In order to solve the mystery presented by my experiment Tangential EMF experiment that shows the lighting of LEDs when a coil rotates tangentially near a magnet, Jos Bergervoet proposed that the lighting may be caused by a tilt of the coil. Effectively, if the coil is tilted at an angle with respect to the direction of the magnetic field B, it will enter the area enclosed by the coil and, when rotating, the flux will vary and induce a voltage in the coil.

Please read the article at
Is the tangential EMF due to a tilt of the coil? http://pengkuanem.blogspot.com/2014/12/is-tangential-emf-due-to-tilt-of-coil.html
or https://www.academia.edu/9826402/Is_the_tangential_EMF_due_to_a_tilt_of_the_coil

Is the tangential EMF due to a tilt of the coil pdf or word with video