DE102007002953A1 - Switching arrangement for outputting switching signal to e.g. machine controller, has switching unit generating analog measuring signal, whose characteristics are independent of type of error-free load by switching components - Google Patents

Abstract

The arrangement (1) has a switching unit for generating a switching condition of a switching signal, where the switching unit is controlled by a computer unit (4). The switching unit is switched for a preset time period for execution of an error control, and generates analog measuring signals, whose characteristics are independent of the type of error-free external load (2) by switching components of the arrangement in the case of no error, where the switching characteristics are read in the computer unit for analysis of error conditions.

Description

The The invention relates to a circuit arrangement for outputting a switching signal.

circuitry of this kind are used in particular for devices which are used in the field of safety engineering. Such devices can scan from optical sensors such as light curtains Distance sensors or the like may be formed by means of which a Hazardous area monitored on a machine or plant becomes. In such a sensor, a binary switching signal is generated, indicate its switching states, whether an object in the danger area or not. If there is no object in the danger area, There is no hazardous condition. Accordingly, about the Switching signal in this case, the machine or system in operation set. If an object is in the danger zone, there is a dangerous condition in front. Accordingly, via the switching signal in this Case the machine or plant out of service.

such Devices, in particular sensors, have output circuits forming circuit arrangements, via which the switching signal to an external load such as a contactor or a Control outputs, by means of which then the machine or Plant is controlled.

Around the devices, or sensors, in the field of Safety technology must be able to use these have the required level of security failure safety. This is especially true for the output circuits forming circuit arrangements of such devices. Dement spreader The circuit arrangements must by suitable methods be checked for error detection.

Such a circuit arrangement and a method for its verification is known from DE 100 59 751 B4 known. The circuit arrangement described therein serves to check an output of an electrical component for high-resistance connection to the supply voltage, the component and / or its connecting line having a capacitance.

through a switch is a short-term, incomplete Discharging the capacity to a residual voltage with a Sample & Hold circuit this Residual voltage stores.

A connected to the output of the electrical component constant current source serves to further discharge the capacity during a predetermined period of time. In a differential voltage measuring device becomes a voltage difference between the residual voltage and the discharge voltage measured at the constant current source. One to the differential voltage measuring device connected output unit is used to output an error signal, when the discharge voltage is equal to or greater than the stored residual voltage remains.

adversely here is that for error control only two measuring points be used, so that different fault patterns of the component only can be distinguished inadequately. Furthermore, can the circuit itself insufficiently checked for errors become. Finally, the error control is on a specific Type of component, that is an external load with a capacity and a resistance limited.

Of the Invention is the object of a comprehensive, each of the connected load largely independent error control for a circuit arrangement of the type mentioned provide.

to Solution of this problem are the features of claim 1 intended. Advantageous embodiments and expedient Further developments of the invention are in the subclaims described.

The Circuit arrangement according to the invention serves for Output of a switching signal to an external load and includes switching means for generating the switching states of the switching signal and a Computer unit, by means of which the switching means can be controlled. To perform an error control is the switching means switched over for a given period of time. One by generated analog measurement signal whose waveform through circuit components the circuit arrangement in error-free case at least largely regardless of the nature of the external load, is in the Computer unit for analyzing error conditions read.

One An essential advantage of the invention is that for error control generated measurement signals by providing suitable circuit components in the circuit arrangement according to the invention at least largely independent for the error-free case from the external load. This means that the measurement signal is independent can be used by the external load for error control that is, by the evaluation of the measurement signal can for different connected to the circuit Loads reliable Error of the circuit itself or be uncovered in the external load.

Another essential advantage of the invention is that an analog measurement signal is generated for error control whose time course in the circuit arrangement for detecting is evaluated by errors in the computer unit.

There thus not only individual discrete measurement points but a waveform curve a measurement signal is a comprehensive and detailed Analysis of different error patterns possible. This one Measurement signal curves are largely load-independent, can these with simple Auswerteroutinen in the computer unit to uncover also complex error images are evaluated.

To these errors, which are revealed in the circuit arrangement can count next to the low-resistance connections In particular, high-resistance compounds, ie direct or indirect conclusions against supply voltage. indirect In particular, conclusions can be made with two channels Circuit arrangements occur in which the switching signal via two switching outputs is specified. In this case can a cross-circuit between both switching outputs is revealed become. Furthermore, in the inventive Circuitry internal conclusions in the circuit arrangement yourself or external conclusions in the connected Load to be uncovered.

In a particularly advantageous embodiment of the invention are used as circuit components for generating a largely load-independent measuring signal a constant current source and a diode is used.

Farther is the analog measurement signal via an analog-to-digital converter read into the computer unit and is then there for evaluation directly available. It is advantageous for error control the respectively read measurement signal curve in the computer unit stored setpoint waveforms compared.

The so constructed circuit arrangement has a small number of discrete circuit elements and is thus rational and cost-effective produced.

The Error control of the circuit arrangement according to the invention expediently takes place cyclically within predefined Test cycles. The error control in the circuit arrangement takes place generally in such a way that thereby the loading operating state of the Circuit arrangement connected load remains unchanged, that is, the function of the load is determined by the functional test not impaired. Conveniently, For this purpose, the switching means is switched so briefly that thereby the operating state of the load does not change.

The Invention will be explained below with reference to the drawing. It shows:

1 Embodiment of a circuit arrangement for outputting a switching signal.

1 shows an embodiment of a circuit arrangement 1 for outputting a switching signal to an external load 2 , The circuit arrangement 1 is part of an implementable in safety technology device, in particular an optical sensor for monitoring a danger zone on a machine or the like. In this case, the sensor monitors whether an object is in the surveillance area or not. Depending on this, the binary switching signal is generated whose switching states indicate whether an object is in the monitoring area or not. To avoid danger to persons, the machine is put out of operation if an object is in the danger zone. On the other hand, the machine is put into operation when there is no object in the danger zone. For this purpose, the switching signal to the external load 2 output, which then controls the machine accordingly. Weight 2 may generally be formed by a contactor, a controller or the like. In the event that the load 2 is formed by a contactor, whose operating conditions are "contactor attracted or dropped" by the switching state of the switching signal.

The circuit arrangement 1 according to 1 has a single-channel structure. Accordingly, the circuit arrangement 1 one a line 3 having switching output, via which the switching signal to the load 2 is issued. The circuit arrangement comprises as essential components a computer unit 4 and an output circuit consisting of discrete circuit components 5 for the output of the switching signal. In a two-channel version of the circuit arrangement 1 these components are duplicated, so that accordingly two switching outputs are provided.

The computer unit 4 the circuit arrangement 1 is formed by a microcontroller or a digital signal processor. In the computer unit 4 is an analog-to-digital converter 6 integrated. The output circuit 5 has switching means in the form of a low-side driver 7 and a high-side driver 8th on. The low-side driver 7 and the high-side driver 8th are designed as semiconductor switches, in particular in the form of transistors. With the low-side driver 7 the switching of the line forming the switching output takes place 3 against ground potential. With the high-side driver 8th a switching of the line takes place 3 against supply voltage V _B , where the output of the high-side driver 8th over at the resistance 8a is performed on supply voltage V _B. The low-side driver 7 is via a supply line 9 from the computer unit 4 controlled. The high-Si de-driver 8th is via a supply line 10 also from the computer unit 4 controlled. By controlling the low-side driver 7 and the high-side driver 8th be through the computer unit 4 the signal levels on the line corresponding to the switching states of the switching signal 3 specified.

The output circuit further comprises a constant current source 11 and a diode 12 on. The constant current source 11 is via another supply line 13 from the computer unit 4 from controlled.

The external load 2 is in 1 flat rate as an equivalent circuit diagram with a capacity 14 and a resistance 15 characterized.

at For example, contactors are also inductive load characteristics possible.

To meet the requirements for use in the field of safety technology is used for the circuit arrangement 1 according to 1 cyclically carried out an error control. This error control is performed in such a way that I thereby the operating state of the connected load 2 does not change.

The error control is via the computer unit 4 controlled. Within a test cycle is generally a measurement signal in response to switching the switching means of the circuit 1 evaluated.

In the present case, at the beginning of a test cycle, first the high-side driver 8th opened and then over the supply line 9 the low-side driver 7 switched over for a short time. In this case, in this embodiment, the low-side driver 7 briefly switched so that the line 3 of the switching output is connected to ground potential. This pre-discharges the capacity of the load. Then the low-side driver 7 opened again. Then the circuit is defined via the constant current source 11 loaded. That by the line 3 Generated analog measurement signal is via the diode 12 guided and via the analog-to-digital converter 6 in the computer unit 4 read.

The time course of the measurement signal is thus as an analog measurement signal curve in the computer unit 4 to disposal. To detect different errors, this measurement signal curve is in the computer unit 4 compared with a desired signal curve. From the specific deviations of the measured signal curve from the desired signal curve different fault patterns can be distinguished from each other. For example, a strong signal increase indicates opening of the low-side driver 7 to a hard short circuit to supply voltage V _B out.

During a test cycle, the constant current source becomes 11 switched on. The constant current source 11 forms with the diode 12 Circuit components, by means of which it is achieved that the measurement signal curve in the error-free case and also in certain fault patterns largely independent of the specific design of the load 2 is. This means that regardless of whether an inductive or capacitive load 2 or the like to the circuit arrangement 1 is connected, at least in error-free case, almost the same measurement signal curve is obtained.

Due to this extensive invariance of the measurement signal curve, the error control in the computer unit 4 be carried out with simple evaluation routines. It is particularly advantageous here that only a limited number of desired signal curves in the computer unit 4 must be deposited in order to be able to discover different errors by comparing them with the respective measurement signal curves.

The detectable errors include, in particular, high-resistance connections to the supply voltage, with direct and indirect inferences from the supply voltage generally being detectable here. Indirect inferences may in particular be cross-circuits between the switching outputs of a two-channel circuit arrangement 1 act.

In general, internal and external conclusions, that is, conclusions within the circuitry, can be used 1 itself or in the pipes 3 to the load 2 or be revealed in this yourself.

In the embodiment, a capacitive load 2 with a resistance 15 and a capacity 14 (For example, a PLC input) to the circuitry 1 connected. At the beginning of a test cycle becomes the high-side driver 8th turned off and then the low-side driver 7 briefly over the computer unit 4 switched so that the line 3 of the switching output is connected to ground potential. This leads to a discharge of capacity 14 the load 2 , Since the switch-off of the switching output is so fast, the operating state of the load remains 2 unchanged during the test cycle.

In the error-free case is by switching the low-side driver 7 the diode 12 via the switched-on constant current source 11 discharge, leaving the measurement signal after switching the low-side driver 7 drops. If there is a break in the supply voltage, the voltage drops across the diode 12 However, not off, so switching to the low-side driver 7 the measuring signal does not drop, but rises. This error can be corrected by comparing the measured signal curve with the setpoint nal curve representing the error-free case.

1

circuitry

2

load

3

management

4

computer unit

5

output circuit

6

Analog to digital converter

7

Low-side driver

8th

High-side driver

9

supply

10

supply

11

Constant current source

12

diode

13

supply

14

capacity

15

resistance

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 10059751 B4 [0005]

Claims (16)

Circuit arrangement ( 1 ) for outputting a switching signal to an external load ( 2 ), with a switching means for generating the switching states of the switching signal, with a computer unit ( 4 ), by means of which the switching means is controllable, wherein the switching means for a predetermined period of time is switched to carry out an error and an analog measurement signal generated thereby, whose waveform through circuit components of the circuit in error-free case at least largely independent of the type of error-free external load ( 2 ) is in the computer unit ( 4 ) is read to analyze error conditions. Circuit arrangement according to Claim 1, characterized that the measurement signal to the by the switching operation of the switching means affected switching signal corresponds. Circuit arrangement according to one of claims 1 or 2, characterized in that the measuring signal via an analog-to-digital converter ( 6 ) in a computer unit ( 4 ) is read. Circuit arrangement according to Claim 3, characterized in that the computer unit ( 4 ) is formed by a microcontroller or digital signal processor. Circuit arrangement according to Claim 4, characterized in that the analog-to-digital converter ( 6 ) in the computer unit ( 4 ) is integrated. Circuit arrangement according to Claim 4, dg of the computer unit ( 4 ) an external analog-to-digital converter ( 6 ) assigned. Circuit arrangement according to one of claims 1 to 6, characterized in that as a circuit components for generating one of the load ( 2 ) at least substantially independent measuring signal a constant current source ( 11 ) and a diode ( 12 ) are provided. Circuit arrangement according to claim 7, characterized in that an internal and external error control can be carried out cyclically within predetermined test cycles for these, wherein within a test cycle the constant current source ( 11 ) is turned on. Circuit arrangement according to one of claims 7 or 8, characterized in that the measuring signal via the diode ( 12 ) the analog-to-digital converter ( 6 ) is supplied. Circuit arrangement according to one of claims 1 to 9, characterized in that as switching means a low-side driver ( 7 ) and a high-side driver ( 8th ) are provided, wherein by means of the low-side driver ( 7 ) a switching of the switching signal leading line ( 3 ) at ground potential and by means of the high-side driver ( 8th ) a switching of the line ( 3 ) to a reference potential. Circuit arrangement according to Claim 9, characterized in that during a test cycle the high-side driver ( 8th ) and then the low-side driver ( 7 ) is switched. Circuit arrangement according to one of claims 1 to 11, characterized in that in the error control of the operating state of the load ( 2 ) remains unchanged. Circuit arrangement according to claim 12, characterized in that the switching of the switching means for error control takes place so briefly that the operating state of the load ( 2 ) does not change. Circuit arrangement according to one of the claims 1 to 13, characterized in that it has a two-channel Structure has. Circuit arrangement according to one of the claims 1 to 14, characterized in that for error control the temporal Gradients of the measured signals compared with setpoint waveforms become. Circuit arrangement according to one of the claims 1 to 15, characterized in that in the error control direct or indirect conclusions against supply voltage detectable are.