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Welcome to Vol. 12 of The Probots Showdown. Three boards. Three price points. Three very different futures for your project.Should you stick with the
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The industrial standard for compact automation. This enclosed DT-R004 module features 4 Relays, 4 Digital Inputs, and a dedicated RS-485 interface. It combines Ethernet & WiFi redundancy with a rugged DIN Rail case, making it perfect for Modbus RTU sensor integration, multi-zone lighting, and industrial switching.
Quick Introduction Upgrade your automation reliability with the DT-R004 (RS-485 Edition). This fully enclosed, DIN-rail mountable unit is more than just a smart switch; it's a protocol gateway. Powered by an ESP32, it provides simultaneous Ethernet and WiFi connectivity to ensure your commands are never interrupted. This specific model includes an RS-485 interface, allowing it to act as a Modbus Master to read external sensors or a Modbus Slave to be controlled by your PLC, all while managing four local high-power relays.
Detailed Specifications
Model: DT-R004-485-CASE (RS485 Variant with Housing).
Controller: ESP32 (WiFi + Bluetooth).
Network Interfaces:
Ethernet: RJ45 (10/100 Mbps) with magnetic isolation.
WiFi: 2.4GHz 802.11 b/g/n (AP + Station Mode).
Serial Interface: RS-485 (A/B) for Modbus RTU communication.
Outputs: 4x Relays (NO/NC, 10A 250VAC).
Inputs: 4x Opto-isolated Digital Inputs (Dry/Wet Contact).
Enclosure: Industrial ABS DIN Rail Case (C45 Standard).
Power Input: 12V DC or 24V DC (Non-PoE, Screw Terminals).
Protocols: MQTT, Modbus TCP (Ethernet), Modbus RTU (RS-485), HTTP CGI.
Quality Advantage & Differentiation: Why choose the RS-485 Enclosed Version?
RS485 Bridge Mode: Unique to this variant, the "Transparent Transmission" feature allows you to send serial commands via Ethernet (TCP/UDP) directly out the RS485 port. It effectively replaces a separate "Ethernet-to-RS-485" converter.
Protection: The included DIN rail case protects the PCB from dust, accidental shorts, and physical damage in electrical cabinets.
Hybrid Connectivity: Unlike standard Modbus relays that only use RS-485 wires, this unit can be controlled wirelessly via WiFi or wired LAN, providing flexibility for retrofit installations where running new LAN cables is difficult.
Key Applications & Usage
Modbus Gateway: Use the DT-R004 to read a daisy-chain of RS-485 Soil Moisture Sensors or Energy Meters and report the data to Home Assistant via MQTT.
Multi-Zone Lighting: Control 4 separate lighting circuits via Ethernet, with local wall switches connected to the Digital Inputs for manual override.
Industrial Watchdog: Monitor critical equipment via Digital Inputs. If a fault is detected, trigger a Relay to reset power and send an MQTT alert instantly over Ethernet.
What's Included & Required
Included: 1x DT-R004 Relay Module (RS485 Version), 1x DIN Rail Plastic Housing (Pre-assembled),1x RC Snubber Kit
Required: 12V/24V DC Power Supply, Ethernet Cable, RS485 Cabling (if using serial features).
The "Virtual Technician" Support Panel
⚠️ FIRMWARE TYPE CHECK (Crucial):
Standard Firmware (Default): Comes locked. Excellent for Modbus/MQTT users. Cannot be flashed with ESPHome.
Development Firmware: If you plan to code your own firmware (Arduino/ESPHome), you MUST contact us to ship the "Dev/Test Version".
⚠️ RS485 WIRING TIP:
Always use twisted pair cable for RS-485 (Data+ and Data-).
If the cable run is long (>100m), you may need a 120-ohm termination resistor at the far end of the bus (not included on the board).
⚠️ INPUT CONFIGURATION:
The 4 Digital Inputs are active-low by default. You can configure them in the Web UI to "Link" to the relays (e.g., Input 1 ON -> Relay 1 ON) without needing an external controller.
EXTERNAL RESOURCE INTEGRATION
1. Official Manual & SDK:
Resource Name: Dingtian Relay Board SDK & User Manual
Link: Download SDK (Zip)
Description: Essential documentation for Register Maps (Modbus), HTTP Commands, and Configuration Tools.
2. Configuration Tool:
Resource Name: Relay Upgrade & IP Tool
Link: Download Tool
Description: Use this to find the device IP address if you forget it or if DHCP is enabled.
3. Firmware Guide (Dev Version Only):
Resource Name: Custom Firmware Repository
Link: GitHub - Relay Dev Demo
Description: Reference code for flashing your own firmware (Requires Unlocked/Dev Board).


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Probots sells every Electronics Part for your next Project. You can order 10,000+ Electronic Parts Online - Arduino, Raspberry Pi, NodeMCU Development Boards, Sensors, Motors, Motor Drivers, SMPS, Plastic Enclosures etc in India directly on probots.co.in
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