This is a single relay board with two status indicator LEDs and screw-in terminal blocks for input and output.
At the input terminal, there are three contacts:
DC+ : Connect to 5V to power the relay
DC- : Connect to ground
IN : Connect to signal that triggers the relay (HIGH/LOW)
The output terminal has three contacts as well. The relay itself is essentially an SPDT switch:
NO : Normally-open
COM : Common
NC : Normally-closed
The relay is opto-isolated. This means, there is no electrical connection between the high voltage device and the low voltage circuit that switching the relay. Therefore, it is much more safe and reduce the chances of accidentally destroying the micro controller or sensor that controlling the relay.
Features:
5V single channel relay board with optocoupler, requires 15-20mA driving current
SPDT type relay with one normally open terminal, one normally closed terminal and one common terminal
Screw terminal for input power (5V DC) and relay control
