Samsung SSAS21-DO Digital Output Module
The Samsung SSAS21-DO Digital Output Module serves as a core actuator control interface for Samsung’s SSAS21 programmable logic controller (PLC) platform. Designed for high-density industrial control applications, it routes logic output signals from the central processing unit to drive external field devices such as solenoids, contactors, relays, pilot lamps, and motor starters.
Technical Table
| Specification Parameter | Details / Value |
| Model Code | SSAS21-DO |
| Series | Samsung SSAS21 Automation Platform |
| Module Type | Discrete Digital Output Module |
| Output Channels | 16 / 32 Points per Module |
| Output Type | Transistor (Sink/Source) or Electromagnetic Relay |
| Rated Load Voltage | 24V DC / 120–240V AC (Relay models) |
| Max. Current Per Point | 0.5A per point (Transistor) / 2.0A per point (Relay) |
| Isolation Method | Photocoupler / Galvanic Isolation (1500V AC) |
| Response Time | OFF → ON: ≤ 1 ms / ON → OFF: ≤ 1.5 ms (Transistor) |
| Status Display | Channel-specific Green LED Indicators |
| Internal Power Draw | Powered via 5V DC backplane bus |
Environmental Tolerance Conditions
Operating Temperature: 0°C to +55°C (32°F to 131°F)
Storage Temperature: -25°C to +70°C (-13°F to 158°F)
Operating Relative Humidity: 5% to 95% RH (non-condensing)
Vibration Resistance: Conforms to IEC 60068-2-6 (10–57 Hz @ 0.075 mm; 57–150 Hz @ 1.0g)
Shock Immunity: 15g peak acceleration, 11 ms duration
Enclosure Rating: IP20 (Requires installation inside an IP54 or higher industrial enclosure)
Operating Instructions
Module Installation: Ensure rack power is fully disconnected. Slide the SSAS21-DO into the designated backplane slot until the rear connector latches, then tighten panel lock screws.
Wiring Configuration: Connect external 24V DC auxiliary power to the terminal block. Ensure external flyback/freewheeling diodes are installed across inductive loads (solenoids, relay coils) to suppress back-EMF spikes.
Power-On Sequence: Apply main backplane power before energizing external field load supplies to prevent unintended switching states.
Load Management: Never exceed the specified maximum current per channel or total module current capacity to prevent thermal overload.
Fault Diagnosis & Troubleshooting
Output Channel LED OFF, Load Inactive: Verify PLC CPU state is in RUN mode; check output logic bit status in PLC program; inspect external 24V DC load supply.
Output Channel LED ON, Load Inactive: Check terminal connection tightness; inspect external fuse in the load circuit; test field device for open circuit or coil failure.
Module ERROR LED ON: Indicates backplane bus communication fault or over-current shutdown; turn off system power, re-seat module, and inspect field wiring for short circuits.
Transistor Channel Stuck ON: Indicates output transistor damage caused by short circuit or unsuppressed inductive load back-EMF; module replacement required.
Related Models of the Same Series
SSAS21-CPU: Main Central Processing Unit Module
SSAS21-DI: Discrete Digital Input Module (24V DC)
SSAS21-AI: Analog Input Processing Module (4–20mA / 0–10V)
SSAS21-PWR: System Main Power Supply Module
SMTB-DO: External DIN-Rail Digital Output Terminal Board
Storage Conditions
Storage Environment: Store in clean, dry indoor facilities away from direct sunlight, corrosive gases, and chemical fumes.
Temperature & Humidity: -25°C to +70°C (-13°F to 158°F) at 5% to 95% RH non-condensing.
Electrostatic Protection: Keep enclosed within anti-static ESD shielding packaging until ready for panel assembly.