2B-Metal Detector




This project can identify the iron from metals like iron gold, copper, silver & brass etc.  Thus this project is very useful for the metal businessman.  If any body wants to sell iron after polishing it with copper this instrument will detect it and give the indication alarm with the speaker.

Technical Description & Working System


This project has been developed and tested in our TV Engineering Technical LAB.  The component and PCB used in the projects published in our books are available for sale. You can send your order giving the project code number.   The information

about project code is given in the beginning and end of the book.  You can give you order through telephone.

This project works as a Ferrous Metal Detector.  It detects the presence of iron among other metals and indicates by alarm to speaker.  A transformer of 0-12V/500mAmp rating is taken and carefully its core is taken out.  The coil left behind is used as metal detector.  The primary and secondary windings of the transformer are wound on plasting bobbin and center portion of bobbin is left open.  If any iron rod is inserted in this open space then AC 50Hz voltage are produced in the primary of the transformer.  This voltage is rectified by the diode D1 [IN4007], filtered with condenser C2 [1MFD/16V] and after controlled by the preset VR2 [10KE] given to the base of transistors T1 [BC548] and transistor T2 [BC548B].  Both these two transistors are connected in darlington pair.   A preset VR1 [1KE] which is connected at the emitter of transistor T1 [BC548B].  The middle end of this VR1 goes to the pin no. 4 of IC [NE555].  When the reset pin no. 4 of IC NE555 is high the IC is triggered and output is available at its pin no. 3.  A speaker is connected at output pin no. 3 which gives the alarm sound.  The sound is only produced when the rod of metal is made of iron.


In case rod is not made of iron then when it is kept between primary and secondary coil it will not induce the voltage.  Due to this IC NE555 will not triggered and output will not be available at the output pin no. 3 of the IC.  The speaker connected with this pin will not give the alarm.   In the circuit a 12-0-12V/ 500mAmp transformer is used to provide the supply to the circuit.  A bridge rectifier is connected with this transformer to convert 0-12V AC into DC.  Which is filtered by the condenser C5 [1000MFD/40V].  The output is given to the alarm circuit.  The other 0-12V AC supply is given to the secondary coil of transformer whose core is taken out through the resistance R2 [10E/5W]


In this way this project helps to distinguish between FERROUS & NON FERROUS METALS.


Precaution while assembling the project


  1. Use IC base while fixing IC on PCB. 2. Take care that while soldering there should be no short on PCB. 3. First of all, check the components so that there are according to the requirement and in good condition. 4.  While soldering diode take care of its polarity.  5.  Always use preset of good quality. 6.  Carefully connect the collector, base & emitter terminals of the transistor. 7.  Remove the core from the 0-12V/500mAmp transformer carefully.