This CPU module delivers powerful processing capabilities for complex automation applications. The Schneider ALU 821 features a 32-bit microprocessor with floating-point arithmetic support. It executes logic programs at high speed, scanning 1,000 boolean instructions in just 0.2 milliseconds. The module supports up to 2,048 I/O points for extensive system integration. Its advanced architecture handles both discrete and analog control with equal efficiency.
Physical Dimensions and Mechanical Design
The CPU module measures 135 mm in height, 110 mm in depth, and 50 mm in width. This robust form factor ensures stable mounting within standard rack systems. Weighing approximately 0.85 kg, the ALU 821 offers substantial durability for industrial environments. A reinforced metal casing provides excellent shielding against electromagnetic interference. This casing also protects internal components from mechanical stress and vibration.
Technical Specifications at a Glance
| Specification | Detail |
|---|---|
| Processor Type | 32-bit microprocessor with FPU |
| Execution Speed | 0.2 ms (1,000 boolean instructions) |
| I/O Capacity | Up to 2,048 points |
| Program Memory | 256 KB (flash) |
| Data Memory | 128 KB (SRAM) |
| Retentive Memory | 64 KB (EEPROM) |
| Dimensions (H × W × D) | 135 mm × 50 mm × 110 mm |
| Weight | 0.85 kg |
| Communication Ports | 1 x RS-232, 1 x RS-485 |
| Ethernet Port | 1 x 10/100 Base-T |
| USB Port | 1 x USB 2.0 (device) |
| Backplane Current | 500 mA at 5 VDC |
| External Supply | 24 VDC ±10% |
| Power Dissipation | 9.5 W |
| Energy Buffer | 330 µF capacitor (12 ms hold-up) |
| Real-time Clock | Yes (battery-backed, 5 years typical) |
| Temperature Range | -25 °C to +65 °C |
| Humidity Range | 5% – 95% RH (non-condensing) |
| Standards | IEC 61131-2, UL 508, CSA, CE |
| Protection Rating | IP20 |
Communication Interfaces and Connectivity
A built-in Ethernet port enables seamless integration into plant-wide networks. This port supports Modbus TCP/IP for efficient data exchange with other devices. The RS-232 port connects directly to programming terminals or HMI panels. An additional RS-485 interface allows multi-drop networking with remote I/O stations. The front-mounted USB port facilitates convenient program downloads and firmware updates. A removable battery compartment provides easy access for clock battery replacement.
Power Architecture and Energy Storage
The Schneider ALU 821 draws 500 mA from the 5 VDC backplane supply for core operations. It also needs a 24 VDC ±10% external supply for peripheral interfaces. An internal 330 µF capacitor provides energy buffering during brief power interruptions. This capacitor sustains CPU operation during supply dips lasting up to 12 milliseconds. Total power dissipation measures 9.5 W under full processing load.
Internal Component Architecture
The main processor integrates a floating-point unit for complex mathematical calculations. A 256 KB flash memory stores the operating system and user application programs. The 128 KB SRAM handles runtime variables and dynamic data tables effectively. An additional 64 KB EEPROM retains critical parameters during power loss events. The PCB contains 180 surface-mount resistors and 112 ceramic capacitors for signal conditioning. A hardware watchdog timer resets the system automatically if software execution stalls.
Environmental Performance and Certifications
This CPU module operates reliably from -25 °C to +65 °C across demanding factory floors. It also performs consistently in humidity conditions from 5% to 95% without condensation. The ALU 821 complies with IEC 61131-2, UL 508, CSA, and CE standards. These certifications ensure dependable integration into global industrial control systems.
Details
| Weight | 0.85 kg |
|---|---|
| Dimensions | 135 × 50 × 110 mm |
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