I am trying to control the speed of a DC motor by using H-Bridge and Arduino UNO. The initial supply is 110 AC which with the help of transformer and a full wave rectifier circuit is converted into 12V DC supply. This 12V is given to the H-Bridge. Now with the help of Buck Converter, the 12V is stepped down to 5V. Now my question is that this 5V, should I use the 5V pin or the Vin pin in Arduino?