A relay is an electrical control device. It is an electrical appliance that causes the controlled quantity to undergo a predetermined step change in the electrical output circuit when the change in the input quantity (excitation quantity) meets the specified requirements. This article introduces how to use the relay correctly. It is introduced from three aspects: the selection of the rated working voltage of the relay, the selection of the contact load and the selection of the relay coil power supply.
1. Selection of the rated working voltage of the relay
The rated working voltage of the relay is one of the most important technical parameters of the relay. When using a relay, you should first consider the working voltage of the circuit where the relay coil is located. The rated working voltage of the relay should be equal to the working voltage of the circuit where it is. Generally, the working voltage of the circuit is 0.86 of the rated working voltage of the relay. Note that the voltage of the workpiece in the circuit must not exceed the rated working voltage of the relay, otherwise the relay coil is easily burned. In addition, some integrated circuits, such as the NE555 circuit, can directly drive the relay to work, while some integrated circuits, such as the CMOS circuit, have a small output current and need to add a transistor amplifier circuit to drive the relay. This should consider that the transistor output current should be greater than The rated working current of the relay.
How to use relays correctly
2, the choice of contact load
Contact load refers to the bearing capacity of the contact. The contacts of the relay can withstand a certain voltage and current during conversion. Therefore, when using a relay, it should be considered that the voltage applied to the contact and the current through the contact cannot exceed the contact load capacity of the relay. For example, the contact load of a relay is 28V(DC)×10A, indicating that the relay contacts can only work on a circuit with a DC voltage of 28V, and the contact current is 10A. If it exceeds 28V or 10A, it will affect the normal use of the relay. , And even burned the contacts.
3, the choice of relay coil power supply
This refers to whether the relay coil uses direct current (DC) or alternating current (AC). Generally, beginners use electronic circuits in electronic production activities, and electronic circuits often use DC power supply, so it must be a relay whose coil is a DC voltage.