The DO802 is a high-performance, highly reliable digital output module, specifically designed for the ABB System 800xA® and S800 I/O systems. This module employs a relay output format, providing 8 independent Normally Open (NO) output channels. It is suitable for industrial automation and control system applications that require driving high-voltage, high-current loads, such as motor control, valve actuation, indicator lights, and alarms.
The DO802 module features a compact design and high integration, supporting a wide voltage range of 24-110 V DC or 250 V AC, with a maximum continuous output current of 2 A. All output channels feature electrical isolation, effectively preventing field interference from affecting the control system and ensuring stable operation. The module is equipped with output status indicators for easy field debugging and status monitoring. Furthermore, it includes an Output Set as Predetermined (OSP) function, which can set outputs to a predefined safe state upon error detection, significantly enhancing system safety and reliability.
As a key component within the ABB Ability™ System 800xA® hardware selection system, the DO802 upholds ABB's consistent standards of high quality and durability. It is suitable for various industrial sectors including power generation, chemicals, oil & gas, water treatment, and manufacturing.
2. Key Features and Benefits
The DO802 digital output module integrates several advanced features, aiming to provide a robust, flexible, and easily maintainable solution for complex industrial environments.
1. High-Performance Multi-Channel Output:
8 Independent Channels: Provides 8 completely independent relay output channels for simultaneous control of multiple devices.
Wide Voltage Range: Supports 24-110 V DC or 250 V AC supply, accommodating various field device requirements.
Strong Load Capacity: Each channel supports a maximum continuous output current of 2 A and a maximum break power of 500 VA AC or 60 W DC, enabling direct drive of most industrial actuators.
2. Exceptional Reliability and Safety:
Full Channel Isolation: Each output channel is individually isolated from ground and from other channels (rated insulation voltage 250 V, dielectric test voltage 2000 V AC), effectively suppressing ground loop interference and faults caused by potential differences, protecting the control system core from damage due to field-side surges, short circuits, etc.
Output Set as Predetermined (OSP) Function: When the module detects a communication fault or internal error via the ModuleBus, it can automatically set all outputs to a predefined safe state (typically open) after a configurable delay (256, 512, or 1024 ms). This prevents equipment malfunction and ensures personnel and equipment safety.
Power Supply Supervision: The driving power for the internal relay coils is derived from the 24 V distributed on the ModuleBus. This power is continuously monitored. If the voltage is lost, the module reports a channel signal error and a module warning signal via the ModuleBus, facilitating prompt diagnosis and corrective action by the host system. This supervision can be enabled or disabled via a parameter.
3. Convenient Installation and Maintenance:
Status Visualization: Each channel is equipped with an output status indicator LED, providing intuitive display of the channel's on/off state. This greatly facilitates field debugging, fault diagnosis, and routine inspections.
Detachable Connectors: Field process signals are connected via detachable terminal blocks, enabling quick installation, replacement, and maintenance without complex wiring on the module itself.
Robust Electromagnetic Compatibility (EMC): Each output channel integrates EMC protection components, ensuring stable operation in harsh industrial electromagnetic environments.
4. System Integration and Compatibility:
Designed for S800 I/O: Perfectly integrates into the ABB S800 I/O station, making it an ideal choice for building distributed control systems within System 800xA.
ModuleBus Communication: Communicates with the controller via the high-speed, reliable ModuleBus, enabling fast output control and status feedback.
3. Functional Description and Working Principle
The DO802 module serves as an intelligent interface between the S800 I/O system and high-power field actuators. Its core function is to convert low-level logic control signals from the controller into strong electrical signals capable of directly driving field devices.
Internal Structure:
Each output channel forms a complete signal chain, containing the following key components:
Optical Isolation Barrier: Provides electrical isolation between the control system side (logic side) and the field side (power side), preventing high voltage and noise from entering the sensitive control system.
Relay Driver: Receives and amplifies the signal from the optocoupler, providing sufficient drive current for the relay coil.
Electromagnetic Relay: The core switching element. When the coil is energized, its Normally Open (NO) mechanical contacts close, connecting the external load circuit. When de-energized, the contacts open via spring force.
Output Status Indicator (LED): Linked to the drive circuit, it illuminates when the channel is activated (output "1"), providing local visual feedback.
EMC Protection Components: Typically include RC snubber circuits, varistors, or freewheeling diodes, etc. These absorb arcs generated during contact switching and back electromotive force (EMF) from inductive loads, protecting relay contacts and suppressing electromagnetic interference.
Workflow:
The system controller sends output commands to the DO802 module via the ModuleBus.
The module's internal circuitry processes the command and transmits the signal via the optocoupler to the corresponding channel's relay driver circuit.
The driver circuit energizes the relay coil, causing the relay contacts to close.
The external load (e.g., contactor coil, indicator light) receives power from the field supply through the closed contacts and operates.
Simultaneously, the channel's status indicator LED illuminates.
The module continuously monitors the 24 V power from the ModuleBus. If this power becomes abnormal, the module immediately reports a fault via the ModuleBus and can activate the OSP function according to its settings, placing all outputs into the safe state after the delay.
4. Installation and Connection
Process Connections:
The DO802 uses a clear and straightforward process connection method. The module is equipped with a detachable connector featuring a total of 16 terminals (8 channels x 2 terminals/channel). The two terminals for each channel are labeled "xA" and "xB" (where x is the channel number 1-8). For a Normally Open (NO) relay output, typically connect one side of the field supply to "xA" and one side of the load to "xB". The other side of the load connects back to the other side of the field supply, completing the circuit.
Wiring Example (Channel 1):
Terminal 1A: Connect to the "positive" or "Line (L)" side of the field supply (e.g., 110V DC or 250V AC).
Terminal 1B: Connect to one terminal of the load device (e.g., motor contactor coil).
Other terminal of the load device: Connect to the "negative" or "Neutral (N)" side of the field supply.
Installation Notes:
Always perform installation and wiring with power disconnected.
Follow the wire size and torque requirements specified in the table above to ensure secure and reliable connections.
For inductive loads (e.g., motors, relay coils), it is essential to add protective circuits (such as parallel freewheeling diodes or RC snubbers) as recommended by the manual or standard practice to extend relay contact life.
Practice proper cable routing by separating power cables from signal cables to reduce interference.
5. Typical Application Areas
Thanks to its high reliability, strong load capacity, and flexible voltage adaptability, the DO802 is widely used in the following industrial sectors:
Power Generation: Controlling the closing/opening of circuit breakers and disconnectors in distribution systems, driving signal indicators and alarms for protection devices.
Oil & Gas: Controlling solenoid valves and motor-operated valves on pipelines, starting/stopping pump equipment, driving audible/visual alarm devices at wellheads and stations.
Chemical Industry: Driving agitator motors for reactors, controlling material transfer pumps, opening/closing various process valves.
Water & Wastewater Treatment: Controlling pump start/stop, regulating valve positions, driving chemical dosing equipment.
Manufacturing: Controlling large machine tools, manipulators, conveyors, heaters, cooling fans, etc., on production lines.
Building Automation: Controlling large fans and pumps in HVAC systems, smoke dampers in fire protection systems, etc.
