I am trying to build an Arduino Uno based robot. My questions are the following:
1) The motor driver also has an on-board 78M05 voltage regulator from ST electronics. I used a 9V battery to power the robot, and the 9V was connected to the input of the voltage regulator, and the +5V output I used to power the Arduino. I did so by connecting the 5V from the regulator to the 5V pin on the Arduino and the GND's together. I read that this is not advised, and solutions ranged from making sure the 5V is regulated, to connecting a diode between +5V and Vin to using one of the ICSP pins and so on. So which is actually a good way to do this?
2) I later realized that the DC motors are rated for max 6V dc, and so switched the 9V battery to 4x AA batteries giving a total voltage of 6V. When I connected this to the regulator, the regulator and the Arduino still turned on, even though the data sheet says the minimum input voltage is 7V. So what is going on here? Can anyone help me understand what is happening?