How to use relays correctly

A relay is an electrical control device that is an electrical device that causes a predetermined step change in the controlled output quantity in the electrical output circuit when the change in the input amount (excitation amount) reaches the specified requirement. This article describes how to use the relay correctly, which is introduced by the selection of the rated operating voltage of the relay, the selection of the contact load and the selection of the power supply of the relay coil.

1, the choice of relay rated working voltage

The rated operating voltage of the relay is one of the most important technical parameters of the relay. When using a relay, you should first consider the operating voltage of the circuit in which it is located (ie, the circuit in which the relay coil is located). The rated operating voltage of the relay should be equal to the operating voltage of the circuit in which it is located. The operating voltage of the circuit is generally 0.86 of the rated operating voltage of the relay. Note that the workpiece voltage of the circuit should not exceed the rated working voltage of the relay, otherwise the relay coil is easy to burn. In addition, some integrated circuits, such as the NE555 circuit, can directly drive the relay. Some integrated circuits, such as COMS circuits, have a small output current. A transistor amplifier circuit is required to drive the relay. This should consider that the transistor output current should be greater than The rated operating current of the relay.

2, contact load selection

Contact load refers to the bearing capacity of the contact. The contacts of the relay can withstand a certain voltage and current during the conversion. Therefore, when using a relay, it should be considered that the voltage applied to the contact and the current through the contact must not exceed the contact load capacity of the relay. For example, a relay has a contact load of 28V (DC) × 10A, indicating that the relay contact can only work on a circuit with a DC voltage of 28V. The contact current is 10A, which exceeds 28V or 10A, which will affect the normal use of the relay. Even burned the contacts.

3, the choice of relay coil power supply

This means that the relay coil uses direct current (DC) or alternating current (AC). Usually, beginners use electronic circuits in their electronic production activities, and electronic circuits are often powered by DC power. Therefore, it is necessary to use a relay whose coil is a DC voltage.