AS-Interface (AS-i) System – Complete Basic Guide

AS-i ----------- Actuator-Sensor Interface

📘 1. Introduction to AS-i System

• Definition: AS-Interface (AS-i) is a networking solution used at the lowest field level of industrial automation systems. It connects sensors and actuators to higher-level controllers like PLCs via a simple two-wire cable.

• Purpose: Reduce wiring complexity, simplify installation, and increase modularity in automation systems.

• Target Audience: Automation technicians, engineers, maintenance personnel.

📜 2. History and Development of AS-i

• Early 1990s: Developed by a consortium of 11 automation companies, including Siemens and Pepperl+Fuchs.

• Standardization: AS-i became an international standard:

• Key Milestones:

• AS-i V2.0: Better diagnostics

• AS-i Power24V: Integration with 24V systems

• AS-i Safety at Work: SIL3/PLe-certified safety over the same network

• AS-i V3.0: Improved configuration and diagnostics

🔧 3. System Components

A. Master

• Central controller communicating with higher-level PLCs or DCS.

• Example: Siemens AS-i Master Module

B. Slaves

• Intelligent I/O modules connected to sensors and actuators.

• Addressed via software or hardware dip switches.

C. Power Supply

• Delivers power and data over a single 2-wire unshielded flat cable.

• Typical: 30 VDC

D. AS-i Cable

• Flat 2-conductor cable (yellow for standard, black for AUX power)

• Piercing technology allows easy installation (IDC connectors).

E. Connectors, Repeaters, Terminators

• Accessories for extending range, simplifying connections.

⚙️ 4. How AS-i Works

• Topology: Tree, line, or star topology.

• Data Transmission: Cyclic polling – Master polls each slave sequentially.

• Addressing: Up to 62 devices (slaves) per AS-i network (with V3.0).

• Cycle Time: ~5 ms for 31 devices, up to 10 ms for 62 devices.

Example:

• An AS-i system controlling conveyor photocells and actuators in a warehouse with a single AS-i master module communicating with 30 I/O blocks over 100 meters.

✅ 5. Advantages of AS-i

📚 10. Resources & References

• AS-International Association

• Siemens AS-i Master Manual

• Pepperl+Fuchs AS-i Integration Guide

• IEC 62026-2 Standard Documentation

Mostafa Sayed