or turn off of the clockwise and counterclockwise rotation of the motor 11 in response to signals from output ports r 1 and r 2 of the microcomputer fig5 is a flow chart which indicates operations of the arrangement and particularly of the control system thereof as described above step 100 is a rotational direction flag setting step at which a flag is set which represents a running direction of the motor 11 and next step 101 is a rotational angle setting step for setting an angle of rotation of the agitating wheel 5 an angle over which the motor is energized thus at step 101 the number of pulses n corresponding to an angle of rotation is set and this value is stored in a register x at next step 102 subsequent step 103 is a rotational direction discriminating step for determining the rotational direction of the motor 11 step 106 is a counter step for counting an angle of rotation of the agitating wheel 5 the number of pulses from the rotational angle detector 8 and the count is inputted to a register t step 107 is a comparing step at which the angle of rotation of the agitating wheel 5 is compared with the preset value n in order to determine if the former reaches.