EP2494534A1

EP2494534A1 - Safety communication system for signaling system states

Info

Publication number: EP2494534A1
Application number: EP10784684A
Authority: EP
Inventors: Jürgen TEUTENBERG; Simon Davis; Thomas Hüttemeier
Original assignee: Phoenix Contact GmbH and Co KG
Current assignee: Phoenix Contact GmbH and Co KG
Priority date: 2009-10-26
Filing date: 2010-10-25
Publication date: 2012-09-05
Anticipated expiration: 2030-10-25
Also published as: DE102009050692B4; WO2011054458A1; EP2494534B1; DE102009050692A1

Abstract

The invention relates to a safety communication system (1) comprising an analyzing unit (10) and a number of nodes (20, 30, 40) which are connected in series and each of which comprises a sensor (23, 33, 43). The invention also relates to a method for signaling system states. The analyzing unit (10) has a signal output (11), a signal input (12), a ground connection (15) and a device for providing a specified signal for the emergency stop units (20, 30, 40). Each node (20, 30, 40) has a signal input (21, 31, 41), a signal output (22, 32, 42), a ground connection (25, 35, 45) for a reference potential, a sensor (23, 33, 43), and an electronic switch (24, 34, 44). Each electronic switch (24, 34, 44) is designed to modulate the specified signal in order to signal the system state of the respective sensor (23, 33, 43). The analyzing unit (10) is designed to analyze the modulated specified signal and to control a safety function in response to the analysis result.

Description

Security communication system for

Signaling of system states

description

The present invention relates to a security communication system with an evaluation unit and a number of connected in series participants, each with a sensor and a method for signaling system states.

To avert danger to people, machinery and equipment in automation usually emergency stop and / or other sensors are provided at appropriate facilities with which the machinery or equipment can be switched off and put in a safe state. For spatially extended installations or

Automation systems, it is also necessary to provide multiple sensors, such as emergency stop button, temperature sensors, pressure sensors, treadmills, photoelectric sensors and the like, for optimum accessibility in

To ensure danger.

It is an object of the invention to provide a security communication system and a method by which a signal for a critical system state, e.g. an emergency signal, reliably signaled and the source of a signal can be clearly located.

To achieve this object, the present invention proposes a security communication system for providing a security function, which is an evaluation unit comprises, to which a number of subscribers connected in series is connected.

The evaluation unit has a signal output, a

Signal input, a ground terminal and means for providing a predetermined signal for the participants.

The subscribers each have a signal input, a signal output, a ground connection for

Reference potential, a sensor and an electronic circuit. Every electronic circuit is for

Modulating the predetermined signal formed to signal the system state, which by the

Output signal of the respective sensor is displayed.

The evaluation unit is for evaluating the modulated predetermined signal and for controlling a

Safety function in response to the

Evaluation result developed.

The sensor may be, for example, a

Emergency stop switch, a temperature sensor, a pressure sensor, a step mat, a light barrier and a protective grid act. The output signal of a sensor indicates a critical or a non-critical system state. A critical system condition causes the

Evaluation unit triggers a safety function.

Advantageously, the predetermined signal is modulated by the subscribers such that the evaluation unit in response to the modulated predetermined signal or which can locate those subscribers who have signaled a critical system condition.

An advantageous embodiment provides that the electronic circuit of each participant a

Logic module and at least one transistor, wherein the transistor is controlled by the logic device. The transistor is arranged between the signal input to the signal output of the respective subscriber and adapted to be applied to the signal input

to modulate predetermined signal and over the

Signal output to the evaluation unit or a

transfer downstream subscribers. The electronic circuit can furthermore be designed to supply a supply voltage for the subscriber directly from the signal input (21, 31, 41)

win predetermined signal so that no separate auxiliary power must be provided.

The electronic circuit expediently comprises a second transistor with which the signal input can be switched to the reference potential. The logic block of the electronic circuit is

preferably with an internal function monitoring

equipped, via the second transistor a

Signaling of an error condition can take place by the predetermined signal pulled to the reference potential and thus no longer transmitted to the input of the evaluation. The above technical problem is further solved by the method steps of claim 6.

Accordingly, a method of signaling

System states of several series-connected participants a safety communication system provided, comprising the following steps:

a) generating a predetermined signal in the

evaluation;

b) outputting the predetermined signal from the

Evaluation unit to the first participant of

Security communication system;

c) modulating the received predetermined signal in the first subscriber in a predetermined manner;

d) outputting the modulated predetermined signal to another subscriber;

e) modulating the received, modulate predetermined signal in the further subscriber in dependence of the state signal, which of the, the further

Subscriber assigned sensor is provided; f) repeating steps d) and e) depending on the number of subscribers in the security

Communication system;

g) outputting the modulated predetermined signal from the last subscriber in the security communication system to the evaluation unit;

h) evaluating, in the evaluation unit, the received,

modulated predetermined signal and controlling a safety function when a critical system state has been signaled by at least one subscriber. In order for each participant to signal the activation of a sensor, the predetermined signal contains a signal pulse whose pulse length depends on the number of subscribers connected in series.

Conveniently, steps c) and e) provide for this that each participant modulates the signal pulse of the predetermined signal as a function of the system state of its sensor.

In order to be able to locate the subscriber who has signaled a critical system status, each subscriber preferably modulates the signal pulse of the predetermined signal according to their position in the security communication system. Preferably, each modulates

Subscribers the signal pulse at its assigned point within the signal pulse and / or preferably with an individual modulation signal. So that the participants secure the predetermined signal

can recognize the predetermined signal

Start impulse and have a first break, the

Precede signal pulse. Furthermore, the signal pulse may include an end pulse followed by a second pause which is longer in time than the first pause.

To monitor a plant throughout

To be able to ensure operation, the steps a) to h) are cyclic or at predetermined times

repeated, whereby the switching states of the participants cyclically or at the predetermined times to the

Evaluation unit can be transmitted. Appropriately, before the execution of step a), a configuration phase is run through, in which the

Evaluation unit determines the number of participants within the security communication system and in which the participants determine their position within the security communication system.

The security communi cation system according to the invention is distinguished from known security systems by a localizability of all in the security communi cation system participants who signal a critical system state. By the automatic

Determining the number and position of the participants, such a security communication system is particularly easy to extend.

The shape and the frequency of the predetermined signal have sufficient robustness against interference, so that safety communication systems with

Cable lengths of more than 1 km in length are possible. The cycle times of the signal transmission are sufficiently short for more than 20 participants to meet the requirements of the

Safety technology for automation systems to meet.

The invention will be described below with reference to an exemplary embodiment with reference to the attached

Drawings described in detail. In the drawings show:

1 an emergency stop circuit with three emergency units and an evaluation unit, 2 is a schematic circuit diagram of an emergency unit with a coupled to an electronic circuit emergency stop switch,

Fig. 3 is a signal-time diagram of the emergency stop circuit

during an automatic configuration phase,

4 shows a signal-time diagram of the emergency stop circuit

during a normal working operation, i. if no emergency stop switch is switched, and

Fig. 5 is a signal timing diagram of the emergency stop circuit at two of three activated.

The security communication system 1 shown by way of example in FIG. 1 may be an emergency shutdown circuit which has an evaluation unit 10 and, for example, three subscribers 20, 30 and 40 connected in series, for example distributed in a field on a wide area

Automation system are attached. The participants 20, 30, 40 are also referred to below as emergency payouts

referred to, which each have an emergency stop button 23, 33, 43 as a sensor, with which a safety function can be requested on an equal basis. The series-connected participants 20, 30, 40 form one

Affiliate chain.

As can be seen from the figure 1, the

Emergency stop switches 23, 33, 43 each connected to an electronic circuit 24, 34, 44, which is for each

Emergency stop provide a secure electronic coupling to the emergency stop circuit. The evaluation unit 10 has a signal output 11 and a signal input 12, at which the three

Emergency units 20, 30 and 40 are connected in series. The emergency units are each one above each other

Signal inputs 21, 31, 41 and signal outputs 22, 32, 42, which are provided by the electronic circuits 24, 34, 44. The evaluation unit 10 may have not shown further signal outputs and signal inputs to which further Notauseinheiten not shown in each case are connected in series, the additional parallel

Form participant chains.

So that the emergency units in particular the operation of the respective emergency switch of the evaluation unit 10th

the evaluation unit 10 generates a predetermined signal UA (see Fig. 4), the

Signal output 11 is output. This signal UA can essentially be embodied as a binary voltage signal which is varied between a high and a low level, wherein the low level preferably corresponds to the reference potential GND at a ground terminal 15 of the evaluation unit 10. The voltage signal UA is used to transmit

Information between the emergency units and the

Evaluation unit and provides an advantageous way

equally a supply voltage for the

electronic circuits 24, 34, 44 and / or for the

Sensors ready. The circuits 24, 34, 44 of the Notauseinheiten 20, 30, 40 of the emergency stop circuit 1 are constructed identically, so that in Figure 2, only the diagram of the emergency unit 20 is exemplified. The circuit diagram represents

In particular, the structure of the circuit 24 is detailed.

The circuit 24 comprises a signal input 21, a signal output 22 and a logic module 210, the

preferably by a microcontroller or alternatively by an FPGA, CPLD or an ASIC can be realized.

The emergency stop switch 23 is two-channel at the logic module 210 via ports P8 and P9 and ports Pll and P12

connected. For such a two-channel and thus secure connection to the circuit, all two-channel emergency stop switches available on the market are basically suitable, i. In principle, both emergency stop with two NC or two NO contacts, as well as a

NC / NO pair can be used for the emergency unit. The appropriately used switch type must only by software or hardware means on the

Logic block 210 can be set. Alternatively, other sensor types, such as running mats, temperature and pressure sensors, light barriers, protective grids, etc., can also be connected to an emergency stop unit. Furthermore, several sensors can be connected via an emergency stop unit via different ports of the logic module 210.

The circuit 24 includes a transistor 220 and, optionally, a transistor 260 connected to its respective one

Gate are connected to the logic device 210. The transistor 220 is between the signal input 21 and the Signal output 22 is connected, while the transistor 260 is connected between the signal input 21 and the ground terminal 25. Alternatively, the second transistor 260 could also be connected between the signal output 22 and the ground connection 25. The logic module 210 controls the

Transistors 220 and 260 such that the am

Signal input 21 applied voltage signal UA, which is the predetermined signal, can be modulated by the transistor 220 and output to the signal output 22.

By means of the transistor 260, the voltage signal UA at the input 21 can be pulled to the reference potential of the ground terminal 25, whereby all participants of the

Emergency stop circuit, i. the evaluation unit 10 and the other in the series circuit following

Notauseinheiten 33, 43 an error condition can be signaled.

The electronic circuit 24 further has a diode 231 and a capacitor 232 connected between the signal input 21 and the ground terminal 25 with the

Reference potential GND are connected in series and provide a power supply 233 a power supply for the logic device 210. For example, the supply device 233 may be designed as a switched-mode power supply or as a voltage regulator.

From a signal varying between 0V and 24V at the signal input 21, a constant supply voltage of e.g. 3.3 V or 5 V are obtained for the logic device, so preferably no additional

Line for an auxiliary power of emergency units 20, 30, 40 is required in an emergency stop circuit. Alternatively, however, can also lead an additional line, the supply voltage to the Notauseinheiten and this associated emergency stop. The power supply does not take place in this case via the signal lines, so that the diode 231 and the capacitor 232 can be omitted in favor of an additional connection.

The operation of the emergency stop circuit 1 as well as of the individual emergency units connected in series is explained below with reference to the signal-time diagrams for various operating states shown in FIGS. 3 to 5. At this point, be explicit

indicated that at the shown in the figure 1

Emergency stop circuit only exemplary three emergency units are connected. The emergency stop circuit 1 is

basically for the operation with a variety of

Notauseinheiten suitable distributed along a route of a spatially extended automation system and are connected to each other in series. Of the

Emergency shutdown circuit 1 in particular allows easy expandability to additional Notauseinheiten, for example, between the emergency unit 30 and the

Emergency unit 40 can be inserted. The

Safety function of the emergency stop circuit is guaranteed from a connected emergency stop unit.

At each startup, the emergency stop circuit 1 first passes through a configuration phase in which the number of connected Notauseinheiten 20, 30, 40 by the

Evaluation unit 10 is determined and determine the Notauseinheiten their position in the series circuit. At the start In this configuration phase, the transistor 220 of a respective emergency unit is initially disabled, so that the configuration signals shown in FIG

Signal inputs 21, 31, 41 of the respective Notauseinheiten not initially to their signal outputs 22, 32, 42nd

to get redirected.

FIG. 3 shows the voltage curves of the configuration signals UAk, UBk, UCk and UDk generated during the configuration phase, which are respectively connected to the signal inputs 21, 31, 41 of the emergency shutdown unit 20, 30 and 40 and to the

Signal input 12 of the evaluation unit 10 abut,

shown. The configuration signal UAk is generated by the evaluation unit and transmitted via the signal output 11 to the input 21 of the first emergency stop unit 20. The configuration signal UAk is e.g. through a

generated in the evaluation unit 10 and follows a predetermined pulse sequence with respect to a system clock. At the time t 1, a first energy pulse 311 is initially applied to the signal output 11, which remains present for a duration of three clock cycles Tb and essentially to the

Supply of emergency units serves. The signal UAk is reset for one clock, so that a signal pause 312 follows the energy pulse 311. Following is a

Signal pulse 313 sent over the duration of a clock, followed by a second pause 314 of two clocks.

With reference to FIG. 2, it becomes clear that the first emergency unit 20 is awakened by the energy pulse 311. The delivered by the evaluation unit 10

Voltage signal UAk is between the input 21 and the Ground connection 25. It provides a charging current over the duration of the three clocks, which flows in the flow direction through the diode 231. The capacitor 232 is charged during this time and thus, in particular in the signal pauses the supply voltage for the

Supply device 233 and the microcontroller 210 ready. The microcontroller of the emergency unit 20 thus starts operating and recognizes via a

Signal recognition device, which is formed from the voltage divider of the resistors 241 and 242, thus the single subsequent signal pulse 313 before the second pause 314. The emergency unit 20 registers itself as the first participant in the series circuit of

Emergency stop circuit 1 after the evaluation unit 10th

Meanwhile, the evaluation unit 10 initially detects no input voltage at its own signal input 12 and concludes that at least one emergency shutdown unit is connected in the emergency shutdown circuit.

Accordingly, the evaluation unit 10 outputs a second energy pulse 321 via the signal output 11, which is followed, after a break 322, by a second signal pulse 323, which is three clocks wide. The first emergency stop unit 20 receives at its signal input 21 the energy pulse 321 and the signal pulse 323 of the signal UAk and outputs these pulses through the now open transistor 220 to the signal output 22 as a second signal UBk, wherein the second signal UBk by the Notauseinheit 20 such

is modulated that the signal pulse 323 during a

Takts Tb is hidden. The second signal UBk contains thus a high level 3231, a low level 3232 and a second high level 3233.

The second emergency stop unit 30 thus receives at its signal input 31, the voltage signal UBk, the

Energy pulse 321 and subsequently the high level 3231, the low level 3232 and the second high level 3233 identifies. The voltage signal UBk thus corresponds to the modulated signal UAk, which has been generated by the evaluation unit 10. The emergency unit 30 is now activated by the energy pulse 321 and recognizes itself as a second party, i. as a second emergency stop unit 30 in the emergency stop circuit. The evaluation unit 10 still recognizes no

Input signal at its signal input 12 and outputs a third energy pulse 331 via the signal output 11, followed by a signal pause 332 and a third signal pulse 333. The third signal pulse 333 is widened compared to the previous cycle second signal pulse 323 by a further two clocks, and thus includes

altogether a width of 5 bars Tb.

The emergency disengaging units 20 and 30 respectively output a modulated signal UBk and UCk (see FIG. 3) via their respective signal output 22, 32. The first emergency stop unit 20 modulates the signal UAk such that the signal pulse 333 is hidden during a clock Tb. The second signal UBk thus contains a high level and a low level of the length Tb and a second high level 333 'of three times the length of Tb. The second emergency stop unit 30 receives the signal UBk and modulates its signal pulse 333 'such that the signal pulse 333' is hidden during a clock Tb. The signal UCk thus contains a high level 3333, a low level 3334 and a second high level 3335 each of the clock length Tb.

The third emergency stop unit 40 receives the signal UCk and recognizes itself as the third emergency stop unit 40 in FIG

Emergency stop circuit, while the evaluation unit 10 continues to receive no input signal at its signal input 12.

The evaluation unit 10 sends in its signal UAk a further energy pulse 341 and a fourth signal pulse 343, which compared to the third signal pulse 331

is again extended by two bars Tb, and thus comprises a total width of seven bars Tb. The

transmitted signal UAk is modulated and forwarded by each emergency stop unit 20, 30, and 40. In this case, each emergency unit modulates the signal UAk in such a way, for example, that each emergency unit outputs a low level of the length Tb in the

Signal pulse 343 inserts, d. H. that in each case a clock within the signal pulse 343 is hidden. The signals UBk, UCk and UDk correspondingly modulated by the emergency cutouts 20, 30 and 40 are shown in FIG. At the signal output 42 of the third emergency stop unit 40, the signal UDk is output, which contains the energy pulse 341 as well as the signal pulse 343 modulated by all three emergency cutouts, which contains four high levels 3431, 3433, 3435 and 3437, each by a low level from each other are separated.

The evaluation unit 10 now receives at its

Signal input 12 that of the emergency unit 40 passed signal UDk and thus registers a total of three connected to the emergency stop circuit

Notauseinheiten 20, 30, 40 and thus closes the

Configuration phase.

If the configuration of the emergency stop circuit fails due to the influence of electromagnetic interference, the configuration phase can also be repeated several times until stable communication is established.

The time profiles of the differential voltages (UAk-UBk), (UBk-UCk) and (UCk-UDk) shown in FIG. 3 show in which time intervals the capacitors 323 of the emergency cutouts 20, 30 and 40 are charged.

Alternatively, at the participants, i. in the present example, the emergency units whose respective position are set manually in a subscriber chain, which are coded for example by DIP switches or stored in a non-volatile memory. In the same way, the number of existing Notauseinheiten can be set or stored on or in the evaluation unit 10. The configuration phase after the commissioning of the

Emergency stop circuit is in this case by a

Initialization phase during which the participants are supplied with energy at the same time. For this purpose, for example, a long energy pulse is provided.

Preferably, after a first start-up a

Manually triggered configuration phase after the configuration data of the emergency stop circuit is stored in the non-volatile memories of the participants, so that after each further commissioning only the

Initialization phase must be completed.

FIG. 4 illustrates the normal operation of the

Notausschaltkreises 1 on the condition that no emergency stop switch 23, 33, 43 has been operated.

After the completion of the configuration phase, the evaluation unit 10 generates an exemplary, cyclical,

predetermined signal UA, which is output via the signal output 11 to the first emergency stop unit 20. The temporal signal course of the signal UA is shown in FIG. 4 above. The signal UA contains in each cycle a start pulse 410 having the width of a clock Tb, followed by a pause or low level 420 of length Tb. The pause 420 is followed by a signal pulse 430 whose length depends on the number of emergency cutouts present in the emergency stop circuit. The signal pulse 430 contains in each case two clocks Tb for each emergency stop unit connected to the emergency stop circuit 1 and an additional end pulse 437 of length Tb. In the present example, with a total of three connected emergency cutouts 20, 30 and 40, this corresponds to a signal width of a total of seven clock cycles Tb Signal pulse 430 is followed by a pause or low level 440 of two clock lengths Tb, with a

Signal cycle is completed.

The emergency stop unit 20 receives the above-described signal UA at the signal input 21 in each cycle and modulates the signal pulse 430, for example, such that during predetermined clocks the signal pulse 430 is hidden. In the present example, the signal pulse 430 is modulated by means of the transistor 70 in such a way that the signal pulse 430 starts with a high level 431 of length Tb, followed by a low level 432, that is to say a hidden section, of length Tb. The remainder of the signal pulse 430, labeled 430 'in FIG. 4, is not modulated. The modulated signal UA is now transmitted as a signal UB to the emergency stop unit 30. The emergency stop unit 30 thus receives the start pulse 410, the pause 420 and the

modulated signal pulses 431, 432 and 430 '. In the present example, the emergency unit 30 modulates only the

Signal pulse 430 'of the received signal UB, in a similar manner as the emergency unit 20. For this purpose, the signal pulse 430' is modulated such that it starts with a high level of length Tb, which is a low level or hidden portion of the Length Tb connects. The remainder of the signal pulse 430 ', labeled 430 "in FIG. 4, is not modulated. The modulated signal UB is now transmitted as a signal UC to the emergency unit 40.

The emergency stop unit 40 thus receives the start pulse 410, the pause 420 and the signal pulse modulated by the upstream emergency units 20 and 30. In the present

Example, the emergency unit 40 modulates only the

Signal pulse 430 '' of the received signal UC, in a similar manner as the emergency units 20 and 30. For this purpose, the signal pulse 430 '' is modulated such that it starts with a high level of length Tb, which is a low level or Hidden section of length Tb connects. The rest of the signal pulse 430 '', the only the final pulse

437 is not modulated. The modulated signal UC is now used as the signal UD to the evaluation unit 10th transfer. The signal pulse 430 initially generated by the evaluation unit 10 now comprises three high levels 431, 433 and 435 corresponding to the number of emergency units present as well as the end pulse 437, each by a

hidden section are separated. The evaluation unit 10 recognizes from the received signal DU that no emergency stop switch has been actuated.

The difference signals (UA-UB), (UB-UC) and (UC-UD) show at which time intervals the capacitors 90 of the emergency cut-off units 20, 30 and 40 are recharged. To recharge the power supply is the respectively

Signal pulse used, which is hidden in the transmission or in the modulation by the respective Notausseinheit.

FIG. 5 shows the signal-time diagrams for the case in which the first and third emergency shutdown units 20 and 40 are connected to the

Time t3 report an actuated emergency stop, while the second emergency stop unit 30 of the series circuit does not send an emergency stop signal. The point in time t3 can be understood as meaning that the evaluation unit 10 has already transmitted a plurality of signals UA, with no actuation of an evaluation unit 10 until the time t3 of the evaluation unit 10

Emergency stop switch has been signaled.

The evaluation unit 10 furthermore generates the cyclic, predetermined signal UA described in FIG. 4, which via the signal output 11 to the first emergency-off unit 20

is issued. The temporal signal profile of the signal UA is shown at the top in FIG. 5 and corresponds to the signal shown in FIG. The emergency stop unit 20 receives in current cycle the already described signal UA at the signal input 21 and modulates the signal pulse 530, which corresponds to the signal pulse 430 of the signal UA shown in FIG. 4, such that the actuation of the emergency stop switch 23 of the evaluation unit 10 can be signaled. For this purpose, the signal pulse 530 shown in Fig. 5 can be modulated by means of the transistor 70 such that the received signal pulse 530 starts with two low levels 531, 532, which have the length 2Tb. In other words, the signal pulse 530 in the emergency off unit 20 is blanked out for the time of a double clock length Tb. The remainder of the signal pulse 530, labeled 530 'in FIG. 5, is not modulated. The modulated signal UA is now used as the signal UB

Emergency unit 30 transferred. The emergency stop unit 30 thus receives the start pulse 510, the pause 520 and the

modulated signal pulse consisting of the low levels 531 and 532 and the high level 530 '. Since the emergency unit 30 does not have to signal an emergency stop signal, it modulates the

Signal pulse 530 'of the received signal UB in the

same as in the example which has been explained with reference to FIG. The signal pulse 530 'is therefore modulated so that it starts with a high level 533 of length Tb, which is a low level 534 or

hidden portion of the length Tb connects. The remainder of the signal pulse 530 ', labeled 530 "in FIG. 4, is not modulated. The modulated signal UB is now transmitted as a signal UC to the emergency unit 40. The emergency stop unit 40 thus receives the start pulse 510, the break 520 and the signal pulse modulated by the upstream emergency units 20 and 30. The emergency unit 40 only modulates the signal pulse 530 "of the received signal UC in such a way that the actuation of the

Emergency stop 43 can be signaled. For this purpose, the signal pulse 530 "is modulated such that it begins with two low levels 535 and 536 and two blanked sections, each with the length Tb. The rest of the

Signal pulse 530 '', which only contains the final pulse 537, is not modulated. The modulated signal UC is now used as the signal UD to the evaluation unit 10th

transfer.

The initially generated by the evaluation unit 10

Signal pulse 530 now comprises a high level 533 and the end pulse 537. The evaluation unit 10 recognizes from the low levels 531, 532 and 535, 536 of the received signal UD that the emergency stop switches 23 and 43 of the emergency shutdown units 20 and 40 have been actuated ,

Instead of the method described above, the configuration phase could initially be followed by a reporting phase, which is not shown in the figures. Within this

Notification units signal the emergency units 20, 30, 40 of the evaluation unit 10 only, if at all

Safety function must be activated or not.

For this purpose, the evaluation unit 10 sends a cyclical, predetermined signal to the first emergency stop unit 20 via its signal output 11. This signal comprises a characteristic start pulse, which preferably differs from the starting pulse of the operating mode, for example in the width, followed by a signal pulse having a predetermined width. The predetermined width the signal pulse is preferably not dependent on the number of Notauseinheiten in a subscriber circle in the reporting phase. All Notauseinheiten 20, 30, 40 receive the predetermined signal at its signal input 21, 31, 41 and forward this non-modulated to the subsequent participants, unless an emergency stop button has been pressed. If a critical system state, ie an actuated emergency stop switch, is to be signaled by one of the emergency shutdown units, then the received signal can be signaled by hiding one

predetermined position in the signal pulse to be modulated. During the reporting phase, all emergency units are assigned the same position in the signal pulse for signaling. The signaling of one or more critical

System states by one or more participants is thus OR-linked.

The evaluation unit 10 is therefore only signaled in this reporting phase, if any critical system state, i. an actuated emergency stop switch is present and whether the safety function is to be activated.

Once an emergency unit 20, 30, 40 actuated one

Emergency stop signaled, the emergency stop circuit from the evaluation unit 10 in the previously described

Work operation staggered. The evaluation unit determines in the method described above which

Emergency unit signals an actuated emergency stop.

The reporting phase offers shorter cycle times compared to the above-described operating mode, as long as no actuated emergency stop switch is signaled. This is particularly advantageous for a large number of emergency units in the subscriber chain. If errors occur, for example, as a result of short circuits or line breaks in the emergency stop circuit 1, then the evaluation unit 10 receives at least no complete signal UD at its signal input 12. In response to an incompletely received signal UD, the

Evaluation unit 10 also a security-based

Trigger function and signal an error.

The microcontroller 210 of the emergency units 20, 30, 40 can additionally determine an internal malfunction, for example a failed channel of a two-channel connected emergency stop switch, independently. Such a

Error can be from an emergency unit, such as the emergency unit 20, the evaluation unit 10 thereby

be signaled that the transistor 260 of the

electronic circuit 24 short-circuits the signal input 21 to the ground terminal 25. The evaluation unit 10 thus receives an incomplete signal UD and closes from the transmitted short-circuit signal to a faulty signal UD and can then trigger a safety-related function and / or an error signal. For control of a modulated signal 42 of a Notauseinheit ^'20, 30 may be at the signal output 22, 32, 40 a second

Signal detection device may be provided, which includes the resistors 251 and 250.

Claims

Security communication system (1) for providing a security function comprising:

an evaluation unit (10) to which a number of subscribers (20, 30, 40) connected in series

is connected, where

the evaluation unit (10) has a signal output (11), a signal input (12), a ground connection (15) and a device for providing a

predetermined signal for the participants, the participants (20, 30, 40) each one

Signal input (21, 31, 41), a signal output (22, 32, 42), a ground terminal (15, 25, 35, 45) for a reference potential, a sensor (23, 33, 43) and an electronic circuit (24, 34, 44), each electronic circuit (24, 34, 44) for

Modulating the predetermined signal is adapted to signal a critical or uncritical system state, which is represented by the output signal of the respective sensor, and wherein

the evaluation unit for evaluating the modulated predetermined signal and for controlling a

Safety function in response to the

Evaluation result is formed.

Security communication system according to claim 1, characterized in that

the evaluation unit (10), in response to the modulated predetermined signal, can locate the subscriber or those subscribers who have signaled a critical system condition. Security communication system according to claim 2, characterized in that the electronic

Circuit (24, 34, 44) of each participant one

Logic module (60) and at least one transistor

(220), wherein the transistor (210) can be controlled by the logic module (210) and is arranged between the signal input (21, 31, 41) and the signal output (22, 32, 42) of the respective subscriber and is designed to operate on the Signal input (21, 31, 41) modulating predetermined signal and via the signal output (22, 32, 42) to the evaluation unit

(10) or a downstream participant

transfer .

Security communication system according to claim 3, characterized in that the electronic

Circuit (24, 34, 44) is designed such that it can gain a supply voltage from the signal input (21, 31, 41) applied to the predetermined signal.

Safety communication system according to claim 3 or 4, characterized in that the electronic circuit (24, 34, 44) comprises a second transistor (260) with which the signal input (21, 31, 42) to the reference potential (25,35, 45) is switchable.

Method for signaling at least one

System state of a security communication system (1), which has an evaluation unit (10) and a plurality of subscribers (20, 30, 40) connected in series, each subscriber having at least one sensor

assigned,

comprising the following steps:

a) generating, in the evaluation unit (10), a predetermined signal (UA);

b) outputting the predetermined signal (UA) from the evaluation unit (10) to the first participant (20) of the security communication system;

c) modulating the received predetermined signal in the first subscriber (10) in dependence on the output signal which is received from a sensor (23) associated with the first subscriber

provided;

d) outputting the modulated predetermined signal to another subscriber (30);

e) modulate the received, modulate

predetermined signal in the further subscriber (30) in dependence on the status signal, which is provided by a, the further subscriber associated sensor (33);

f) repeating steps d) and e) in

Dependence of the number of participants of the

Security communication system;

g) outputting the modulated predetermined signal (UD) from the last participant (40) of the safety communication system to the evaluation unit

(10);

h) Evaluate, in the evaluation unit, the

received, modulated predetermined signal and controlling a safety function when a critical system state has been signaled by at least one participant. A method according to claim 6, characterized in that the predetermined signal includes a signal pulse whose pulse length of the number of in series

switched participants

wherein steps c) and e) follow the steps

include:

Each participant modulates the signal pulse of the predetermined signal in dependence of

System state of his sensor.

Method according to claim 7,

characterized in that

each subscriber receives the signal pulse of the predetermined signal according to their position in the

Security communication system (1) modulated.

A method according to claim 7 or 8, characterized

characterized in that the predetermined signal comprises a start pulse and a first pause preceding the signal pulse and the signal pulse includes an end pulse followed by a second pause which is longer in time than the first pause.

Method according to one of claims 7 to 9, characterized in that the received predetermined

Signal is modulated such that the signal pulse at at least one predetermined location for a

is faded out predetermined time.

A method according to claim 10, characterized in that the hidden part of the signal pulse for Generation of a supply voltage of the subscriber is used.

Method according to one of claims 6 to 9, characterized in that the steps a) to h) are repeated cyclically.

Method according to one of claims 6 to 10, characterized in that prior to step a) a

Configuration phase in which the evaluation unit (10) determines the number of subscribers (20, 30, 40) within the security

Determined communication system and in which the participants determine their position within the security communication system.