Wiring circuit

This metal detector circuit consists of two oscillators, both working at about 465 kHz. One uses a transformer and the other uses an inductor which is the search coil LI. The oscillators are coupled through a capacitor 10 pF. The circuits DE metal detector is a BFO (beat frequency oscillator), a tone beat produced if the two oscillators are working together through the diode is detected and sent to the audio amplifier. 

The oscillator coil is tuned by a variable capacitor of 10-365 pf variable. The search coil is made of wire with 22 turns between 24 and 36 AWG enamel junction to the center. The wire should be wound on a form of about 6 "χ 6" and the phones must be high impedance.

This schema detects the resistance between your fingers to provide an oscillation. The detection-points can detect resistances as high as 300k and because the resistance decreases, the frequency increases.

Separate the 2 bit pads and fasten them to the back of every hand. because the subject feels nervous, he can sweat and alter the frequency of the schema.The photos show the schema engineered on computer boards

with separate bit pads.

This schema detects the resistance between your fingers to turn on the FALSE LED. The schema sits with the TRUE LED illuminated. The 47k pot is adjusted to permit the LEDs to change state when touching the

probes. 

This schema detects the resistance between your fingers to show the four LEDs. As you press tougher, more

LEDs are illuminated.

his schema detects the resistance between your fingers to show the 3LEDs. As you press harder, a lot of LEDs are illuminated. Theschema is less complicated than Lie Detector-3.