Material detecting mechanism of sowing machine, sowing machine, and unmanned aerial vehicle for protecting plants

A sowing machine comprising:

• a stirring mechanism comprising a rotating shaft;
• and
• a material detecting mechanism, comprising:
• a driven member;
• a magnetic member operably coupled to the driven member;
• and
• a Hall effect sensor,
• wherein:
• when the driven member is not blocked by material in the sowing machine, the driven member is configured to rotate under a driving force of the rotating shaft, and drive the magnetic member to rotate;
• and the Hall effect sensor is configured to detect a first signal corresponding to the magnetic member;
• when the driven member is blocked by the material in the sowing machine, the driven member is configured to stop rotating under a resistance of the material, and stop driving the magnetic member to rotate;
• and the Hall effect sensor is configured to detect a second signal corresponding to the magnetic member;
• and
• the material detecting mechanism is further configured to determine whether the material exists in the sowing machine based on at least one of the first signal or the second signal.