Abstract: An electric power tool includes a housing, a motor disposed in the housing, an output shaft connected to the motor and extending out of the housing, a magnetic ring sleeved on the output shaft, a magnetic polarity detector circuit disposed in proximity to the magnetic ring, and a controller connected to the motor and the magnetic polarity detector circuit. The output shaft is driven by the motor to rotate about its axis. The magnetic ring synchronously rotates with the output shaft, and has magnetic portions surrounding the output shaft. Every adjoining two of the magnetic portions have different magnetic polarities. The magnetic polarity detector circuit detects a change of magnetic polarities. The controller controls the motor to stop operating when an inter-change time interval satisfies a predetermined condition.

Abstract: A belt sander includes a main casing, a frame arm rotatably connected to the main casing, an abrasive belt mounted to the frame arm and adapted to be driven by electric power, a positioning member, a first sensor and a second sensor. The positioning member is movably mounted to the main casing and is movable relative to the main casing between a releasing position, where the first and second sensors are in a first sensor state, and where the second sensor generates a first signal for ceasing the electric power, and a first engaging position, where the first and second sensors are in the second sensor state, and where the second sensor generates a second signal for conducting the electric power.

Abstract: A belt sander includes a main casing, a frame arm rotatably connected to the main casing, an abrasive belt mounted to the frame arm and adapted to be driven by electric power, a positioning member, a first sensor and a second sensor. The positioning member is movably mounted to the main casing and is movable relative to the main casing between a releasing position, where the first and second sensors are in a first sensor state, and where the second sensor generates a first signal for ceasing the electric power, and a first engaging position, where the first and second sensors are in the second sensor state, and where the second sensor generates a second signal for conducting the electric power.

Abstract: An automatic mixing machine includes a vessel, a shell, a motor, a mixing unit, a detection and feedback unit, a computing control unit and a drive unit. The shell is connected with the vessel to form a closed space. The motor is arranged in the shell. The first end of the mixing unit is connected with the motor, and the second end of the mixing unit extends into the closed space. The detection and feedback unit is electrically connected with the motor and collects at least one electric parameter of the motor. The computing control unit is electrically connected with the detection and feedback unit and generates a control signal according to the electric parameters and the mixing parameters. The drive unit is electrically connected with the computing control unit and the motor respectively, and outputs a drive signal to drive the motor according to the control signal.

Abstract: An automatic mixing machine including a vessel, a shell, a motor, a mixing unit, a detection and feedback unit, a computing control unit and a drive unit. The vessel is used for accommodating the raw materials. The shell is connected with the vessel to form a closed space. The motor is arranged in the shell. The first end of the mixing unit is connected with the motor, and the second end extends into the closed space. The detection and feedback unit is electrically connected with the motor and collects at least one electric parameter of the motor. The computing control unit is electrically connected with the detection and feedback unit and generates a control signal according to the electric parameters and the mixing parameters. The drive unit is electrically connected with the computing control unit and the motor respectively, and outputs a drive signal to drive the motor according to the control signal.