What it is and how it works
The kit includes one two-channel relay module labelled 5 V. Current through a coil creates a magnetic field that moves a contact. Two channels allow two circuits to switch independently. A module usually includes coil-driving circuitry, but its details must be checked on the actual board.
Contact labels commonly include COM, NO and NC. COM is common; NO is open and NC is closed to COM when the relay is not energised. Switching produces an audible click. These names explain contact operation, not the physical terminal order of this particular board.
What we can use it for
- Switch two low-voltage LED circuits with current-limiting resistors independently.
- Demonstrate normally open and normally closed contacts.
- Build an automation model responding to a timer or sensor.
First exercise
Disconnect the load and identify terminals from labels and documentation. Check contacts with a multimeter, then operate one channel using a suitable control circuit. Only then connect a small low-voltage demonstration load. Repeat separately for the second channel and observe independent switching.
Handling notes
A 5 V module or coil rating does not establish compatibility with 3.3 V GPIO signals. Check supply requirements, input thresholds and active state. Never power coils from a GPIO. Do not assume isolation from appearance. Use low voltage for these exercises; never connect mains to an exposed module or breadboard.
Background: SparkFun — Inventor's Kit relay exercise.