Comprehensive Product Summary – TRP-C28 Isolated 4-Channel Digital Input and 4-Channel AC Relay RS-485 Modbus RTU Module

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### 1. Product Overview

Product Name: TRP-C28
Model: TRP-C28
Series: TRP-C Industrial Communication Modules
Article Number: TRP-C28
Manufacturer: Trycom Technology Co., Ltd.
Manufacturer Address: No. 35, Zhongxing Rd., Guishan Township, Taoyuan County 333, Taiwan
Website: [www.trycom.com.tw](http://www.trycom.com.tw)
Telephone: +886-3-350-3351
Fax: +886-3-350-3352

The Trycom TRP-C28 is an industrial-grade isolated digital I/O module designed for remote control and monitoring applications over RS-485 networks. It integrates four optically isolated digital input channels and four power relay output channels, supporting both ASCII and Modbus RTU communication protocols. The module is engineered for robust performance in industrial automation, process control, and remote data acquisition systems.

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### 2. Key Features

- 4 Isolated Digital Inputs and 4 Power Relay Outputs: Provides four optically isolated digital input channels and four relay output channels for flexible control and monitoring.
- High Isolation Protection: Each input channel features 3750 Vrms optical isolation to protect against high-voltage transients and ground potential differences.
- Dual Communication Protocols: Supports both ASCII and Modbus RTU protocols for versatile integration with various control systems.
- Wide Baud Rate Range: Configurable communication speeds from 1.2 kbps to 115.2 kbps.
- Counter Functionality: Each digital input can function as an independent counter channel with a frequency capability of up to 100 Hz.
- Dual Watchdog System: Includes both hardware and software watchdogs to ensure continuous operation and automatic recovery from communication or system faults.
- LED Indicators: Individual LEDs for each channel and power status provide real-time visual feedback.
- Flexible Mounting Options: Supports both DIN rail and panel mounting for easy installation in control cabinets.
- User-Friendly Configuration: External DIP switch allows quick selection between Modbus RTU and ASCII modes, as well as reset to factory defaults and self-test mode.
- Surge Protection: RS-485 communication lines are protected against surge and transient voltages.
- Power Supply Flexibility: Accepts DC power via screw terminal or external DC adapter.
- Compact and Durable Design: Industrial-grade enclosure with screw terminal connectors for secure wiring.

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### 3. Technical Specifications

Input Channels: 4 digital inputs
Input Isolation: 3750 Vrms optical isolation
Input Logic Levels:
- Logic 0: ±1 V (max)
- Logic 1: ±4.0 V to ±30 V
Input Impedance: 3 kΩ
Counter Function: 4 channels, 100 Hz maximum frequency

Output Channels: 4 relay outputs
Relay Configuration:
- RL1, RL2: Form A (SPST)
- RL3, RL4: Form C (SPDT)
Contact Ratings:
- 6 A @ 24 V DC
- 6 A @ 120 V AC
- 5 A @ 250 V AC
Relay Surge Strength: 4000 V
Relay Operating Time: 6 ms typical
Relay Life Expectancy: 10⁷ operations (mechanical)

Communication Interface: RS-485 (2-wire half-duplex)
Communication Speed: 1.2 kbps to 115.2 kbps
Maximum Communication Distance: 500 meters
Supported Protocols: ASCII and Modbus RTU
Default Communication Settings:
- ID Address: 01
- Baud Rate: 9600 bps
- Data Format: N, 8, 1
- Checksum: Disabled

Power Supply:
- Input Type: Screw terminal or external DC adapter
- Power Consumption: 2.7 W typical
- Connection Type: Screw terminal, supports AWG #12–#32 wires

Environmental Conditions:
- Operating Temperature: 0°C to 65°C
- Storage Temperature: -20°C to 65°C
- Humidity: 10–90% RH, non-condensing

Physical Characteristics:
- Dimensions: 151 mm (L) × 75 mm (W) × 26 mm (H)
- Weight: 400 g
- Mounting: DIN rail or panel mount

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### 4. Functionality

The TRP-C28 functions as a remote digital I/O expansion module for RS-485 networks. It allows a host computer, PLC, or HMI to monitor digital inputs and control relay outputs through ASCII or Modbus RTU commands.

Operation Overview:
- Digital Inputs: Each input channel detects logic states or counts pulses. The optical isolation ensures reliable operation in noisy environments.
- Relay Outputs: The four relays can switch AC or DC loads, enabling control of external devices such as solenoids, lamps, or contactors.
- Communication: The RS-485 interface supports multi-drop networking, allowing up to 247 devices on a single bus.
- Configuration: DIP switches enable quick selection of communication mode (ASCII/Modbus), reset to default settings, or entry into self-test mode.
- Self-Test Mode: Allows verification of LED indicators and relay operation without host communication.
- Dual Watchdog: Ensures system reliability by monitoring both internal firmware and host communication. If a fault occurs, the module resets or enters safe mode to prevent uncontrolled outputs.
- Safe Mode: When communication is lost or watchdog timeout occurs, outputs revert to predefined safe states.

Typical Applications:
- Industrial automation and process control
- Remote monitoring and control systems
- Building management and HVAC control
- Machine status monitoring
- Energy management systems
- Security and alarm systems

Compatibility:
Compatible with Modbus RTU master devices, SCADA systems, PLCs, and PC-based control software. It can also be configured and tested using Trycom’s TRPCOM utility or third-party Modbus tools such as Modbus Poll or ModbusScan.

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### 5. Components & Accessories

Included Items:
- TRP-C28 module
- User manual (printed or digital)
- Configuration utility software (TRPCOM) on CD
- Mounting hardware (DIN rail clip or panel screws)

Optional Accessories:
- External DC power adapter
- RS-485 communication cables
- USB-to-RS-485 converter (for PC connection)

Connectors:
- Screw terminal blocks for all I/O and power connections
- RS-485 terminal block for differential data lines (A/B)

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### 6. Installation & Setup

Power Requirements:
The module operates from a DC power source connected via screw terminals or an external adapter. Ensure the supply voltage matches the module’s rated input range.

Mounting Options:
- DIN Rail Mounting: Snap the module onto a standard 35 mm DIN rail.
- Panel Mounting: Secure the module using screws through the mounting holes provided.

Wiring Guidelines:
- Use twisted-pair shielded cable for RS-485 communication lines.
- Maintain proper termination resistors at both ends of the RS-485 bus.
- Connect digital inputs and relay outputs according to the wiring diagram in the manual.
- Observe polarity and voltage limits for all connections.

Configuration Procedure:
1. Set the DIP switch to select communication mode (Modbus RTU or ASCII).
2. Connect the module to the RS-485 network and power supply.
3. Use the TRPCOM utility or Modbus master software to configure device ID, baud rate, and data format.
4. Verify communication by reading module name or firmware version.
5. Test digital inputs and relay outputs using command sequences or the utility interface.

Default Settings:
- ID Address: 01
- Baud Rate: 9600 bps
- Data Format: N, 8, 1
- Checksum: Disabled

Reset to Factory Defaults:
Adjust DIP switch to the “INIT” position and reboot the module.

Self-Test Mode:
Set DIP switch to “ON ON” and reboot to enter self-test mode, verifying LED and relay operation.

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### 7. Performance & Capabilities

Communication Performance:
- Baud rate adjustable from 1.2 kbps to 115.2 kbps
- Reliable data transmission up to 500 meters over RS-485
- Supports multi-drop networking with up to 247 devices

Input Performance:
- 4 optically isolated channels
- 3750 Vrms isolation
- 3 kΩ input impedance
- Counter frequency up to 100 Hz

Output Performance:
- 4 relay outputs (2 Form A, 2 Form C)
- Contact ratings up to 6 A at 24 V DC or 120 V AC
- Fast switching time (6 ms typical)
- Long mechanical life (10 million operations)

Reliability Features:
- Dual watchdog system ensures continuous operation
- Surge protection on RS-485 lines
- Safe mode prevents unintended output activation during communication loss

Limitations:
- Maximum communication distance limited to 500 m without repeaters
- Relay outputs not suitable for high-frequency switching applications
- Operating temperature limited to 65°C

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### 8. Standards & Compliance

Communication Standards:
- RS-485 (EIA/TIA-485) compliant
- Modbus RTU protocol compliant (per Modbus.org specifications)
- ASCII command protocol supported

Electrical Safety:
- 3750 Vrms isolation between input and logic circuits
- 4000 V surge strength for relay contacts

Environmental Compliance:
- Designed for industrial environments with wide temperature and humidity tolerance
- Non-condensing humidity operation up to 90%

Regulatory Compliance:
- CE compliant (EMC and safety)
- RoHS compliant (lead-free manufacturing)

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### 9. Additional Information

Warranty:
Standard manufacturer warranty (typically one year) covering defects in materials and workmanship.

Technical Support:
Trycom provides technical assistance via email, phone, and online resources. Firmware updates and configuration utilities are available from the Trycom website.

Maintenance:
- Periodically inspect wiring and terminal connections.
- Ensure adequate ventilation and avoid exposure to excessive dust or moisture.
- Relays are mechanical components; verify operation periodically in high-duty applications.

Software & Utilities:
- TRPCOM Utility: Windows-based configuration and testing tool for RS-485 communication. Allows scanning, configuration, and I/O control.
- Modbus Poll / ModbusScan: Third-party utilities recommended for Modbus RTU testing and monitoring.
- Firmware Updates: Available through Trycom’s support portal.

Documentation:
- User’s Manual (Rev. 1.3, September 2013)
- Command reference for ASCII and Modbus RTU protocols
- Wiring diagrams and configuration examples

Support Resources:
- Website: [www.trycom.com.tw](http://www.trycom.com.tw)
- Email and phone support available during business hours
- Online downloads for drivers, utilities, and manuals

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### Summary

The Trycom TRP-C28 is a robust, industrial-grade RS-485 I/O module combining four optically isolated digital inputs and four relay outputs in a compact, DIN-rail mountable form factor. Its dual-protocol support (ASCII and Modbus RTU), high isolation protection, and dual watchdog system make it ideal for mission-critical automation and remote control applications. With flexible configuration options, reliable communication, and comprehensive command support, the TRP-C28 provides a cost-effective and dependable solution for distributed digital I/O control in industrial environments.