LM7812 and LM7805 chips are used to obtain 12V and 5V voltages. Their applications should pay attention to the following points: (2) the output current should not be too large. 1.5a is the limit value. Large current output, the size of the radiator fin should be large enough, otherwise it will lead to high temperature protection or thermal breakdown; (3) the input-output pressure difference should not be too small, so the size efficiency is very poor. Among them, 12V voltage supplies power to stepper motor and 5V voltage supplies power to MCU. As shown in FIG. 3-2 and FIG. 3-3, respectively.