need help in metal detector circuit!! urgent!

Discussion in 'The Projects Forum' started by haha, Sep 13, 2010.

  1. haha

    Thread Starter New Member

    Sep 13, 2010
    i have construct a metal detector circuit, but my circuit cant be function. i am using my hand make coil. is that the circuit problem or my coil? can anyone provide any other metal detector circuit ? i am using metal detector in my traffic light control system.
    this is the circuit i use..
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    Welcome to AAC
    can u show us what u made.
    The coil and the PCB.

    Photo's explains a lot
  3. windoze killa

    AAC Fanatic!

    Feb 23, 2006
    Can you explain why you need another circuit? Is this one not working? If it isn't was is it not doing or what is it doing wrong?
  4. haha

    Thread Starter New Member

    Sep 13, 2010
    i didnt do the PCB yet. Juz construct in project board. that is my constructed circuit and my inductor. That inductor can be function as a magnet but when i put it in my circuit and pass some metal through the inductor, the LED have no any respond.(No metal pass through- LED light up: when metal detected,lamp should be dim or switch off)
    i am using vehicle loop detector circuit diagram from Internet. Welcome for any other circuit diagram for metal detector. i need the simple circuit.
    the inductance generate by inductor r too small. i need something that can be detect the small toy metal car. My prototype cant be too big bcoz i am doing T junction traffic light, that each lane will consist 3 sensor circuit.

    THX A LOT FOR UR ALL HELP! View attachment my metal detector circuit.pdf
  5. SgtWookie


    Jul 17, 2007
    Well, the original schematic calls for a 6' diameter loop with 4 turns of wire.

    That would make an inductor of about 64uH.

    You obviously need a much smaller loop.

    If you used a form that was 3" in diameter, 18 turns of wire around it would also be about 64uH.

    However, your big problem is that a vehicle has a LOT of metal in it, and will change the inductance of the big loop inductor by quite a bit. A little toy car made from "pot metal" will have almost no effect on it.
  6. haha

    Thread Starter New Member

    Sep 13, 2010
    ya.. so i will add a magnet in that toy car. may i know around how big the coil should be? how to know the value of inductance that sufficient to detect the metal?

  7. marshallf3

    Well-Known Member

    Jul 26, 2010
    A magnet isn't the answer as there is no effect from the magnetism, it's the mass of ferrous metal that matters. A thin plate of steel would be better.

    A lot of today's products are made from what's commonly referred to as pot metal which, by nature, isn't always all that ferrous: