AU687187B2

AU687187B2 - Process for the low-energy interrogation of binary states over long lines

Info

Publication number: AU687187B2
Application number: AU22135/95A
Authority: AU
Inventors: Siegmar Zirkl
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1994-04-19
Filing date: 1995-04-07
Publication date: 1998-02-19
Anticipated expiration: 2015-04-07
Also published as: JPH09512116A; CN1145701A; EP0756773A1; DE4413467C1; AU2213595A; EP0756773B1; DE59503173D1; WO1995028760A1; ATE169782T1

Abstract

A process for the low-energy interrogation of binary states over long lines (5) by means of a monitoring circuit (4). The latter is connected via a bus coupling circuit (2) to bus lines (1) of a bus system for energy and information transmission in a building system. A long line (5) is charged with low-energy pulses of one polarity with respect to reference potential as long as a connected actor or sensor (component (6)) has a high voltage or is open. The potential of the long line (5) is discharged via the actor or sensor (component (6)) when the latter is at a low voltage or is closed.

Description

METHOD FOR THE LOW-ENERGY INTERROGATION OF BINARY STATES OVER LONG LINES The invention relates to a method and apparatus for the low energy s interrogation of binary states over long lines.

It has been disclosed to charge a long line with respect to reference potential by means of low-energy pulses of one polarity as long as a connected actuator or sensor is at high voltage or is in the open state, the capacitance of the long line being discharged via the actuator or sensor when the latter is at low voltage or is in the closed state. An optocoupler between the long line and a bus coupler circuit performs the interrogation in an isolated fashion with respect to the bus line. Such power monitoring is disclosed by a corresponding circuit arrangement (DE-A-4 142 254).

When it is necessary for actuators or sensors with a binary output or with an output which acts approximately as a binary output to be connected via long lines to a bus system, the capacitance of the long line is disturbing. If, for example, switched contacts have to be interrogated for their circuit state over long lines, only 10 mA, for example, are available in conjunction with a potential of 5 volts in a bus system at the user interface, AST. It is therefore the intention for the interrogation of the circuit state of the binary output to be performed with as little power as possible, not to say without power, and without the expense of an additional conventional information transmission system.

soas In order to monitor binary outputs or inputs in the case of switching contacts S. so as to obtain information on the circuit state of the switching contact, it is known to carry out low-power interrogation for an installation bus in building systems 25 engineering in conjunction with electrical isolation between the contact and binry input :elements of a monitoring circuit (DE-A-4 142 254). When low-energy pulses are sent via a line for the purpose of interrogating a binary state and as a consequence of the closed state arrive again at a coupling element of a monitoring circuit, the current pulses are transformed into voltage pulses, entered by a memory with the action of a 30 flip-flop and converted into a continuous hRA," 1"'ATO Ili.ilibEl0l41 1:VXF 111~-- GR 94 P 3188 P 2 PCT/DE 95/00472 output signal, which represents the closed contact to be monitored with one potential value and represents the opened contact with a lower potential value.

In monitoring systems in which pulses run to an actuator or sensor to be monitored, difficulties increasingly occur with increasing line length because of the capacitance thereof. Precisely in the case of low-energy short pulses, the latter are short-circuited with increasing line length as a result of the capacitance thereof, with the result that the circuit state of the actuator or sensor to be monitored is no longer reliably indicated. Such actuators to be monitored can, for example, be motion detectors and anemometers or dusk detectors. Sensors can indicate door and window positions or serve as glass breakage detectors.

When thinking of carrying out low-energy monitoring by means of particularly small currents, the difficulty is encountered that, seen in the longer term, with currents of below 1 mA contacting problems occur which increase with the number of contacts situated in series.

It would be necessary from this point of view to use higher currents which, however, would require an impermissibly high drawing of current from the bus system. On the other hand, because of the low available energy and the increased expenditure associated therewith, drivers are excluded for economic reasons. The measured line capacitances for long monitoring lines which are to be connected to a bus system are of the order of magnitude of 120 pF/m. In the case of a line of a length of 100 m, such as is easily encountered in glass breakage detectors, the line then already attains a capacitance of 12,000 pF or 12 nF.

0 AMENDED SHEET

C)

GR 94 P 3188 P PCT/DE 95/00472 2a It is the object of the invention to develop a method for the low-energy interrogation of binary states over long lines, in which method it is possible to interrogate reliably the circuit state of an element to be monitored.

-r rAJ~W AMENDED SHEET In accordance with one aspect of tile present invention, there is provided a method of interrogating a binary device connected to a monitoring circuit having at least one long line therebetween, said at least one long line including a capacitance related to its length, the monitoring circuit being further connected to an energy and information carrying bus line associated with a building via a bus coupled circuit, said method comprising the steps of.

applying low energy single polarity pulses to the long line, so that when the binary device is at a high or open state, the long line charges with respect to a reference voltage, and further so that when the binary device is at a low or closed state, the long line discharges with respect to the reference voltage, and outputting a signal from an output of an optocoupler means associated with the monitoring circuit in accordance with the state of the binary device, wherein: if the binary device is at a high or open state, the pulses are applied only until the long line has charged with respect to the reference voltage.

In this case, a long line is respectively charged with respect to reference potential via a filter circuit by means of low-energy pulses of one polarity as long as a connected actuator or sensor is at high voltage or is in the open state. A specific voltage at the line input of the filter circuit causes a voltage switchover to the optocoupler, as a result of which the latter is activated. This event is avaflable as signalling event for the open state of the line. In the case of the closed state and voltage reduction on the long line, the activating voltage is drawn from the optocoupler by means of the filter circuit, something which is available as signalling event for the closed state of the long line. However, circulating pulses are avoided, and the energy, drawn from the bus system, for low-energy pulses is used, as in the case of a memory circuit, to build up a DC voltage potential. Thus, for example, pulses of a duration of approximately 50 its can be repeated at an interval of approximately 4 ins, The pulses, increased to a voltage of the order of magnitude of 24 volts, for example, ensure currents of over I mA over the long line and to the closed contact 6.

During interrogation, electrical isolation between the actuators or sensors to be interrogated and the bus system is ensured in a tried and tested fashion by means of optocouplers.

The circuit arrangement has a pulse generator which is connected to a filter arrangement which, on the one hand, leads via the long line to an actuator or sensor which is to be connected, and leads, on the other band, via an optocoupler which leads on its other potential side to the user interface, AST, of a bus coupler, Depending on the potential level of the long line, on the one hand from low potential the potential in the long line is then built up, and in the case of high potential O jn:VibE101411:VXF GR 94 P 3188 P 3a PCT/DE 95/00472 with an open contact a path is produced starting from the filter arrangement via the optocoupler, with the result that the open state can be indicated via the optocoupler with particularly low losses by the optocoupler emitting and controlling its other potential side to be conductive. In the case of a circuit arrangement for carrying out the method, it is advantageous in this case to set the line capacitance, in conjunction with a resistor, for example in AMENDED SHEET GR 94 P 3188 P 4 the circuit arrangement for example, to a time constant which is small, as far as possible negligibly timall, by comparison with operating delays of the bus system.

It is particularly advantageous to arrange circuit means for pulse rounding in the current path between the pulse generator and long line in order, upon build-up of the DC voltage potential in the long line, not to permit any pulses. with steep edges to run into the long line. This prevents the long line from being able to act as an antenna and radiating interference which is to be avoided for the purpose of EMC. Such circuit means for pulse rounding can be composed of RC elements in the simplest case. It is also possible to use resonance circuits having a free-wheeling diode for cutting off the ring-back during the pulse generation. This is particularly advantageous on the secondary side of a transformer for multiplying the voltage of the pulses generated by the pulse generator on the primary side.

Exemplary embodiments of the invention are now to be explained in more detail with the aid of a drawing reproduced in a coarsely diagrammatic fashion in which Figure 1 shows an arrangement of bus line, bus coupler, monitoring circuit and long line to an element which is to be monitored for its binary state, and Figure 2 shows an exemplary embodiment of a monitoring circuit for four elements, that is to say actuators or sensors, to be monitored.

In the arrangement according to Figure 1, a bus line 1 leads from two conductors to a bus coupler circuit 2 such as is customary, for example, in the bus system of the European Installation Bus Association, EIBA (see also Siemens printed publication: instabus EIB, 11/92, Order No. E20001-P311-A613-Vl, pages 26-29). Connected to the user interface 3, AST, is a monitoring circuit 4 which monitors an element 6, which is to be monitored, -for its circuit state via a GR 94 P 3188 P long line 5. The element to be monitored can be regarded as a switching contact; however, it can equally well be a customary binary input, a so-called standard binary input. It is essential that the element 6 to be monitored, that is to say a connected actuator or sensor, is monitored for its circuit state by charging the long line 5 with respect to reference potential as long as a connected actuator or sensor is at high potential or is in the open state and the drop in the potential as a consequence of the discharging of the line potential via an actuator or sensor in the case of the closed state of the latter or in the case of low voltage is used to detect the other circuit state. The entire supply for the monitoring circuit and for the interrogation of the element 6 to be monitored is to be extracted from the voltage source, limited to 10 mA at 5 volts, from the user interface 3 from the bus system.

The pulse generator 7 can be designed, for example, for repeating pulses with a duration of approximately 50 ps at an interval of 4 ms. In the case of an open circuit state of the element 6 to be monitored, a potential is built up with respect to reference voltage in the long line 5 by means of the pulses 8 of the pulse generator 7. In the exemplary embodiment, the pulse generator 7 is connected to a filter circuit 9 which, on the one hand, produces a connection to the long line 5 as long as in the case of an open state af the element 6 to be monitored the potential is built up on the line 5, and which, with the potential built up, produces a connection to the optocoupler 10. The optocoupler serves the purpose of electrical isolation between the long line 5 and bus line 1. The interrogation is then performed in an isolated fashion with respect to the bus line 1. The response of the optocoupler 10 serves as a sign that the element 6 to ,be monitored is in the "high" binary state. Apart from power losses, virtually no kind of energy transport then takes place over the long line 5. The capacitance of the line 5 is demonstrated by the capacitors [sic] 11.

i GR 94 P 3188 P 6 The monitoring circuit 4 according to Figure 2 draws energy for pulse generation in the pulse generator 7 from the bus coupler circuit 2. In conjunction with an amplifier circuit 14 and a filter circuit 15, pulses are fed to a voltage multiplier connection 16, a transformer in the exemplary embodiment of the primary winding.

Capacitors 12 and resistors 13 in the filter circuit are advantageously tuned to a time constant RC of 20 ms for switching operations of the order of magnitude of 100 ms in the bus system. In any case, the time constant should be very much smaller than the time of the switching operations in the bus system. Reactions of the pulses on the bus coupler circuit 2, which effects the power supply, are avoided by the filter circuit The voltage multiplier connection 16 in the embodiment as a transformer has the advantage that electrical isolation occurs. On the secondary side of the transformer, a circuit 17 ensures the pulses 8 are rounded. The circuit 17 essentially comprises a resonance circuit 18, and a free-wheeling diode 19 for cutting off the ring-backs on the secondary side of the transformer.

From the circuit 17 for rounding the pulses, branches lead to four filter circuits 9 for four elements 6 to be monitored. The filter circuits are connected, on the one hand, to a common return conductor via the long line 5 and, on the other hand, to optocouplers 10. The voltage multiplier connection 16, designed as a transformer, and the optocouplers 10 form a plane 20 of electrical isolation. Each element 6 can be considered as representative of a series circuit composed of elements 6.

In the case of voltage multiplication to 24 volts on the secondary side of the voltage multiplier connection 16, and at the given -[alues for the pulse generation, the current flow via the contacts is limited -to 6 mA. The assigned current flow simultaneously has the task of charging the line A GR 94 P 3188 P 7 PCT/DE 95/00472 capacitance of the long line 5, of the order of magnitude of 120 pF/m upon opening of the contacts as quickly as possible. Te time constant formed by the line capacitance and the internal resistance of the current source should be negligible by comparison with operating delays on the bus 1. Upon closure of the contacts of elements 6 to be monitored, the time delay advantageously acts only to a reduced extent, since the line capacitance is quickly discharged via the relatively low resistance of the line. A new circuit state is thereby indicated in the shortest time. A relatively high initial current flows in a long line 5 upon discharge of the long line, for example upon closure of a switching contact of a sensor or element 6 to be monitored. A binary state of the element 6 to be monitored is also meant in this case by an open and closed circuit state. Both switching contacts and binary outputs are subsumed under this. As already explained at the beginning, a high initial current over the long line 5 promotes contact stability, since oxidation residues are burnt off to a certain extent.

The potential on the long line 5 is built up in the case of an open contact 6 of the element to be monitored in each case via the resistor R and the valve V 1 of the filter circuit 9. The voltage drop across the valve V 1 is far smaller than the sum of the flow voltages of the diode V 2 of the filter circuit 9 and of the diode 21 of the optocoupler. The optocoupler thus does not respond yet; as a result of which the downstream capacitor 22 remains discharged. The output 23 of an inverter 24 thereby remains "high", that is to say inactive. If, after the potential has been built up, contacts of elements 6 to be monitored are now closed, a relatively high initial current, which promotes contact stability, flows in the case of relatively long lines of the orde: of magnitude of from 100 m. These AMENDED SHEET GR 94 P 3188 P 8- PCT/DE 95/00472 currents, which do not load the bus system, burn off oxidation residues, with the result that contact stability remains ensured.

Lines of up to 1000 m can be connected by means of low-energy pulse operation and with a low outlay using the mode of procedure outlined. Current-carrying driver stages are nevertheless superfluous. In each case, instead of one element 6 to be monitored, it is possible to conceive of a corresponding series circuit of elements to be monitored, along the lines of Figure 2.

The inverters, 24 reproduced in Figure 2 and the inverters in the pulse generator 7 and in the amplifier section 14, can, in particular, be chips on an inverter gate such as is available on the market.

AMENDED SHEET

Claims

1. A method of interrogating a binary device connected to a monitoring circuit having at least one long line therebetween, said at least one long line including a capacitance related to its length, the monitoring circuit being further connected to an energy and information carrying bus line associated with a building via a bus coupled circuit, said method comprising the steps of: applying low energy single polarity pulses to the long line, so that when the binary device is at a high or open state, the long line charges with respect to a reference voltage, and further so that when the binary device is at a low or closed state, the long line discharges with respect to the reference voltage, and outputting a signal from an output of an optocoupler means associated with the monitoring circuit in accordance with the state of the binary device, wherein: if the binary device is at a high or open state, the pulses are applied only until the long line has charged with respect to the reference voltage.

2. A method of interrogating a device as claimed in claim 1, wherein the single polarity pulses have an amplitude of at least 24 volts. 20

3. A circuit arrangement for performing the method according to claim 1 or 2, wherein: the monitoring circuit includes a pulse generator for providing the single polarity pulses, a filter connected between the pulse generator and the long line is provided for opening an input of the optocoupler means when a specific voltage on the long line has i been reached, and for closing the input of the optocoupler means when the specific voltage has not been reached, the bus coupler circuit includes a user interface connected to the output of the optocoupler means, and the switching of the filter is influenced by an RC network having a time constant smaller than that of an operating delay time associated with said bus system.

4. A circuit arrangement according to claim 3, wherein a pulse rounding circuit is arranged between the pulse generator and the long line. A circuit arrangement according to claim 4, wherein the pulse rounding circuit includes an RC network.

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6. A circuit arrangement according to claim wherein the pulse rounding circuit comprises a resonance circuit and a free wheeling diode for cutting off the ring-back.

7. A circuit arrangement according to claim 6, wherein a voltage multiplier is provided to multiply the voltage of the pulses generated by the pulse generator.

8. A circuit arrangement according to claim 7, wherein the voltage multiplier is a transformer.

9. A method for interrogating a device, substantially as herein described with reference to Figs 1 and 2. *e 20 a* S a

10. to Figs 1 and 2. A circuit arrangement, substantially as herein described with reference DATED this Eleventh Day of November 1997 Siemens Aktiengesellschaft Patent Attorneys for the Applicant SPRUSON FERGUSON *a a a. IN.\LIBEIO 41 1:VXF