This is where I am up to in my build. Have Uno displaying soil moisture and ultrasonic in water bucket. Searching for weeks how to connect submersible pond pump. Have a relay and 12v adapter , do I need a shield To protect Uno? Or a micro motor controller? I have read about? Just don’t know what to get to makemotor work. Should I have a shield for the lcd?
Glad to see you are progressing with your project.
Please add links for the components you are using when posting. It makes it sooooo much easier to answer your questions.You should not require a motor driver, but a relay coil is big inductor, and the voltages generated when the relay is switched can damage the Arduino. Either use a relay shield, or ensure that the Arduino is protected from these large voltage spikes.
The output of the relay controls the on/off state and voltage to the pump motor.
In the meantime, the tutorial on Arduino s and relays might help.