TTL ↔ RS485 Adapter Module | Single Chip Serial Level Converter w/ RXD & TXD LEDs - RS1791

Description:

This TTL ↔ RS485 Adapter Module is a reliable single-chip serial level converter. It enables microcontrollers or devices using TTL serial (3.3 V or 5 V) to communicate over long distances using the RS-485 differential standard. Indicator LEDs for RXD and TXD provide live visual feedback of serial activity.

Specifications:

Logic level support	3.3 V / 5 V TTL input/output
Communication mode	Half-duplex serial (TTL ↔ RS-485)
Differential bus lines	A (non-inverting), B (inverting)
Transceiver IC	MAX485 or equivalent
Operating voltage	Typically 5 V, module supports 3.3/5 V logic
Termination resistor	120 Ω option (via solder pad or jumper)
LED indicators	RXD, TXD for serial activity
Data rate	Up to ~2.5 Mbps under ideal conditions
Max bus distance	Typically up to 1200 meters in suitable wiring conditions
Operating temperature	~ –40 °C to +85 °C
Board dimensions	Varies by module model (e.g. ~44 × 14 mm for MAX485 module)

Features:

• Compatible with 3.3 V and 5 V TTL logic levels (can operate under both)
• Uses onboard MAX485 (or equivalent low-power slew-rate transceiver)
• Screw terminal block or terminal pads for RS-485 A / B differential lines
• 120 Ω termination resistor option (sometimes onboard or via solder pad)
• RXD / TXD LEDs for visual serial activity indication
• Supports half-duplex serial communication (one direction at a time)
• Operating temperature range often −40 °C to +85 °C (typical for MAX485 modules) 
  

Applications / Use Cases:

• Long-distance UART communication (especially in noisy environments)
• Industrial sensor networks, Modbus RTU, RS-485 bus systems
• Microcontroller projects requiring robust serial links
• Automation, robotics, building control systems

Usage Notes:

• Tie DE and RE pins appropriately (often connected together) to switch between transmit & receive modes
• Use twisted pair cables for RS-485 A/B lines to minimize interference
• Use termination resistor (120 Ω) at ends of RS-485 bus if distance is large
• Ensure a common ground reference (GND) between TTL and RS-485 sides
• Power module with stable 3.3 V or 5 V supply

Package Included:

• 1 x TTL to RS485 Power Supply Converter Board 3.3V 5V Hardware Auto Control Module
• 1 x Connection Cable