The module is a universal pulse metal detector on a microprocessor and uses
Clone PI-W circuit and software solutions. Designed to search for metal objects in the soil, sand, walls, thick grass and others. The use of sensors of different sizes allows you to solve a wide range of search tasks.
Specifications
➔ The depth of detection of the coin with the sensor Ø22, cm ................. up to 28
➔ The depth of detection of large objects with sensor Ø22, cm to 150
➔ Power supply, V ....................................................................... 9-14
➔ Current consumption not more than, mA ............................................ .. …… ...... 90
➔ Display Type ................................………....... LED / Audible
➔ Overall dimensions of the board ShhVhG, mm ......................... ........ 75h35h36
Device description
The principle of operation of the metal detector is based on the excitation of pulsed eddy
currents in a metal object and the measurement of the secondary electromagnetic field
induced by these currents. In the OU U1 and U5 circuit, a differential and non-inverting
amplifier, as well as a measuring integrator, are implemented. Chip U2 is an analog key. The U3 chip is a microcontroller that performs analog-to-digital conversion. On the field-effect transistor T1 assembled a powerful key. LEDs D3 - D12 are designed to indicate the detected target and indicate the device settings, which is carried out using the buttons SW2 - SW6.
Making a search coil
For the manufacture of the search coil will need a rigid non-metallic mandrel Ø from 20 cm or more. The larger the diameter of the coil - the higher the "intuition" of the metal detector to large objects (for small and medium-sized objects the diameter of the coil is about 25 cm) 25-27 turns of enamelled copper winding enamelled wire (Ø0.5 - 0.8 mm ). The ends of the wire to fix and solder on the board to the contacts L1. In order to give a rigid form to the sensor, you can use impregnations that do not conduct current and do not dissolve the enamel insulation of the wire. For example, "TSAPON varnish", "Epoxy resin" or "polyurethane foam".
Assembly and configuration of the metal detector
The + VCC- contacts are supplied with voltage from 9 to 14 volts. A search coil is connected to L1, and an 8 ohm 0.5 W speaker must be connected to SP1 for an audible indication of a detected target. Adjustment is carried out away from industrial noise and large metal objects. When the metal detector is turned on, the scale of ten D3 - D12 LEDs will turn on, decreasing to zero, with a corresponding soundtrack - this device adapts to the sensor and the environment, taking it for the "no metal" position. With a well-made coil and proper adjustment of the resistor R3, all LEDs should go out to the end. If at this moment any metal object appears near the sensor coil, the device will not be configured correctly. After that, a characteristic sound signal sounds, indicating that the device is configured. We bring it to the metal and check the "sensitivity" of the metal detector. Then twisting the resistor R3, tune to a maximum "sensitivity."