Metal Detector Circuit
Description
This is the circuit diagram of a low cost metal detector using a single transistor circuit and an old pocket radio..This is nothing but a Colpitts oscillator working in the medium band frequency and a radio tuned to the same frequency.First the radio and the circuit are placed close.Then the radio is tuned so that there is no sound from radio.In this condition the radio and the circuit will be in same frequency and same frequencies beat off to produce no sound.This is the set up.When the metal detector circuit is placed near to a metal object the inductance of its coil changes , and so do the frequency of oscillations.Now the two frequency will be different , there will be no canceling and radio produces a hissing sound.The metal is detected.
Note
To make L1 make 60 turns of 36SWG enameled Copper wire on a 1 cm PVC tube.
Powering the circuit using a adapter rather than a battery induces noise. It is always good to power radio projects from battery.
Circuit Diagram & Parts List .
Comment: good circuit but need more clarifications for beginners like me.
where should be placed radio, i.e how far ?
can u make a detector to operate a relay ?
thanks
Author:The radio should be placed at least with in 1 meter from the circuit.It is always better to keep radio as close as possible.
It is a bit difficult to make this circuit to operate a relay.I am working on it.
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here no any discribtion about the circuit elelments so add this also
is it possible that the frequency of radio and the oscillator to be tuned at same so easily?or we have to calculate the frequency of the oscillator?
Hi radio will tune to the frequency without much difficulty. just tune the radio for the quite spot by keeping the radio close to the metal detector
i wanna ask how i can make the coil l1 it is really very hard to find a wire with 0.19 mm thickness plz help??
and then to make 60 turns with 1 cm diameter?
Hi Lama you can use any super enamelled copper wire any size from 26 to 36 SWG. You use 10mm dia plastic tubing (1/2″ plastic pipe) of 8″ in length. wind the wire starting from one end after properly anchoring it. winding should be side by side without any over lapping. once 60 turns are completed anchor this end also( anchoring can be done with cello tape or make a small hole in the plastic tube and route the through it). L1 is ready for use. (You can use insulated hook up wire single stranded of 0.2mm dia or 7 stands thin insulated copper wire also for L1)
TO TAKE DETAILS, METAL DETECTORS(KITS OR PCB).
Thank u very much to the attention for me.
I visit your web site & I found some details about your Circuits. I need to build a metal detector which can find metal (Gold coins) at a depth of 0.5m (0.2m< depth <0.5m) in rock (stone).
It’s good, if the m/c detects only GOLD & Simple indicating system is enough(LED bulbs or uv meter). Please give me the full details soon.
Thank U
How to mack a metal detector
This will sense the proximity of metals, which will change the frequency of the running oscillator.
Hi,
I was wondering if any other part of the circuit has a change besides for the oscillation frequency (ie: a change of voltage drop over the resistor or capacitor)- surely something else that is actually measurable must also change?
thanx