Mobile phone shielding circuit that can be used as a charger

The circuit shared today can be used as a mobile phone charger or as a mobile phone shield. And when someone tries to take away the phone, it is capable of producing a loud chirping sound.

The circuit consists of the rectifier diodes D1 and D2 of the step-down transformer The mobile phone shielding circuit uses two optional NE555 timer ICs: a very simple multivibrator (IC2), and a second monostable multivibrator (IC3). The multivibrator has timing resistors R1 and R2, but no timing capacitor as it works with stray capacitance. Its pins 6 and 2 are directly added to the protective shield built on a 10cm x 10cm copper clad board.

The inherent stray capacitance of the circuit is sufficient to provide an output frequency of approximately 25 kHz with R1 and R2. This arrangement provides better sensitivity and allows the circuit to be used with manual capacitance effects. The output pulse assigned to the oscillator immediately triggers the monostable on pin 2 of the multivibrator. The monostable utilizes low value capacitor C6, resistor R3 and preset timing VR1. As shown below.