a printed circuit board disposed thereon a first magnetic sensor and a second magnetic sensor; and

a direction control unit provided on the printed circuit board, and including:

a first rotating driving body and a second rotating driving body, each being a rotatable elongated arc-shaped structure and each having an elongated center hole disposed in a center of the corresponding elongated arc-shaped structure, wherein the first rotating driving body is disposed above and crossed perpendicularly with the second rotating driving body so that the elongated center holes are aligned with each other;

a first sliding driving body and a second sliding driving body respectively movably connected to one end of the first rotating driving body and one end of the second rotating driving body;

a first magnet and a second magnet respectively fixed on one side of the first sliding driving body and one side of the second sliding driving body;

a lower cover having a first slide groove and a second slide groove respectively corresponding to the first sliding driving body and the second sliding driving body,

wherein the first sliding driving body is slidably disposed in the first slide groove, and the second sliding driving body is slidably disposed in the second slide groove;

a shaft stick having an upper end and a lower end, wherein the upper end passes through the elongated center holes from bottoms of the first rotating driving body and the second rotating driving body;

a balance washer disposed under the shaft stick and in contact with the first rotating driving body and the second rotating driving body; and

an annular spring disposed under the balance washer and in contact with the balance washer,

wherein the first magnetic sensor and the second magnetic sensor are arranged to respectively correspond to the first slide groove and the second groove.