In this article we will consider the modified version of this metal detector – VINTIK-PI (ver.2). (See the previous version VINTIK-PI V1)
Pulsed metal detector “VINTIK-PI” is assembled on four chips, designed to search for small metal objects. It is not much more difficult than the previous version. The circuit also does not contain programmable microcircuits, and there are no expensive and scarce radio components in it either.
Its sensitivity is slightly better than the previous version ” VINYIK-PI V1” and easier to configure.
The principle of operation of the VINTIK-PI
The circuit consists of the transmitting and receiving parts .
The principle of operation of a pulsed metal detector “VINTIK-PI” is based on the excitation of pulsed eddy currents in the area of a metal object. These currents induce a secondary electromagnetic field in the search coil, which is then processed by the receiver (amplified, the necessary part of the signal is cut, the result is converted into a pulse duration and modulated by an audio frequency generator)
The transmitting part consists of a rectangular pulse generator on IC1 – NE555 and a powerful transistor – IRF740 (IRF840). To adjust the duration and frequency of the pulse, select the resistance R10 and R11, respectively.
The receiving node is assembled on the IC2 – TL074 IC. It consists of four low-noise operational amplifiers. At the input of the first stage of the amplifier is the signal limiter on the diodes VD1, VD2, connected in anti-parallel. To cut the desired part of the reflected signal between the first and second amplifier, a switch is turned on at the field-effect transistor T3 (BF245), controlled by a delay circuit on IC 3 (NE555).
On IC 2.3 (NE555), a repeater is assembled which, using T4 (2N3906), starts an audio frequency generator (about 6 kHz) on IC 4 (NE555). So the sound generator is triggered when a metal appears in the coil area. When a metal appears, a crackle appears, and when the coil is brought closer, the sound of the generator appears. The desired tone can be selected by capacitor C16.
Diode VD3 IN4001 together with a fuse (0.5A installed on the board in the form of a thin track) are needed to protect the circuit from accidental power reversal.
Characteristics of the metal detector:
Power supply – 9 – 12 volts
Current consumption – 48 – 65 mA
Alarm – Sound
Metal Discrimination – No
Sensitivity (maximum at 12V) – a telephone microphone (45 mm) – 32 cm, a gold ring – 22 cm, 5 rubles – 20 cm, a cell phone – 37 cm, a Kron battery – 30 cm.