Maximum detection range: 5CM (Best detection range: 1 CM - 2 CM)
Principle explanation: Q1, L1, L2, C2, C3, R1, W composed of high-frequency oscillation circuit, adjustment potentiometer W, you can change the oscillation stage gain, the oscillator oscillating in a critical state, that is just the oscillator start-up. Q2, Q3 when the composition of the detection circuit, the circuit normally oscillate voltage AC voltage exceeds 0.6V, Q2 will be in the negative half cycle of conducting the C4 discharge short circuit, resulting in Q3 ends; when it detects metal objects near the coil L1, will be metal conductor eddy current is generated, the oscillation circuit of the energy loss increases, positive feedback weakened in the critical state of the oscillator weakened, if not impossible to maintain the minimum required energy oscillations and to stop, so Q2 is turned off, R2 to C4 charge, Q3 is turned on, pushing the buzzer sounds. According to whether the sound, you can determine whether the detection coil underneath the metal object.
Note: If you need longer detection than 5CM range and higher sensitivity, please create their own search coil, search coil diameter of the larger suppliers will be farther away from the probe
1 x DIY Metal Detector Kit (unassembled - require soldering)
Schematic - please see auction pic
Technical support is NOT included in this auction