Summary

• RS-485 half-duplex line driver
• 1kV galvanic isolation

What is it?

This little board acts much like the familiar Maxim MAX481 or MAX485 chips, providing a half-duplex RS-485 line transmitter and receiver. It adds in addition a 1kV galvanic isolation barrier that allows a logic signal to pass to and from the line driver chip, while electrically separating it. This lets the RS-485 line operate at a different electrical potential - useful if the line has to travel some distance, especially between buildings or if there's a potential for different systems running on different electrical power phases. This is often used in stage equipment that uses DMX-512 for example.

Why did you make it?

I've been building a lot of DMX-512-controlled equipment. A DMX receiver is ideally supposed to be electrically isolated from the sender, to avoid electrical issues across stages. It's also useful whenever the line has to travel a long distance; which is typically where RS-485 is most used.

What makes it special?

Unlike most of the other RS-485 driver modules you tend to find, this one combines the power and logic isolation elements right there on the board, giving a complete RS-485 handling in one convenient place.

If you're looking for an isolated RS-485 line driver with an onboard microcontroller, perhaps to contain an entire application, or at least offload the serial line communication of a larger project into a module that could be attached by SPI or I²C, you might instead be interested in the RS-485 Isolated ATtiny814 Board or RS-485 Isolated ATtiny841 Board products.