Simple Metal Detector using CA3140 IC

In this tutorial, we are making a very easy and interesting project of a Simple metal detector using a CA3140 IC. There are lots of metal detectors available in stores etc. to build but they are most complicated. The circuit that we are making is easy to build, beginner-friendly, and not so expensive. It is able to detect a metal object from a distance of 2 to 3 inches away.

Hardware Components

The following components are required to make Metal Detector Circuit

S.no	Component	Value	Qty
1.	Input Supply DC	9-12V	1
2.	Coil	–	1
3.	IC	CA3140	1
4.	Transistor	2N3904	1
5.	Buzzer	Piezo	1
6.	LED	–	1
7.	Resistor	1MΩ, 470Ω, 1KΩ	2, 1, 1

CA3140 Pinout

For a detailed description of pinout, dimension features, and specifications download the datasheet of CA3140

Metal Detector Circuit

Working Explanation

This circuit is working on the basis of a BiMOS operational amplifier IC CA3140 and can be operated at 9-12V. A coil is used to sense the presence of any metal around the circuit. After detecting a metal it sends an input signal to the op-amp IC. A 2N3904 transistor is connected at the output of this IC to drive the piezo buzzer and the Led. So when metal is around the circuit the op-amp sends an input signal to the transistor it acts as a switch and turns on the piezo buzzer and LED in that way you will be notified.

In this circuit for coil L1, we have used a guitar pickup coil but you can experiment with different coils also you can use any similar NPN transistor like BC547, 2N2222, etc. instead of  2N3904. The performance can be accurate with the right kind of transistor and coil.

When you are done with building the circuit, fit it in a suitable casing. To make sure if it’s working fine moves the coil around any metal object if you hear a beep it means the circuit is working if not then you must have made an error while building it.