This module is based on 2-Coil Latching Relay. In contrast to the ordinary relay, this latching relay does not need continuous power to keep the state, only a rising/falling pulse is needed to change the work state. Even the power can be removed when the work state does not need to change, making this module especially suitable for low-power projects.

What are latching relays?

Relays are common electromechanical devices in circuits and come in two types: latching and non-latching. Latching relays retain their last switching position even after a complete power failure, whether single or dual coil types.

Single-coil latching relays use only one coil to set or reset the switch position but require both positive and negative voltages. When a positive voltage is applied, current flows in one direction and puts the relay into the set state (i.e. the relay switch is closed). If a negative voltage is applied, it reverses the direction of the current flow and puts the relay into the reset state (i.e. the switch is open).

A dual coil latching relay, on the other hand, uses only a positive voltage but requires two power supplies or drivers. This type of relay has a set coil and a reset coil. When the set coil is energized, the relay enters the set state. Conversely, when the reset coil is energized, the relay enters the reset state. However, both coils are never energized at the same time.