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How to correctly understand the latching relay

                       
Update:21-08-2020
Summary:

The complete name of the relay is electromagnetic armat […]

The complete name of the relay is electromagnetic armature relay, which is different from solid-state relay. The full name is not commonly used, and it is usually represented by abbreviations. Some people also refer to relays as motor relays, but when the name relay is usually mentioned, people know that they are not solid state relays.

The function of the relay is to enable a certain signal or pulse to open or cut off another current.
The relay contains a coil, a set of armature and at least a pair of contacts. The current will flow through the coil. The coil is like an electromagnet and generates a magnetic field. The magnetic field therefore pushes the armature. The shape of the armature is similar to a rotating bracket and will release (or attract). Close) Two contacts. For easy identification, the armature is usually painted green, the coil and the contact are red and orange respectively. The two blue areas are insulated, the left one is used to support the contact, and the right one is on the armature because of the coil. When the magnetic field changes and moves, the contacts will be pulled and closed, and the line between the contacts and the coil is ignored for simplicity.

There are two basic forms of relays: latching (latching) and non-latching (nonlatching). Non-latching relays are also called single-side stable relays. This form is the most common. It is like a temporary switch (or button). When the power of the relay is cut off, the connector will spring back to the original The default state. This is very important in some applications. As soon as the power supply disappears, the relay will return to its original state. Conversely, latching relays have no preset state, and almost all have double-cut contacts, so there is no need to use electricity.
In the case of a single-coil latching relay, the polarity of the applied voltage will determine which pair of contacts will close; and in a dual-coil latching relay, the second coil will move the armature between the two states.