Question on Battery vs USB for 3.3v when running Motor

I'm hoping someone could help me test and/or understand what the problem is with my circuit.

I'm trying to do this example: https://www.arduino.cc/en/Tutorial/TransistorMotorControl

I have a few changes however:

  1. I'm running a 3.3v Arduino
  2. My transistor is P2N2222A
  3. My diode is 1N4148

I notice that if my Arduino is connected to my computer via the USB wire, the circuit works correctly (please note, I am still using the 3.3v pin from the Arduino to the motor curcuit even though the computer is supplying 5v to the Arduino).

If I run the Arduino from a 650mah 3.8v Lipo, the circuit will not work. It will not run the motor.

I suspect this is the Transistor not "opening". I've ordered a Mosfet to try that..but I'm pulling at strings...

I've tried this on my test setup (Arduino UNO) and the actual boards (Adafruit 3v Feather) I'd like to use with the same results.

I'm hoping someone can shed some light on what is going on.

Any help would be appreciated.

Thank you!

If I run the Arduino from a 650mah 3.8v Lipo, the circuit will not work. It will not run the motor.

How are you supplying the Lipo voltage to the Arduino ?

In the case of the UNO, I'm doing it through the barrel jack...on the Feather there is a connector for a battery directly.

You need 7v minimum on Uno's barrel jack. That is about twice what you are giving it.

scampa:
In the case of the UNO, I'm doing it through the barrel jack...on the Feather there is a connector for a battery directly.

3.3V to the barrel jack of a Uno is never going to work as it need at least 7V to work to allow for the voltage regulator

Thank you for the responses!

The real project will run from the Adafruit Feather, not the UNO…so my UNO test was invalid.

The Feather is made to work from a 3.7v battery…

“We wanted to make the Feather easy to power both when connected to a computer as well as via battery. There’s two ways to power a Feather. You can connect with a MicroUSB cable (just plug into the jack) and the Feather will regulate the 5V USB down to 3.3V. You can also connect a 4.2/3.7V Lithium Polymer (Lipo/Lipoly) or Lithium Ion (LiIon) battery to the JST jack. This will let the Feather run on a rechargable battery.”

I’m still thinking it may be the transistor causing the issue. If the transistor is removed and the power is fed directly from the ground and 3.3v of the Arduino the motor will spin…

One nuance I see is that if the USB cable and the battery are both plugged into the Feather, the motor starts. I realize the USB is providing the power and overrides the battery. If I remove the USB, the battery is then able to start and stop the motor....It's almost like a jump start...

If I simply only provide the battery, I cannot get the motor to start...

Maybe that helps shed some light as to what is happening...

I just tried replacing the original Transistor with a RFP30N06LE MOSFET, however I seem to be seeing the same sort of behavior.