Hacked Gadgets Forum

March 31, 2007

DIY BFO Metal Detector

at 5:24 am. Filed under Cool Gadgets, DIY Hacks, Electronic Hacks

Here is a simple design for a DIY metal detector that uses a beat frequency oscillator.

“BFO ( beat frequency oscillator ) metal detectors use two oscillators, each of which produces a radio frequency. One of these oscillators uses a coil of wire that we call the search loop. The second oscillator uses a much smaller coil of wire, and is usually inside the control box and is called the reference oscillator. By adjusting the oscillators so their frequencies are very nearly the same, the difference between them is made audible as a beat note, this beat note changes slightly when the search loop is moved over or near to a piece of metal. It has been found in practice best to make the search oscillator fixed say at 100khz and to arrange for the reference oscillator to be adjustable 100khz plus or minus 250hz. This gives a beat note of 250hz to 0 to 250hz. The beat note disappears or nulls when the two oscillators are about equal. This type of detector is most sensitive when the beat note is close to zero, about 5hz ( motor boating ) any slight change being noticeable.

Parts list

Power source:
Any 9v battery PP3 is ideal.

Capacitors:
2 off 220uF 16v electrolytic.
5 off .01uF polyester.
5 off .1uF polyester.

Resistors:
All resistors 1/4 watt 5%
6 off 10k
1 off 1K
1 off 2.2m ===== 2.2 Mega ohm
2 off 39k”


 

Feb 2012, might wondering it safe, it and happens I it decide have I going share antabuse prescription . Antabuse the that you if drink by the of enzyme...


Related Posts

Metal Finding Robot
Geek Flip Flops
Pinewood Derby Finish Line Detector
IR Detector Circuit
DIY Metal Hunting Robot
Droidalyzer – Android Phone Alcohol Detector Accessory
Speaker Power Detector
DIY SMD Metal Stencil using a Pop Can

 


 

14 Responses to “DIY BFO Metal Detector”

  1. NGinuity Says:

    Very neat. I spent some time looking at the “Treasure Act” webpage on that site. Good grief.

  2. Chris Rybitski Says:

    It only detects objects about 120 mm down… Not as impressive, but still interesting. What would the detection depth on a retailed metal detector be?

  3. Hacking Gadgets! - One Blog A Day - Analyzing Web Ventures: One Blog A Day - Daily Blog Reviews! Says:

    […] Alan Parekh regularly talks about hacking gadgets in his blog Hacked Gadgets. His discussions range anywhere from Cool Gadgets to Insane Equipments. Here is how he does it: […]

  4. DIY HACK - How to make your own Metal Detector! | zedomax.com - blog about DIYs and Review on reviews of gadgets and technologies... Says:

    […] via audible, beat note, build, Circuits, coil of wire, Consumer, Cool, diy, DoItYourself!, Earth, educational, Entertainment, frequency one, frequency oscillator, gadget, gadgets, Hack, hacks, high tech, how to, howto, Industrial, made, magic, make, makers, making, metal detectors, motor boating, oscillators, projects, radio frequency, science, search loop, tech, technology, web2.0, Zedomaxaudible, beat note, build, Circuits, coil of wire, Consumer, Cool, diy, DoItYourself!, Earth, educational, Entertainment, frequency one, frequency oscillator, gadget, gadgets, Hack, hacks, high tech, how to, howto, Industrial, made, magic, make, makers, making, metal detectors, motor boating, oscillators, projects, radio frequency, science, search loop, tech, technology, web2.0, Zedomax […]

  5. Hexypoo Says:

    Its still pretty kewl in that its something anyone could do for the most part. I would love to use this as a fun weekend project for my kids.

  6. bayara Says:

    hi, i made this bfo metal detector but the detector doesnt work, pls help me how i can be getting right and working it!!!
    give me defenition of this metal detector, i think i made it following ur advice what pcb layout, electron element and making coil are, my mail address http://www.b_bayar33@yahoo.com. sent me more information how i work it

  7. Alan Parekh Says:

    Hi bayara,

    Looks like the site has moved. I updated the link to point to the new site location.
    http://www.easytreasure.co.uk/bfo.htm

    I would suggest that you contact the creator of the device for assistance. Let us know how well it works when you get it going. :)

  8. Larry Says:

    Dear Sirs,

    Could you please tell me what makes a metal detector, detect deeper?

    The detector I have is old and it only detects a few inches down.

    Is there a way to make it detect a few feet down?

    Thank You,

    Larry

  9. Daffa Says:

    Good Job. Hacked Gadgets
    http://broadcasthardware.blogspot.com

  10. rakesh Says:

    very use full

  11. Matt Says:

    fred flintstone called and said he wants his head back

  12. gilbert Says:

    is there an easy way to do this

  13. Alpha Delta Says:

    My coursemate and I wants to construct a BFO METAL DETECTOR as our final year project.

    We’ve downloaded the procedure for it and we need now is where to get the items and a complete circuit with all items (cap, resistors etc) are fixed on it.

  14. Luigi Fulk Says:

    Nice post

Leave a Reply

Internal Links:

Categories:

Search:

Google
Hacked Gadgets
Web

Site Sponsors:

Nuts and Volts Electronic Labs Trossen Robotics Free Technical Publications Blue LED

 

Recent Comments:

Site Rating:

More RSS Feed Options

Site Sponsors:

 

Interesting Sites:

Site Videos:

Incoming Links: