So i have been trying to make a metal detector and got it working. I used a collpitts Oscillator from a simulation page (Circuits->Transistors->Oscillators->collpitts) to tune it to the frequency i have.

enter image description here

I want to increase the current that flows inside the coil to make a stronger magnetic field using a higher voltage at the input. In the simulation it works, however in reality when i tried this out the output voltage only decreased.
Why is that? (the amplitude decreased)

enter image description here
This is a rough overview of the whole build. You won't be able to make out the oscillator from the photos as its a big cable salad. I can assure you however that the oscillator is exactly the same with the Parameters (except the inductance which is just a rough assumption based on some online calculators). The frequency of the wave according to oscilloscope is at about 80kHz to 100kHz.

  • \$\begingroup\$ When you say "in reality", you mean in real life, right? Do you have a picture of what you've set up so far? \$\endgroup\$
    – user103380
    Jul 11, 2018 at 21:33
  • \$\begingroup\$ @KingDuken Yes i have built it, however the circuit itself is impossible to read from photos. I will include a rough overview in the EDIT1 though. \$\endgroup\$
    – RIJIK
    Jul 11, 2018 at 21:54
  • \$\begingroup\$ This not the best method for a metal detector \$\endgroup\$ Jul 12, 2018 at 0:40
  • \$\begingroup\$ Bronze is also non magnetic unless it has Manganese or other magnetic minerals. But may have small eddy current losses unlike Aluminum which has large eddy current losses which require a higher frequency. \$\endgroup\$ Jul 12, 2018 at 0:47
  • \$\begingroup\$ @TonyEErocketscientist I thought it was supposed to work just by eddy currents. I used bronze as a sample, as its the biggest chunk of metal I had on hand. I also tried it with copper and iron where both worked, but of course not to the same intensity. According to the research i have done many metal detectors use frequencies between 1kHz to 100 kHz. Lower frequencies give more range but are less sensible to smaller parts. You said that this is not the best method; i know there are several different coil sizes, frequencies and coil layouts. If that isn't what you meant, what do you suggest? \$\endgroup\$
    – RIJIK
    Jul 12, 2018 at 9:54


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.