The DO840 is a high-performance 16-channel digital output module within the ABB Ability™ System 800xA® series, designed for industrial automation control systems requiring high reliability and diagnostic capabilities. This module supports redundant or single applications, features advanced on-board diagnostics, output status indication, and multiple protection mechanisms, making it suitable for demanding industrial environments such as process control, manufacturing, power generation, and rail transportation.
The module utilizes 24V DC current sourcing outputs, with a maximum continuous output current of 0.5A per channel. It incorporates overcurrent and overtemperature protection, offering excellent load adaptability and system safety. All channels are divided into two groups, each containing 8 output channels and an independent voltage monitoring input. Electrical isolation between groups and support for process voltage supervision further enhance system reliability and maintainability.
2. Key Features & Benefits
1. High Channel Density & Flexible Configuration
16 independent digital output channels, divided into two isolated groups (8 channels per group).
Each group includes a process voltage monitoring input for real-time power supply status.
Supports single or redundant configurations to meet different availability requirements.
2. Advanced Diagnostics & Status Indication
Each channel features a bi-color LED indicator:
Yellow: Output energized.
Off: Output de-energized.
Red: Channel fault (external or internal).
Module-level LEDs provide overall status feedback.
OSP (Output Set as Predetermined) function automatically sets outputs to a predefined safe state upon fault detection.
Pulse Test function periodically inverts outputs (<1ms) to detect open or short circuits; this function can be enabled or disabled via parameters.
3. Comprehensive Protection Mechanisms
Overcurrent Protection: Current limiting per channel, with a maximum short-circuit current of 2.5A.
Overtemperature Protection: Output stage shuts down automatically when temperature exceeds 150°C (302°F) and resumes when temperature drops to about 140°C (284°F) (Automatic Reset mode).
Latch on Fault Mode: Option to latch outputs off during overload until the fault is cleared and acknowledged.
EMC Protection & Inductive Load Suppression: Built-in EMC protection components and load suppression circuitry.
4. High Electrical Performance & Compatibility
Wide operating voltage range: 19.2 – 32 V DC.
Low on-state voltage drop (≤0.3V), reducing power consumption and heat dissipation.
Supports field cable lengths up to 600 meters (656 yards).
Compatible with various Mounting Termination Units (MTUs), including TU810, TU812, TU814, TU830, TU833, TU842, TU843, and TU852, accommodating different mechanical mounting and wiring needs.
3. Fault Diagnostics and Handling
The DO840 features multi-level diagnostic capabilities, distinguishing between:
External Channel Fault: Low process supply voltage or channel overload.
Internal Channel Fault: Failure of the output driver or main power switch.
Module-Level Fault: Failure of internal power supply or the internal communication link between modules in redundant applications.
The module supports two overload handling modes:
Automatic Reset Mode: Output automatically resumes after overtemperature protection triggers and temperature decreases.
Latch on Fault Mode: Output remains off until the overload condition is removed and manually acknowledged.
4. Installation and Wiring
The DO840 can be used with various MTUs to suit different mechanical layouts and wiring methods:
| Application Type | Supported MTU Models | Description |
| Single Application | TU810 / TU814 | Standard terminal-style MTU |
| TU812 | Compact MTU with D-Sub 25-pin male connector |
| TU830 / TU833 | Extended MTU |
| Redundant Application | TU842 / TU852 | For mounting on a horizontal DIN rail |
| TU843 | For mounting on a vertical DIN rail |
The wiring tables detail the corresponding terminals or pins for each channel and power supply on various MTUs, facilitating quick deployment and maintenance by engineers.
5. Typical Application Scenarios
The DO840 is suitable for the following industrial applications:
Process Automation: Valve control, pump start/stop, alarm output in chemical, oil, and gas industries.
Manufacturing: Production line control, robot outputs, assembly equipment control.
Power Systems: Switchgear control, protection device outputs, backup power switching.
Transportation Control: Signal light control, barrier gate control, platform equipment management.
Building Automation: Fan control, group lighting control, security system outputs.
6. Design and Usage Recommendations
Thermal Management & Environment: In high-temperature environments, ensure the total module current does not exceed the rated value to avoid protection triggers due to temperature rise.
Power Supply Design: It is recommended to independently configure power supplies for each group and utilize the voltage supervision function for early power fault warnings.
Cable Selection: Consider voltage drop for long-distance transmission; use cables with sufficient cross-sectional area.
Redundant Configuration: For applications with extremely high system availability requirements, a redundant configuration with communication link monitoring enabled is recommended.
Maintenance & Diagnostics: Regularly enable the Pulse Test function and combine LED status with system diagnostic information for predictive maintenance.
