cheap metal detector circuit schematic

Cheap Metal Detector Circuit

The working principle of this cheap and easy to build metal detector circuit consists in mixing two equal frequencies which causes a low-frequency interference. When one of the oscillators become unstable then the frenquency of the interference will be modified. The metal detector circuit is built with CD4011.

The oscillator is built with NAND N1 and a ceramic filter of intermediary freq. (470kHz). The second oscillator is with N3 and a LC combination. The freq. of this osc. is adjusted in such way that will produce an audible oscillation of both freqs.

Thru N4, the signal from the variable osc. is amplified. If the sensor coil L1 is closer to a metal object then it will modify the auto-induction of the coil, the osc. is unbalanced and the sound will modify.

The metal detector’s coil is made of: 70 turns of enamelled copper with diam. of 0.3-0.6 mm on a 5 cm diam.

Easy to build metal detector schematic

cheap metal detector circuit schematic


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  • hobbiest

    how can i build that kind of circuit if the author of this didn`t specified well the pins of i.c. where are the number of leads that are needs to connect to the other components…

    • Popescu Marian

      It is quite easy, just look at the datasheet of 4011 IC and you will see 1 and 2 are inputs, 3 is the output pin, 5 and 6 inputs and 4 the output, and so on.

  • shubham kaushik

    hey i want to make a iron metal detector for my project can u send me a simple easy to make iron metal detector circuit with its full explanation.Thank you.

  • Jeroi

    It does not work. Please update this circuit with 8ohm speaker or Headphone connector. It will detect difference when metal comes to coil. But it seems that it makes sound in 420khz better. But adding proper metaldetector coil arround 1.11nF inductance do not provide good sound at all. ALso the detecting range is only 10cm or less. SO the circuit needs more voltage for coil to make better magnetic field for the coil.

    Recommended: Do not use this circuit.

  • Julian

    Umm, what’s the 9380 label?

  • Jenny Tan

    What is the maximum distance between the coil and the metal? Thank you very much!:)

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