Introduction and Usage of Relays

1. Origin of Relays

Relays are electronic control devices that first appeared in the early 19th century. They were initially invented for use in telegraph systems to remotely control and amplify signals. Relays achieve circuit on/off control through an electromagnetic coil driving a mechanical switch. With the advancement of technology, the application range of relays has expanded and is now widely used in household appliances, industrial automation, communication equipment, and more.

2. Usage Norms for Relays

To ensure the proper functioning and longevity of relays, the following points should be noted during use:

1. Electrical Specifications: Choose appropriate electrical specifications, including operating voltage, current, and power. Exceeding these specifications can cause relay damage or failure.
2. Installation Environment: Relays should be installed in dry, well-ventilated environments to avoid moisture or high temperature impacts.
3. Operating Frequency: The switching frequency of relays should be controlled within the rated range, as excessively high frequencies can accelerate contact wear.
4. Load Type: Understand the characteristics of the load, such as inductive or capacitive loads, to select the appropriate type of relay.

3. Selection of Relays

When choosing relays, consider the following aspects:

1. Load Capacity: Select a relay that can handle the current and voltage of the control circuit to ensure proper switching of the load.
2. Control Signal: Choose the working voltage and current of the relay coil based on the output signal of the control circuit.
3. Contact Form: Select the form of relay contacts as needed, such as normally open, normally closed, or changeover contacts.
4. Environmental Requirements: If the working environment has high temperatures, high humidity, or corrosive gases, choose relays with environmental resistance features.