My group and I are currently working on a biomedical engineering project for our class. Our design idea is a wearable metal detector that uses metallic tracers in the blood to determine the concentration of glucose in the blood. There are multiple aspects of this design, but we wanted to reduce this project down to a proof of concept. We want to make a metal detector that is REALLY sensitive that can detect objects that we can make as small as possible (think iron fillings) that could simulate the tracer.

We plan to use an Arduino to read the changes in coil inductance. The main problem that we are running into is that, being biomed majors, we do not really know much about the electronics and circuits that will make this concept work. We found a few circuits for metal detectors, but we really don't understand what's going on in them. Here's a link to one that I found http://3.bp.blogspot.com/-iu_ERGb6vzQ/Ue2DyIWZYFI/AAAAAAAAAd8/yl2Wk05B37A/s1600/IMG_20130722_202500.jpg.

Main questions so far: Can someone explain whats going on in this circuit? What would the input and output waveforms look like? Can we use a simpler circuit and still get around the same sensitivity? If we want a more sensitive detector would a small coil with a ton of turns be a safe option? We'd like to use two coils concentric setup (one transmitter on receiver) would that add to sensitivity?

Thanks in advance!

  • $\begingroup$ I could explain it to you, but it won't help you much. There's the resonant LC circuit (search coil, 2 22n caps), amplifier circuit using the transistor, to overcome natural losses of the LC circuit and keep it resonating, and readout on pin 5, to detect the state of the LC circuit (which is then transformed to frequency in software). Frequency changes as inductance of coil changes in presence of metal. But you won't get nearly good enough sensitivity out of it - it's good for searching something the size of coins or nails, not stuff as small as you need. $\endgroup$ – SF. Nov 10 '17 at 10:56
  • $\begingroup$ ...just find a good electronics engineer to join your team. Even understanding how an existing device works won't suffice for creating a working one - you WILL experience problems with noise on the input, to such a degree the signal will be completely indistinguishable from noise, and both increasing signal:noise ratio until any usable data can be extracted, and then actually extracting that usable data will require quite a bit of expertise. $\endgroup$ – SF. Nov 10 '17 at 11:02

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