Which device automates the on/off operation of irrigation valves?

• A. Manual switch
• B. Irrigation controller
• C. Pressure regulator
• D. Soil moisture sensor

Answer: (B)

The irrigation controller is the device that automates the on/off operation of irrigation valves. It serves as the central controller for a sprinkler system, programmed with start times, durations, and which zones to water. It sends electrical signals to each valve’s solenoid to open or close, turning water flow on and off according to the programmed schedule or sensor inputs. This is what makes irrigation occur automatically without human intervention.

The other devices don’t automate valve operation. A manual switch requires someone to flip it to start or stop watering. A pressure regulator changes the water pressure (to protect components and ensure even spray patterns) but doesn’t control valve states. A soil moisture sensor helps determine when watering should occur by indicating soil moisture levels, but the actual valve actuation is carried out by the irrigation controller via its programmed commands or sensor-driven control.