The DO818 is a high-performance, high-reliability digital output module specifically designed for the ABB System 800xA® and S800 I/O systems. As a critical interface component in industrial automation control systems, this module is responsible for reliably converting digital commands from the control system into the drive signals required by field execution devices (such as solenoid valves, relays, indicator lights, small motors, etc.). With its exceptional channel density, robust protection mechanisms, flexible configuration options, and broad industrial certifications, the DO818 is an ideal choice for demanding industrial environments.
The core design philosophy of the DO818 is to provide a safe, stable, and easily integrated output solution. The module employs advanced electronic design and stringent manufacturing processes to ensure long-term stable operation in harsh industrial field environments. Its modular design allows flexible pairing with various Module Termination Units (MTUs), meeting different wiring methods and installation space requirements, greatly enhancing system integration convenience and scalability.
2. Key Features and Benefits
The DO818 module integrates multiple advanced features designed to meet the high demands of modern industrial automation for I/O modules:
High Channel Density with Group Isolation: The module provides 32 independent digital output channels, significantly saving space inside control cabinets and improving system integration. These 32 channels are divided into two electrically isolated groups, each containing 16 channels and equipped with an independent process voltage supervision input. This group isolation design (Rated Insulation Voltage RIV 50V) effectively prevents faults or interference in one group from affecting the other, greatly enhancing system reliability and safety. It is particularly suitable for applications requiring isolation of different electrical circuits or safety等级 signals.
Wide Voltage Range and Stable Driving Capability: The output channels support a wide process voltage range of 12 V DC to 32 V DC, nominally 24 V DC. Each channel can deliver a maximum continuous output current of 0.5 A, providing strong driving capability to directly power various industrial loads. The wide voltage range accommodates potential voltage fluctuations in the field, ensuring stable equipment operation under different power supply conditions.
Comprehensive Multi-Level Protection Mechanisms:
Short-Circuit Protection: The high-side driver in each output channel has built-in short-circuit protection. Upon detecting a short circuit, the current limiting function activates. The initial short-circuit peak current is limited to a typical value of 1.4A, after which it enters a repetitive mode, limiting the short-circuit current to a typical value of 1.1A, effectively protecting the module and field wiring.
Overtemperature Protection: A two-stage overtemperature protection is employed. When the chip junction temperature exceeds 135°C, the first stage activates, switching the affected output channel(s) to a low-duty-cycle PWM mode (selective thermal shutdown with automatic restart) to reduce power dissipation and temperature. If the temperature continues to rise to a critical level, the second stage protection turns off all 8 outputs in the relevant group until the temperature normalizes.
Overvoltage Protection: The output is designed with dedicated protection circuits to withstand certain overvoltage surges.
Process Voltage Supervision: The voltage supervision input in each group continuously monitors the process power supply voltage. If the voltage drops below 12V, the module generates a fault signal readable via the ModuleBus. When the voltage falls below 11V, the output circuitry automatically shuts off, preventing abnormal operation under low voltage.
Comprehensive Diagnostics and Status Indication: The module front panel provides abundant LED indicators, including: F(ault), R(un), O(SP) Output Set as Predetermined, and status indicators for all 32 channels. Combined with detailed diagnostic information (such as Module Error, Module Warning, Channel Error) readable via the ModuleBus, rapid fault location and system maintenance are enabled, reducing downtime.
Excellent Electromagnetic Compatibility (EMC) and Industrial Durability: The module design complies with stringent EMC standards (EN 61000-6-2, EN 61000-6-4), possessing strong noise immunity. It features a wide operating temperature range (0 to +55°C) and an even wider storage range (-40 to +70°C), meets requirements for high pollution severity (ISA-S71.04: G3) and corrosion resistance, and has a protection rating of IP20, ensuring stable operation in various harsh industrial environments.
Flexible Compatibility and Connection Methods: The DO818 can be used with three types of S800 Module Termination Units (MTUs), offering different field wiring solutions:
TU830 (Extended MTU): Provides separate terminals for all 32 outputs and 16 common return terminals, suitable for applications requiring individual wiring or high-density traditional wiring.
TU818 (Compact MTU, 1-wire connection): Uses a single-wire connection to the load, simplifying wiring and saving space.
TU819 (Compact MTU, D-Sub interface): Equipped with two 25-pin D-Sub connectors, facilitating quick connection to field devices via prefabricated cables, improving installation efficiency.
This flexibility allows the DO818 to easily adapt to various architectures, from traditional control cabinets to distributed I/O stations.
Extensive International Certifications: The product carries the CE mark, complies with multiple electrical safety standards (e.g., EN/UL 61010-1, -2-201), and holds certifications from major marine classification societies (ABS, BV, DNV, LR), making it suitable for industrial and marine applications. Furthermore, the product complies with RoHS directives in the EU, UAE, China, etc., and the WEEE directive, reflecting an eco-design philosophy.
3. Working Principle and Protection Mechanism in Detail
The core of the DO818 module is its high-side driver output circuit. Each channel contains an optimized power transistor (high-side driver) responsible for switching the current to the load on or off based on commands from the control system. The circuit design integrates several key components:
Optical Isolation Barrier: Provides electrical isolation between the control side (ModuleBus) and the field side (process power and load), preventing high voltage or noise interference from entering the control system.
EMC Protection Components: Such as transient voltage suppressors, used to absorb surges and pulses from field wiring, ensuring stability of the module itself and the system bus.
Inductive Load Suppression Circuit: Suppresses the back electromotive force (EMF) generated when switching off inductive loads (e.g., relay coils, solenoids), protecting the output transistor.
Status Indicator LED: Directly reflects the on/off state of that output channel for easy field observation.
Its multi-level protection mechanism is the essence of ensuring reliability. When an output short circuit occurs, the current limiting circuit acts quickly to restrict the current to a safe value. If the short circuit persists causing the chip temperature to rise, overtemperature protection takes over. This progressive protection strategy—from current limiting to thermal shutdown PWM mode, to complete shutdown—aims to maximize hardware protection while attempting to automatically restore function (e.g., restart in PWM mode) after the fault is eliminated, embodying intelligent fault handling.
4. Compatibility and System Integration
As a member of the S800 I/O family, the DO818 integrates seamlessly into the ABB System 800xA® or Symphony Plus control architecture. Communicating with the controller via the ModuleBus, its configuration, diagnostics, and commissioning can all be performed through unified engineering tools (e.g., Control Builder), greatly simplifying engineering lifecycle management.
The pairing with different MTUs exemplifies its flexibility. Engineers can select the most suitable MTU based on the project's specific wiring practices, space constraints, and cost considerations. For example, in centralized control cabinets requiring numerous independent loops, the TU830's individual terminals offer the highest wiring clarity and flexibility. In distributed remote I/O stations or space-constrained locations, using the TU819 with D-Sub connectors can significantly reduce field wiring effort and improve sealing.
5. Typical Application Areas
Thanks to its high performance and reliability, the DO818 module is widely used in the following industrial sectors:
Process Industries: Valve control, pump start/stop, alarm indicator driving in chemicals, oil & gas, pharmaceuticals, water treatment, etc.
Manufacturing: Control of manipulators, conveyor motor start/stop, fixture actuation in automotive, food & beverage, packaging, and semiconductor production lines.
Energy & Infrastructure: Auxiliary equipment control in power plants, fan and pump control in building automation, lighting control.
Marine & Offshore Engineering: Certified by classification societies for controlling cabin equipment, driving alarm systems on vessels, etc.
