I have a coil with solid core, there is an small magnet that pass over it (like on the image) but not touching the coil (there is an small plastic between them, no more than 0.5mm thick). I need to detect when the magnet pass over the coil, i've investigated the hall effect devices but i'm not sure if they will work here as the magnet pass over the coil and not over the sensor.
I've connected an oscilloscope to the coil and watched while the magnet pass but i didn't recognize anything over all the noise (I connected the probe to one side of the coil and ground to the other side).
Any help or ideas will be highly appreciated.
Edit: The coil is not made from 4 turns, it has way more than that (around 50) but i was too lazy to draw 50 turns on the image. Also on the best escenario the coil should remain there, but i'm open to other devices like the reed switch (that i'm going to try soon).
Best Answer
If you are looking to see an induced voltage on the coil when the magnet moves over it you may find that you need higher speed. Induced voltage is proportional to speed and therefore if you move it slowly, your oscilloscope may not see the tiny change in induced voltage.
If your coil has only 4 turns this won't help pick-up the movement. Induced voltage is proportional to number of turns so try winding with a hundred turns to see what you get.
Alternatively, if you set up a free running oscillator that uses the coil inductance and move the magnet towards the coil, the material (not the magnetism) that forms the magnet will alter the field pattern produced by the oscillator and you may see a change of frequency.