When the mains power supply is used in the rural cable television network, the power failure phenomenon is often encountered. A dual power automatic switching device (see the drawing) is designed, which is described below.
The device can be divided into a power supply part and a control part. The power supply part is composed of a transformer, a rectification and filtering circuit and a three-terminal regulator 7812. The control part is composed of a JQX-13F type relay, and the working current of the relay is 12V direct current.
When the main power supply has electricity, the power supply part is rectified, filtered and regulated, and outputs 12V DC power. The relays are connected to the relays 10 and 11 to make the relay work. The 4-7 feet and the 6-9 feet are turned on, and the main power supply passes through the 4-7 feet. And 6-9 feet enter the power supply input terminal: When the main power supply is cut off, the backup power supply has no relay, 4-7 feet, 6-9 feet are disconnected, 1-7 feet, 3-9 feet are turned on, The backup power supply enters the input end of the power supply; when the main and backup power supplies have power, the relay works, the backup power supply is disconnected, and the main power supply enters the power supply.
The device occupies a small space and is installed in an empty space at one end of the power supply. It can be fixed with screws and installed in the cable TV network. It works well today.
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