Feeble click in relay but it doesn't get activated when connected to Arduino circuit I have an Arduino uno board and I have a soil moisture sensor


connected the digital output pin of the sensor to Arduino input pin 
connected an output pin of Arduino to the INPUT pin of the relay board 
programmed the Arduino such that if input is HIGH then the OUTPUT should be HIGH as well 
connected 5 v pin of Arduino to vcc of the relay board
connected gnd pin of Arduino to gnd of the relay board 


When my sensor outputs a HIGH DO (digital output), the relay only creates a feeble click sound and does not get activated. The Relay board LED does light up but the relay itself does not work (NC remains closed and NO remains open).

Do I need to supply an external VCC to the relay board? If yes then how should I set up the circuit?

A picture of the relay board is attached. You are right ... it is a 12 v relay. Do I need a 12 v external power source with IN1 coming from Arduino? Any help will be much appreciated.
You need to join the ground of the external supply to the ground being supplied from the Arduino.  The 12V supply must be capable of at least 100ma

There appears to be a transistor and resistor on the board.  This is probably to drive the relay coil from the Arduino.  However, I would need to look at the circuit diagram of the board to be certain.  Can you supply images of the copper side and component side of the board to see what the connections are.

Ideally the circuit diagram from the manufacturer would be even better.