RS-232 to RS-485 Converter - Port-Powered, 115.2k baud

Our review of the B&B Electronics port-powered RS-232 to RS-485 converter finds it a focused, practical tool for technicians who need a simple, reliable interface between legacy RS-232 equipment and 2-wire RS-485 networks. The single biggest reason to buy is its port-powered design: it draws power from RS-232 data and handshake lines so no external supply is required when those signals are available, which simplifies installation in tight or retrofitted environments. For projects that demand long run communications and automatic direction control, this unit offers a compact, no-frills solution.

Key Features

• Port-powered operation: The converter runs without an external power supply when RS-232 handshake lines are available, reducing cable clutter and installation steps.
• Two-channel conversion: It converts transmit and receive RS-232 lines to balanced half-duplex RS-485, enabling communication with standard 2-wire RS-485 networks.
• Automatic transmit control: The built-in control circuit enables the RS-485 driver only when transmitting to prevent bus contention and simplify wiring.
• Receiver disable on transmit: The receiver is disabled during transmission to avoid echo back to the RS-232 device, keeping data clean on the serial link.
• Long distance capability: Depending on port power, the converter will transmit up to 4000 ft at lower baud rates, useful for industrial or remote serial runs.

Who It's For

The converter is aimed at technicians, integrators, and hobbyists who need to bridge legacy RS-232 equipment to RS-485 networks without adding a power adapter. It is particularly useful in industrial automation, building controls, and retrofit jobs where space and access for a power supply are limited.

If you require multi-drop RS-485 networks with full-duplex communication, or need isolated interfaces or surge protection for harsh electrical environments, this simple port-powered unit may be too basic; look for dedicated isolated or powered converters instead.

Pros & Cons

Pros

• Compact DB-9 female connectors on both sides make it easy to plug into existing RS-232 and RS-485 cabling.
• Port-powered design removes the need for an external power source when handshake lines are present, simplifying installs.
• Automatic direction control and receiver disable during transmit prevent echo and bus conflicts without manual control wiring.
• Supports up to 115.2k baud for use with faster serial equipment when cabling and distance permit.

Cons

• Because it relies on RS-232 handshake lines for power, some hosts without those outputs may require an alternative power solution.
• Half-duplex 2-wire operation only, so it is not suitable where full-duplex RS-485 is required.

Specifications

Brand	B&B Electronics
Model type	Port-powered RS-232 to RS-485 converter
Connectors	DB-9 female on RS-232 and DB-9 female on RS-485
Data rates	Up to 115.2 k baud
Distance	Up to 4000 ft (depending on port power and baud rate)
Operation	2-wire half-duplex with automatic transmit control
Dimensions	2.50 x 1.30 x 0.80 in

Our Verdict

The B&B Electronics RS-232 to RS-485 port-powered converter is a practical, compact choice for converting single RS-232 ports to 2-wire RS-485 when you want minimal wiring and no external power. It is good value for integrators who need automatic direction control, reliable echo prevention, and the ability to span long distances at modest baud rates, but those needing isolation, surge protection, or full-duplex operation should consider purpose-built alternatives.

Frequently Asked Questions

Does the converter need an external power supply?
It does not require external power if two RS-232 handshake or output lines are available; otherwise a powered alternative is needed.

Can it do full-duplex RS-485?
No, the unit supports 2-wire half-duplex RS-485 only with automatic driver control.

How far will it transmit?
Distance depends on available port power and baud rate; the device can transmit up to 4000 ft at lower speeds such as 19,200 baud.