This Electricity Failure Alarm designed as a power supply monitoring device that will trigger a buzzer when the mains supply cuts off. At the same time, the light-emitting diode will be turned ON. This device function to inform the loss of power supply to some critical installation such as pump in fish tank. When the buzzer sounds, you’ll know there’s been a power outage. And steps must be made to correct the issue, such as supplying other power or moving the facility.
The circuit comprises mostly of an AC relay. Use a 120V AC relay if the mains input is 120V AC. Use a 240V AC relay if the mains input is 240V AC. The relay is a Single Pole Double Throw (SPDT) type, and if it is not powered, the COM will be connected to the NC terminal. The COM terminal will be linked to the NO terminal once it has been activated.
This sort of relay may be found at almost any electronics store. Ensure that the coil of the relay is rated for the power supply you’re using. The relay will be damaged or will simply not operate if the rating is incorrect, even if it is correctly connected to the mains supply. When connecting the mains to the relay, use extreme caution. Before connecting the relay, make sure you take the required precautions, such as isolating the mains.