I am a newbie to Arduino and need some advice please.
Due to a past mishap when trying to use a separate supply to a motor shield stacked with an Arduino Mega that damaged the Mega, I need guidance on how I prevent overloading the Arduino due to a feedback situation from shield supply. I was feeding the Mega via the computer USB and blew the Mega when I connected a 12v supply to the motor shield. I guess this is a no-no.
However this begs the question how do I prevent it happening in the future?
I have since noticed a jumper on the motor shield PWR which can be removed. I assumed that negates any feedback to the Arduino.
However, I actually just established that the jumper needs to be in place to feed a DC source to the motor shield when it is not stacked. However the jumper makes no difference (on or off) when stacked and Arduino is plugged into the computer via USB. I.e. With no external supply to the shield, the USB is feeding the shield as well.
So I am still rather confused as to what I should do when I need to feed a few small (say 12v) motors fitted to the shield and not have that back feed to the Arduino thus damaging it. Can anyone help please?