The 5V relay (SRD-05VDC-SL-C) operates from the regulated 3.3V DC supply; This V4.0 module has three 10KΩ pull-up resistors (RESET/GPIO0/CH_PD) A PC817 optocoupler drives the relay control MOSFET ...

The module I received was marked “485 Relay 2CH V1.1” on the top. There’s a AMS1117-3.3 (www.advanced-monolithic.com) LDO voltage regulator (3.3V), a Shenzhen Hangshun Chip Technology Development ...