Description
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I. Product Overview
The AUTO-MASKIN RK-66 Interface Module (Article No. 75410, Version R2.2, AUX power configuration) is a dedicated interface wiring module designed by the Norwegian company Auto-Maskin to complement the DCU 305 series of marine engine controllers (DCU 305 R2 / R3 / R3 LT). The RK-66 is an essential component of the engine monitoring and control system; all external sensors, switches, actuation relays, and power supplies connect first to the RK-66, which then routes these signals to the DCU 305 main control unit.
Designed for standard DIN-rail mounting and powered by 24 VDC, the module integrates 12 digital inputs, five 4–20 mA analog inputs, and two speed (pickup) sensor inputs. It also features approximately nine relay outputs—including start/stop and overspeed relays—and supports expansion via the AK-6 analog expansion unit and MK-6/MK-14 relay expansion units. It is widely used in monitoring and protection systems for marine main engines, generator sets, and industrial diesel engine units.
II. Operating Principle
The RK-66 essentially serves as a “signal aggregation and interface layer” between field signals and the DCU 305 main control unit. Its operation can be summarized in three stages:
Signal Acquisition and Conditioning: Field transmitters (measuring pressure, temperature, liquid level, etc.) connect to analog channels via 4–20 mA current signals; operational status switches and protection switches connect to digital input channels via passive contacts; and speed probes (pickups) capture gear-tooth pulse signals via two speed channels. The RK-66 supplies +24 VDC power to these sensors and performs signal filtering, shaping, and range matching.
Logic Processing and Protection Execution: Acquired signals are routed to the DCU 305 main control CPU, where built-in control logic handles functions such as idle control, run control, overspeed protection, alarm monitoring, and shutdown logic. When an action is required, the main controller outputs signals via the RK-66’s relays (K1–K9) to drive external circuits for preheating, starting, stopping, common alarms, and overspeed shutdowns.
Communication and Redundancy: The DCU 305 transmits unit data to the ship’s alarm system or the RSP 305 remote panel using the Modbus RTU protocol (Comli compatible); the R3 version also supports the J1939 CAN bus. Additionally, the system features a built-in, always-powered backup monitoring circuit; if the main control CPU malfunctions, this backup circuit automatically triggers the common alarm relay output, providing hardware-level redundant protection.
Notably, digital input channels 1–6 feature wire-break detection specifically for shutdown protection circuits, while analog channels trigger a “sensor fault” alarm if the signal drops below 2 mA or if the connection is open.
III. Product Advantages
Integrated design for streamlined installation and reliable wiring: All field cables connect directly to the RK-66 unit, which features a clear terminal layout; this prevents the main control unit from bearing the direct stress of field wiring connections, thereby simplifying maintenance and troubleshooting.
Flexible and scalable I/O configuration: While some channel functions are fixed, others can be customized via the Rudolf R3 configuration software to perform any available function or event; capacity can be expanded using external modules such as the AK-6 (6-channel 4–20 mA) and MK-6/MK-14 (6/14-channel relay units).
Engineered for marine environments and classification society certification: Complies with IACS requirements and features robust shielding and electromagnetic compatibility (EMC) design, ensuring reliable operation amidst engine room vibration, humidity, and electrical interference.
Comprehensive hardware redundancy and protection: Ensures safe diesel engine operation through multiple protective measures, including overspeed protection, wire-break detection, sensor fault alarms, and backup monitoring circuits.
Ease of installation and maintenance: Supports standard DIN-rail mounting; compact and lightweight (approx. 0.8 kg) with standardized terminals and expansion interfaces, ensuring excellent spare part interchangeability.
Open communication: Supports Modbus RTU and Comli protocols, allowing for easy integration with various marine alarm and supervisory control systems.
IV. Role in Industry Applications
The RK-66 primarily serves the sectors of marine automation and diesel generator set control, offering significant value through:
Monitoring of marine main engines and auxiliary engines: Acts as a signal hub for engine controllers, collecting and transmitting critical parameters—such as oil temperature, water temperature, oil pressure, rotational speed, and fluid levels—in real-time to support centralized monitoring from the bridge and central control room. Generator Set (Genset) Protection and Automation: Facilitates automatic start/stop, synchronization readiness, load-bearing condition assessment, and protection against overspeed and low oil pressure; it serves as a critical interface for power station automation.
Marine Alarm and Safety Systems: Integrates alarm and shutdown signals into the vessel-wide alarm system via Modbus, ensuring compliance with classification society standards for Unmanned Machinery Spaces (UMS) and safety protection.
Industrial Diesel Gensets and Backup Power: Performs similar signal interfacing and protection functions in industrial applications such as land-based diesel generator sets and emergency pumping stations.
In summary, while the RK-66 does not directly generate control algorithms, it provides the physical foundation—offering visibility, connectivity, and robust protection—for the entire engine control system, directly determining the system’s wiring reliability, expandability, and safety.
V. Installation and Operation
Mechanical Installation: Mount the RK-66 onto a standard DIN rail in a location that facilitates wiring and is away from strong electromagnetic interference; ensure adequate clearance for the unit and cable bending radii.
Power Supply Connection: Connect the starter battery supply to terminals 1 and 2 (main power) and the auxiliary power supply to terminals 3 and 4 (AUX); the use of twisted-pair cabling is recommended to minimize electrical interference.
Sensor Wiring: Connect 4–20 mA transmitters to the corresponding channel terminals for +24 V and 4–20 mA signals (analog channels 1–5 correspond to terminals 19–28); connect speed probe 1 to terminals 5 and 6, ensuring the signal amplitude is between 2.5 Vpp and 30 Vpp.Digital Input Wiring: Connect all status/protection switches to the 0 V terminal (using passive contacts); do not apply +24 V to the digital input terminals.
Relay and Expansion: Connect outputs such as Start/Stop, Pre-heat, and Common Alarm to the RK-66 relay terminals according to the wiring diagram; for expansion, connect terminals 27, 28, and 29 of the AK-6 directly to the corresponding terminals (27, 28, and 29) of the RK-66.
Configuration and Commissioning: Use the Rudolf R3 (Windows) configuration software and a Rudolf cable connected to the DCU 305’s P3 port to configure channel functions, alarm limits, and overspeed setpoints for the specific project.
Functional Testing: During commissioning, enter RPM test mode and temporarily lower the overspeed setpoint to a value near the rated speed to verify correct overspeed protection operation.
VI. Precautions
Shielding and Grounding: Shielded cables are recommended for all connections; connect the shield to Ground, not to 0 V. Follow the manual to distinguish between single-end and double-end grounding requirements to prevent ground loops.
Digital Input Restrictions: Strictly prohibit connecting +24 V to digital input terminals; connect switch contacts to 0 V only, as other connections may damage the input circuitry.
Analog Signal Criteria: For 4–20 mA channels, a signal below 2 mA or an unconnected wire will trigger a “Sensor Fault” alarm. If 0–10 V or 0–20 mA modes are selected, this fault alarm is disabled, and protection reliability must be evaluated separately. Probes and Cables: Speed probe cables must be shielded and grounded; the minimum bending radius must be at least eight times the cable diameter, and the cables must not be sharply bent or deformed.
Expansion Unit Characteristics: Connecting the AK-6 increases the refresh time for expansion channels and the fifth standard channel; it is recommended to connect “slow-varying” inputs (such as temperature transmitters) to the AK-6, while reserving channels on the RK-66 main unit for fast-acting protection signals.
Power Supply and Jumpers: Jumper J1 inside the main unit determines whether the controller remains permanently powered on; the jumper must be removed or retained according to the manual before enabling specific functions, and the rear cover must be opened to remove it.
Pre-power-up Checks: After wiring, verify power polarity and terminal numbering, and ensure the fuse is intact before applying 24 VDC power; configuration parameters must match the specific project drawings, and the overspeed setpoint must align with the actual configuration for the project in Rudolf R3.
Maintenance Safety: Disconnect the battery and auxiliary power supply before performing live wiring or module replacement; use only spare parts of the same version (75410 / R2.2) or manufacturer-approved alternatives.
VII. Summary
The AUTO-MASKIN RK-66 (75410, R2.2, AUX) interface module serves as a core wiring and signal-routing unit within the DCU 305 engine control system. Featuring a centralized, scalable, interference-resistant, and redundant design, it provides a reliable platform for field signal input and control output for marine main engines, generator sets, and industrial diesel units. A proper understanding of its operating principles, strict adherence to wiring and configuration standards, and attention to critical requirements regarding shielding, grounding, and protection circuits are essential for ensuring long-term system stability, passing classification society inspections, and minimizing the risk of downtime.
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I. Product Overview
The AUTO-MASKIN RK-66 Interface Module (Article No. 75410, Version R2.2, AUX power configuration) is a dedicated interface wiring module designed by the Norwegian company Auto-Maskin to complement the DCU 305 series of marine engine controllers (DCU 305 R2 / R3 / R3 LT). The RK-66 is an essential component of the engine monitoring and control system; all external sensors, switches, actuation relays, and power supplies connect first to the RK-66, which then routes these signals to the DCU 305 main control unit.
Designed for standard DIN-rail mounting and powered by 24 VDC, the module integrates 12 digital inputs, five 4–20 mA analog inputs, and two speed (pickup) sensor inputs. It also features approximately nine relay outputs—including start/stop and overspeed relays—and supports expansion via the AK-6 analog expansion unit and MK-6/MK-14 relay expansion units. It is widely used in monitoring and protection systems for marine main engines, generator sets, and industrial diesel engine units.