Music test pen circuit

Principle circuit diagram of the music electroscope. The detection circuit is composed of a field effect transistor VII and a transistor VT. When there is electricity,
the alternating magnetic field generated by the mains power generates an induced electromotive force in the detection circuit, causing the conductive field effect transistor VF to become inactive and VT is turned on. , & the photodiode
LED lights up, and the music card circuit plays the sound. When there is no power, VT is turned on, and VSD is less than 0.7V, causing VT to be turned off.
    The field effect transistor vF in the music electroscope is a 3DJ6 trench junction field effect transistor. VT uses 3DX2QIB silicon NPN type low-
frequency transistor. The magnification p value is greater than 100. The music card circuit can use an ordinary music card circuit. LEDs should be
light-emitting diodes that are transparent at ordinary times and emit red light when powered on to facilitate comparison in strong light environments. The crystal radio for power supply uses 4F2 type 6V laminated battery... the resistors and capacitors are all
small components. The shell can be replaced by a commercially available remote control shell. The reference size is .i20m .X3enm .xzsmm. 1: Figure l_53b is the printed circuit board
of the music electroscope pen . The size of the printed circuit board is 32mmX 32mm. The wire diameter of the hysteria coil of the music electroscope is -l. Make a small piece of 13n plastic insulated wire with an inner diameter of 3mm, stick it to the printed circuit board, move the induction coil away from the power cord, and turn on the power switch. Adjust the resistance of resistor R2 to make the transistor VT well cut off. Then put the induction coil close to the phase line. Due to the action of the electric field, VF is cut off and VT is turned on. The LED lights up. Reduce the resistance R3 from large to large, so that the voltage at both ends of the music card is between 2-3V, and the music card circuit works to drive the piezoelectric ceramic piece to produce sound. If you stick the pen on the wall and move it slowly, you can use the light emitting diode and the sound of music to determine whether there are hidden live wires in the wall. This can avoid the risk of electric shock when drilling holes in the wall. At the same time, you can also find the in-line breaks in live wires .