If i connect dc motor to my arduino in this way:
How could i know what is the current that flows through the motor when the transitor is on? there is no any resistor between the 5v to the motor..
What is Q1?
Groove:
What is Q1?
BJT Transistor
No shit.
Groove:
No shit.
what?
What is the type of Q1?
Groove:
What is the type of Q1?
BJT !!
In that case, the current through the motor will contain many, many electrons.
More electrons than you can easily count, or imagine.
Does that help?
I'd suggest don't use the Arduino 5V as the motor supply, its risking spikes and dropouts/resets.
The point is without knowing anything about the actual transistor or motor the answer is "use a
multimeter"
If Q1 is a darlington and the motor has winding resistance of 8 ohms, then the answer would be
"about 0.5A stalled, less when running no-load"
If Q1 is a BJT then the motor would probably be overloading the transistor if it was less than 15 ohms,
although reducing the base resistor to 150 ohms might double that if the device can take the collector
current.