Home Made - Simple Metal Detector "Beat Frequency Oscillator"

It uses a single 4093 quad Schmitt NAND IC and a search coil. A lead from IC needs to be attached to a MW radio aerial, or should be wrapped around the radio. The metal detector is set up by tuning the MW radio to pick up a whistle (a harmonic of ). Note that not every such harmonic works best, and the most suitable one needs to be found. The presence of metal will then clearly change the tone of the whistle.

Component list:
1. Integrated circuit = CD4093 ( HEF4093)
2. 390pF capacitor (up to 470pF)
3. 22pF capacitor (up to 47pF )
4. Detection coil L1 = 50 turns of 0.1 -0/2mm solid wire (air-wound) / 120 mm diameter coil. You may use wire reclaimed from an old transformer. If you can't find wire to recycle need to buy enamel covered wire as in the specialized shops selling "magnet wire" (also search for shops which specialize in rewinding electric motors). Practically 50 turns need to be wound on a CD plastic case. Later cover the coil with a piece of aluminum foil. The aluminum foil must be tied to ground (negative power supply) with a separate wire. Leave a small gap on the aluminum shield.
5. Variable capacitor 10pF up to 330pF ( any variable capacitor starting from 0pF up to 510 pF)
6. Oscillator coil 60 up to 90 turns 0.1-0.2 mm solid wire on a small diameter ferrite core ( 2-3mm diameter, height 10mm up to 20mm)
7. 100nF capacitor -- power supply decoupling capacitor

Category:

Science & Technology

Tags:

• BFO
• metal
• detector
• simple
• CD4093
• coil
• DIY
• radiofrequency
• electronic
• circuit
• home
• made
• Easy

[xMusiicloveex]

Hi, I have a question, do you know if it's possible to connect this metal detector to a PIC? or how could it be possible to put it on a system that will skip obstacles but that has to find a metal piece, or at least that when it find it an electromagnet be activated? :/ Thanks

[LEDchaser]

@xMusiicloveex

You need to rectify the output signal in order to obtain a positive indication of the metal object’s proximity to the search coil. The inductance of the search loop has Faraday shielding to reduce capacitive-coupling effects by simply wrapping the completed loop with the foil tape. Make sure the tape has a gap at one point around the loop, or a shorted-turn transformer results and you should mechanically secure the search coil to a nonmetallic form to prevent microphonics.

[TypesEvilAspieEyes]

Did you put it in a exoskeleton??

[LEDchaser]

@TypesEvilAspieEyes

No, not for the moment, that was just a simple test. These fun and simple experiments can teach you the basic principle of metal detectors...

[LEDchaser]

Un astfel de detector nu este greu de confectionat, dar montajul respectiv trebuie plasat langa un radio clasic cu receptie in banda de unde medii, in asa fel incat modificarile de frecventa ale oscilatorului (in prezenta obiectelor metalice) sa fie sesizate de catre receptorul radio.

In plus, montajul nu este foarte stabil si trebuie refacut permanent acordul receptorului radio.

[avalanchexy]

Dupa moneda de 1 ban mi-am dat seama ca e made in Romania. Ai un canal foarte interesant. Subscribed!

[ScopedOUT2]

I'm coming "Free Willy" just hang on.

[micmoable]

can it detect down to six inches on a penny or dime?

[hugovelocity]

This is like baby cries =(

[willallerbr]

Thank you very much for share knowledge. I'll try make this device.

[smartboy140597]

mi-am dat seama ca esti roman dupa moneda:)) 1Ban :))

[elothin]

that's cool but what is the depth detection 

[sttefann77]

tipule..esti roman...:D Bv pt detector;)