MAX485 TTL to RS-485 Interface Module — Half-Duplex, Modbus RTU, Arduino

MAX485 TTL to RS-485 Interface Module — Half-Duplex, Modbus RTU, Arduino

The MAX485 module converts between TTL serial (UART) and RS-485 differential signals, enabling Arduino and other microcontrollers to communicate over RS-485 industrial networks at distances up to 1200m. RS-485 differential signaling provides excellent noise immunity in industrial environments, and the multi-drop bus topology supports up to 32 devices on a single twisted-pair cable. Compatible with Modbus RTU, DMX512, and other RS-485 protocols.

Electrical Specifications

• IC: Maxim MAX485
• Mode: Half-duplex (transmit or receive, not simultaneously)
• Data Rate: Up to 2.5Mbps
• Range: Up to 1200m (at lower baud rates)
• Bus Nodes: Up to 32 devices per bus segment
• Supply Voltage: 3.3V – 5V
• Control Pins: DE (Driver Enable) + RE (Receiver Enable)
• Signaling: Differential (A/B lines) — excellent noise immunity

Arduino Wiring

• VCC → 5V | GND → GND
• DI (Data In) → Arduino TX pin
• RO (Receiver Out) → Arduino RX pin
• DE + RE → Arduino digital pin (tie together, HIGH=transmit, LOW=receive)
• A/B → RS-485 bus twisted pair
• Add 120Ω termination resistor at each end of the bus

RS-485 vs UART vs I²C

• RS-485: 1200m range, 32 nodes, noise-immune differential — for industrial networks
• UART: ~15m range, point-to-point — for short-distance serial communication
• I²C: ~1m range, multi-device — for on-board sensor communication

Typical Applications

• Arduino Modbus RTU master/slave — communicate with industrial sensors, meters, and PLCs
• Building automation RS-485 bus — HVAC, lighting, and access control networks
• Energy monitoring — smart meter and power analyzer communication
• DMX512 lighting control — stage and architectural lighting
• Multi-node sensor network — up to 32 Arduino nodes on one cable

MAX485 half-duplex RS-485 module — 1200m range, 32 nodes, Modbus RTU compatible for Arduino industrial networking and long-distance serial communication.

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