2. Test the soil moisture sensor module: Connect the fork probe and the transmitter module with two lines. The transmitter module VCC is connected to 5V and GND is grounded. When powered on, the red power light is always on and the green (blue) indicator is The light flashes faintly once: insert the fork probe directly into the water, the green (blue) indicator light turn on 1. Test the relay module: Connect the VCC of the relay module to 5V, connect GND to ground, connect IN to GND and the relay jump. If IN is left floating, the relay recover. If you repeat this, you can hear the relay's "stuck" sound. 3. Connect the red wire of the water pump to 5V, and the black wire to ground. The water pump works. Note that the test only takes 1 second. Do not expose it to the air for a long time., Weight: 0.25242928999 Pounds, Manufacturer: Jaywool