Selectron DDC711

Model Series Definition

• DDC: Direct Digital Control distributed automation module series
• 711: Bus coupler I/O logic controller hardware revision number

Technical & Performance Parameters

1. Bus Communication Specs
   • Backplane Local Bus: Selectron proprietary Selebus high-speed serial bus
   • External Network Interface: RS485 Modbus RTU
   • Bus Data Transmission Rate: 19.2 kbps maximum
2. Electrical Power Specs
   • Operating Supply Voltage: 24 VDC ±10%
   • Module Power Consumption: 6 W maximum
3. I/O Expansion Capacity
   • Expandable Local I/O Modules: Up to 8 digital I/O slave modules per DDC711
   • Digital Signal Processing Cycle: 1 ms minimum logic scan cycle
4. Environmental Specs
   • Operating Temperature Range: -20°C to +70°C
   • Operating Humidity: 5%–95% non-condensing
   • Protection Class: IP20 indoor cabinet installation
5. Mechanical Dimensions & Weight
   • Overall Size (W × H × D): 127 mm × 102 mm × 152 mm
   • Net Weight: 0.4 kg

Material Composition

• Module Housing: Self-extinguishing PA66 engineering plastic
• Internal Control PCB: FR4 industrial circuit board with gold-plated bus connectors
• Bus Isolation Components: Digital signal isolation transformers
• Terminal Hardware: Spring-cage nickel-plated copper wiring terminals

Structural Features

• Standard DIN rail snap mounting modular housing
• Left side: Selebus backplane gold finger connector for stacking expansion I/O modules
• Right side: RS485 Modbus communication terminal block, 24 VDC power input terminals
• Front panel: Module running status green LED, bus communication fault red LED, power indicator LED
• Stackable multi-module expansion structure without additional wiring between local I/O slaves

Working Principle

Core Function Features

1. Proprietary Selebus backplane supporting hot-plug local digital I/O expansion modules
2. Local distributed logic execution function, independent operation when upper master communication is interrupted
3. RS485 Modbus RTU standard industrial communication for third-party control system interconnection
4. Real-time bus communication fault diagnosis with front panel LED visual alarm
5. 24 VDC short-circuit hardware protection for external signal wiring
6. Non-volatile memory storage of user interlock logic programs, data retention without power supply

Advantage Highlights

1. Distributed local logic processing reduces upper master PLC bus communication load
2. Stackable modular expansion design simplifies cabinet wiring layout for multi-point digital signal collection
3. Wide temperature operating range suitable for building HVAC automation and factory auxiliary equipment control
4. Built-in communication isolation transformer eliminates ground loop interference between field bus and control cabinet

Applicable Industries

Installation Requirements

1. Mount on standard 35 mm DIN rail inside IP30 electrical control cabinet
2. RS485 Modbus communication cable must use shielded twisted pair, install 120 Ω terminal matching resistor at bus terminal end
3. Stacked I/O modules must be locked via side interlocking buckles to avoid loose bus gold finger contact
4. 24 VDC power supply wiring separate from Modbus communication signal wiring

Operation & Maintenance Precautions

1. Product official discontinuation date: 09.09.2022; replacement spare parts must be confirmed before project design
2. Do not stack more than 8 expansion I/O modules per DDC711 unit to avoid bus communication delay
3. Disconnect 24 VDC power supply before adding/removing stacked I/O expansion modules
4. Regularly check Modbus bus shielding layer grounding integrity every 6 months
5. Ambient temperature exceeding +70°C causes automatic logic scan cycle extension and communication delay