Ultra High Sensitivity Metal Detector Circuit

Posted on Jun 5, 2017

This circuit is a metal detector capable of detecting large metallic objects. at a depth of 2m to 3m. It depends on the size of the object, and often on the type of soil. Construction is very easy to implement even for a beginner. The necessary components are easy to find everywhere. This detector has the ability to detect a gold coin of 20mm and a thickness of 1.5mm and a depth of 90cm. The two present frequencies are the one that is generated by the circuit and the one that is returning for comparison. By placing the coil near a metallic object the returning frequency is changed. Those two frequencies are the subject of comparison by our circuit. At modern metal detectors, the reference generator operates at a frequency that has different magnitude from that which appears in the field of the search coil.

Ultra High Sensitivity Metal Detector Circuit
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How the circuit works

The circuit uses the IC1 which is the CD4011 and the IC2, the CD4023, both of these are logic ICs. The reference generator is implemented in two logic elements of the integrated circuit IC2. Its frequency is stabilized and is determined by the quartz crystal X which is 1MHz. The generator with a variable frequency is made on the first two elements of the IC1. The oscillating circuit here is formed by the search coil L, the capacitors and the varicap. The potentiometer 10K is for tuning to a frequency of 100kHz, this actually sets the required voltage to the varicap VD1.

The circuit use the signal logic elements IC1-3 and IC2-3 as buffer amplifiers and the signal mixer is the IC1-4. The speaker should be a high resistance phone capsule. And the capacitor C10 is used as a shunt capacitor for the high frequency coming from the mixer.

The metal detector circuit is powered by a 9V DC battery or you can use 6 AA batteries for much longer working times. The capacitors C8 and C9 work as a filter. The search coil requires special precision and attention in its construction. 

It should be wound on a plastic tube with an external diameter of 20cm. The coil should contain 100 turns of 0.3mm wire. When the winding of the coil is completed, it should be wrapped in aluminum foil to create an electrostatic shield (this will reduce the effect of the capacitance between the coil and ground). It is important not to allow electrical contact between the winding wire and the foil. The aluminum foil itself should be protected from physical damage, so it should be wounded well with an insulating tape. Then you should secure the coil in a water proof hard casing, to protect it from damaging it and to get wet.

The diameter of the coil can be different than 20cm. But the smaller the coil, the more sensitive the circuit becomes, but the area of ​​searching for hidden metal objects narrows. When the diameter of the coil is increased, the same effect is reversed.

Having located the search coil close to the ground surface, adjust the detector with the potentiometer. And so that in the speaker capsule the sound is almost none. Now you are ready to use it and search. If a metallic object will be in the range of the coil the sound will get loud. 

Update: Missing resistor value R = 150KΩ.

Leave Comment

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Roshan   Oct 11, 2021

Where to buy components for this circuit.let me know. In witch site.

roshan   Oct 2, 2021

hi im bigginer of this please send about coil sizw and how many turns,and what is blue arrow ro down?it can gold detert

4.7uf is what (±)   Sep 29, 2021

4.7uf what is + -

Cultavero   Sep 13, 2021

Finaly its working!!! Yeeeeeeyyy .. Well I take back all blame.. I love this circuit!. Thanks!

khin linn   Sep 5, 2021

Please send to me pcb layout design image.

Erf   Aug 25, 2021

hello,Can u plz send circuit pic

Did anyone tried with different qartz value other than 1 mhz   Apr 25, 2021

Did anyone tried with different qartz value other than 1 mhz

Ultra High Sensitivity Metal Detector Circuit    Mar 10, 2021

Greetings to you I did not understand the electronic chart, as if it had mirrored or deleted pieces, is there an explanation

Bobkulusa   Mar 10, 2021

Its working guys, I found the problem!

Yousef   Feb 7, 2021

I'll try to make it soon, thanks allot.

[email protected]   Dec 19, 2020

Hello, I made it. But the earphone will only emit sound, which will disappear from sharp to smooth by adjusting the resistor, but it can not detect metal. I replaced the 50u capacitor with a 47u capacitor and a 3.3u capacitor connected in parallel. I don't know what the problem is.

Ultra high sensitivity mattle decttor    Sep 16, 2020

I m no found quartz 1mhz are u used 4mhz

Plise send to me search coil ditals   Sep 7, 2020

Please send to me search coil details

Retula   Aug 24, 2020

hello the circuit finally is working fine!! thanks bro!

egxon   Aug 8, 2020

will the results be the same if I use two cd4011 ics

BobNU   Jul 14, 2020

I will make it! thanks!

berk   May 10, 2020

hello everbody. ı cant find 50 uF 16 electrolitc capacitor can ı use 47 uf 16v instead, and are there any body help me to construct this circuit

jeonwoo   Feb 26, 2020

Hi, what are those component parts!?

Hello Sir   Feb 22, 2020

Dear Sir, Is there a photo or PCB layout for this circuit ? For ultra high sensitive metal detector Kind regards Mohammad Tareefi Jordan

Max   Jan 31, 2020

Hello. I love making this. But the necessary equipment is hard to find in my country. Could you please send me the equipment to make this circuit? I will give the money. How much Great help.

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