AS-Interface
The AS-Interface ( AS -i abbreviated for engl Actuator Sensor Interface, . German Actuator Sensor Interface ) is a standard for field bus communication, which has been developed for connecting actuators and sensors. The aim is to replace the existing parallel cabling. The AS-Interface is used here mainly on the Sensor-/Aktuatorebene. The AS-Interface is since 1999 an international standard according to EN 50295 and IEC 62026-2.
History
1990 initiated the company Balluff, Baumer, Elesta, Festo, ifm electronic, Leuze electronic, Pepperl Fuchs, Sick, Siemens, Turck and Visolux a system for networking sensors and actuators. The idea for the AS-Interface system was born. In a consortium, the implementation began with the simple and cost-effective system solution, partially funded by the Federal Ministry of Education and Research (formerly the Federal Ministry for Research and Technology ) funded and in cooperation with the Technical University of Leipzig, Institute of Automation Systems ( IfAS, Director: Werner Kriesel ) and the University of Karlsruhe, Forschungszentrum computer science ( FZI, conductor: Klaus Bender). Just one year later, the club eV was founded to promote bus-capable interfaces for binary sensors and actuators (Head: H. Walker, Managing Director: OW Madelung ), the AS-International Association today as the interests of the rd. 300 member companies representing the world and this representative offices in 13 industrialized countries, maintains (Head: D. Knauer, R. Becker). The project was divided into three sub- objects, where one member of the consortium took over the sponsorship to support the development. The projects were: slave electronics, MasterCard, including software and electrical engineering ( Technical direction: A. Schiff).
Use
The AS-Interface (. From the English Actuator Sensor Interface) has been developed as an alternative to conventional parallel wiring of sensors and actuators, and provides the following benefits:
- Flexibility
- Economy
- Simplicity
- Reduction of installation errors
- High distribution
- Best networking opportunities
By determinism and simplicity of use of this bus type to the lowest level of control is limited.
Technology
The AS- Interface is a single -master system, ie, a master cyclically polls all configured slaves and exchanges them with the input and output data. A telegram consists of 4-bit payload. The master communicates with a serial communication protocol with the participants.
Each slave is assigned by an addressing or via the master a unique address. You can connect a maximum of 62 participants ( the specification version 2.1) originally were only 31 stations can be addressed (version 2.0), since only 5 bits are used for addressing. The address 0 must not be used, since all the slaves in the delivery state have this address, this address is also used for the Automatic address programming. Each slave can have four inputs or outputs for actuators or sensors, making 124 inputs or outputs can be controlled ( in version 2.0), or 248 inputs and 186 outputs ( in version 2.1).
The transmission medium is an unshielded two-wire yellow ribbon cable is used, the same time the power supply ( 24-30 VDC ) photocells used for communication electronics and for participants with low power requirements, eg. Consumers with a higher energy requirement such as valve terminals receive a separate, usually black ribbon cable for power supply. This transported 24 V DC voltage. For actuators that require 230 V, a supply via a red 230 - V cable is alternatively possible.
The sensors and actuators are often connected via the so-called penetration technique. Here, the isolation of the reverse-polarity protected profiled ribbon cable by means of two Piercing pins is pierced in the assembly without this has to be prepared in advance, which slaves can be added without major installation costs at any time. Sensors and actuators, which have no AS-interface connection can be connected to the bus via Anschaltungsmodule.
For modules in an insulation a special AS -Interface flat cable must be used. Serial communication is modulated onto the power supply. Occur while the Manchester encoding and an APM coding ( alternating pulse modulation ) is used. By the Manchester encoding DC-free signals are obtained. Then, a sinusoidal voltage signal is generated. The signal can be produced with the aid of two comparators again. There are bit - times of 6 microseconds realized.
About 150 microseconds are required by the Master Pro subscriber; For 31 participants is the cycle of 5 ms, including the management time ( 150 s ) and the exposure time ( 150 s ). To address 62 participants, two cycles are required.
The topology of the AS-Interface is arbitrary (except for a ring structure ) without repeaters or extenders, the line length 100 m but not exceed. Due to the low frequency of 167 kHz no terminating resistors are required. Through a special terminator ( a combination of resistive and capacitive load), it is possible to increase the maximum cable length to 300 m.
Diagnostic devices or master with built-in diagnostic functions simplify troubleshooting in networks. Unusual Slaves can be replaced easily and automatically re-addressed by the master.
Standardization
The AS interface is standardized in EN 50295 and IEC 62026-2. The certification of AS -i products assumes the AS -International Association. Tests or certifications ensure that devices from different manufacturers to work together.
The current standard is the AS-Interface Specification 3.0. With 2:11 to 62 slaves at 2.0 but only 31 slaves can be controlled.
With AS- i Safety at Work, a certified standard was developed, which allows the use of safety-related components in the AS -Interface network. These include safety monitors, emergency- off operations, Door locks, light grids / curtains and optical scanners. The concept of Safety at Work has been certified by TÜV (Technical Inspection Association ) and the Institute for Occupational Safety and German Social Accident Insurance.