Working Principles of Common Solenoid Valves

    Normally Closed (NC) 2/3-Way Solenoid Valve: When the coil is energized, the air circuit opens. Once de-energized, the circuit closes immediately—this is “momentary” or “jog” operation.

    Normally Open (NO) 2/3-Way Single-Solenoid Valve: When the coil is energized, the air circuit closes. Once de-energized, the circuit reopens—also “momentary” operation.

    Double-Solenoid 2/5-Way Valve: Energizing the “forward” coil opens the forward air path (air exits the forward port). Even after de-energizing this coil, the valve remains in this position—latching until the “reverse” coil is energized.

    Similarly, energizing the “reverse” coil opens the reverse path and latches it until the “forward” coil is re-energized. This behavior is known as “self-locking” or “memory” function.

    Due to this latching characteristic, when designing electromechanical control circuits or PLC programs, the solenoid coil only needs to be pulsed for 1–2 seconds. This minimizes coil heating and significantly extends valve life.