The relay coil is represented by a rectangular frame symbol in the circuit. If the relay has two coils, please draw two parallel rectangular boxes. At the same time, mark the text symbol "J" of the relay in or beside the long box. There are two ways to represent the relay contacts: one is to draw them directly on the side of the long box, which is more intuitive. The other is to introduce each contact into its own control circuit according to the need of circuit connection. Usually, the same text symbols are marked next to the contacts and coils of the same relay, and the contact groups are numbered. Show the difference.
There are 3 basic forms of relay contacts:
When the coil is not energized, the two contacts of the movable (normally open, H-type) coil are disconnected, and the two contacts are closed after energization.
The two contacts of the dynamic-break (normally closed, D-type) coil are closed when the coil is not energized, and the two contacts are disconnected after energization.
The conversion type (Z type) is the contact group type. This kind of contact group has 3 contacts in total, that is, the middle is mobile contact, and the upper and lower sides are static contacts. When the coil is not energized, the movable contact is disconnected from one of the static contacts, and the other static contact is closed. After the coil is energized, the movable contact moves to close the original open state and make the original closed open state to achieve the purpose of conversion. Such contact groups are called converted contacts.