaud). Ytterligare ändamål är att uppnå en okom- plicerad ledningsdragning och fri grenbarhet där några krav ej g ställes på ledningstyp. Vidare skall det föreligga en central spänningsförsörjning av terminalenheternas linjedel. Slutligen är ett väsentligt ändamål att anläggningen skall kunna.byggas > till låg kostnad. 459 948 10 15 20 25 30 35 2 long distances (at least 3 km) with high transmission speeds (about 19.2 kbaud). An additional purpose is to achieve an uncompromising pliable wiring and free branchability where no requirements g set on line type. Furthermore, there must be a central voltage supply of the line part of the terminal units. Finally is an essential purpose that the facility can be.built> at low cost.

De uppställda ändamâlen kan förverkligas genom förfarandet enligt uppfinningen som kännetecknas av att signalöverföringen på tvåtrådsnätet i en riktning sker genom alstring av balanse- rade spänningsvariationer medan signalöverföringen i motsatt riktning sker genom alstring av strömvariationer, som detekteras differentiellt av centralenheter.The stated objectives can be realized through the procedure according to the invention characterized in that the signal transmission on the two-wire network in one direction takes place by generating voltage variations while the signal transmission in the opposite direction takes place by generating current variations, which are detected differential of central units.

Detta förfarande kan i enlighet med uppfinningen genom- föras med en anläggning där centralenheten medelst ett organ som e orsakar polaritetsomkastning av en på tvåtrâdsnätet utmatad balanserad spänning, vilken polaritetsomkastning är detekterbar vid terminalenheterna, samt där varje terminalenhet innefattar strömreglerande organ för utmatning av en strömsignal från en strömgenerator till tvåtrådsnätet, vilken strömsignal är detek- terbar i centralenheten över tvâ, mot tvåtrådsnätet svarande strömavkännande organ, exempelvis resistorer.This method can be carried out in accordance with the invention. operated with a facility where the central unit by means of a body that e causes polarity reversal of an output on the two-wire network balanced voltage, which polarity reversal is detectable at the terminal units, and where each terminal unit includes current regulating means for outputting a current signal from a power generator to the two-wire network, which current signal is detected in the central unit over two, corresponding to the two-wire network current sensing means, such as resistors.

Föredragna utföringsformer Den föreliggande uppfinningen kommer nedan att beskrivas mer i detalj under hänvisning till bifogade ritningar, där -fig. 1 visar ett principschema för-anläggningen enligt uppfinningen, fig. 2 visar ett kopplingsschema för en utföringsform av centralenheten, fig. 3 visar ett kopplingsschema för en utföringsform av en terminalenhet enligt uppfinningen och fíg. 4 visar ett kopplingsschema för en modifierad utfö- ringsform av en terminalenhet enligt uppfinningen.Preferred embodiments The present invention will be described below in more detail with reference to the accompanying drawings, there -fig. 1 shows a schematic diagram for the installation according to the invention, Fig. 2 shows a wiring diagram for an embodiment of the central unit, Fig. 3 shows a wiring diagram for an embodiment of a terminal unit according to the invention and fig. 4 shows a wiring diagram for a modified embodiment form of a terminal unit according to the invention.

Datakommunikation över ett tvâtrådsnät N enligt den före- liggande uppfinningen sker i en riktning medelst balanserad spänningsmatning och i motsatt riktning medelst ström- É matning. Detta åskâdliggörs i ett principschema enligt fig. 1, som tillväm§æm'visar en centralenhet_C och till höger en av ett flertal likartat utformade terminalenheter T, vilka är à 10 15 2'o 25 30 35 .än Uï \O \ﬂ .Ps a) \ 3 parallellkopplade till tvåtràdsnätet N. Till tvåtrådsnätet N kan i princip ett obegränsat antal terminalenheter T anslutas.Data communication over a two-wire network N according to the the present invention takes place in a direction by means of balanced voltage supply and in the opposite direction by means of current- É feed. This is illustrated in a schematic diagram according to Fig. 1, which shows a central unit_C and to the right one of a plurality of similarly shaped terminal units T, which are à 10 15 2'o 25 30 35 .than Ui \O \ ﬂ .Ps a) \ 3 connected in parallel to the two-wire network N. To the two-wire network N In principle, an unlimited number of terminal units T can be connected.

Centralenheten C uppvisar en spänningsmatning +U, -U för terminalenheternas T linjedelar. Spänningsmatningen sker via en omkopplare, vars kontakter K1, K2 pâverkas av en relä- spole Re1. Reläspolen Re1 aktiveras med sänddata S1, som skall överföras från centralenheten C till en eller flera av terminal- enheterna T. Sålunda sker en omkastning av spänningsmatningen +U, -U på tvåtrådens N branscher N1, N2 vid sändning av data från centralenheten C.The central unit C has a voltage supply + U, -U for the line sections of the terminal units T. The voltage supply takes place via a switch, the contacts K1, K2 of which are affected by a relay coil Re1. The relay coil Re1 is activated with transmission data S1, which shall transmitted from the central unit C to one or more of the terminal units T. Thus a reversal of the voltage supply takes place + U, -U on the two-wire N branches N1, N2 when transmitting data from the central unit C.

Varje terminalenhet T är utformad med en spänningsdetek- tor för att avkänna den från centralenheten C utgående balanse- rade spänningssignalen +U, -U. I fig. 1 åskådliggöra spännings- detektorn med en differentialförstärkare D1 med inbyggd hysteres, vars utgång avger mottagna data M1. Den mottagna datasignalen M1 har en amplitud som utgör skillnaden mellan +U eller -U mätt mellan branscherna N1 och N2 såsom åskådliggörs i fig. 1A. Efter- som spänningssignalen +U, -U är balanserad (differential mode) kommer eventuella störningar (common mode) B ej att påverka den mottagna datasignalens M1 amplitud enär störningarna B uppträder riktade åt samma håll i tvâtrådsnätets N båda grenar, varvid ur- sprunglig skillnadssignal mellan +U och -U bibehålles.Each terminal unit T is designed with a voltage detector to detect the balancing output of the central unit C the voltage signal + U, -U. In Fig. 1 illustrate the voltage the detector with a differential amplifier D1 with built-in hysteresis, whose output outputs received data M1. The received data signal M1 has an amplitude that is the difference between + U or -U measured between industries N1 and N2 as illustrated in Fig. 1A. After- as the voltage signal + U, -U is balanced (differential mode) any interference (common mode) B will not affect it the amplitude of the received data signal M1 as the disturbances B occur directed in the same direction in both branches of the two-wire net N, whereby original difference signal between + U and -U is maintained.

För datakomunikation från en terminalenhet T användes ett strömreglerande organ, som i fig. 1 åskâdliggörs.med en brytare K3 vilken styrs av en reläspole Re2. Reläspolen Re2 aktiveras av sänddata S2 som skall överföras från terminalenheten T till centralenheten C. Brytaren K3 sluter och bryter en ström- krets, som via en likriktare L spänningsmatas från den centrala spänningsmatningen +U, -U och som inbegriper en strömgenerator G. Vid strömkretsens slutning alstras sålunda en ström i två- trådsnätet N. För att den i terminalenheten T ingående differen- tialförstärkaren D1 icke skall pâverkas av strömsignalen är differentialförstärkaren D1 utbalanserad såsom antyds med be- teckningarna V+ och V-.For data communication from a terminal unit T was used a current regulating means illustrated in Fig. 1 by a switch K3 which is controlled by a relay coil Re2. Relay coil Re2 is activated by transmission data S2 to be transmitted from the terminal unit T to the central unit C. The switch K3 closes and breaks a current circuit, which is supplied with voltage from the central via a rectifier L. voltage supply + U, -U and which includes a current generator G. Thus, at the end of the circuit, a current is generated in two wire network N. In order for the differential included in the terminal unit T The amplifier D1 shall not be affected by the current signal differential amplifier D1 balanced as indicated by the drawings V + and V-.

Den genom sänddata S2 alstrade balanserade strömsignalen inmatas sålunda på tvåtrâdsnätets N båda grenar. Vid central- enheten avkännes strömsignalen över två resistorer R1, R2, var- vid strömsignalen avkännes som två spänningsfallssignaler med 459 948 'i 10 15' 20 25 30 35 4 en kurvform i enlighet med fig. 1Ä. Dessa signaler är differen- s tiella till skillnad från störningar och inmatas på en differen- tialförstärkare D2 med hysteres via deriveringskretsen RC2. Den på differentialförstärkarens D2 utgång uppträdande mottagna data- signalen M2 är störningsokänslig av samma anledning som ovan an- förts beträffande den mottagna datasignalen M1.The balanced current signal generated by transmission data S2 is thus fed on both branches of the two-wire network N. At central unit, the current signal is sensed across two resistors R1, R2, each at the current signal is sensed as two voltage drop signals with 459 948 'i 10 15 ' 20 25 30 35 4 a curve shape according to Fig. 1Ä. These signals are different as opposed to disturbances and is entered on a different amplifier D2 with hysteresis via the derivation circuit RC2. The received data received at the output of the differential amplifier D2 the signal M2 is interference-sensitive for the same reason as above regarding the received data signal M1.

En utföringsform av centralenheten C visas i form av ett kopplingsschema i fig. 2. Därvid användes samma hänvisnings- beteckningar som i fig. 1 för organ som svarar mot varandra i de båda figurerna. Utöver vad som redovisas ovan i samband med fig. 1 kan noteras att centralenhetens C sänddata S1 inmatas via en fototransistor och däri detekterade mottagna data M2 uttages via en fotodiod. En schmidttrigger ST är ansluten till differen- tialförstärkarens D2 utgång för ytterligare undertryckning av eventuella störningar. Vidare kan noteras att centralenhetens C anslutning till tvâtrâdsnätet N är utförd medelst en skyddskopp- ling innefattande en högfrekvensdämpande transformator T1 och PTC-resistorer som skyddar vid kortslutning.An embodiment of the central unit C is shown in the form of a wiring diagram in Fig. 2. In doing so, the same reference designations as in Fig. 1 for corresponding bodies in the two figures. In addition to what is reported above in connection with Fig. 1 it can be noted that the transmission data S1 of the central unit C is input via a phototransistor and the received data M2 detected therein are taken out via a photodiode. A forge trigger ST is connected to the differential output of the amplifier D2 for further suppression of any disturbances. Furthermore, it can be noted that the central unit's C connection to the two-wire network N is made by means of a protective coupling comprising a high frequency attenuating transformer T1 and PTC resistors that protect in the event of a short circuit.

En utföringsform av terminalenheterna T visas i form av ett kopplingsschema i fig. 3. Därvid användes samma hänvisnings- beteckningar som i fig. 1 för organ som svarar mot varandra i de båda figurerna. Denna utföringsform är ej någon "äkta" ut- balanserad terminalenhet, men kan med fördel användas för många ändamål. Utöver vad som redan beskrivits i samband med fig. 1 kan noteras att terminalenheten T är galvaniskt isolerad från övrig utrustning som är ansluten till terminalenheten. Sålunda inmatas sänddata S2 via en fototransistor och detekterad balan- serad spânningssignal uttages via tvâ fotodioder P1, P2 före in- matningen på differentialförstärkaren D1, vars utgång uppvisar mottagna data M1. Anslutningen av terminalenheten T till två- trådsnätet N sker via en PTC-resistor som skyddar vid kortslut- å ning.An embodiment of the terminal units T is shown in the form of a wiring diagram in Fig. 3. The same reference designations as in Fig. 1 for corresponding bodies in the two figures. This embodiment is not a "genuine" embodiment. balanced terminal unit, but can be used to advantage for many purpose. In addition to what has already been described in connection with Fig. 1 it can be noted that the terminal unit T is galvanically isolated from other equipment connected to the terminal unit. Thus transmission data S2 is input via a phototransistor and detected balance voltage signal is taken out via two photodiodes P1, P2 before input the supply of the differential amplifier D1, the output of which has received data M1. The connection of the terminal unit T to two the wire mesh N takes place via a PTC resistor which protects in the event of a short circuit. å ning.

En modifierad utföringsform av terminalenheten T, som ger en "äkta" balansering av signaler som terminalenheten mottar Q från centralenheten C,visas i fig. 4. Balansering uppnås genom att spänningsdetektorn, som härvid utgörs av en dubbel vipp- c¿ 1» anordning D1' vilken företrädesvis har inbyggd hysteresfunktion, spänningsmatas symmetriskt i förhållande till tvâtrâdens N 10 15 e _459 948 5 potential. Genom den i fig. 4 visade kopplingen kan den mottag- na datasignalen M1 icke ändras med annat än att tvåtrâdens båda branscher N1, N2 samtidigt ändrar polaritet åt skilda håll.A modified embodiment of the terminal unit T, which provides a "true" balancing of signals received by the terminal unit Q from the central unit C, is shown in Fig. 4. Balancing is achieved by that the voltage detector, which in this case consists of a double flip-flop c¿ 1 » device D1 'which preferably has a built-in hysteresis function, voltage is supplied symmetrically with respect to the two-wire N 10 15 e _459 948 5 potential. Through the coupling shown in Fig. 4, the receiving The data signal M1 is not changed by anything other than both two-wire industries N1, N2 at the same time change polarity in different directions.

Kretsen G arbetar som en konstant strömgenerator genom att basspänningen på den i kretsen ingående transistorn hâlles inom ett snävt omrâde medelst en zenerdiod Z, som ingår 1 den ström- reglerande kretsen Re2, K3. Konstant basspänning ger konstant emitterspänning som ger konstant ström genom emittermotståndet Rg och därmed genom transistorn i kretsen G. Även om uppfinningen ovan i samband med fig. 2 - 4 be- skrivits och âtergivits som för närvarande föredragna utförings- former, så bör det inses att den i fig. 1 âskâdliggjorda upp- finningsprincipen kan förverkligas på olika sätt med olika elektronikkomponenter. Uppfinningen får därför ej anses vara be- gränsad till vad som ovan redovisats utan mâ anses omfatta hela den principiella lösning som definieras av efterföljande patent- krav.Circuit G operates as a constant current generator by the base voltage of the transistor included in the circuit is kept within a narrow range by means of a zener diode Z, which is included in the current regulating circuit Re2, K3. Constant bass voltage gives constant emitter voltage that provides constant current through the emitter resistor Rg and thus through the transistor in the circuit G. Although the invention above in connection with Figs. written and reproduced as currently preferred embodiments forms, it should be appreciated that the the principle of discovery can be realized in different ways with different electronic components. The invention must therefore not be considered limited to what has been reported above but must be considered to cover the whole the principal solution defined by the subsequent patent requirement.

Claims

4s9 94à 10 15 20 25 30 35 PATENTKRAV

Method for transmitting data via a two-wire network (N) between a central unit (C) and a plurality of centrally voltage-supplied terminal units (T), the central unit and the terminal units being connected in parallel to the two-wire network to allow bidirectional signal transmission between the central unit and the terminal units, whereby signal transmission in one direction takes place by generating voltage variations in the two-wire network (N) while signal transmission in the opposite direction takes place by generating current variations in the two-wire network, the voltage variations as well as the current variations on the two-wire network). (N1, N2) constitute balanced signals (Fig. 1A), which with respect to the voltage variations are generated by simultaneous reversal (via K1, K2) of the voltage supply (+ U, -U) in each industry and with respect to the current variations generated by breaking and closing (via K3) of a circuit (L, K3, G) connected to the said two branches er, the balanced signals being detected differentially by means of detection circuits (D1; D1 '; D2) with built-in hysteresis function.

Method according to Claim 1, characterized in that the current variation signal is used to balance (via V +, V-) the voltage variation sensing detection circuit (D1) so that it is unaffected by the generated current variations.

3. A method according to claim 1, characterized in that voltage drop signals generated over two resistors (R1, R2) of the current variation signal obtained from the two branches (N, N2) of the two-wire network (N) are supplied via a derivation circuit (RC2). to the detection circuit sensing the current variations (02).

A data communication system for two-wire network (N) and comprising a central unit (C) and a plurality of terminal units (T), the central unit and the terminal units being connected in parallel to each other to the two-wire network to allow bidirectional signal transmission between the central wires. 45 30 35 459 9418. 7 the signal and the terminal units, which signal transmission takes place in the form of voltage variations which emanate from the central unit (C) through a means (Re1, K1, K2) included therein and are detectable in the terminal units (T) by means of a first detection circuit (D1; D1 '), and in the form of current variations emanating from the respective terminal unit (T) through a current regulating means (Re2, K3) contained therein and fed to the two-wire network (N), the central unit (C) ) comprises current sensing means (R1, R2) corresponding to the two-wire network, over which the current signal supply coming from the two-wire network can be detected by means of a second detection circuit (D2), characterized in that the means (Re1, K1, K2) included in the central unit (C) comprise a two-pole two-position switch (K1, K2) arranged to generate a simultaneous polarity reversal of a balanced voltage output on the two-wire network (N) from the central unit (+ U, -U) in the respective industry (N1, N2), in that the current regulating means (Re2, K3) included in each terminal unit (T) comprise a switch (K3) for breaking and terminating a balanced current signal from a current generator (G) to the respective branch of the two-wire network (N) (N1, N2) via a rectifier (L), and by said first and second detection circuits (D1; D1 '; D2) has a built-in hysteresis function for detecting balanced voltage or balanced current signal that occurs in the two-wire network (N).

5. A system according to claim 4, characterized in that the two-position switch (K1, K2) is designed by means of bridge-connected transistor elements (Fig. 2).

Plant according to claim 4, characterized in that the current sensing means (R1, R2) consist of two resistors, arranged to generate voltage drop signals detectable by said second detection circuit (D2) via a derivation circuit (RC2).

7. A system according to claim 6, characterized in that the second detection circuit (D2) comprises a comparator, one input (-) of which is supplied with the voltage generated by the current signal supply across one resistor (R1). - the case and whose second input (+) is supplied with the voltage increase generated by the current signal supply across the second resistor (82) by the UAuçv 459 948 10 15 8.

Plant according to claim 7 ,. knows that a forging trigger (ST) is connected to the output of the comparator (D2), whereby both the forging trigger and the comparator have a built-in hysteresis function.

9. A system according to claim 4, characterized in that the First detection circuit comprises a differential amplifier (D1) with a built-in hysteresis function (Fig. 3).

10. n a d in that the first detection circuit comprises a double system according to claim 4, characterized by a flip-flop (D1 ') with a built-in hysteresis function (Fig. 4).

11. A system according to any one of claims 4 - 10, in that both the central unit's (C) and the terminal units' (T) connection to the two-wire network (N) is made via the PTC resistor (PTC), the central unit's connection also comprising a high-frequency attenuator transformer (T1).