Latching relays, also known as “bistable relays” or “memory relays,” are a special type of relay that can maintain their switched state even when the controlling power is turned off. Unlike regular relays that require continuous power to stay in a particular state, latching relays need only a short pulse to switch between two states： one where the relay is “latched” or in an active state, and another where it is “unlatched” or in an idle state. This feature makes latching relays an essential component in a variety of applications, especially in systems where energy efficiency is crucial or where a persistent state must be maintained without continuous power supply.
Working Principle of Latching Relay The working principle of a latching relay revolves around its ability to “latch” onto a state after a brief input pulse. This pulse drives a mechanism that changes the position of the relay’s contacts, either switching them from the normally open (NO) state to the normally closed (NC) state, or vice versa. A latching relay typically has two coils： a “set” coil and a “reset” coil. These coils control the switching actions. Set Coil： When a pulse is applied to the set coil, it changes the state of the relay, usually activating it and causing the contacts to latch into the “set” position.