I want to ask some more questions again to you now to clarify my mind ( thank you every much for answering my questions here patiently all the time ) :
When I take of this jumper ( at the above screenshot that is on my motor shield ) I can put 1 power supply to power shield and 1 power supply to my arduino at the same time without any problem, right ? thanks.
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Grumpy_Mike, what do you mean by " the -ve terminals should be connected together " , it will be like above picture ? if not, would you be more clear please ? thanks.
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One " 8 AA battery " is enough to move my 4 of above dc motor smoothly with a good acceleration that motor wants 9-12V ) ? I am asking because my tank weightness is 6 kg total, thanks.
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How much voltage and amper Arduino and motor shield solo itself handle ? thanks.
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Do you have any suggestions about what kind of dc motor I should use with how much rpm I need to move and accelerate my 6 kg tank ( for my tank project ) ? thanks.