# .15A Motor

I have a 5V DC Motor but it pulls .15A which is too much for an I/O pin because the maximum current should be 40mA. Is there anyway I could put a resistor between the pin and the motor so the motor cant draw as much current? I don't need the motor to run at it's maximum speed, but I do need it to be powered from an I/O pin. Thanks for the help!

So why not use a simple transistor to “amplify” the current to the motor (1 resistor + 1 transistor extra)

If I use an NPN transistor, a 10k ohm resistor, and a diode would that be okay for powering the motor? Are there certain types of diodes and transistors that would work best for this? If I set it up this way I might as well just pull the voltage from the 5V pin and have an I/O set High or Low determine if the motor is on or off. Any help or further explanation is greatly appreciated!

I attached a rough sketch of what my breadboard would look like. I still don’t see how this limits the amount of current being pulled from the positive rail (5V pin). I feel like all this would do is switch the motor on and off when the I/O pin is high or low.

It's rough alright!

You don't show where the 5v rail gets its 5v from.... if it gets it from the Arduino, then you're right, it won't help.

The idea is to give the Arduino its own power, and a separate supply for the motor, with the grounds from both parts connected.

I need to use the 5V pin from the Arduino for my 5V/.15A motors. Is there anyway to do this to limit the amount of current being drawn from the pins?

I'm not sure what current the Arduino 5v pin can supply (not an i/o pin)... if it's enough (and I can't see that this page says what it is) then you could use that 5v as the power to the motor thru the transistor per your sketch, with the i/o pin switching the transistor.

Some one in the last day or three posted what the 5v pin's current is, iirc, but I don't know who or in what thread.

(Edit- Your original post spoke of the 40mA from an I/O pin, which is not the same as the 5v pin....)

Yeah if the 5V pin can handle 150mA then that would be perfect. Can anyone confirm how much current you can draw from the 5V pin?