Figure 1
Driving a Double coil polarised latching relay


Figure 2
Driving a single coil polarised latching relay

The driving coils of the latching relays are equipped with three connectors (centre-tapped). This enables the user to choose between a single coil and a double coil configuration.

The position of the relay depends on the current through the driving coil. Figure 1 shows the circuit with a douple coil using two transistors, one for each switching position.

The centre tapped Pin is connected to a DC supply, but also a capacitor discharge can be used. Without utilisation of the centre tapped Pin the coil can be driven as a single coil relay through a Triac as shown in Figure 2.

The power for the douple coil can be taken from a storage capacitor or a battery, the single coil in Figure 2 can only be driven when the AC voltage from the mains is present. Therefore the single coil only requires half the power of a double coil. The latching relay does not require a large power supply, because of its low energy consumption. Even battery driven applications are possible, depending on how often the relay is switched on and off.