The relay coil is represented by a long box symbol in the circuit. If the relay has two coils, draw two long boxes in parallel. At the same time, the letter symbol "J" of the relay is marked inside or beside the long box. There are two ways to represent the contacts of the relay: one is to draw them directly on the side of the long box, which is more intuitive. The other is to draw each contact into its own control circuit according to the needs of circuit connection. Usually, the same text symbol is marked beside the contact and coil of the same relay, and the contact group is numbered. To show the difference.
There are three basic forms of relay contacts:
1. The two contacts are disconnected when the coil of dynamic closing type (H type) is not energized. After energization, the two contacts are closed. It is represented by the pinyin prefix "H" in the Chinese character.
2. The two contacts are closed when the dynamic break type (D type) coil is not energized, and the two contacts are disconnected after energization. It is represented by the hyphenated pinyin prefix "D".
3. Conversion type (Z type) This is a contact group type. There are three contacts in this kind of contact group, that is, the middle is the moving contact, and the upper and lower ones are static contacts. When the coil is not energized, the moving contact and one of the static contacts are opened and the other is closed. After the coil is energized, the moving contact moves, so that the original open is closed, and the original closed is open, reaching the transition purpose. Such a contact group is called a switching contact. It is represented by the pinyin prefix "z" of the word "zhuan".