Metal detector circuit diagram composed of CD4046

Crystal oscillator

Industrial Router Crystal 3.2*2.5mm 3225 26M (26.000MHZ) 12PF 10PPM 20PPM 30PPM

A typical metal detector is composed of two main components: the detection unit and an automatic rejection system, with the detection unit being the core part. Inside the detector, there are three sets of coils — a central transmitting coil and two identical receiving coils. The oscillator connected to the transmitting coil generates a high-frequency alternating magnetic field. In a normal, undisturbed state, the receiving coils produce equal induced voltages, which cancel each other out, resulting in a balanced condition.

The circuit involving VT, C1, C2, and the probe’s inductor L forms an oscillator operating at around 300 kHz. The probe itself uses a large coil with a diameter of 440 mm. When this coil approaches a metal object buried underground, the metal acts like a short-circuit loop, reducing the inductance of L. This causes the oscillation frequency to increase, leading to a change in the deflection angle of the meter needle. The meter is typically designed with a zero indicator, where the zero point is located at the center of the dial. This type of circuit still functions as a frequency-to-voltage converter.

When metal impurities enter the magnetic field, the equilibrium is disrupted. The induced voltages from the two receiving coils can no longer cancel each other out. These unbalanced voltages are then amplified by the control system, generating an alarm signal that indicates the presence of metal contaminants. This signal can be used to activate an automatic rejection mechanism, helping to remove unwanted metal particles from the production line.

The following image shows a circuit diagram of a metal detector based on the CD4046 IC. This design is commonly used in industrial applications due to its reliability and accuracy in detecting small metal objects. Whether it's for food processing, pharmaceuticals, or manufacturing, such detectors play a crucial role in ensuring product safety and quality control.