电机用的实验室找的, 电源用的学生电源 和 5V USB接了5K电位器,大概分压电阻在100Ω到200Ω之间

I found it in the laboratory for motors. I used a student power supply and a 5V USB connected to a 5K potentiometer. The voltage dividing resistor is probably between 100Ω and 200Ω.