Time Delay Relays are a type of industrial electronic switchgear designed to increase and optimize automation with reliable, repeatable, and accurate timing. They are typically used for applications requiring a delay of a few seconds or minutes, such as controlling clearance for motors, circuit boards, or other automation tasks. H3FA-AU-DC12V is one of the Time Delay Relays that can be used for various applications.The H3FA-AU-DC12V Time Delay Relay has a compact size and is powered by a 12V DC power source. It is equipped with a time setting knob and three output terminals for connection. It also features a built-in LED indicator light, which notifies users when the relay is ready to operate. The H3FA-AU-DC12V Time Delay Relay supports both adjustable delay and fixed delay timing mode, and can be used for various applications including delay control with motor, fan, and light, as well as timing control with hot water tanks, pumps, compressors, and vending machines.The working principle of the H3FA-AU-DC12V Time Delay Relay is based on a timer-generated delay cycle. An electro-mechanical timer is built into the relay. The timer begins to run when the power is applied. The timer can be set to the desired time period by turning the setting knob. When the timer reaches the end of the set time period, the output of the relay will be activated, causing the connection of the terminals. The LED indicator light will then turn on, indicating that the timer has been activated and the relay is ready to operate. If the user wishes to restart the timer, they must turn the setting knob back to 0 and then reapply power to the relay.The H3FA-AU-DC12V Time Delay Relay is extremely reliable and can be used in a variety of industrial, commercial, and residential applications. It offers repeatable, precise, and accurate timing, making it an efficient and cost-effective solution for automation tasks. It is ideal for controlling clearance for motors, circuit boards, and other automation tasks.