Saia PCD2 AP103 V3.5 CPU Module (PCD2 Series PLC)

The Saia PCD2 AP103 is a powerful CPU module belonging to the PCD2 series of programmable logic controllers from Saia-Burgess Controls (now part of Honeywell). Version V3.5 indicates the firmware revision, offering enhanced communication and real-time performance. This module is designed for medium to large automation applications, including building automation, industrial machinery, water treatment, and energy management. It combines a high-speed 32-bit processor with integrated I/O and multiple fieldbus interfaces.

Processor and Memory

• CPU: 32-bit ARM Cortex-M3, 72 MHz

• Program Memory: 512 KB Flash (for user application)

• Data Memory: 128 KB RAM (retainable via supercapacitor)

• Retain Memory: 32 KB EEPROM (100,000 write cycles)

• Execution Speed: 0.15 µs per boolean instruction

• Real-Time Clock: Yes, with 7-day backup (lithium battery)

Integrated I/O

The AP103 module includes onboard I/O for basic control without expansion modules: 16 digital inputs (24V DC, sink/source, 4 mA, with selectable filter 0.5–32 ms), 12 digital outputs (transistor, 24V DC, 0.5A per point, total 4A), and 2 analog inputs (0-10V, 12-bit resolution). These I/O points are sufficient for small standalone machines or as a local controller in a distributed system. For larger systems, the PCD2 series supports up to 1024 digital I/O and 256 analog I/O via expansion buses.

Communication Ports and Protocols

The CPU is equipped with: 2 RS-232 ports (9-pin D-sub) for programming and ASCII communication; 1 RS-485 port (isolated) for Modbus RTU master/slave; 1 Ethernet port (10/100 Base-T) with integrated web server, Modbus TCP, and PROFINET IO (optional license). Additionally, the PCD2 backplane supports Profibus-DP, CANopen, DeviceNet, and BACnet via plug-in communication modules. The AP103 V3.5 firmware adds support for MQTT and OPC UA (pub/sub) for IIoT applications.

Programming Software and Languages

Programming is done using Saia PG5 (version 2.0 or higher), which supports all IEC 61131-3 languages: Ladder Diagram (LD), Function Block Diagram (FBD), Structured Text (ST), Instruction List (IL), and Sequential Function Chart (SFC). The AP103 also supports C-code blocks for complex algorithms. A built-in real-time operating system (RTOS) allows deterministic cycle times as low as 1 ms for time-critical applications. The Ethernet port includes an integrated web server that can display custom HTML5 dashboards for remote monitoring.

Environmental and Mechanical Specifications

Dimensions: 160mm (H) × 120mm (W) × 75mm (D). Weight 450 g. Mounting on DIN rail (35mm) or directly on backplane. Operating temperature: -20°C to +60°C (no condensation). Storage: -40°C to +85°C. Humidity: 5–95% non-condensing. Vibration: 2 g at 10–150 Hz. Shock: 15 g for 11 ms. Enclosure IP20 (requires cabinet).

Power Supply and Redundancy

The AP103 requires a 24V DC supply (±20%), consuming 200 mA typical (without I/O load). An onboard supercapacitor retains data RAM for 30 days (at 25°C). Optional battery module (PCD2.BB) extends retention to 5 years. The CPU supports hot standby redundancy when paired with a second AP103 and a redundancy link module, achieving bumpless switchover for critical processes.

Typical Applications

The Saia PCD2 AP103 is commonly used in: HVAC central plants (chillers, air handlers), lighting control systems, water pumping stations, packaging machines (with motion control via pulse outputs), and renewable energy monitoring (solar inverters, wind turbines). Its integrated Ethernet and web server allow remote access without additional gateways.

Diagnostics and Maintenance

The CPU features a 4-line LCD display (backlit) for showing status, error messages, and IP address. It also includes a microSD card slot for data logging, firmware updates, and program backup. The AP103 V3.5 supports remote diagnostics via SNMP and email alerts (SMTP) for predefined alarms (e.g., CPU overload, I/O fault).

Standards and Compliance

The PCD2 AP103 complies with CE (EN 61131-2 for PLCs), UL 508, cUL, and RoHS. It meets the marine classification (DNV-GL) for vibration and humidity, suitable for shipboard automation.

Ordering Information

Order code: PCD2.AP103 (V3.5 firmware). Accessories: terminal blocks (PCD2.TBxx), battery module (PCD2.BB), and expansion I/O modules (PCD2.Wxxx series).

Conclusion

The Saia PCD2 AP103 V3.5 is a feature-rich PLC CPU module offering 32-bit processing, integrated I/O, multiple communication options, and IIoT readiness. Its rugged design and wide temperature range make it suitable for demanding industrial and building automation environments.