A relay is an electrical control device that has an interactive relationship between the control system (input loop) and the controlled system ( output loop). Its working principle is using one circuit (usually with a small current) to control another circuit (usually with a larger current). The electromagnetic effect takes place during this process to control the mechanical contact and achieve the "on" or "off" of a circuit.
Although the structure of relays is different, they are composed of the following three parts:
1. Induction mechanism (receiving input signal): It can reflect certain input variables such as current, voltage, power, impedance, frequency, temperature, pressure, speed, light, etc.).
2. Comparison mechanism (providing comparison amount): Between the input part and the output part of the relay, there is an intermediate mechanism (driving part) that couples and isolates the input amount, processes the function, and drives the output part.
3. Operating mechanism (output switch signal): It controls a circuit to close or open.
Generally speaking, the relay is a controllable switch that can turn on or turn off the circuit when the set conditions are met. It always plays the role of automatic adjustment, safety protection, and conversion circuit in a circuit.