Driving system and sensing ratchet set thereof adapted for bike

A bike driving system comprising

• a chainring rotating with human input;
• a chain connected to the chainring;
• a cassette sprocket comprising a plurality of sprockets coaxially stacked on a rear axle, the cassette sprocket being connected to the chain through one of the plurality of sprockets, such that the cassette sprocket is driven by the chain and synchronously linked with the chainring;
• and
• a sensing ratchet set axially connected to a side of the cassette sprocket, the sensing ratchet set comprising:
• a ratchet base;
• a ratchet shell rotatably disposed on the ratchet base;
• a bottom case rotatably disposed at an end of the ratchet base;
• and
• a bike rotation speed sensor disposed between the ratchet base and the bottom case, the bike rotation speed sensor being configured to sense a rotation speed of the ratchet base relative to the bottom case;
• wherein if a gear ratio of the cassette sprocket to the chainring is between 1 and 0.5, and when the chainring rotates once in a full circle, a number of pulse signals output by the bike rotation speed sensor is between 24 and 150.