Many products use solenoids to open and close valves. A microcontroller can control solenoids programmatically using a GPIO pin and a simple circuit.
Using Pull-Up and Pull-Down Resistors
An embedded microcontroller utilizes input/output (IO) signals to communicate with the outside world. The simplest form of IO is commonly referred to as general purpose input/output (GPIO) where the GPIO voltage level can be high, low, or high-impedance. Pulling resistors are used to ensure GPIO is always in a valid state.
Understanding Microcontroller Pin Input/Output Modes
General purpose input/output (GPIO) pins on microcontrollers have various modes for both input and output. Input modes may include pull-up or pull-down resistors, hysteresis, or some combination. Output modes can be push-pull, high-drive or open-drain.