说明：  步进电机使用电压适当容量较大的另一电源， 单片的输出电流较小，不能直接驱动步进电机，要经过驱动器，或驱动芯片，或由分立元器件搭建的驱动电路。
(Stepper motor voltage appropriate to use another power supply of larger capacity , monolithic output current is small , can not directly drive a stepper motor , to go through the drive , or drive chip , a drive circuit built discrete components .)