1x relay with normally open contact (NO) + normally closed contact (NC) Version: v2
power a higher power device with a relay.contact normally open (circuit interrupted when the relay is not active) and a contact normally closed (closed circuit when the relay is not active).
The relays provide galvanic isolation to fully isolate the low voltage circuit (the Wemos) from the power circuit (usually with a higher voltage, 12V and higher). The relay shield has the circuits necessary to control the relay (namely, transistor and protective diode).
The manufacturer mentions the following information about the relay shield: