Two simple mains leakage alarm circuits and production

 Two simple mains leakage alarm circuits and production

　The two alarms introduced here have simple circuits and sensitive triggering. They can be directly installed into the combined socket . They are suitable for leakage alarms of household appliances. They are cheap and easy to make. The circuits of these two alarms are shown in Figure 1 (A) and (B) respectively. Picture (A) is a leakage alarm made with a CMOS six-inverter CD4069. Normally, the audio oscillator composed of gate A, gate B, R2, and YD does not produce sound when no current passes through it. When an electrical appliance with a leaky shell is inserted into a three-hole socket, the leakage current flows from the live wire of the power supply through the electrical shell to the ground jack of the three-hole socket , and then returns to the neutral wire of the power supply through the alarm to form a loop. The leakage current is stepped down by R1 and rectified by VD. The pulsating current behind makes the alarm sound. The leakage alarm current of this circuit is less than 0.3mA.

　　Figure (B) uses a piece of CW9300 music IC to make a leakage alarm. Since R1 and VT form a highly sensitive trigger circuit, the alarm has high sensitivity and its leakage alarm current is less than 10uA. The working voltage of the music IC is supplied by R2 step-down, VD rectification, and C filtering. Since the voltage is taken from the 220V mains live wire, compared with some alarm circuits that rely on leakage current and voltage to maintain IC sound, not only the alarm volume is larger, but also it overcomes the shortcomings of the above-mentioned circuit volume changing with the leakage current.

Leakage alarm circuit