Refrigerator shell leakage alarm circuit composed of NE555 and CW9561

As shown in the figure, this is the refrigerator shell leakage alarm circuit. The circuit consists of a power supply circuit, a monostable trigger, a detection and filtering circuit, an alarm circuit, etc.

When a refrigerator plugged into a three-hole socket leaks electricity, the leakage current flows from the live wire of the power supply through the refrigerator shell to the ground terminal of the three-wire socket, and then passes through R11 and R12 to the neutral wire of the power supply to form a loop. The leakage current is divided by R11 and R12, and then detected by D5 and filtered by C5, triggering the controllable 3CT1A to turn on, so that the potential clamp at point A is around 0.6V, the corresponding BG2 tube is turned off, the relay is released, and the power supply of the refrigerator is cut off. At the same time, the BG5 tube is turned on,

The power supply of the alarm circuit is turned on, the light-emitting diode LED2 lights up, and the audio signal sent by the integrated circuit CW9561 is amplified by BG6 and drives Y to send out an alarm signal similar to that of a fire truck. If the power plug of the refrigerator is pressed, and then the total clear switch AN is pressed, the output signal of the monostable trigger turns on the BG2 tube, the relay is energized, and the circuit is reset to normal.

During installation and debugging, be sure not to connect the live wire in reverse. The secondary voltage of the transformer is 14V. The relay is a JRX13-1 small relay with four pairs of contacts. Three pairs of contacts are connected in parallel to power the refrigerator.

In addition to automatically cutting off the power supply and sending out sound and light alarm signals when leakage occurs in the refrigerator casing, this circuit also has the overvoltage, undervoltage and delay functions of general protectors.