Simply, it’s an Arduino library for communicating with Modbus slaves over RS232/485 via RTU (remote terminal unit) protocol. In conclusion, the Modbus 2-channel 5V relay module is a very useful device ...

This Arduino Uno setup can be powered by a 6F22 9V battery or other suitable power source, but it is up to you. The next piece of hardware is a dual-channel, low-trigger, 5V relay module. This relay ...