A gold detector circuit that is capable of detecting gold or metal at a distance of approximately 20 cm is shown. The gold detector is basically an oscillator that oscillates at frequency of 140KHz. This frequency or its harmonics is picked up by another AM radio circuit and sound from this AM radio alarms the detection of gold. Thus by tuning the AM radio we can search for gold on the ground.

The following picture shows you the overall design. The detector consist of mechanical parts and electronics parts. There is a wooden handle and wooden base to hold the circuit assembly and for moving around the detector. There are two electronics circuit- one is the detector circuit which is assembled in the base and there is a AM radio which is fasten in the wooden handle. The distance between the two circuit is shown to be 30 cm.


As you can see the detector consist of large coil connected to the core detector circuit labeled as PC board. This circuit layout is shown below.


The circuit schematic is shown below. It is basically an oscillator that is designed to oscillate at around 140KHz. The search coil together with the capacitors and the BC547 transistor makes up the tuning circuit. The circuit runs with 9V battery.


The PCB with components is shown below.


The AM circuit is easily available.

You can create the circuit and simulate online using the online Proteus simulator or Multisim simulator.

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