Metal detector with 4030 CMOS

Posted on Oct 19, 2012

This battery-powered metal detector uses four exclusive-OR gates contained in the 4030 CMOS integrated circuit. The gates are wired as a twin-oscillators and a search coil serves as the inductance element in one of the oscillators. When the coil is brought near metal, the resultant change in its effective inductance changes the oscillator's frequency. Gates A1 and A2 form the two oscillators which are tuned to 160 and 161 kilohertz respectively.

Metal detector with 4030 CMOS
Click here to download the full size of the above Circuit.

The pulses produced by each oscillator are mixed in A3, its output contains sum and difference frequencies at 1 and 321 kHz. The 321 kHz signal is filtered out by the 10 kHz low-pass filter at A4, leaving the 1 kHz signal to be amplified for the crystal headset connected at the output. The device's sensitivity is sufficient to detect coin- sized objects a foot away.

Leave Comment

characters left:

New Circuits



Popular Circuits

4-Decade Square-Wave Generator
Circuit to convert a voltage output of a Hall device to a current
USB Powered Stereo Computer Speaker
switch mode power supply How does this circuit regulate voltage
Led display digital Voltmeter
Captret and Tesla switch
Digital circuit strain with MAX1494
Novel delay lighting switch circuit
Bistable circuit control motor reversing circuit