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.
BFO Metal detectors Circuit Diagram:
![BFO Metal detectors Circuit Diagram BFO Metal detectors Circuit Diagram](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjGf7_sjBbu443-IA_tQ7TRXUxkkHtm6v38Q9i6GSVn6NvkYL1_L7gDAkoNw1b1P-HlD3NRYG6t9vVUsD-oJeWiMLUXFXqCNdwiOy0iPUF-20dScLtVNy6ca-PnS-grrsMQ-4eidBnohCY/s400/BFO+Metal+detectors+Circuit+Diagram.gif)
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.
BFO Metal detectors Circuit Diagram:
![BFO Metal detectors Circuit Diagram BFO Metal detectors Circuit Diagram](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjGf7_sjBbu443-IA_tQ7TRXUxkkHtm6v38Q9i6GSVn6NvkYL1_L7gDAkoNw1b1P-HlD3NRYG6t9vVUsD-oJeWiMLUXFXqCNdwiOy0iPUF-20dScLtVNy6ca-PnS-grrsMQ-4eidBnohCY/s400/BFO+Metal+detectors+Circuit+Diagram.gif)
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.
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