Make a simple metal detector

The concept of the device is shown in Figure 1. 1, it can be done in a couple of minutes. Metal detector consists of two almost identical LC-generators, inverters from DD DD 1.1-1.4; VD1, VD2 rectifier and high headphone BF1. When the eroids domestic search coil to the metal objects to the tone of the sound in the headphones will change.

Schematic diagram

The model generator, inverters DD DD 1.1 and 1.2, self-initiated at 465 kHz. Coil L1 is applied from a filter IF the radio. L2 coil wrapped on a 200 mm diameter, it contains 30 turns of enameled wire diameter 0.4 mm.

With the help of a metal detector is tuned to C2 KPE find objects of different mass.

In the manufacture of metal detector can I chip K155JIA3, Rectifier diodes – any high-frequency, variable capacitor of any compact receiver, such as a “Climber”.